Mesenchymal Stem Cell Secretome: Toward Cell-Free Therapeutic Strategies in Regenerative Medicine

Earlier research primarily attributed the effects of mesenchymal stem cell (MSC) therapies to their capacity for local engrafting and differentiating into multiple tissue types. However, recent studies have revealed that implanted cells do not survive for long, and that the benefits of MSC therapy could be due to the vast array of bioactive factors they produce, which play an important role in the regulation of key biologic processes. Secretome derivatives, such as conditioned media or exosomes, may present considerable advantages over cells for manufacturing, storage, handling, product shelf life and their potential as a ready-to-go biologic product. Nevertheless, regulatory requirements for manufacturing and quality control will be necessary to establish the safety and efficacy profile of these products. Among MSCs, human uterine cervical stem cells (hUCESCs) may be a good candidate for obtaining secretome-derived products. hUCESCs are obtained by Pap cervical smear, which is a less invasive and painful method than those used for obtaining other MSCs (for example, from bone marrow or adipose tissue). Moreover, due to easy isolation and a high proliferative rate, it is possible to obtain large amounts of hUCESCs or secretome-derived products for research and clinical use.

New agents that target senescent cells: the flavone, fisetin, and the BCL-XL inhibitors, A1331852 and A1155463

Senescent cells accumulate with aging and at sites of pathology in multiple chronic diseases. Senolytics are drugs that selectively promote apoptosis of senescent cells by temporarily disabling the pro-survival pathways that enable senescent cells to resist the pro-apoptotic, pro-inflammatory factors that they themselves secrete. Reducing senescent cell burden by genetic approaches or by administering senolytics delays or alleviates multiple age- and disease-related adverse phenotypes in preclinical models. Reported senolytics include dasatinib, quercetin, navitoclax (ABT263), and piperlongumine. Here we report that fisetin, a naturally-occurring flavone with low toxicity, and A1331852 and A1155463, selective BCL-X_L inhibitors that may have less hematological toxicity than the less specific BCL-2 family inhibitor navitoclax, are senolytic. Fisetin selectively induces apoptosis in senescent but not proliferating human umbilical vein endothelial cells (HUVECs). It is not senolytic in senescent IMR90 cells, a human lung fibroblast strain, or primary human preadipocytes. A1331852 and A1155463 are senolytic in HUVECs and IMR90 cells, but not preadipocytes. These agents may be better candidates for eventual translation into clinical interventions than some existing senolytics, such as navitoclax, which is associated with hematological toxicity.

Targeting senescent cells enhances adipogenesis and metabolic function in old age

Senescent cells accumulate in fat with aging. We previously found genetic clearance of senescent cells from progeroid INK-ATTAC mice prevents lipodystrophy. Here we show that primary human senescent fat progenitors secrete activin A and directly inhibit adipogenesis in non-senescent progenitors. Blocking activin A partially restored lipid accumulation and expression of key adipogenic markers in differentiating progenitors exposed to senescent cells. Mouse fat tissue activin A increased with aging. Clearing senescent cells from 18-month-old naturally-aged INK-ATTAC mice reduced circulating activin A, blunted fat loss, and enhanced adipogenic transcription factor expression within 3 weeks. JAK inhibitor suppressed senescent cell activin A production and blunted senescent cell-mediated inhibition of adipogenesis. Eight weeks-treatment with ruxolitinib, an FDA-approved JAK1/2 inhibitor, reduced circulating activin A, preserved fat mass, reduced lipotoxicity, and increased insulin sensitivity in 22-month-old mice. Our study indicates targeting senescent cells or their products may alleviate age-related dysfunction of progenitors, adipose tissue, and metabolism.

DOI:http://dx.doi.org/10.7554/eLife.12997.001

The likelihood of developing metabolic diseases such as diabetes increases with age. This is, in part, because the cells within fat and other tissues become less sensitive to the hormone insulin as people and other animals get older. Also, the stem cells that give rise to new, insulin-responsive fat cells become dysfunctional with increasing age. This is related to the accumulation of “senescent” cells, which, unlike normal fat cell progenitors, release molecules that are toxic to nearby and distant cells.

Xu, Palmer et al. have now investigated if senescent cells interfere with the activity of stem cells from human fat tissue, and if getting rid of these senescent cells might restore the normal activity and insulin responsiveness of aged fat tissue. The experiments revealed that human senescent fat cell progenitors release a protein called activin A, which impedes the normal function of stem cells and fat tissue. Additionally, older mice had higher levels of activin A in both their blood and fat tissue than young mice.

