We hope this project will demonstrate the feasibility of bona fide rejuvenation biotechnologies - therapies that remove, replace, repair or render harmless the pre-existing burden of cellular and molecular damage of aging in persons who have already suffered substantially from the degenerative aging process. It requires that new therapies be tested in animal models that have already undergone significant biological aging. Many of these therapies will be best demonstrated using gene therapy in animal models, and may ultimately require gene therapy for maximal efficacy in humans. Conventional transgenic animals bear their novel genes in the germ line, and although convenient methods for inducing the expression of therapeutic transgenes late in life exist, doing so still requires the custom generation of a line of transgenic animal for each new tested gene, and then allowing it to age, typically for two or more years, before the induced transgene's effects can be tested. This greatly slows down the development cycle of testing, refining, and iteratively re-testing therapeutic genes.

A promising alternative is the use of integrases from bacteriophages (or "phages,"), a class of virus whose hosts in nature are bacteria. Phage integrases are enzymes that catalyze precisely-targeted, unidirectional recombination between paired DNA recognition sequences: one (attB) a specific site in the bacterial host where the viral DNA is inserted, and another (attP) in the phage genome, from which the viral DNA is copied. Moreover, phage integrases can be used to insert arbitrary amounts of DNA into the host genome. To exploit phage integrases for gene therapy in mammals, one plasmid is generated containing the gene(s) to be inserted linked to an attB site, and another is generated containing the phage integrase; the plasmid DNA is translated in the host cell, generating the integrase, which then inserts the attB-bearing gene of interest into the host genome, with essentially no risk of gene disruption; the attP and attB sites are both destroyed in the process. The serine integrase from the mycobacteriophage Bxb1, in particular, is extremely precise: it will only mediate integration at specific attB sites. The Bxb1 integrase has already been demonstrated as a highly effective tool for somatic gene therapy in Drosophila, and has been shown to allow repeated, high-titer delivery of novel genes.

Unfortunately, mammals lack attP sites in their genomes, and thus the Bxb1 integrase cannot be used to insert new genes into mammalian model organisms such as the mouse. This limitation could be overcome with a one-time germline insertion of the Bxb1 insertion sequence into a transcriptionally-active but safe genomic location in the mouse genome: in such mice, the Bxb1 integrase system could be used at any time during the lifespan to insert therapeutic genes of any size, and with repeated rounds of gene dosing with multiple delivery methods to hit all the relevant tissues in the animals' body, with only a very low risk of mutagenesis. The effects of such genes on age-related disease could then be rapidly evaluated, and if improvements need to be made, a new transgene constructed and tested immediately in mice who are already the same age, without having to wait for a new generation of transgenic animal to be generated, born, mature, and age with every round of testing.

SENS Research Foundation (SRF) has launched a new research program focused on somatic gene therapy in collaboration with the Buck Institute for Research on Aging. Brian Kennedy, PhD, a leading expert on the biology of aging, will be running the project in his lab at the Buck. Many potential treatments of age related diseases require the addition of new genes to the genome of cells in the body, a technology known as somatic gene therapy. The technology has been hampered, up until now, by the inability to control where the gene is inserted. That lack of control resulted in a significant risk of insertion in a location that encourages the cell to become malignant.

SRF has devised a new method for inserting genes into a pre-defined location. In this program, this will be done as a two-step process, in which first CRISPR is used to create a "landing pad" for the gene, and then the gene is inserted using an enzyme that only recognizes the landing pad. SRF has created "maximally modifiable mice" that already have the landing pad, and this project will evaluate how well the insertion step works in different tissues. "Somatic gene therapy has been a goal of medicine for decades. Being able to add new healthy genes will enable us to address treatments of such age-related diseases as atherosclerosis and macular degeneration. Our collaboration with SRF will substantially move us toward finding effective treatments to genetically based age related diseases."

Researchers have discovered that macrophages, a type of immune cell that clears debris at injury sites during normal wound healing and helps produce scar tissue, are required for complex tissue regeneration in mammals. Their findings shed light on how immune cells might be harnessed to someday help stimulate tissue regeneration in humans. "With few examples to study, we know very little about how regeneration works in mammals; most of what we know about organ regeneration comes from studying invertebrates or from research in amphibians and fish. If we want to apply what we learn from basic regenerative biology to humans, it would be helpful to understand what cell types and molecules regulate regeneration in a mammal where it occurs naturally."

Scientists have been trying to learn for years why some animals, like salamanders and zebrafish, are able to regrow body parts following injury, while others - like humans - can only produce scar tissue in response. Researchers learned nearly eight years ago that African spiny mice are one of the few mammalian models capable of complex tissue regeneration, making them particularly fascinating subjects. But what remained unclear was exactly how an identical injury in spiny mice and non-regenerating lab mice could produce dramatically different healing responses. The researchers decided to investigate how the inflammatory environment might differ between the regenerative response observed in spiny mice compared to the typical scarring response observed in lab mice. Although white blood cell profiles were the same in uninjured animals from both species, injury elicited different local responses. "Comparing spiny mice to common house mice, we discovered that subtypes of macrophages active during regeneration are different than those active during scarring."

