Microvesicles as Vehicles for Tissue Regeneration: Changing of the Guards

The multifaceted benefits of walking for healthy aging: from Blue Zones to molecular mechanisms

Physical activity, including walking, has numerous health benefits in older adults, supported by a plethora of observational and interventional studies. Walking decreases the risk or severity of various health outcomes such as cardiovascular and cerebrovascular diseases, type 2 diabetes mellitus, cognitive impairment and dementia, while also improving mental well-being, sleep, and longevity. Dose-response relationships for walking duration and intensity are established for adverse cardiovascular outcomes. Walking's favorable effects on cardiovascular risk factors are attributed to its impact on circulatory, cardiopulmonary, and immune function. Meeting current physical activity guidelines by walking briskly for 30 min per day for 5 days can reduce the risk of several age-associated diseases. Additionally, low-intensity physical exercise, including walking, exerts anti-aging effects and helps prevent age-related diseases, making it a powerful tool for promoting healthy aging. This is exemplified by the lifestyles of individuals in Blue Zones, regions of the world with the highest concentration of centenarians. Walking and other low-intensity physical activities contribute significantly to the longevity of individuals in these regions, with walking being an integral part of their daily lives. Thus, incorporating walking into daily routines and encouraging walking-based physical activity interventions can be an effective strategy for promoting healthy aging and improving health outcomes in all populations. The goal of this review is to provide an overview of the vast and consistent evidence supporting the health benefits of physical activity, with a specific focus on walking, and to discuss the impact of walking on various health outcomes, including the prevention of age-related diseases. Furthermore, this review will delve into the evidence on the impact of walking and low-intensity physical activity on specific molecular and cellular mechanisms of aging, providing insights into the underlying biological mechanisms through which walking exerts its beneficial anti-aging effects.

Microvesicle-Mediated Tissue Regeneration Mitigates the Effects of Cellular Ageing

Extracellular vesicles (EVs), comprising microvesicles (MVs) and exosomes (Exos), are membranous vesicles secreted by cells which mediate the repair of cellular and tissue damage via paracrine mechanisms. The action of EVs under normative and morbid conditions in the context of ageing remains largely unexplored. We demonstrate that MVs, but not Exos, from Pathfinder cells (PCs), a putative stem cell regulatory cell type, enhance the repair of human dermal fibroblast (HDF) and mesenchymal stem cell (MSC) co-cultures, following both mechanical and genotoxic stress. Critically, this effect was found to be both cellular age and stress specific. Notably, MV treatment was unable to repair mechanical injury in older co-cultures but remained therapeutic following genotoxic stress. These observations were further confirmed in human dermal fibroblast (HDF) and vascular smooth muscle cell (VSMC) co-cultures of increasing cellular age. In a model of comorbidity comprising co-cultures of HDFs and highly senescent abdominal aortic aneurysm (AAA) VSMCs, MV administration appeared to be senotherapeutic, following both mechanical and genotoxic stress. Our data provide insights into EVs and the specific roles they play during tissue repair and ageing. These data will potentiate the development of novel cell-free therapeutic interventions capable of attenuating age-associated morbidities and avoiding undesired effects.

Protective effects of endothelial progenitor cell microvesicles on Ang II‑induced rat kidney cell injury

Chronic hypertension can lead to kidney damage, known as hypertensive nephropathy or hypertensive nephrosclerosis. Further understanding of the molecular mechanisms via which hypertensive nephropathy develops is essential for effective diagnosis and treatment. The present study investigated the mechanisms by which endothelial progenitor cells (EPCs) repair primary rat kidney cells (PRKs). ELISA, Cell Counting Kit-8 and flow cytometry assays were used to analyze the effects of EPCs or EPC-MVs on the oxidative stress, inflammation, cell proliferation, apoptosis and cycle of PRKs induced by AngII. A PRK injury model was established using angiotensin II (Ang II). After Ang II induction, PRK proliferation was decreased, apoptosis was increased and the cell cycle was blocked at the G₁ phase before entering the S phase. It was found that the levels of reactive oxygen species and malondialdehyde were increased, while the levels of glutathione peroxidase and superoxide dismutase were decreased. Moreover, the levels of the inflammatory cytokines IL-1β, IL-6 and TNF-α were significantly increased. Thus, Ang II damaged PRKs by stimulating oxidative stress and promoting the inflammatory response. However, when PRKs were co-cultured with EPCs, the damage induced by Ang II was significantly reduced. The current study collected the microvesicles (MVs) secreted by EPCs and co-cultured them with Ang II-induced PRKs, and identified that EPC-MVs retained their protective effect on PRKs. In conclusion, EPCs protect PRKs from Ang II-induced damage via secreted MVs.