Xu, Palmer et al. then analyzed older mice that had been engineered to have senescent fat cells that could be triggered to essentially kill themselves when the mice were treated with a drug. Eliminating the senescent cells from these mice led to lower levels of activin A and more fat tissue (due to improved stem cell capacity to become fully functional fat cells) that expressed genes required for insulin responsiveness. This showed that senescent cells are a cause of age-related fat tissue loss and metabolic disease in older mice.

Next, Xu, Palmer et al. treated older mice with drugs called JAK inhibitors, which they found reduce the production of activin A by senescent cells isolated from fat tissue. After two months of treatment, the levels of activin A in the blood and in fat tissue were indeed reduced. The fat tissue in treated mice also showed fewer features associated with the development of diabetes than the fat tissue of untreated mice. As such, these results paralleled those after selectively eliminating the senescent cells.

Together these findings suggest that JAK inhibitors or drugs (called senolytics) that selectively eliminate senescent cells may have clinical benefits in treating age-related conditions such as diabetes and stem cell dysfunction.

DOI:http://dx.doi.org/10.7554/eLife.12997.002

Exosomes from adipose-derived stem cells and application to skin wound healing

Skin wound healing is an intractable problem that represents an urgent clinical need. To solve this problem, a large number of studies have focused on the use of exosomes (EXOs) derived from adipose‐derived stem cells (ADSCs). This review describes the mechanisms whereby ADSCs‐EXOs regulate wound healing and their clinical application. In the wound, ADSCs‐EXOs modulate immune responses and inflammation. They also promote angiogenesis, accelerate proliferation and re‐epithelization of skin cells, and regulate collagen remodelling which inhibits scar hyperplasia. Compared with ADSCs therapeutics, ADSCs‐EXOs have highly stability and are easily stored. Additionally, they are not rejected by the immune system and have a homing effect and their dosage can be easily controlled. ADSCs‐EXOs can improve fat grafting and promote wound healing in patients with diabetes mellitus. They can also act as a carrier and combined scaffold for treatment, leading to scarless cutaneous repair. Overall, ADSCs‐EXOs have the potential to be used in the clinic to promote wound healing.

Exosome loaded alginate hydrogel promotes tissue regeneration in full-thickness skin wounds: An in vivo study

Wound healing is known as one of the most complicated biological processes for injured skin caused by surgical, trauma, burns, or diabetic diseases, which causes a nonfunctioning mass of fibrotic tissue. Recent reports have suggested that exosomes (EXOs) secreted by this type of stem cells may contribute to their paracrine effect. In this study, the EXOs were isolated from the supernatant of cultured adipose-derived stem cells (ADSCs) via ultracentrifugation and filtration. The EXO loaded in the alginate-based hydrogel was used as a bioactive scaffold to preserve the EXO in the wound site in the animal model. The physical and biochemical properties of EXO loaded Alg hydrogel were characterized and results proved that fabricated structure was biodegradable and biocompatible. This bioactive wound dressing technique has significantly improved wound closure, collagen synthesis, and vessel formation in the wound area. Results offer a new viewpoint and a cell-free therapeutic strategy, for wound healing through the application of the composite structure of EXO encapsulated in alginate hydrogel.

Single-Cell Profiles and Clinically Useful Properties of Human Mesenchymal Stem Cells of Adipose and Bone Marrow Origin

BACKGROUND

Mesenchymal stem cells (MSCs) can be isolated from various tissues and can present themselves as a promising cell source for cell-based therapies. Although adipose- and bone marrow-derived mesenchymal stem cells have already been used in a considerable number of clinical trials for osteoarthritis treatment, systematic analyses from single- to bulk-cell resolution as well as clinical outcomes of these 2 MSCs are still insufficient.

PURPOSE

To explore the characteristics and differences of adipose-derived stem cells (ADSCs) and bone marrow MSCs (BMSCs) at single- and bulk-cell levels, to study the clinical outcomes of these 2 cells on the treatment of osteoarthritis, and to provide potential guidance on the more precise clinical application of these MSCs.

STUDY DESIGN

Controlled laboratory study and meta-analysis.

METHODS

Same donor-derived ADSCs and BMSCs were isolated and cultured. Single- and bulk-cell assays were used to identify the characteristics of these 2 cells. Meta-analysis of clinical trials was done to compare the clinical therapeutic effects in osteoarthritis treatment with ADSCs and BMSCs.