When the team looked at different types of macrophages in healing tissue they found that a pro-inflammatory type of macrophage was highly abundant during scarring, but very rare during regeneration. "Our findings imply that macrophage activation in our model favors regeneration. The next step is to identify the components of macrophage activation that are necessary for regeneration. Since we are actively developing clinically feasible therapies that selectively activate macrophages, identifying targetable components of macrophage activation opens new areas of discovery with real potential for improving tissue regeneration in humans."

When an animal is injured, immune cells such as macrophages rush to the wounded site to clear debris and help repair the damage. Macrophages come in different forms and subtypes, and express different protein markers on their surface, depending on where in the body they reside. Few mammals can completely renew or regrow a damaged tissue - a process known as tissue regeneration. Instead, humans and most other mammals repair injuries by producing scar tissue, which has different properties compared to the original tissue it replaces. One exception is the African spiny mouse (Acomys cahirinus), which, unlike other rodents studied, can regrow skin and fur, nerves, muscles, and even cartilage. It has been shown that in highly regenerative animals such as salamanders and zebrafish, macrophages are necessary to initiate tissue regeneration. Documented cases of tissue regeneration in mammals are rare and therefore less understood. Until now, it was not clear why two species as closely related as spiny mice and house mice would heal identical injuries in different ways.

Here, we report how the two main orchestrators of inflammation, neutrophils and macrophages, respond to injury during regeneration in Acomys cahirinus compared to scarring in the house mouse (Mus musculus). Acomys and Mus exhibit the same circulating leukocyte profiles, and we demonstrate a robust acute inflammatory response in both species. We demonstrate higher neutrophil activity in the scarring system compared to higher reactive oxygen species (ROS) activity in the regenerative system. We show that macrophages between the two species display similar in vitro properties providing a comparable baseline prior to and following injury. We also observed distinct differences in the spatiotemporal distribution of macrophage subtypes during regeneration and scarring. Finally, depletion of macrophages, prior to and during injury, inhibited blastema formation and regeneration, thus demonstrating a necessity for these cells.

A popular hypothesis to explain why most mammals heal injuries with scar tissue is that they evolved a strong inflammatory and adaptive immune response that induces intense fibrosis in lieu of regeneration. Yet, the fact that some mammals exhibit epimorphic regeneration (e.g. rodent and primate digit tips, rabbit and spiny mice ear punches and skin) suggests that regeneration can occur despite a complex adaptive immune system. It is possible that macrophages provide an initiating signal for regeneration or remove subpopulations of local cells secreting inhibitory signals (e.g. senescent cells). In support of the first idea, ROS production has been suggested as an essential early signal for regeneration based on studies in zebrafish tail models of regeneration. Macrophages are a major source of ROS after injury, and we observed significantly stronger and prolonged ROS production during regeneration compared to scarring. In support of the idea that macrophages may limit inhibitory signals through selective removal of senescent cells, recent work in salamanders suggested that clearance of senescent cells is important for limb regeneration and persistence of senescent cells during liver regeneration leads to excessive fibrosis. Furthermore, the accumulation of senescent cells with age has been suggested to shorten lifespan, degrade tissue function, and increase the expression of pro-inflammatory cytokines in mammals. These and other studies suggest that proper clearance of senescent cells from damaged tissues may promote regenerative outcomes.

The idea that people can be fat but medically fit is a myth. Early work, as yet unpublished, involved looking at the GP records of 3.5 million people in the UK. The researchers say people who were obese but who had no initial signs of heart disease, diabetes or high cholesterol were not protected from ill health in later life, contradicting previous research. A summary of their study was discussed at the European Congress on Obesity.

The term "fat but fit" refers to the alluring theory that if people are obese but all their other metabolic factors such as blood pressure and blood sugar are within recommended limits then the extra weight will not be harmful. In this study, researchers analysed data of millions of British patients between 1995 and 2015 to see if this claim held true. They tracked people who were obese at the start of the study, defined as people with a body mass index (BMI) of 30 or more, who had no evidence of heart disease, high blood pressure, high cholesterol or diabetes at this point. They found these people who were obese but "metabolically healthy" were at higher risk of developing heart disease, strokes and heart failure than people of normal weight.

Several studies in the past have suggested that the idea of "metabolically healthy" obese individuals is an illusion, but they have been smaller than this one. The new study involved 3.5 million people, approximately 61,000 of whom developed coronary heart disease. The scientists examined electronic health records from 1995 to 2015 in the Health Improvement Network - a large UK general practice database. They found records for 3.5 million people who were free of coronary heart disease at the starting point of the study and divided them into groups according to their BMI and whether they had diabetes, high blood pressure (hypertension), and abnormal blood fats (hyperlipidemia), which are all classed as metabolic abnormalities. Anyone who had none of those was classed as "metabolically healthy obese".

The study found that those obese individuals who appeared healthy in fact had a 50% higher risk of coronary heart disease than people who were of normal weight. They had a 7% increased risk of cerebrovascular disease - problems affecting the blood supply to the brain - which can cause a stroke, and double the risk of heart failure. While BMI results for particular individuals could be misleading, the study showed that on a population level, the idea that large numbers of people can be obese and yet metabolically healthy and at no risk of heart disease was wrong. "So-called metabolically healthy obesity is not a harmless condition and perhaps it is better not to use this term to describe an obese person, regardless of how many metabolic complications they have."