Involvement of extracellular vesicles in aging process and their beneficial effects in alleviating aging-associated symptoms

Aging is a gradual and unavoidable physiological phenomenon that manifests in the natural maturation process and continues to progress from infanthood to adulthood. Many elderly people suffer from aging-associated hematological and nonhematological disorders. Recent advances in regenerative medicine have shown new revolutionary paths of treating such diseases using stem cells; however, aging also affects the quality and competence of stem and progenitor cells themselves and ultimately directs their death or apoptosis and senescence, leading to a decline in their regenerative potential. Recent research works show that extracellular vesicles (EVs) isolated from different types of stem cells may provide a safe treatment for aging-associated disorders. The cargo of EVs comprises packets of information in the form of various macromolecules that can modify the fate of the target cells. To harness the true potential of EVs in regenerative medicine, it is necessary to understand how this cargo contributes to the rejuvenation of aged stem and progenitor populations and to identify the aging-associated changes in the macromolecular profile of the EVs themselves. In this review, we endeavor to summarize the current knowledge of the involvement of EVs in the aging process and delineate the role of EVs in the reversal of aging-associated phenotypes. We have also analyzed the involvement of the molecular cargo of EVs in the generation of aging-associated disorders. This knowledge could not only help us in understanding the mechanism of the aging process but could also facilitate the development of new cell-free biologics to treat aging-related disorders in the future.

Chondrocyte Aging: The Molecular Determinants and Therapeutic Opportunities

Osteoarthritis (OA) is a joint degenerative disease that is an exceedingly common problem associated with aging. Aging is the principal risk factor for OA, but damage-related physiopathology of articular chondrocytes probably drives the mechanisms of joint degeneration by a progressive decline in the homeostatic and regenerative capacity of cells. Cellular aging is the manifestation of a complex interplay of cellular and molecular pathways underpinned by transcriptional, translational, and epigenetic mechanisms and niche factors, and unraveling this complexity will improve our understanding of underlying molecular changes that affect the ability of the articular cartilage to maintain or regenerate itself. This insight is imperative for developing new cell and drug therapies for OA disease that will target the specific causes of age-related functional decline. This review explores the key age-related changes within articular chondrocytes and discusses the molecular mechanisms that are commonly perturbed as cartilage ages and degenerates. Current efforts and emerging potential therapies in treating OA that are being employed to halt or decelerate the aging processes are also discussed.

Therapeutic mesenchymal stromal stem cells: Isolation, characterization and role in equine regenerative medicine and metabolic disorders

Mesenchymal stromal cells (MSC) have become a popular treatment modality in equine orthopaedics. Regenerative therapies are especially interesting for pathologies like complicated tendinopathies of the distal limb, osteoarthritis, osteochondritis dissecans (OCD) and more recently metabolic disorders. Main sources for MSC harvesting in the horse are bone marrow, adipose tissue and umbilical cord blood. While the acquisition of umbilical cord blood is fairly easy and non-invasive, extraction of bone marrow and adipose tissue requires more invasive techniques. Characterization of the stem cells as a result of any isolation method, is also a crucial step for the confirmation of the cells' stemness properties; thus, three main characteristics must be fulfilled by these cells, namely: adherence, expression of a series of well-defined differentiation clusters as well as pluripotency. EVs, resulting from the paracrine action of MSCs, also play a key role in the therapeutic mechanisms mediated by stem cells; MSC-EVs are thus largely implicated in the regulation of proliferation, maturation, polarization and migration of various target cells. Evidence that EVs alone represent a complex network 0involving different soluble factors and could then reflect biophysical characteristics of parent cells has fuelled the importance of developing highly specific techniques for their isolation and analysis. All these aspects related to the functional and technical understanding of MSCs will be discussed and summarized in this review.