RESULTS

Single-cell RNA sequencing analysis showed that the population of ADSCs showed lower transcriptomic heterogeneity when compared with BMSCs. Additionally, as compared with BMSCs, ADSCs were less dependent on mitochondrial respiration for energy production. Furthermore, ADSCs had a lower expression level of human leukocyte antigen class I antigen and higher immunosuppression capacity when compared with the BMSC population. Meta-analysis of current clinical trials of osteoarthritis treatment with MSCs consistently showed that ADSCs are more stable than BMSCs in their therapeutic effect.

CONCLUSION

These results provide basic biological insights into human ADSCs and BMSCs at the single-cell resolution. Findings indicated that ADSCs may be a more controllable stem cell source, may be more adaptable to surviving in the hypoxic articular cavity niche, and may exhibit superiority in regulating inflammation. Based on the meta-analysis results of the different characteristics of ADSCs and BMSCs, ADSCs were implicated as being a better cell source for osteoarthritis treatment.

CLINICAL RELEVANCE

These results guide a more precise clinical application of adipose and bone marrow mesenchymal stem cells.

Collagen microarchitecture mechanically controls myofibroblast differentiation

Altered microarchitecture of collagen type I is a hallmark of wound healing and cancer that is commonly attributed to myofibroblasts. However, it remains unknown which effect collagen microarchitecture has on myofibroblast differentiation. Here, we combined experimental and computational approaches to investigate the hypothesis that the microarchitecture of fibrillar collagen networks mechanically regulates myofibroblast differentiation of adipose stromal cells (ASCs) independent of bulk stiffness. Collagen gels with controlled fiber thickness and pore size were microfabricated by adjusting the gelation temperature while keeping their concentration constant. Rheological characterization and simulation data indicated that networks with thicker fibers and larger pores exhibited increased strain-stiffening relative to networks with thinner fibers and smaller pores. Accordingly, ASCs cultured in scaffolds with thicker fibers were more contractile, expressed myofibroblast markers, and deposited more extended fibronectin fibers. Consistent with elevated myofibroblast differentiation, ASCs in scaffolds with thicker fibers exhibited a more proangiogenic phenotype that promoted endothelial sprouting in a contractility-dependent manner. Our findings suggest that changes of collagen microarchitecture regulate myofibroblast differentiation and fibrosis independent of collagen quantity and bulk stiffness by locally modulating cellular mechanosignaling. These findings have implications for regenerative medicine and anticancer treatments.

Mesenchymal Stem Cells from Adipose Tissue in Clinical Applications for Dermatological Indications and Skin Aging

Operating at multiple levels of control, mesenchymal stem cells from adipose tissue (ADSCs) communicate with organ systems to adjust immune response, provide signals for differentiation, migration, enzymatic reactions, and to equilibrate the regenerative demands of balanced tissue homeostasis. The identification of the mechanisms by which ADSCs accomplish these functions for dermatological rejuvenation and wound healing has great potential to identify novel targets for the treatment of disorders and combat aging. Herein, we review new insights into the role of adipose-derived stem cells in the maintenance of dermal and epidermal homeostasis, and recent advances in clinical applications of ADSCs related to dermatology.

Immunomodulatory Effect of Adipose-Derived Stem Cells: The Cutting Edge of Clinical Application

Adipose-derived stem cells (ASCs) represent a promising tool for soft tissue engineering as well as for clinical treatment of inflammatory and autoimmune pathologies. The well-characterized multi-differentiation potential and self-renewal properties of ASCs are coupled with their immunomodulatory ability in providing therapeutic efficacy. Yet, their impact in immune or inflammatory disorders might rely both on cell contact-dependent mechanisms and paracrine effects, resulting in the release of various soluble factors that regulate immune cells functions. Despite the widespread use of ASCs in clinical trials addressing several pathologies, the pathophysiological mechanisms at the basis of their clinical use have been not yet fully investigated. In particular, a thorough analysis of ASC immunomodulatory potential is mandatory. Here we explore such molecular mechanisms involved in ASC immunomodulatory properties, emphasizing the relevance of the milieu composition. We review the potential clinical use of ASC secretome as a mediator for immunomodulation, with a focus on in vitro and in vivo environmental conditions affecting clinical outcome. We describe some potential strategies for optimization of ASCs immunomodulatory capacity in clinical settings, which act either on adult stem cells gene expression and local microenvironment. Finally, we discuss the limitations of both allogeneic and autologous ASC use, highlighting the issues to be fixed in order to significantly improve the efficacy of ASC-based cell therapy.

