Heterogeneous Stem Cells in Skin Homeostatis and Wound Repair

BACKGROUND: The skin protects mammals from insults, infection and dehydration and enables thermoregulation and sensory perception. Various skin-resident cells carry out these diverse functions. Constant turnover of cells and healing upon injury necessitate multiple reservoirs of stem cells. The skin is a complex organ harboring several distinct populations of stem cells and a rich array of cell types. Advances in genetic and imaging tools have brought new findings about the lineage relationships between skin stem cells and their progeny. Such knowledge may offer novel avenues for therapeutics and regenerative medicine.CONTENT: In the past years, our view of the mechanisms that govern skin homeostasis and regeneration have markedly changed. New populations of stem cells have been identified that behave spatio-temporally differently in healthy tissues and in situations of damage, indicating that a great level of stem cell heterogeneity is present in the skin. There are believed to be distinct populations of stem cells in different locations. The lineages that they feed are normally constrained by signals from their local environment, but they can give rise to all epidermal lineages in response to appropriate stimuli. Given the richness of structures such as blood vessels, subcutaneous fat, innervation and the accumulation of fibroblasts under the upper parts of the rete ridges (in the case of human skin), it is reasonable to speculate that the microenvironment might be essential for interfollicular epidermal homeostasis. The bloodstream is probably the main source of long-range signals reaching the skin, and cues provided by the vascular niche might be essential for skin homeostasis.SUMMARY: A key function of the interfollicular epidermis is to act as a protective interface between the body and the external environment, and it contains several architectural elements that enable it to fulfill this function. All elements of the epidermis play active roles in regulating skin function, which might not have been anticipated from their role in maintaining skin integrity. Skin cell research benefits from the integration of complementary technologies and disciplines. How skin function is regulated and how it may be possible to intervene to treat a variety of skin conditions. Ultimately also impairing the maintenance of self-renewing satellite cells. Therefore, only anti-aging strategies taking both factors, the stem cell niche and the stem cells per se, into consideration may ultimately be successful

Adipose Tissue, Inflammation (Meta-inflammation) and Obesity Management

BACKGROUND: Obesity-induced inflammation contributes to the development of type 2 diabetes, metabolic syndrome, and cardiovascular disease.CONTENT:The last decade has seen a sharp increase in our appreciation for the macrophage as a critical regulator of metabolic status in obesity. Activation of adipose tissue (AT) macrophages within fat depots is coupled with the development of obesity-induced proinflammatory state and insulin resistance (IR). The activation of classically activated M1 macrophages at the expense of anti-inflammatory M2 macrophages has been causally linked to the development of AT inflammation and metabolic syndrome, a pathophysiological state aptly termed as ‘metainflammation'. It is recognized that several proinflammatory cytokines, including interleukin (IL)-1β, are implicated in disrupting insulin signaling. Our developing appreciation of links among obesity, inflammation and cardiovascular disease will require multiple complementary approaches to leverage new concepts into translatable outcomes. Careful characterization of human patients, particularly analysis of AT distribution, will be needed to stratify subjects that are most likely obese/metabolically healthy from those that are obese/metabolically unhealthy.SUMMARY: It has been suggested that individuals with the condition known as metabolically healthy obese (MHO) may not have the same increased risk for the development of metabolic abnormalities as their non-metabolically healthy counterparts. A complications-centric model for the medical management of obesity emphasizes the identification and staging of complications, and treatment paradigm directed at patients who would gain the most benefit from weight loss

Personalized Medicine: the Future of Health Care

BACKGROUND: Most medical treatments have been designed for the “average patients”. As a result of this “one-size-fits-all-approach”, treatments can be very successful for some patients but not for others. The issue is shifting by the new innovation approach in diseases treatment and prevention, precision medicine, which takes into account individual differences in people\u27s genes, environments, and lifestyles. This review was aimed to describe a new approach of healthcare performance strategy based on individual genetic variants.CONTENT: Researchers have discovered hundreds of genes that harbor variations contributing to human illness, identified genetic variability in patients\u27 responses to different of treatments, and from there begun to target the genes as molecular causes of diseases. In addition, scientists are developing and using diagnostic tests based on genetics or other molecular mechanisms to better predict patients\u27 responses to targeted therapy.SUMMARY: Personalized medicine seeks to use advances in knowledge about genetic factors and biological mechanisms of disease coupled with unique considerations of an individual\u27s patient care needs to make health care more safe and effective. As a result of these contributions to improvement in the quality of care, personalized medicine represents a key strategy of healthcare reform