The human heart beats approximately 35 million times every year, effectively pumping blood into the circulation via four different heart valves. Unfortunately, in over four million people each year, these delicate tissues malfunction due to birth defects, age-related deteriorations, and infections, causing cardiac valve disease. Today, clinicians use either artificial prostheses or fixed animal and cadaver-sourced tissues to replace defective valves. While these prostheses can restore the function of the heart for a while, they are associated with adverse comorbidity and wear down and need to be replaced during invasive and expensive surgeries.

A team lead recently developed a nanofiber fabrication technique to rapidly manufacture heart valves with regenerative and growth potential. The researchers fabricated a valve-shaped nanofiber network that mimics the mechanical and chemical properties of the native valve extracellular matrix (ECM). To achieve this, the team used a rotary jet spinning technology in which a rotating nozzle extrudes an ECM solution into nanofibers that wrap themselves around heart-valve-shaped mandrels. "Our setup is like a very fast cotton candy machine that can spin a range of synthetic and natural occurring materials. In this study, we used a combination of synthetic polymers and ECM proteins to fabricate biocompatible JetValves that are hemodynamically competent upon implantation and support cell migration and re-population in vitro. Importantly, we can make human-sized JetValves in minutes - much faster than possible for other regenerative prostheses."

Another group of researchers have previously developed regenerative, tissue-engineered heart valves to replace mechanical and fixed-tissue heart valves. In their approach, human cells directly deposit a regenerative layer of complex ECM on biodegradable scaffolds shaped as heart valves and vessels. The living cells are then eliminated from the scaffolds resulting in an "off-the-shelf" human matrix-based prostheses ready for implantation. In collaboration the two teams successfully implanted JetValves in sheep using a minimally invasive technique and demonstrated that the valves functioned properly in the circulation and regenerated new tissue. "In our previous studies, the cell-derived ECM-coated scaffolds could recruit cells from the receiving animal's heart and support cell proliferation, matrix remodeling, tissue regeneration, and even animal growth. While these valves are safe and effective, their manufacturing remains complex and expensive as human cells must be cultured for a long time under heavily regulated conditions. The JetValve's much faster manufacturing process can be a game-changer in this respect."

In support of these translational efforts, a larger initiative will commence to generate a functional heart valve replacement with the capacity for repair, regeneration, and growth. The team is also working towards a GMP-grade version of their customizable, scalable, and cost-effective manufacturing process that would enable deployment to a large patient population. In addition, the new heart valve would be compatible with minimally invasive procedures to serve both pediatric and adult patients.

Tissue engineered scaffolds have emerged as a promising solution for heart valve replacement because of their potential for regeneration. However, traditional heart valve tissue engineering has relied on resource-intensive, cell-based manufacturing, which increases cost and hinders clinical translation. To overcome these limitations, in situ tissue engineering approaches aim to develop scaffold materials and manufacturing processes that elicit endogenous tissue remodeling and repair. Yet despite recent advances in synthetic materials manufacturing, there remains a lack of cell-free, automated approaches for rapidly producing biomimetic heart valve scaffolds.

Here, we designed a jet spinning process for the rapid and automated fabrication of fibrous heart valve scaffolds. The composition, multiscale architecture, and mechanical properties of the scaffolds were tailored to mimic that of the native leaflet fibrosa and assembled into three dimensional, semilunar valve structures. We demonstrated controlled modulation of these scaffold parameters and show initial biocompatibility and functionality in vitro. Valves were minimally-invasively deployed via transapical access to the pulmonary valve position in an ovine model and shown to be functional for 15 h.

One of the things that happens to our bodies as we age is that certain cells start to accumulate. So-called senescent cells - cells that "retire" and stop dividing but refuse to undergo cellular death - are always present, and they even serve some important functions, in wound repair, for example. But in aging organs, these cells don't get cleared away as they should, and they can clutter up the place. Researchers are revealing just how these cells are tied to disorders of aging and why they refuse to go away. The work is not only opening new windows onto the aging process, but is pointing to new directions in treatments for many of these disorders and diseases.

Research into cellular senescence has taken off in recent years, due to findings that clearing these cells from various parts of the body can reverse certain aspects of aging and disease processes. Pharmaceutical industries have taken note, as well, of research that could lead to the development of drugs that might target senescent cells in specific organs or tissues. In basic research conducted on human cell culture and on mice, researchers have asked exactly what ties senescent cells to aging. Are they, for example, a primary cause of age-related disease, or a side effect? And why don't these cells die, despite being damaged, so that the "clean-up crews" of the immune system have to clear them away?

The researchers hypothesized that the answer to the second question might lie in a family of cellular proteins that regulate a type of cell suicide known as apoptosis. They identified two proteins in this family that prevent apoptosis and which were overproduced in the senescent cells, BCL-W and BCL-XL. When they injected mice that had an extra supply of senescent cells with ABT-737 molecules that inhibit these two proteins, the cells underwent apoptosis and were then eliminated, and there were signs of improvement in the tissue. "In small amounts, these cells can prevent tumors from growing, help wounds clot and start the healing process. But as they amass, they trigger inflammation and even cancer."