Precise and long-term tracking of adipose-derived stem cells and their regenerative capacity via superb bright and stable organic nanodots

Monitoring and understanding long-term fate and regenerative therapy of administrated stem cells in vivo is of great importance. Herein we report organic nanodots with aggregation-induced emission characteristics (AIE dots) for long-term tracking of adipose-derived stem cells (ADSCs) and their regenerative capacity in living mice. The AIE dots possess high fluorescence (with a high quantum yield of 25±1%), excellent biological and photophysical stabilities, low in vivo toxicity, and superb retention in living ADSCs with negligible interference on their pluripotency and secretome. These AIE dots also exhibit superior in vitro cell tracking capability compared to the most popular commercial cell trackers, PKH26 and Qtracker 655. In vivo quantitative studies with bioluminescence and GFP labeling as the controls reveal that the AIE dots can precisely and quantitatively report the fate of ADSCs and their regenerative capacity for 42 days in an ischemic hind limb bearing mouse model.

Concise Review: Adipose-Derived Stem Cells (ASCs) and Adipocyte-Secreted Exosomal microRNA (A-SE-miR) Modulate Cancer Growth and proMote Wound Repair

Adipose-derived stem cells (ASCs) have been routinely used from several years in regenerative surgery without any definitive statement about their potential pro-oncogenic or anti-oncogenic role. ASCs has proven to favor tumor progression in several experimental cancer models, playing a central role in regulating tumor invasiveness and metastatic potential through several mechanisms, such as the paracrine release of exosomes containing pro-oncogenic molecules and the induction of epithelial-mesenchymal transition. However, the high secretory activity and the preferential tumor-targeting make also ASCs a potentially suitable vehicle for delivery of new anti-cancer molecules in tumor microenvironment. Nanotechnologies, viral vectors, drug-loaded exosomes, and micro-RNAs (MiR) represent additional new tools that can be applied for cell-mediated drug delivery in a tumor microenvironment. Recent studies revealed that the MiR play important roles in paracrine actions on adipose-resident macrophages, and their dysregulation has been implicated in the pathogenesis of obesity, diabetes, and diabetic complications as wounds. Numerous MiR are present in adipose tissues, actively participating in the regulation of adipogenesis, adipokine secretion, inflammation, and inter-cellular communications in the local tissues. These results provide important insights into Adipocyte-secreted exosomal microRNA (A-SE-MiR) function and they suggest evaluating the potential role of A-SE-MiR in tumor progression, the mechanisms underlying ASCs-cancer cell interplay and clinical safety of ASCs-based therapies.

Exosomes from adipose-derived stem cells ameliorate phenotype of Huntington's disease in vitro model

Huntington's disease (HD) is a hereditary neurodegenerative disorder caused by the aggregation of mutant Huntingtin (mHtt). Adipose-derived stem cells (ASCs) have a potential for use in the treatment of incurable disorders, including HD. ASCs secrete various neurotrophic factors and microvesicles, and modulate hostile microenvironments affected by disease through paracrine mechanisms. Exosomes are small vesicles that transport nucleic acid and protein between cells. Here, we investigated the therapeutic role of exosomes from ASCs (ASC-exo) using in vitro HD model by examining pathological phenotypes of this model. Immunocytochemistry result showed that ASC-exo significantly decreases mHtt aggregates in R6/2 mice-derived neuronal cells. Western blot result further confirmed the reduction in mHtt aggregates level by ASC-exo treatment. ASC-exo up-regulates PGC-1, phospho-CREB and ameliorates abnormal apoptotic protein level in an in vitro HD model. In addition, MitoSOX Red, JC-1 and cell viability assay showed that ASC-exo reduces mitochondrial dysfunction and cell apoptosis of in vitro HD model. These findings suggest that ASC-exo has a therapeutic potential for treating HD by modulating representative cellular phenotypes of HD.