Targeting Premature Renal Aging: from Molecular Mechanisms of Cellular Senescence to Senolytic Trials

The biological process of renal aging is characterized by progressive structural and functional deterioration of the kidney leading to end-stage renal disease, requiring renal replacement therapy. Since the discovery of pivotal mechanisms of senescence such as cell cycle arrest, apoptosis inhibition, and the development of a senescence-associated secretory phenotype (SASP), efforts in the understanding of how senescent cells participate in renal physiological and pathological aging have grown exponentially. This has been encouraged by both preclinical studies in animal models with senescent cell clearance or genetic depletion as well as due to evidence coming from the clinical oncologic experience. This review considers the molecular mechanism and pathways that trigger premature renal aging from mitochondrial dysfunction, epigenetic modifications to autophagy, DNA damage repair (DDR), and the involvement of extracellular vesicles. We also discuss the different pharmaceutical approaches to selectively target senescent cells (namely, senolytics) or the development of systemic SASP (called senomorphics) in basic models of CKD and clinical trials. Finally, an overview will be provided on the potential opportunities for their use in renal transplantation during ex vivo machine perfusion to improve the quality of the graft.

The protective effects of human umbilical cord mesenchymal stem cell-derived extracellular vesicles on cisplatin-damaged granulosa cells

OBJECTIVE

Long term exposure to gonadotoxic chemotherapy is becoming a major cause of premature ovarian failure/insufficiency (POF/POI) with the increasing cancer incidence among young women. The present study was designed to investigate the protective effects of human cord mesenchymal stem cells (HUCMSCs)-derived extracellular vesicles (EVs) on cisplatin (CDDP)-damaged granulosa cells (GCs) in vitro.

MATERIALS AND METHODS

EVs were obtained from supernatant of cultured HUCMSCs by ultracentrifugation method, purified by Sucrose density gradient centrifugation, and then were co-cultured with cisplatin-damaged GCs of 3-weeks female Sprague-Dawley (SD) rats. PKH26 labeled EVs could be observed in normal and CDDP-damaged GCs after 6 h co-culture.

RESULTS

The surviving GCs were significantly higher and apoptotic GCs were significantly lower in EVs + CDDP group compared with CDDP group. Meanwhile, the levels of E2 and StAR (the key gene related to synthesis of steroid hormone) were significantly higher in EVs + CDDP group compared with CDDP group. Furthermore, the mRNA expression of Caspase 3 was down-regulated significantly and the ratio of Bcl-2/Bax was up-regulated significantly in EVs + CDDP group. Moreover, the protective effect of EVs on CDDP-damaged GCs showed a dose-dependent effect.

CONCLUSION

HUCMSCs-derived EVs could become incorporated to CDDP-damaged GCs, and increase the number of living cells, therefore playing important roles in promoting resistance to cisplatin-induced GCs apoptosis and restoring synthesis and secretion of steroid hormone in GCs. This study might provide a theoretical and experimental basis for use of mesenchymal stem cells (MSCs) derived EVs instead of MSCs as a cell-free therapeutic strategy for the patients with POI induced by chemotherapeutic agents.

Ageing and mesenchymal stem cells derived exosomes: Molecular insight and challenges

Ageing induces a great risk factor that participates in progressing various degenerative diseases morbidities. The main characteristic of ageing is the failure in maintaining homeostasis in the organs with a cellular senescence. Senescence is characterized by reduced cell growth, evade cellular death, and acquiring a senescence-associated secretory phenotype (SASP). Mesenchymal stem cells (MSCs) are advantageous cells in regenerative medicine, exerting pleiotropic functions by producing soluble factors, such as exosomes. MSCs and their exosomes (MSCs-Exo) kinetic are affected by ageing and other aged exosomes. Exosomes biogenesis from aged MSCs is accelerated and their exosomal cargoes, such as miRNAs, vary as compared to those of normal cells. Besides, exosomes from aged MSCs loss their regenerative potential and may negatively influence the function of recipient cells. MSCs-Exo can improve ageing and age-related diseases; however, the detailed mechanisms remain yet elusive. Although exosomes-therapy may serve as a new approach to combat ageing, the translation of preclinical results to clinic needs more extensive investigation on exosomes both on their biology and related techniques. Overall, scrutiny on the effect of ageing on MSCs and vice versa is vital for designing novel therapy using MSCs with focus on the management of older individuals.