Certain common age-related diseases have been shown to be associated with this build-up of senescent cells, for example, chronic obstructive pulmonary disease (COPD), and researchers hope to apply these findings to research into treatments for such diseases. The trick will be to target the offensive cells without causing undue side effects. Researchers have been developing mouse models of COPD and asking whether clearing senescent cells just from the lungs can prevent or ease the disease. They are now working to patent and license these discoveries.

A senolytic (from the words "senescence" and "lytic" - destroying) is among the class of senotherapeutics, and refers to small molecules that can selectively induce death of senescent cells. Senescence is a potent tumor suppressive mechanism. It however drives both degenerative and hyperplastic pathologies, most likely by promoting chronic inflammation. Senescent cells accumulate in aging bodies and accelerate the aging process. Eliminating senescent cells increases the amount of time that mice are free of disease. The goal of those working to develop senolytic agents is to delay, prevent, alleviate, or reverse age-related diseases. Targeting premalignant senescent cells could also be a preventive and therapeutic strategy against late-life cancer given the deteriorated efficacy of the senescence response in stopping cancer.

Senolytics are arguably the best rejuvenation therapy currently available, and though costly, FOXO4-DRI is the most effective senolytic. This site is a repository for the first human experiences with this exciting new substance. And, though anecdotal, the hope is this information will prove valuable to early adopters and science. I'm a lifelong experimenter, a member of AAAS, and proud supporter of SENS. I'm hoping the risks I'm taking will benefit many people, and advance the science. I know, I know, this is not a controlled, double-blind experiment. I am patient zero in an n=1 study. But, is there something that can be learned here? Yes, especially if I have a serious reaction or die. Alternatively, if a remarkable rejuvenation becomes evident credibility will be lent to this therapy.

Scars form when the collagen scaffolding in skin is broken apart. Instead of re-forming in their original and neat basket-weave arrangement, the collagen fibres grow back in parallel bundles that create the characteristic lumpy appearance of scars. One way to reduce scarring is to apply decorin, a skin protein involved in collagen organisation. But because decorin has a highly complex physical structure it is hard to synthesise and therefore not used in the clinic.

To get round this problem, researchers have created a simplified version of decorin. They combined a small section of the decorin protein with a collagen-binding molecule and a sticky substance secreted by mussels. The resulting glue was tested on rats with deep, 8-millimetre-wide wounds. The glue was spread over each wound and covered with clear plastic film. Rats in a control group had their wounds covered in plastic without any glue. By day 11, 99 per cent of the wound was closed in the treated rats compared with 78 per cent in the control group. By day 28, treated rats had fully recovered and had virtually no visible scarring. In comparison, control rats had thick, purple scars.

Closer inspection under the microscope confirmed that collagen fibres in the treated wounds had returned to their original basket-weave arrangement. The new skin had also developed hair follicles, blood vessels, oil glands and other structures that aren't regenerated in scars. The glue is able to promote normal collagen growth because negative charges on the decorin fragments hold the fibres apart. In doing so, the fibres are more easily able to weave in and out between each other instead of sticking together randomly. The results are impressive but there is still a way to go before this can be translated to humans. "Rats have loose skin, whereas we have tight skin, and they tend to heal better and have less scarring than we do." As a result, the glue may not be as effective in people as in rats. The glue will now be tested in pigs, whose skin better resembles our own.

Cognitive aging is a consequence of molecular and biochemical aging. Alterations in gene expression, influencing the levels of proteins in many biological pathways, can be regarded as a hallmark of molecular aging. Changes in the biochemical composition of neural cells, which affect the efficiency of their synapses and whole circuits, impair the plasticity of the brain, that is the ability to reorganize, learn and remember. In this way, the disturbances of synaptic machinery profoundly contribute to the cognitive impairments as well as to the age-related brain disorders.

The majority of studies concerning the plasticity of neural circuits have focused on excitatory synapses. However, the role of inhibitory interactions in neuroplastic changes has recently been widely recognized. The most basic role of inhibitory neurons is to control the excitability of the principal cells, ensuring a proper homeostatic balance and preventing runaway excitation. Strong network inhibition suppresses the excitatory population response, providing the circuit with an intrinsic mechanism enabling precise contrast-gain control. Therefore, even though excitatory neurons are a large majority of cortical neurons, local inhibitory interneurons shape their firing and timing. There is increasing support for the hypothesis that disruption of inhibitory circuits is responsible for some of the clinical features of many neurodegenerative disorders. Many of them have been proposed to be synaptopathies - diseases related to the dysfunction of synapses. Brain aging is, in this context, considered a phenomenon promoting biological alterations associated with the above-mentioned disorders, resulting in so-called late-onset diseases.

The difficulty in understanding the mechanisms of interneurons aging, along with its relationship to plasticity impairments, cognitive decline and brain disorders, lies in the tremendous diversity of inhibitory neurons. Inhibition can be performed by perisomatically, dendritically or axonally targeting interneurons, which can be devoted to different inhibitory tasks. Furthermore, over 20 subtypes of potentially inhibitory neurons using GABA as a neurotransmitter have been recognized. Nevertheless, this diversity makes interneurons a potent and complex regulatory machinery controlling the physiology of neural circuits, and their molecular and biochemical aging can significantly contribute to the cognitive deficits observed in the aged brain. The role of neuroplasticity is to compensate for those age-related changes and to maintain the proper function of inhibitory circuits, supporting the balance between excitation and inhibition and the correct cognitive performance.