Adipose-Derived Stem Cells Secretome and Its Potential Application in "Stem Cell-Free Therapy"

Adipose-derived stem cells (ASCs) secrete many cytokines, proteins, growth factors, and extracellular vesicles with beneficial outcomes that can be used in regenerative medicine. It has great potential, and the development of new treatment strategies using the ASCs secretome is of global interest. Besides cytokines, proteins, and growth factors, the therapeutic effect of secretome is hidden in non-coding RNAs such as miR-21, miR-24, and miR-26 carried via exosomes secreted by adequate cells. The whole secretome, including ASC-derived exosomes (ASC-exos) has been proven in many studies to have immunomodulatory, proangiogenic, neurotrophic, and epithelization activity and can potentially be used for neurodegenerative, cardiovascular, respiratory, inflammatory, and autoimmune diseases as well as wound healing treatment. Due to limitations in the use of stem cells in cell-based therapy, its secretome with emphasis on exosomes seems to be a reasonable and safer alternative with increased effectiveness and fewer side effects. Moreover, the great advantage of cell-free therapy is the possibility of biobanking the ASCs secretome. In this review, we focus on the current state of knowledge on the use of the ASCs secretome in stem cell-free therapy.

Monodispersed bioactive glass submicron particles and their effect on bone marrow and adipose tissue-derived stem cells

Spherical monodispersed bioactive particles are potential candidates for nanocomposite synthesis or as injectable particles that could be internalized by cells for the local sustained delivery of inorganic therapeutic ions (e.g., calcium or strontium). Particles are also likely to be released from porous bioactive glass and sol-gel hybrid scaffolds as they degrade; thus, it is vital to investigate their interaction with cells. Spherical monodispersed bioactive glass particles (mono-SMBG), with diameters of 215 ± 20 nm are synthesized using a modified Stöber process. Confocal and transmission electron microscopy demonstrate that mono-SMBGs are internalized by human bone marrow (MSCs) and adipose-derived stem cells (ADSCs) and located within cell vesicles and in the cytoplasm. Particle dissolution inside the cells is observed. Alamar Blue, MTT and Cyquant assays demonstrate that 50 μg mL(-1) of mono-SMBGs did not inhibit significantly MSC or ADSC metabolic activity. However, at higher concentrations (100 and 200 μg mL(-1)) small decrease in metabolic activity and total DNA is observed. Mono-SMBG did not induce ALPase activity, an early marker of osteogenic differentiation, without osteogenic supplements; however, in their presence osteogenic differentiation is achieved. Additionally, large numbers of particles are internalized by the cells but have little effect on cell behavior.

Transplantation of adipose-derived stem cells combined with collagen scaffolds restores ovarian function in a rat model of premature ovarian insufficiency

STUDY QUESTION

Does the transplantation of adipose-derived stem cells (ADSCs) on soluble collagen scaffolds (collagen/ADSCs) have better therapeutic effect than transplantation of ADSCs alone, to treat premature ovarian insufficiency (POI) in a rat model induced by Tripterygium Glycosides (TG)?

SUMMARY ANSWER

The transplantation of collagen/ADSCs increased the short-term retention of ADSCs in ovaries and contributed to long-term restoration of ovarian function, as well as the fertility of rats with TG-induced ovarian damage.

WHAT IS KNOWN ALREADY

About 50% of young women in China, who have been treated with TG, have subsequently developed ovarian insufficiency. Rats exhibit similar symptoms to these patients when given an equivalent dose of TG. Transplantation of ADSCs improves ovarian function impaired by chemotherapy in rodent models.

STUDY DESIGN, SIZE, DURATION

After the administration of TG, 54 POI model rats were randomly assigned to 4 groups: phosphate buffered saline (PBS) ( ITALIC! n = 14), collagen ( ITALIC! n = 11), ADSCs ( ITALIC! n = 16) and collagen/ADSCs ( ITALIC! n = 13). Seventeen normal rats were assigned as control group. The retention of ADSCs in ovaries was confirmed immediately or at 3, 7, 14 and 28 days after transplantation ( ITALIC! n = 9). Four weeks after transplantation, ovarian function was evaluated from estrous cycle, estradiol level, the follicle number, granulosa cell proliferation and a fertility test.

PARTICIPANTS/MATERIALS, SETTING, METHODS

To establish the POI model, rats were administered 60 mg TG/kg/day intragastrically for 50 days. The estrous cycles were assessed by vaginal smear. The concentration of plasma estradiol in diestrus stage was measured using a radioimmunoassay kit. Disordered estrous cycles and low serum estradiol levels indicated the successful establishment of the POI model. Four types of suspensions (PBS, collagen, ADSCs and collagen/ADSCs) were transplanted directly into the core of the ovaries. The short-term retention of ADSCs in ovaries was evaluated by small-animal positron emission tomography images immediately after transplantation of (18)F-Fluorodeoxyglucose ((18)F-FDG) labeled ADSCs. The long-term retention of ADSCs in ovaries was observed by immunohistochemistry after transplantation of green fluorescent protein (GFP)-labeled ADSCs. Serial sections of ovaries were prepared for histological analysis, follicle counting, and immunohistochemistry for Ki67 and Cleaved-Caspase-3. For the assessment of fertility, rats were mated with proven fertile male rats for 10 days.