Telomere in Aging and Age-Related Diseases

BACKGROUND: The number of elderly population in the world keep increasing. In their advanced ages, many elderly face years of disability because of multiple chronic diseases, frailty, making them lost their independence. Consequently, this could have impacts on social and economic stability. A huge challenge has been sent for biomedical researchers to compress or at least eliminate this period of disability and increase the health span.CONTENT: Over the past decades, many studies of telomere biology have demonstrated that telomeres and telomere-associated proteins are implicated in human diseases. Accelerated telomere erosion was clearly correlated with a pack of metabolic and inflammatory diseases. Critically short telomeres or the unprotected end, are likely to form telomeric fusion, generating genomic instability, the cornerstone for carcinogenesis. Enlightening how telomeres involved in the mechanisms underlying the diseases' pathogenesis was expected to uncover new molecular targets for any important diagnosis or therapeutic implications.SUMMARY: Telomere shortening was foreseen as an imporant mechanism to supress tumor by limiting cellular proliferative capacity by regulating senescence check point activation. Many human diseases and carcinogenesis are causally related to defective telomeres, asserting the importance of telomeres sustainment. Thus, telomere length assessment might serve as an important tool for clinical prognostic, diagnostic, monitoring and management

Mitochondrial Dysfunction in Stem Cell Aging

BACKGROUND: Regardless of the precise underlying molecular mechanisms, the fundamental defining manifestation of aging is an overall decline in the functional capacity of various organs to maintain baseline tissue homeostasis and to respond adequately to physiological needs under stress. There is an increasingly urgent need for a more complete understanding of the molecular pathways and biological processes underlying aging and age-related disorders.CONTENT: Mitochondria constitute the most prominent source of adenosine triphosphate (ATP) and are implicated in multiple anabolic and catabolic circuitries. In addition, mitochondria coordinate cell-wide stress responses and control non-apoptotic cell death routines. The involvement of mitochondria in both vital and lethal processes is crucial for both embryonic and postembryonic development, as well as for the maintenance of adult tissue homeostasis. Age-associated telomere damage, diminution of telomere ‘capping' function and associated p53 activation have emerged as prime instigators of a functional decline of tissue stem cells and of mitochondrial dysfunction that adversely affect renewal and bioenergetic support in diverse tissues. Constructing a model of how telomeres, stem cells and mitochondria interact with key molecules governing genome integrity, ‘stemness' and metabolism provides a framework for how diverse factors contribute to aging and age-related disorders.SUMMARY: Cellular senescence defined as an irreversible proliferation arrest promotes age-related decline in mammalian tissue homeostasis. The aging of tissue-specific stem cell and progenitor cell compartments is believed to be central to the decline of tissue and organ integrity and function in the elderly. Taken into consideration that the overwhelming majority of intracellular reactive oxygen species (ROS) are of mitochondrial origin, it is reasonable to posit that the elevated ROS production might be caused by alteration in mitochondrial function during senescence. It is likely that mitochondria and stem cells will remain at the forefront of aging research also for the next decade

Cancer Stem Cell Hypothesis: Implication for Cancer Prevention and Treatment

BACKGROUND: Cancer is a disease of genomic instability, evasion of immune cells, and adaptation of the tumor cells to the changing environment. Genetic heterogeneity caused by tumors and tumor microenvironmental factors forms the basis of aggressive behavior of some cancer cell populations.CONTENT: Cancers arise in self-renewing cell populations and that the resulting cancers, like their normal organ counterparts, are composed of hierarchically organized cell populations. Self – renewing “cancer stem cells” (CSC) maintain tumor growth and generate the diverse populations constituting the tumor bulk. CSCs in multiple tumor types have been demonstrated to be relatively resistant to radiation and chemotherapy. The clinical relevance of these studies has been supported by neoadjuvant breast cancer trials that demonstrated increases in the proportions of CSCs after therapy. The CSC hypothesis has tremendously important clinical implications.SUMMARY: In summary, a large and accumulating body of evidence supports the CSC hypothesis, which has important implications for cancer prevention and therapy. The ultimate test of this hypothesis will require clinical trials demonstrating that targeting of these pathways reduces cancer incidence and improves outcomes for patients with cancer

Genome Editing with Crispr-Cas9 Systems: Basic Research and Clinical Applications

BACKGROUND: Recently established genome editing technologies will open new avenues for biological research and development. Human genome editing is a powerful tool which offers great scientific and therapeutic potential.CONTENT: Genome editing using the clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPRassociated protein 9 (Cas9) technology is revolutionizing the gene function studies and possibly will give rise to an entirely new degree of therapeutics for a large range of diseases. Prompt advances in the CRISPR/Cas9 technology, as well as delivery modalities for gene therapy applications, are dismissing the barriers to the clinical translation of this technology. Many studies conducted showed promising results, but as current available technologies for evaluating off-target gene modification, several elements must be addressed to validate the safety of the CRISPR/Cas9 platform for clinical application, as the ethical implication as well.SUMMARY: The CRISPR/Cas9 system is a powerful genome editing technology with the potential to create a variety of novel therapeutics for a range of diseases, many of which are currently untreatable