Age-related loss of synaptic contacts, decreased neurotransmitter release and reduced postsynaptic responsiveness to neurotransmitters result in a decline in synaptic strength, contributing to age-related cognitive decline. Molecular aging, defined as age-related transcriptome changes, and biochemical protein-related alterations within synapses weaken the plastic potential of neurons. Inhibitory neurons, despite being in the minority, are powerful regulators of neuronal excitability and, being particularly susceptible to aging-related alterations, are involved in many aging-induced cognitive impairments and brain disorders.

In the aged mouse somatosensory cortex, we have shown that although potential for learning-related plasticity is preserved there, the corresponding mechanisms are weakened and need longer stimulation to trigger plastic changes. We have postulated that the decreased effectiveness of the GABAergic system in the aged mouse somatosensory cortex contributes to the deficits in learning-induced plasticity. We posit that aging-induced impairments of the GABAergic system lead to an inhibitory/excitatory imbalance, thereby decreasing neuron's ability to respond with plastic changes to environmental and cellular challenges, leaving the brain more vulnerable to cognitive decline and damage by synaptopathic diseases. This is an intermediate stage of the transition from healthy aging to age-related cognitive decline and then to disease. Pharmacological and/or environmental reinforcement of the GABAergic system thus seems to be a promising therapeutic target for aging-related brain disorders.

New lung "organoids" have been created from human pluripotent stem cells. Researchers used the organoids to generate models of human lung diseases in a lab dish, which could be used to advance our understanding of a variety of respiratory diseases. Organoids are 3-D structures containing multiple cell types that look and function like a full-sized organ. By reproducing an organ in a dish, researchers hope to develop better models of human diseases and find new ways of testing drugs and regenerating damaged tissue. "Researchers have taken up the challenge of creating organoids to help us understand and treat a variety of diseases. But we have been tested by our limited ability to create organoids that can replicate key features of human disease."

The lung organoids created in this study are the first to include branching airway and alveolar structures, similar to human lungs. To demonstrate the functionality of the organoids, the researchers showed that the organoids reacted in much the same way as a real lung does when infected with respiratory syncytial virus (RSV). Additional experiments revealed that the organoids also responded as a human lung would when carrying a gene mutation linked to pulmonary fibrosis. RSV is a major cause of lower respiratory tract infection in infants and has no vaccine or effective antiviral therapy. Idiopathic pulmonary fibrosis, a condition that causes scarring in the lungs, causes 30,000 to 40,000 deaths in the United States each year. A lung transplant is the only cure for this condition. "Organoids, created with human pluripotent or genome-edited embryonic stem cells, may be the best, and perhaps only, way to gain insight into the pathogenesis of these diseases."

Mammalian fingertips and toes can partially regrow under certain conditions; however, regeneration is greatly limited compared to urodele amphibians such as newts and salamanders that can completely regrow an amputated limb. The question is why there is such a difference between the regenerative potentials of mammals and amphibians. Embryonic, neonatal, and adult mice can regenerate digit tips if the amputation is midway through the third phalanx; however, if the amputation occurs proximal to the midway point of the third phalanx in mice, regeneration of the digit tip does not typically occur. Similarly, young patients have also been documented to regrow the tips of amputated fingers if treated conservatively. Although adults and even elderly individuals have potentially regenerated amputated digit tips, the regenerative process may not be as efficient as it is in younger patients and usually results in fibrous scars in adults. The regeneration process of the digit following injury may be related to the age of the host, with decreased restoration in adults compared to fetal or neonatal mammals. Injured adult mammalian tissues are usually replaced with fibrotic scar tissue, whereas scarless healing typically occurs in fetal wound healing which results in complete tissue recovery. Stem cell activation and scarless wound healing are considered to be essential requisites for quality tissue regeneration; however, for some regenerative processes a dedifferentiation process, but not stem cell activation, is required.

Many theories have been proposed to explain why successful regeneration occurs in urodele amphibians but not in mammals. First, the immune system has been shown to play a major role in the regeneration process of amputated limbs in newts. In mammals, fetal wounds can regenerate because they have an immature immune system; however, in adults, clearing pathogens appears to be evolutionarily favored compared to retaining the ability to regenerate a limb or digit. Second, amphibians have retained limb regeneration-specific genes not found in mammals, which allow their cells to dedifferentiate. A related theory is that mammals have evolved tumor suppression genes that inhibit regeneration. The Ink4a locus is present in mammals but not amphibians; this region encodes the tumor suppression genes p16ink4a and Alternative Reading Frame (ARF). Inactivation of both tumor suppressors retinoblastoma (Rb) and ARF allows terminally differentiated mammalian muscle cells to dedifferentiate. An extension of this theory is that differentiated mammalian tissues can regenerate if the cells are induced to reenter the cell cycle, which occurs in the Murphy Roths Large (MRL) mouse and the p21-deficient mouse. Third, bioelectric signaling (e.g., membrane voltage polarity, ionic channels) may also play a role in the tissues' regeneration potential. Nonregenerating wounds display a positive polarity throughout the healing process, whereas in regenerating animals the polarity is initially positive but then quickly changes to negative polarity with the peak voltage occurring at the time of maximum cellular proliferation.