MAIN RESULTS AND THE ROLE OF CHANCE

The (18)F-FDG signal decreased more slowly in ovaries injected with collagen/ADSCs than in ovaries with injected with ADSCs alone. Significantly more GFP-positive cells were observed in ovaries injected with collagen/GFP-ADSCs than in ovaries injected with GFP-ADSCs alone up to 14 days after the injection. However, in both groups very few GFP-positive cells were present at 4 weeks after transplantation. The collagen/ADSCs and ADSCs groups both showed better estrous cycle recovery than the PBS and collagen groups. The estradiol (E2) level in the collagen/ADSCs group was significantly increased compared with that of the PBS group ( ITALIC! P < 0.05). The number of antral follicles in the collagen/ADSCs group and the ADSCs group significantly increased compared with the PBS group ( ITALIC! P < 0.05). The granulosa cell proliferation in the collagen/ADSCs group was better than in the PBS group ( ITALIC! P < 0.01). The mating rates of the collagen/ADSCs group (88.9%) and the ADSCs group (90.9%) were higher than that of PBS group (60%, ITALIC! P < 0.05). The pregnancy rates of the collagen/ADSCs group (77.8%) and the ADSCs group (72.7%) were higher than the PBS group (50%, ITALIC! P < 0.05).

LIMITATIONS, REASONS FOR CAUTION

We chose ADSCs for their accessibility, convenience and safety. We did not use other cells or materials for POI treatments to show that the collagen/ADSCs are the most promising materials.

WIDER IMPLICATIONS OF THE FINDINGS

Soluble collagen scaffolds may be useful in stem cells transplantation therapy for POI.

STUDY FUNDING/COMPETING INTERESTS

This work is supported by grants from the 'Strategic Priority Research Program' of the Chinese Academy of Sciences (XDA01030000); Maternal-Fetal Medicine from Jiangsu Province Health Department of China (XK2011027); Clinical Center of Obstetric, Gynecologic and Genetic Diseases, Nanjing Health Department of Jiangsu Province, China; Fundamental Research Funds for the Central Universities (20620140652). The authors declare no competing financial interests.

TRIAL REGISTRATION NUMBER

Not applicable.

Adipose-derived stem cells for wound repair and regeneration

INTRODUCTION

The use of undifferentiated cells for cell-based tissue repair and regeneration strategies represents a promising approach for chronic wound healing. Multipotent adult stem cells isolated from adipose tissue, termed adipose-derived stem cells (ASCs), appear to be an ideal population of stem cells because they are autologous, non-immunogenic, plentiful, and easily obtained. Both preclinical and clinical studies have revealed that ASCs have potential for wound healing due to the mechanisms described below.

AREAS COVERED

Both in vitro and in vivo studies demonstrated that ASCs not only differentiate into keratinocytes, fibroblasts, and endothelial cells, as evidenced by their morphology, expression of cell surface markers, and gene expression, but also secrete several soluble factors, which positively contribute to wound healing in a paracrine manner. Clinical trials have been conducted using autologous ASCs with great success.

EXPERT OPINION

There remain many concerns regarding the use of ASCs, including how these cells act as precursors of keratinocytes, fibroblasts, and endothelial cells, or as a secretion vehicle of soluble factors. Further studies are necessary to establish the optimal strategy for the treatment of chronic wounds in patients with different disease backgrounds.

Chondrogenic potential of injectable κ-carrageenan hydrogel with encapsulated adipose stem cells for cartilage tissue-engineering applications

Due to the limited self-repair capacity of cartilage, regenerative medicine therapies for the treatment of cartilage defects must use a significant amount of cells, preferably applied using a hydrogel system that can promise their delivery and functionality at the specific site. This paper discusses the potential use of κ-carrageenan hydrogels for the delivery of stem cells obtained from adipose tissue in the treatment of cartilage tissue defects. The developed hydrogels were produced by an ionotropic gelation method and human adipose stem cells (hASCs) were encapsulated in 1.5% w/v κ-carrageenan solution at a cell density of 5 × 10(6) cells/ml. The results from the analysis of the cell-encapsulating hydrogels, cultured for up to 21 days, indicated that κ-carrageenan hydrogels support the viability, proliferation and chondrogenic differentiation of hASCs. Additionally, the mechanical analysis demonstrated an increase in stiffness and viscoelastic properties of κ-carrageenan gels with their encapsulated cells with increasing time in culture with chondrogenic medium. These results allowed the conclusion that κ-carrageenan exhibits properties that enable the in vitro functionality of encapsulated hASCs and thus may provide the basis for new successful approaches for the treatment of cartilage defects.