Comparative Analysis of Adipose-Derived Stromal Cells and Their Secretome for Auricular Cartilage Regeneration

Adipose-derived stromal cells (ADSCs) can repair auricular cartilage defects. Furthermore, stem cell secretome may also be a promising biological therapeutic option, which is equal to or even superior to the stem cell. We explored the therapeutic efficacies of ADSCs and their secretome in terms of rabbit auricular cartilage regeneration. ADSCs and their secretome were placed into surgically created auricular cartilage defects. After 4 and 8 weeks, the resected auricles were histopathologically and immunohistochemically examined. We used real-time PCR to determine the levels of genes expressing collagen type II, transforming growth factor-β1 (TGF-β1), and insulin-like growth factor-1 (IGF-1). ADSCs significantly improved auricular cartilage regeneration at 4 and 8 weeks, compared to the secretome and PBS groups, as revealed by gross examination, histopathologically and immunohistochemically. ADSCs upregulated the expression of collagen type II, TGF-β1, and IGF-1 more so than did the secretome or PBS. The expression levels of collagen type II and IGF-1 were significantly higher at 8 weeks than at 4 weeks after ADSC injection. Although ADSCs thus significantly enhanced new cartilage formation, their secretome did not. Therefore, ADSCs may be more effective than their secretome in the repair of auricular cartilage defect.

Investigating the effect of age on platelet ultrastructure using transmission electron microscopy

In the present study, the age- and sex-related differences in platelet ultrastructure were investigated using transmission electron microscopy (TEM). A total of 15 healthy volunteers were grouped according to age, with 5 people in each of the following groups: young group (25-45 years), middle-aged group (46-65 years), and old-aged group (> 65 years). In the TEM micrographs, the internal components, specifically the α-granules, dense granules, and lysosomal granules, of 20 platelets were counted for each group. Two-way analysis of variance of age and sex variance was used to compare the results. The ultrastructure of the platelets in the old-aged group was observed to be quite different from those of the young and middle-aged groups. Specifically, with ageing, the platelet membrane becomes more irregular in shape and non-smooth, and multiple platelet membrane ruptures are observed. Furthermore, the pseudopodia and protuberances become more numerous and slender, and the number of α-granules is significantly reduced. These morphological changes indicate that ageing may affect the function of platelets, which in turn affects the efficacy of platelet concentrates. Thus, the effects of age should be considered when using platelet concentrates prepared from elderly autologous blood.

Contribution of Extracellular Vesicles in Rebuilding Injured Muscles

Skeletal myofibers are injured due to mechanical stresses experienced during physical activity, or due to myofiber fragility caused by genetic diseases. The injured myofiber needs to be repaired or regenerated to restore the loss in muscle tissue function. Myofiber repair and regeneration requires coordinated action of various intercellular signaling factors-including proteins, inflammatory cytokines, miRNAs, and membrane lipids. It is increasingly being recognized release and transmission of these signaling factors involves extracellular vesicle (EV) released by myofibers and other cells in the injured muscle. Intercellular signaling by these EVs alters the phenotype of their target cells either by directly delivering the functional proteins and lipids or by modifying longer-term gene expression. These changes in the target cells activate downstream pathways involved in tissue homeostasis and repair. The EVs are heterogeneous with regards to their size, composition, cargo, location, as well as time-course of genesis and release. These differences impact on the subsequent repair and regeneration of injured skeletal muscles. This review focuses on how intracellular vesicle production, cargo packaging, and secretion by injured muscle, modulates specific reparative, and regenerative processes. Insights into the formation of these vesicles and their signaling properties offer new understandings of the orchestrated response necessary for optimal muscle repair and regeneration.