Patients undergoing treatment regimens that eradicate their disease, such as cancer, may be left with diminished ovary function. Therefore, the oncofertility field is tasked to develop a whole organ replacement that restores long-term hormone function and fertility for all patients. In past work, we and others have sought to create an engineered ovary with biomaterials and isolated follicles. Ovarian follicles are spherical, multicellular aggregates that include a centralized oocyte (female gamete) and surrounding support cells, granulosa and theca, that produce hormones in response to stimulation from the pituitary. The spheroid shape of a follicle is critical to its survival in that the support cells must maintain contact with the oocyte until it has matured and is ready for ovulation. Consequently, a three-dimensional (3D) material environment is critical to maintaining these cell-cell interactions and follicle shape.

Thus far, there have been several reports of live births from biomaterial implants in mice, and all have used isolated follicles or whole ovarian tissue encapsulated in a plasma clot or similar fibrin hydrogel bead containing growth factor components or purified vascular endothelial growth factor. These results are very encouraging and have validated both the model procedure and the need for graft vascularization for complete restorative organ function of isolated follicles in a biomaterial. However, hydrogel encapsulation of follicles poses several challenges, especially with respect to the size of anticipated transplants. Specifically, when translating this work to a large animal or human, the implant must house a significantly larger population of follicles and therefore must be considerably larger than those used in mice. At these scales, diffusion limits may become a concern.

Future strategies must permit channels within the hydrogels (to facilitate host vasculature infiltration) or including pre-embedded vasculature to sustain follicle viability and circulate follicular hormones. Moreover, the ovary is a heterogeneous organ that compartmentalizes different follicle pools (quiescent and growing) into the cortex and medulla regions that have varying stiffness. It is believed that this compartmentalization will be critical to providing long-term (multiple decades) function with an implant. Therefore, a biomaterial strategy that can produce a mimetic construct of spatially varying material properties may be required for optimal implant function and longevity.

3D printing can be used to address all of these future implant requirements for creating a human bioprosthetic ovary, a bioengineered functional tissue replacement. As the first steps towards this goal, here, we investigated porous hydrogel scaffolds with murine follicles seeded throughout the full depth of the scaffold layers to create a murine bioprosthetic ovary. Microporous architectures were achieved through 3D printing partially crosslinked, thermally regulated gelatin. We found that specific scaffold architectures created a 3D feel by providing appropriate depth and multiple contact sites for the ovarian follicle, which resulted in optimal murine follicle survival and differentiation in vitro. The open micropores within the hydrogel scaffold provided sufficient space and nutrient diffusion for follicle survival and maturation in vitro and in vivo, as well as space for vasculature to infiltrate when implanted in vivo without the need for significant scaffold degradation as is required when using hydrogel encapsulation.

Follicle-seeded scaffolds become highly vascularized and ovarian function is fully restored when implanted in surgically sterilized mice. Moreover, pups are born through natural mating and thrive through maternal lactation. These findings present an in vivo functional ovarian implant designed with 3D printing, and indicate that scaffold pore architecture is a critical variable in additively manufactured scaffold design for functional tissue engineering.

It was odd that I ended up studying aging. I got into it not really knowing that, just seeing a profoundly mysterious process that there was no papers on, as far as I could tell. In the last 25 years, we've got textbooks on worm aging, we have signaling pathways and hormones and so, so much, it's great. But I still struggle to tell people what aging is. I tell them narratives about protein and protein insolubility during aging and how that could be driving dysfunction, but it's still hard to really say to someone, "This is what aging is". And now more than ever, beyond curiosity it's this idea that while it's been a great privilege to just be able to mess around and do science and find stuff out, actually what we've found out could be useful for people. It motivates the research somewhat, but also how I talk about the research, and my willingness to go off and do public stuff to try and turn people's heads to thinking about this. And it drives me crazy that we're training a group of scientists who are very comfortable with the biology of aging and the idea that it causes multiple diseases, who are very comfortable moving from discipline to discipline as you have to do in aging research, and unfortunately there's no jobs for these people.

Funding has been flat for 15 years in aging research. We're still here, the institute's growing. It wasn't for a while, but we're gonna be hiring again and creating some new jobs, so it's not like nothing's happening, but compared to what should be happening, and what the science is telling us we should be doing, it can be a little frustrating. We've seen our own people go to Calico and Unity Biotechnology, which is a spinout biotech from the Buck Institute that's doing very well. There have been many false dawns of aging companies and aging biotechnology going back 15 or more years, but with Calico and Unity it feels different. It feels like they're serious about finding cures to diseases based on aging technologies. And I hope they're going to be big employers.