Molecular Regulation and Rejuvenation of Muscle Stem (Satellite) Cell Aging

BACKGROUND: Age-related muscle loss leads to lack of muscle strength, resulting in reduced posture and mobility and an increased risk of falls, all of which contribute to a decrease in quality of life. Skeletal muscle regeneration is a complex process, which is not yet completely understood.CONTENT: Skeletal muscle undergoes a progressive age-related loss in mass and function. Preservation of muscle mass depends in part on satellite cells, the resident stem cells of skeletal muscle. Reduced satellite cell function may contribute to the age-associated decrease in muscle mass. Recent studies have delineated that the aging process in organ stem cells is largely caused by age-specific changes in the differentiated niches, and that regenerative outcomes often depend on the age of the niche, rather than on stem cell age. It is likely that epigenetic states will be better define such key satellite cell features as prolonged quiescence and lineage fidelity. It is also likely that DNA and histone modifications will underlie many of the changes in aged satellite cells that account for age-related declines in functionality and rejuvenation through exposure to the systemic environment.SUMMARY: Skeletal muscle aging results in a gradual loss of skeletal muscle mass, skeletal muscle function and regenerative capacity, which can lead to sarcopenia and increased mortality. Although the mechanisms underlying sarcopenia remain unclear, the skeletal muscle stem cell, or satellite cell, is required for muscle regeneration. Decreased muscle stem cell function in aging has long been shown to depend on altered environmental cues, whereas the contribution of intrinsic mechanisms remained less clear. Signals in the aged niche were shown to cause permanent defects in the ability of satellite cells to return to quiescence, ultimately also impairing the maintenance of self-renewing satellite cells. Therefore, only anti-aging strategies taking both factors, the stem cell niche and the stem cells per se, into consideration may ultimately be successful

In Search for Anti-Aging Strategy: Can We Rejuvenate Our Aging Stem Cells?

BACKGROUND: Recent evidence suggested that we grow old partly because of our stem cells grow old as a result of mechanisms that suppress the development of cancer over a lifetime. We believe that a further, more precise mechanistic understanding of this process will be required before this knowledge can be translated into human anti-aging therapies.CONTENT: A diminished capacity to maintain tissue homeostasis is a central physiological characteristic of aging. As stem cells regulate tissue homeostasis, depletion of stem cell reserves and/or diminished stem cell function have been postulated to contribute to aging. It has further been suggested that accumulated DNA damage could be a principal mechanism underlying age-dependent stem cell decline. It is interesting that many of the rejuvenating interventions act on the stem cell compartments, perhaps reflecting shared genetic and biochemical pathways controlling stem cell function and longevity. Strategy to slow down the aging processes is based on caloric restriction refers to a dietary regimen low in calories but without undernutrition. Sirtuin (SIRT)1 and 3, increases longevity by mimicking the beneficial effects of caloric restriction. SIRT3 regulates stress-responsive mitochondrial homeostasis, and more importantly, SIRT3 upregulation rejuvenates aged stem cells in tissues. Resveratrol (3,5,4\u27-trihydroxystilbene), a natural polyphenol found in grapes and wine, was the most powerful natural activator of SIRT1. In fact, resveratrol treatment has been demonstrated to rescue adult stem cell decline, slow down bodyweight loss, improve trabecular bone structure and mineral density, and significantly extend lifespan.SUMMARY: Tissue-specific stem cells persist throughout the entire lifespan to repair and maintain tissues, but their self-renewal and differentiation potential become dysregulated with aging. Given that adult stem cells are thought to be central to tissue maintenance and organismal survival, SIRT3 may promote organismal longevity by maintaining the integrity of tissue-speciic stem cells

Resveratrol: a Sirtuin Activator and the Fountain of Youth

BACKGROUND: An organism\u27s lifespan is inevitably accompanied by the aging process, which involves functional decline, a steady increase of a plethora of chronic diseases, and ultimately death. Thus, it has been an ongoing dream of mankind to improve healthspan and extend life.CONTENT: There are only a few proposed aging interventions: caloric restriction, exercise, and the use of low-molecular-weight compounds, including spermidine, metformin, resveratrol, and rapamycin. Resveratrol, a constituent of red wine, has long been suspected to have cardioprotective effects. Interest in this compound has been renewed in recent years, first from its identification as a chemopreventive agent for skin cancer, and subsequently from reports that it activates sirtuin deacetylases and extends the lifespans of lower organisms. Resveratrol have been shown to prevent and reduce the severity of age-related diseases such as atherosclerosis, stroke, myocardial infarct, diabetes, neurodegenerative diseases, osteoarthritis, tumors and metabolic syndrome, along with their ability to extend lifespan.SUMMARY: The purpose of aging research is the identification of interventions that may avoid or ameliorate the ravages of time. In other words, the quest is for healthy aging, where improved longevity is coupled to a corresponding healthspan extension. It is only by extending the healthy human lifespan that we will truly meet the premise of the Roman poet Cicero: “No one is so old as to think that he may not live a year.