Microvesicles: ROS scavengers and ROS producers

This review analyzes the relationship between microvesicles and reactive oxygen species (ROS). This relationship is bidirectional; on the one hand, the number and content of microvesicles produced by the cells are affected by oxidative stress conditions; on the other hand, microvesicles can directly and/or indirectly modify the ROS content in the extra- as well as the intracellular compartments. In this regard, microvesicles contain a pro-oxidant or antioxidant machinery that may produce or scavenge ROS: direct effect. This mechanism is especially suitable for eliminating ROS in the extracellular compartment. Endothelial microvesicles, in particular, contain a specific and well-developed antioxidant machinery. On the other hand, the molecules included in microvesicles can modify (activate or inhibit) ROS metabolism in their target cells: indirect effect. This can be achieved by the incorporation into the cells of ROS metabolic enzymes included in the microvesicles, or by the regulation of signaling pathways involved in ROS metabolism. Proteins, as well as miRNAs, are involved in this last effect.

Intra-Vitreal Administration of Microvesicles Derived from Human Adipose-Derived Multipotent Stromal Cells Improves Retinal Functionality in Dogs with Retinal Degeneration

This study was designed to determine the influence of microvesicles (MVs) derived from multipotent stromal cells isolated from human adipose tissue (hASCs) on retinal functionality in dogs with various types of retinal degeneration. The biological properties of hASC-MVs were first determined using an in vitro model of retinal Muller-like cells (CaMLCs). The in vitro assays included analysis of hASC-MVs influence on cell viability and metabolism. Brain-derived neurotrophic factor (BDNF) expression was also determined. Evaluation of the hASC-MVs was performed under normal and oxidative stress conditions. Preliminary clinical studies were performed on ten dogs with retinal degeneration. The clinical studies included behavioral tests, fundoscopy and electroretinography before and after hASC-MVs intra-vitreal injection. The in vitro study showed that CaMLCs treated with hASC-MVs were characterized by improved viability and mitochondrial potential, both under normal and oxidative stress conditions. Additionally, hASC-MVs under oxidative stress conditions reduced the number of senescence-associated markers, correlating with the increased expression of BDNF. The preliminary clinical study showed that the intra-vitreal administration of hASC-MVs significantly improved the dogs’ general behavior and tracking ability. Furthermore, fundoscopy demonstrated that the retinal blood vessels appeared to be less attenuated, and electroretinography using HMsERG demonstrated an increase in a- and b-wave amplitude after treatment. These results shed promising light on the application of cell-free therapies in veterinary medicine for retinal degenerative disorders treatment.

Adipose may actively delay progression of NAFLD by releasing tumor-suppressing, anti-fibrotic miR-122 into circulation

Nonalcoholic fatty liver disease (NAFLD) is the most common liver pathology. Here we propose tissue-cooperative, homeostatic model of NAFLD. During early stages of NAFLD the intrahepatic production of miR-122 falls, while the secretion of miRNA-containing exosomes by adipose increases. Bloodstream carries exosome to the liver, where their miRNA cargo is released to regulate their intrahepatic targets. When the deterioration of adipose catches up with the failing hepatic parenchyma, the external supply of liver-supporting miRNAs gradually tapers off, leading to the fibrotic decompensation of the liver and an increase in hepatic carcinogenesis. This model may explain paradoxical observations of the disease-associated decrease in intrahepatic production of certain miRNAs with an increase in their levels in serum. Infusions of miR-122 and, possibly, some other miRNAs may be efficient for preventing NAFLD-associated hepatocellular carcinoma. The best candidates for exosome-wrapped miRNA producer are adipose tissue-derived mesenchymal stem cells (MSCs), known for their capacity to shed large amounts of exosomes into the media. Notably, MSC-derived exosomes with no specific loading are already tested in patients with liver fibrosis. Carrier exosomes may be co-manufactured along with their cargo. Exosome-delivered miRNA cocktails may augment functioning of human organs suffering from a variety of chronic diseases.