The biggest obstacles right now is funding at every level. Translation. We've got a lot of information and compounds that we need to move forward. Obviously those two things are tightly related. Funding also is at the heart of the inability to grow the field with these new scientists. It's just so sad, people with fantastic skillsets leaving science or going into industry, and not in an aging context at all. I don't think that there's a problem with the science. In past years we could have said that there's a big problem because people don't understand the evolutionary origins of aging, or problems in the past where people were very dogmatic about it being down to one mechanism or another. And there was literally a time when many people in the field thought cellular senescence was an artefact of the culture dish and couldn't really be important in aging, because it didn't happen frequently enough in animals. And now we're at a point where we're thinking no, chances are it's really important. So a lot of the factions are melting away and you're seeing much more unity in this paradigm of what aging is.

One possibility is that most of the modifications that we've made or interventions that we've made are really just optimizing interventions. That they're not really affecting the underlying biology of aging. It's hard to draw a hard distinction between optimization and changing the underlying biology, but essentially all the models that we use, flies, yeast and worms, they all come from the same ecological niche. They all have laboratory drift and we use lab strains that aren't the same as wild strains, and during that process we may have been creating problems and shortening lifespan for years, and now all we're doing is fixing some of those laboratory-based problems. That's one view of a lot of what we've done. If that were true, it would be a bit of a crisis. It's certainly the case that we seem to be hitting some sort of upper limit with things. We don't see lifespan being extended in mice by two- or threefold, like we've seen in worms. Even in flies we haven't seen twofold life extension. It's possible that we're hitting limits in our ability to extend lifespan. I don't know.

Yet there is no biological upper limit on lifespan. We have clams living over 500 years, bristlecone pines that are living hundreds of years and things. In theory, we could all live to 122, because one human has done that. So in theory we can at least do that well, which is amazing in itself. In theory, there are mammals that live even longer than that, so we should be able to live longer than the oldest human. Clams have a circulatory system, there's a beating heart, so if there are hearts on earth that have been beating for 500 years, why not our hearts. I don't believe in biological limits, because even in human life expectancy, every time someone says there's an upper limit, someone breaks it. I don't believe in limits of that sort, but how much you have to change the human condition to attain greatly extended longevity, I don't think we know. The empirical observation so far is that it's harder to produce strong effects in more complex animals. It could be because it's just that the experiments in more complex animals are more expensive, so a tiny fraction of the experiments we've done in worms have been done in mice. It may be that we just haven't hit on it yet.

Emerging research revealed the essential role of mitochondria in regulating stem/progenitor cell differentiation of neural progenitor cells and other stem cells through reactive oxygen species (ROS), Notch or other signaling pathway. Inhibition of mitochondrial protein synthesis results in hair loss upon injury. However, alteration of mitochondrial morphology and metabolic function during hair follicle stem cells (HFSCs) differentiation and how they affect hair regeneration has not been elaborated upon.

Hair follicle (HF) is a cystic tissue surrounding the hair root, controlling hair growth. It consists of two parts: an epithelial part (hair matrix and outer root sheath) and a dermal part (dermal papilla and connective tissue sheath). The hair follicle goes through cycles of anagen phase (growth), catagen phase (degeneration) and telogen phase (rest). In the late telogen phase, hair follicle bulge stem cells differentiate into matrix cells upon stimulation, to re-enter the anagen phase. While in the catagen phase, proliferation and differentiation of hair follicle cells gradually attenuates, leaving with HFSCs and a dormant hair germ, re-entering the telogen phase.

As an essential organelle for anaerobic respiration, mitochondria attracted more research attention to its morphology and function during stem cell differentiation. Mitochondria show less mass in embryonic stem cells (ESCs) than that in differentiated cells, with a reduced oxygen consumption rate and less ROS produced. Effective control of mitochondrial morphology and function is critical for the maintenance of energy production and the prevention of oxidative stress-induced damage resulting from ROS. Besides, mitochondria play an essential role in determining hair cell differentiation and proliferation upon injury though regulating energy metabolism. In addition, ROS inhibit stem cell differentiation and proliferation through redox signaling pathway. Therefore, to counteract the adverse effect of ROS, the level of enzymes such as SOD2 is subsequently up-regulated.

We compared the difference in mitochondrial morphology and activity between telogen bulge cells and anagen matrix cells. Expression levels of mitochondrial ROS and superoxide dismutase 2 (SOD2) were measured to evaluate redox balance. In addition, the level of pyruvate dehydrogenase kinase (PDK) and pyruvate dehydrogenase (PDH) were estimated to present the change in energetic metabolism during differentiation. To explore the effect of the mitochondrial metabolism on regulating hair regeneration, hair growth was observed after application of a mitochondrial respiratory inhibitor upon hair plucking. The results revealed that disrupting mitochondrial respiration delays hair regrowth. It is possible that hair regeneration might be retarded due to insufficient energy supply. Another possibility is that mitochondrial dysfunction affects HFSCs differentiation through regulating redox balance or other signaling pathways, leading to the delay of hair growth.