Obesity-Associated Hypermetabolism and Accelerated Senescence of Bone Marrow Stromal Stem Cells Suggest a Potential Mechanism for Bone Fragility

Obesity is associated with increased risk for fragility fractures. However, the cellular mechanisms are unknown. Using a translational approach combining RNA sequencing and cellular analyses, we investigated bone marrow stromal stem cells (BM-MSCs) of 54 men divided into lean, overweight, and obese groups on the basis of BMI. Compared with BM-MSCs obtained from lean, obese BM-MSCs exhibited a shift of molecular phenotype toward committed adipocytic progenitors and increased expression of metabolic genes involved in glycolytic and oxidoreductase activity. Interestingly, compared with paired samples of peripheral adipose tissue-derived stromal cells (AT-MSCs), insulin signaling of obese BM-MSCs was enhanced and accompanied by increased abundance of insulin receptor positive (IR+) and leptin receptor positive (LEPR+) cells in BM-MSC cultures. Their hyper-activated metabolic state was accompanied by an accelerated senescence phenotype. Our data provide a plausible explanation for the bone fragility in obesity caused by enhanced insulin signaling leading to accelerated metabolic senescence of BM-MSCs.

Controlling differentiation of adipose-derived stem cells using combinatorial graphene hybrid-pattern arrays

Control of stem cell fate by modulating biophysical cues (e.g., micropatterns, nanopatterns, elasticity and porosity of the substrates) has emerged as an attractive approach in stem cell-based research. Here, we report a method for fabricating combinatorial patterns of graphene oxide (GO) to effectively control the differentiation of human adipose-derived mesenchymal stem cells (hADMSCs). In particular, GO line patterns were highly effective for modulating the morphology of hADMSCs, resulting in enhanced differentiation of hADMSCs into osteoblasts. Moreover, by generating GO grid patterns, we demonstrate the highly efficient conversion of mesodermal stem cells to ectodermal neuronal cells (conversion efficiency = 30%), due to the ability of the grid patterns to mimic interconnected/elongated neuronal networks. This work provides an early demonstration of developing combinatorial graphene hybrid-pattern arrays for the control of stem cell differentiation, which can potentially lead to more effective stem cell-based treatment of incurable diseases/disorders.

Conductive Hydrogen Sulfide-Releasing Hydrogel Encapsulating ADSCs for Myocardial Infarction Treatment

Hydrogen sulfide (H₂S) exhibits extensive protective actions in cardiovascular systems, such as anti-inflammatory and stimulating angiogenesis, but its therapeutic potential is severely discounted by the short half-life and the poorly controlled releasing behavior. Herein, we developed a macromolecular H₂S prodrug by grafting 2-aminopyridine-5-thiocarboxamide (a small-molecule H₂S donor) on partially oxidized alginate (ALG-CHO) to mimic the slow and continuous release of endogenous H₂S. In addition, tetraaniline (a conductive oligomer) and adipose-derived stem cells (ADSCs) were introduced to form a stem cell-loaded conductive H₂S-releasing hydrogel through the Schiff base reaction between ALG-CHO and gelatin. The hydrogel exhibited adhesive property to ensure a stable anchoring to the wet and beating hearts. After myocardial injection, longer ADSCs retention period and elevated sulfide concentration in rat myocardium were demonstrated, accompanied by upregulation of cardiac-related mRNA (Cx43, α-SMA, and cTnT) and angiogenic factors (VEGFA and Ang-1) and downregulation of inflammatory factors (tumor necrosis factor-α). Echocardiography and histological analysis strongly demonstrated an increase in the ejection fraction value and smaller infarction size, suggesting a remarkable improvement of the cardiac functions of Sprague-Dawley rats. The ADSC-loaded conductive hydrogen sulfide-releasing hydrogel dramatically promoted the therapeutic effects, offering a promising therapeutic strategy for treating myocardial infarction.