Delivery of an Artificial Transcription Regulator dCas9-VPR by Extracellular Vesicles for Therapeutic Gene Activation

The CRISPR/Cas system has been developed as a potent tool for genome engineering and transcription regulation. However, the efficiency of the delivery of the system into cells, particularly for therapeutic in vivo applications, remains a major bottleneck. Extracellular vesicles (EVs), released by eukaryotic cells, can mediate the transfer of various molecules, including nucleic acids and proteins. We show the packaging and delivery of the CRISPR/Cas system via EVs to the target cells, combining the advantages of both technological platforms. A genome editing with designed extracellular vesicles (GEDEX) system generated by the producer cells can transfer the designed transcriptional regulator dCas9-VPR complexed with appropriate targeting gRNAs enabling activation of gene transcription. We show functional delivery in mammalian cells as well in the animals. The therapeutic efficiency of in vivo delivery of dCas9-VPR/sgRNA GEDEX is demonstrated in a mouse model of liver damage counteracted by upregulation of the endogenous hepatocyte growth factor, demonstrating the potential for therapeutic applications.

Targeting extracellular vesicles to injured tissue using membrane cloaking and surface display

BACKGROUND

Extracellular vesicles (EVs) and exosomes are nano-sized, membrane-bound vesicles shed by most eukaryotic cells studied to date. EVs play key signaling roles in cellular development, cancer metastasis, immune modulation and tissue regeneration. Attempts to modify exosomes to increase their targeting efficiency to specific tissue types are still in their infancy. Here we describe an EV membrane anchoring platform termed "cloaking" to directly embed tissue-specific antibodies or homing peptides on EV membrane surfaces ex vivo for enhanced vesicle uptake in cells of interest. The cloaking system consists of three components: DMPE phospholipid membrane anchor, polyethylene glycol spacer and a conjugated streptavidin platform molecule, to which any biotinylated molecule can be coupled for EV decoration.

RESULTS

We demonstrate the utility of membrane surface engineering and biodistribution tracking with this technology along with targeting EVs for enhanced uptake in cardiac fibroblasts, myoblasts and ischemic myocardium using combinations of fluorescent tags, tissue-targeting antibodies and homing peptide surface cloaks. We compare cloaking to a complementary approach, surface display, in which parental cells are engineered to secrete EVs with fusion surface targeting proteins.

CONCLUSIONS

EV targeting can be enhanced both by cloaking and by surface display; the former entails chemical modification of preformed EVs, while the latter requires genetic modification of the parent cells. Reduction to practice of the cloaking approach, using several different EV surface modifications to target distinct cells and tissues, supports the notion of cloaking as a platform technology.

Extracellular Vesicles, Ageing, and Therapeutic Interventions

A more comprehensive understanding of the human ageing process is required to help mitigate the increasing burden of age-related morbidities in a rapidly growing global demographic of elderly individuals. One exciting novel strategy that has emerged to intervene involves the use of extracellular vesicles to engender tissue regeneration. Specifically, this employs their molecular payloads to confer changes in the epigenetic landscape of ageing cells and ameliorate the loss of functional capacity. Understanding the biology of extracellular vesicles and the specific roles they play during normative ageing will allow for the development of novel cell-free therapeutic interventions. Hence, the purpose of this review is to summarise the current understanding of the mechanisms that drive ageing, critically explore how extracellular vesicles affect ageing processes and discuss their therapeutic potential to mitigate the effects of age-associated morbidities and improve the human health span.

Application of plasma-combined regeneration technology in managing facial acne scars

BACKGROUND AND OBJECTIVES

Plasma skin regeneration (PSR) and platelet-rich plasma（PRP） have gained popularity in the treatment of acne scars due to their efficacy and improved tolerability. The objective of this investigation was to evaluate the synergistic effect of PRP plus PSR (plasma-combined regeneration technology, PCRT) in managing facial acne scars.