The average lifespan of the human population is increasing worldwide, mostly because of declining fertility and increasing longevity. It has been predicted that, in 2035, nearly one in four individuals will be 65 years or older. With age being the dominant risk factor for the development of cardiovascular diseases, their prevalence increases dramatically with increasing age. At the end of the twentieth century, researchers announced the emergence of two new epidemics of cardiovascular disease: heart failure and atrial fibrillation. The prevalence of heart failure in the adult population in developed countries is 1-2%, which rises to more than 10% among persons 70 years or older. The same trend is seen for atrial fibrillation, with a prevalence rising from 0.12 - 0.16% in persons younger than 49 years, to 3.7-4.2% in persons aged 60-70 years, to 10-17% in persons aged 80 years or older. Since there is a clear association between aging of the population and increasing prevalence of cardiovascular disease, cardiovascular aging most likely affects pathophysiological pathways also implicated in the development of cardiovascular disease. Therefore, a better insight into cardiac aging may unravel factors implicated in cardiac pathophysiology and help towards improved prevention of human cardiovascular disease.

On a structural level, the most striking phenomenon seen with age is an increase in the thickness of the left ventricle (LV) wall as a result of increased cardiomyocyte size. This hypertrophy affects the LV in an asymmetrical way, leading to a redistribution of cardiac muscle. In the elderly, atrial contraction plays a much greater role in LV filling during diastole than in the young population. This change in function is associated with the development of atrial hypertrophy and dilation. Left atrial size has been associated with the presence of atrial fibrillation, indicating that atrial remodeling favors the development of this arrhythmia.

Remodeling at the cellular level includes a loss of cardiomyocytes and sinoatrial node pacemaker cells with age, and may contribute to the compensatory development of hypertrophy. This compensatory remodeling process may also involve changes in the composition of the extracellular matrix. The function of the extracellular matrix is to maintain the myocardial structure throughout the cardiac cycle. Hereby it plays an important role in the elastic and viscous properties of the LV. Changes in both the quantity of fibrosis and in the type of collagen fibers have been associated with old age in human hearts. It is easy to imagine that changes in the elastic properties of the LV caused by fibrosis may eventually lead to diastolic dysfunction. Indeed, in hypertensive heart disease patients, more severe diastolic dysfunction has been associated with a more active fibrotic process.

Another histopathological change found in cardiac tissue of old people is amyloid deposition. An autopsy study on a Finnish population aged 85 or over showed the presence of amyloid deposits in 25%, with a strong correlation between the presence of amyloid and the age at time of death. Amyloid found in heart of the elderly is derived from the transthyretin molecule. With age, this molecule may become structurally unstable and result in the development of misfolded intermediates that aggregate and precipitate as amyloid, mainly in the heart. In some cases, amyloid deposition in the heart occurs at a level that will lead to the progressive development of heart failure. This infiltrative cardiomyopathy is defined as systemic senile amyloidosis (SSA).

Cardiac function requires an enormous amount of energy and mitochondria are critical for the required ATP production in the myocardium. They also play a fundamental role in the survival and function of cardiomyocytes. Cardiac senescence is accompanied by a general decline in mitochondrial function, clonal expansion of dysfunctional mitochondria, increased production of reactive oxygen species (ROS), suppressed mitophagy and dysregulation of mitochondrial quality processes such as fusion and fission. Of these processes, the development of oxidative stress as a consequence of excessive ROS generation is the most frequently described phenomenon. The mitochondrial free radical theory of aging is debated, but in the context of cardiac disease, ample evidence exists for the existence of a pathogenic link between enhanced ROS production, mitochondrial dysfunction and the development of heart failure.

The cell nucleus is typically depicted as a sphere encircled by a smooth surface of nuclear envelope. For most cell types, this depiction is accurate. In other cell types and in some pathological conditions, however, the smooth nuclear exterior is interrupted by tubular invaginations of the nuclear envelope, often referred to as a "nucleoplasmic reticulum," into the deep nuclear interior. We have recently reported a significant expansion of the nucleoplasmic reticulum in postmortem human Alzheimer's disease brain tissue. We found that dysfunction of the nucleoskeleton, a lamin-rich meshwork that coats the inner nuclear membrane and associated invaginations, is causal for Alzheimer's disease-related neurodegeneration in vivo.

Neurons of tau transgenic Drosophila and of postmortem human Alzheimer's disease brains harbor significant invaginations of the nuclear envelope and have reduced levels of B-type lamin protein compared to controls. Dysfunction of B-type lamins has functional consequences in adult neurons in regard to heterochromatin formation, cell cycle activation, and neuronal survival. Taken together, our results suggest that pathological tau-induced stabilization of filamentous actin disrupts the LINC complex, which reduces lamin protein levels and causes the nuclear envelope to invaginate. Lamin reduction or dysfunction, in turn, causes constitutive heterochromatin to relax, allowing expression of genes that are normally silenced by heterochromatin and activating the cell cycle in postmitotic neurons, which causes their death.

Our findings suggest that Alzheimer's disease and associated tauopathies are, in fact, acquired neurodegenerative laminopathies. We demonstrate that loss of lamin function can lead directly to age-related neurodegeneration, indicating that basic mechanisms of aging are conserved between neurons and other somatic tissues. The lamin nucleoskeleton is thus a plausible molecular link between aging, the single most important risk factor for developing common neurodegenerative diseases, including Alzheimer's disease, and basic mechanisms of cellular senescence. Functional consequences of nucleoplasmic reticulum expansion in physiological aging and pathological conditions including cancer and Alzheimer's disease remain to be determined, however.