Revisiting the Advances in Isolation, Characterization and Secretome of Adipose-Derived Stromal/Stem Cells

Adipose-derived stromal/stem cells (ASCs) seems to be a promising regenerative therapeutic agent due to the minimally invasive approach of their harvest and multi-lineage differentiation potential. The harvested adipose tissues are further digested to extract stromal vascular fraction (SVF), which is cultured, and the anchorage-dependent cells are isolated in order to characterize their stemness, surface markers, and multi-differentiation potential. The differentiation potential of ASCs is directed through manipulating culture medium composition with an introduction of growth factors to obtain the desired cell type. ASCs have been widely studied for its regenerative therapeutic solution to neurologic, skin, wound, muscle, bone, and other disorders. These therapeutic outcomes of ASCs are achieved possibly via autocrine and paracrine effects of their secretome comprising of cytokines, extracellular proteins and RNAs. Therefore, secretome-derivatives might offer huge advantages over cells through their synthesis and storage for long-term use. When considering the therapeutic significance and future prospects of ASCs, this review summarizes the recent developments made in harvesting, isolation, and characterization. Furthermore, this article also provides a deeper insight into secretome of ASCs mediating regenerative efficacy.

Adipose Tissue-Derived Stem Cells: Immunomodulatory Effects and Therapeutic Potential

Adipose-derived stem cells (ASCs) can self-renew and differentiate along multiple cell lineages. ASCs are also potently anti-inflammatory due to their inherent ability to regulate the immune system by secreting anti-inflammatory cytokines and growth factors that play a crucial role in the pathology of many diseases, including multiple sclerosis, diabetes mellitus, Crohn's, SLE, and graft-versus-host disease. The immunomodulatory effects and mechanisms of action of ASCs on pathological conditions are reviewed here.

Regenerative treatment of male stress urinary incontinence by periurethral injection of autologous adipose-derived regenerative cells: 1-year outcomes in 11 patients

OBJECTIVES

To assess the efficacy and safety of a novel cell therapy for male stress urinary incontinence consisting of periurethral injection of autologous adipose-derived regenerative cells, and to determine the 1-year outcomes.

METHODS

A total of 11 male patients with persistent stress urinary incontinence after prostate surgery were included in the study. The Celution system was used to isolate adipose-derived regenerative cells from abdominal adipose tissue obtained by liposuction. Subsequently, these regenerative cells, and a mixture of regenerative cells and adipose tissue were transurethrally injected into the rhabdosphincter and submucosal space of the urethra, respectively. The 1-year outcomes were assessed using a 24-h pad test, a validated patient questionnaire, urethral pressure profile, transrectal ultrasonography and magnetic resonance imaging.

RESULTS

Stress urinary incontinence improved progressively in eight patients during the 1-year follow up, as determined by a 59.8% decrease in the leakage volume in the 24-h pad test, decreased frequency and amount of incontinence, and improved quality of life. One patient achieved total continence. The mean maximum urethral closing pressure and functional profile length increased from 35.5 to 44.7 cmH₂O, and from 20.4 to 26.0 mm, respectively. Magnetic resonance imaging showed the sustained presence of the injected adipose tissue, and enhanced ultrasonography showed a progressive increase in blood flow to the injected area in all patients. No significant adverse events were observed peri- or postoperatively.

CONCLUSION

Periurethral injection of autologous adipose-derived regenerative cells might represent a safe and feasible treatment modality for male stress urinary incontinence.

Mesenchymal Stem Cells Empowering Tendon Regenerative Therapies

Tendon tissues have limited healing capacity. The incidence of tendon injuries and the unsatisfactory functional outcomes of tendon repair are driving the search for alternative therapeutic approaches envisioning tendon regeneration. Cellular therapies aim at delivering adequate, regeneration-competent cell types to the injured tendon and toward ultimately promoting its reconstruction and recovery of functionality. Mesenchymal stem cells (MSCs) either obtained from tendons or from non-tendon sources, like bone marrow (BM-MSCs) or adipose tissue (ASCs), have been receiving increasing attention over the years toward enhancing tendon healing. Evidences from in vitro and in vivo studies suggest MSCs can contribute to accelerate and improve the quality of tendon healing. Nonetheless, the exact mechanisms underlying these repair events are yet to be fully elucidated. This review provides an overview of the main challenges in the field of cell-based regenerative therapies, discussing the role of MSCs in boosting tendon regeneration, particularly through their capacity to enhance the tenogenic properties of tendon resident cells.