METHODS

From March 2015 to June 2017，a total of 25 cases with facial atrophic acne scars were treated with PCRT treatment for three to five times. Treatments were repeated at an interval of 8 weeks．Treatment parameters were titrated to an immediate end point of moderate erythema. The clinical end point for cessation of treatment was the attainment of satisfactory clinical results. Results were monitored photographically up to 6 months after treatment. The efficacy and adverse effects were evaluated by using the following outcome parameters： the duration of edema,erythema and crusting; the degree of hyperpigmentation, hypopigmentation and scarformation; subjective effective rate was evaluated by patients and physicians.

RESULTS

22 of 25 participants completed the study, and were followed up for 6-12 months. After three to five treatments, evaluation by patients showed that the total effective rate was 90.91%. Evaluation by two physicians showed that the total effective rate was 86.36%. Treatment was well tolerated by all participants. The total duration of side effects was 6.7 ± 1.7 days of edema, 8.1 ± 2.3 days of erythema,6.5 ± 1.8 days of crusting, respectively. No hyperpigmentation, depigmentation, and worsening of scarring were observed by the conclusion of the follow-up period． Conclusion: These results provide initial evidence for the safety and effectiveness of PCRT as a well-tolerated modality for the treatment of acne scars. PCRT is an ideal treatment for facial acne scars with minimal side effect．.

Comparative efficacy of stem cells and secretome in articular cartilage regeneration: a systematic review and meta-analysis

Articular cartilage defect remains the most challenging joint disease due to limited intrinsic healing capacity of the cartilage that most often progresses to osteoarthritis. In recent years, stem cell therapy has evolved as therapeutic strategies for articular cartilage regeneration. However, a number of studies have shown that therapeutic efficacy of stem cell transplantation is attributed to multiple secreted factors that modulate the surrounding milieu to evoke reparative processes. This systematic review and meta-analysis aim to evaluate and compare the therapeutic efficacy of stem cell and secretome in articular cartilage regeneration in animal models. We systematically searched the PubMed, CINAHL, Cochrane Library, Ovid Medline and Scopus databases until August 2017 using search terms related to stem cells, cartilage regeneration and animals. A random effect meta-analysis of the included studies was performed to assess the treatment effects on new cartilage formation on an absolute score of 0-100% scale. Subgroup analyses were also performed by sorting studies independently based on similar characteristics. The pooled analysis of 59 studies that utilized stem cells significantly improved new cartilage formation by 25.99% as compared with control. Similarly, the secretome also significantly increased cartilage regeneration by 26.08% in comparison to the control. Subgroup analyses revealed no significant difference in the effect of stem cells in new cartilage formation. However, there was a significant decline in the effect of stem cells in articular cartilage regeneration during long-term follow-up, suggesting that the duration of follow-up is a predictor of new cartilage formation. Secretome has shown a similar effect to stem cells in new cartilage formation. The risk of bias assessment showed poor reporting for most studies thereby limiting the actual risk of bias assessment. The present study suggests that both stem cells and secretome interventions improve cartilage regeneration in animal trials. Graphical abstract ᅟ.

The role of epigenetics in renal ageing

An ability to separate natural ageing processes from processes specific to morbidities is required to understand the heterogeneity of age-related organ dysfunction. Mechanistic insight into how epigenetic factors regulate ageing throughout the life course, linked to a decline in renal function with ageing, is already proving to be of value in the analyses of clinical and epidemiological cohorts. Noncoding RNAs provide epigenetic regulatory circuits within the kidney, which reciprocally interact with DNA methylation processes, histone modification and chromatin. These interactions have been demonstrated to reflect the biological age and function of renal allografts. Epigenetic factors control gene expression and activity in response to environmental perturbations. They also have roles in highly conserved signalling pathways that modulate ageing, including the mTOR and insulin/insulin-like growth factor signalling pathways, and regulation of sirtuin activity. Nutrition, the gut microbiota, inflammation and environmental factors, including psychosocial and lifestyle stresses, provide potential mechanistic links between the epigenetic landscape of ageing and renal dysfunction. Approaches to modify the renal epigenome via nutritional intervention, targeting the methylome or targeting chromatin seem eminently feasible, although caution is merited owing to the potential for intergenerational and transgenerational effects.