Human mesenchymal stem cell grafts enhance normal and impaired wound healing by recruiting existing endogenous tissue stem/progenitor cells

Clinical updates in mesenchymal stromal cell therapy for osteoarthritis treatment

INTRODUCTION

Osteoarthritis (OA) is a common chronic musculoskeletal disease with heterogeneous clinical manifestations and variable responses to different treatments. Unfortunately, there is no effective disease modifying therapy at present that can alter the natural course of the disease. Cell therapy based on mesenchymal stromal cells (MSCs) may offer an attractive therapeutic option for OA with their multiple modes of action, particularly immune-regulatory and regenerative capacities.

AREAS COVERED

In this narrative review, updates on mode of action based on patient's data, factors that can influence the efficacy of MSC treatment, current status in clinical application of MSCs as seen from randomized, controlled OA trials are introduced as well as the author's perspectives in the future of MSCs as OA therapeutics.

EXPERT OPINION

Symptomatic relief is not sufficient to justify the high cost associated with culture-expanded stem cells. Its advantages and efficacy over simple and low risk/cost modalities should be seriously reevaluated. Also, as the short-term strategy, efforts should be made to lower the cost of MSC therapy. In the future, multiomics technology may help to predict that subgroup of patients who will favorably respond to stem cell treatment, which would enhance the cost effectiveness and therapeutic benefit of MSC therapy.

Efficient Treatment of Psoriasis Using Conditioned Media from Mesenchymal Stem Cell Spheroids Cultured to Produce Transforming Growth Factor-β1-Enriched Small-Sized Extracellular Vesicles

Psoriasis is a common chronic inflammatory disease in which keratinocytes proliferate abnormally due to excessive immune action. Psoriasis can be associated with various comorbidities and has a significant impact on health-related quality of life. Although many systemic treatments, including biologic agents, have been developed, topical treatment remains the main option for psoriasis management. Consequently, there is an urgent need to develop topical treatments with minimal side effects and high efficacy. Mesenchymal stem cells (MSCs) exhibit excellent immune regulation, anti-inflammatory activities, and therapeutic effects, and MSC-derived extracellular vesicles (EVs) can serve as crucial mediators of functional transfer from MSCs. Therefore, this study aimed to develop a safe and easy-to-use emulsion cream for treating psoriasis using MSC conditioned media (CM) containing EVs. We developed an enhanced Wharton's jelly MSC (WJ-MSC) culture method through a three-dimensional (3D) culture containing exogenous transforming growth factor-β3. Using the 3D culture system, we obtained CM from WJ-MSCs, which yielded a higher EV production compared to that of conventional WJ-MSC culture methods, and investigated the effect of EV-enriched 3D-WJ-MSC-CM cream on psoriasis-related inflammation. Administration of the EV-enriched 3D-WJ-MSC-CM cream significantly reduced erythema, thickness, and scaling of skin lesions, alleviated imiquimod-induced psoriasiform lesions in mice, and ameliorated histopathological changes in mouse skin. The upregulated mRNA expression of inflammatory cytokines, including IL-17a, IL-22, IL-23, and IL-36, decreased in the lesions. In conclusion, we present here a new topical treatment for psoriasis using an MSC EV-enriched cream.

An Injectable Hydrogel Loaded with GMSCs-Derived Neural Lineage Cells Promotes Recovery after Stroke

Ischemic stroke is a devastating medical condition with poor prognosis due to the lack of effective treatment modalities. Transplantation of human neural stem cells or primary neural cells is a promising treatment approach, but this is hindered by limited suitable cell sources and low in vitro expansion capacity. This study aimed (1) use small molecules (SM) to reprogram gingival mesenchymal stem cells (GMSCs) commitment to the neural lineage cells in vitro, and (2) use hyaluronic acid (HA) hydrogel scaffolds seeded with GMSCs-derived neural lineage cells to treat ischemic stroke in vivo. Neural induction was carried out with a SM cocktail-based one-step culture protocol over a period of 24 h. The induced cells were analyzed for expression of neural markers with immunocytochemistry and quantitative real-time polymerase chain reaction (qRT-PCR). The Sprague-Dawley (SD) rats (n = 100) were subjected to the middle cerebral artery occlusion (MCAO) reperfusion ischemic stroke model. Then, after 8 days post-MCAO, the modeled rats were randomly assigned to six study groups (n = 12 per group): (1) GMSCs, (2) GMSCs-derived neural lineage cells, (3) HA and GMSCs-derived neural lineage cells, (4) HA, (5) PBS, and (6) sham transplantation control, and received their respective transplantation. Evaluation of post-stroke recovery were performed by behavioral tests and histological assessments. The morphologically altered nature of neural lineages has been observed of the GMSCs treated with SMs compared to the untreated controls. As shown by the qRT-PCR and immunocytochemistry, SMs further significantly enhanced the expression level of neural markers of GMSCs as compared with the untreated controls (all p < 0.05). Intracerebral injection of self-assembling HA hydrogel carrying GMSCs-derived neural lineage cells promoted the recovery of neural function and reduced ischemic damage in rats with ischemic stroke, as demonstrated by histological examination and behavioral assessments (all p < 0.05). In conclusion, the SM cocktail significantly enhanced the differentiation of GMSCs into neural lineage cells. The HA hydrogel was found to facilitate the proliferation and differentiation of GMSCs-derived neural lineage cells. Furthermore, HA hydrogel seeded with GMSCs-derived neural lineage cells could promote tissue repair and functional recovery in rats with ischemic stroke and may be a promising alternative treatment modality for stroke.

Senescence in Adipose-Derived Stem Cells: Biological Mechanisms and Therapeutic Challenges

Adipose tissue-derived stem cells (ADSCs) represent a subset of the mesenchymal stem cells in every adipose compartment throughout the body. ADSCs can differentiate into various cell types, including chondrocytes, osteocytes, myocytes, and adipocytes. Moreover, they exhibit a notable potential to differentiate in vitro into cells from other germinal lineages, including endothelial cells and neurons. ADSCs have a wide range of clinical applications, from breast surgery to chronic wounds. Furthermore, they are a promising cell population for future tissue-engineering uses. Accumulating evidence indicates a decreased proliferation and differentiation potential of ADSCs with an increasing age, increasing body mass index, diabetes mellitus, metabolic syndrome, or exposure to radiotherapy. Therefore, the recent literature thoroughly investigates this cell population's senescence mechanisms and how they can hinder its possible therapeutic applications. This review will discuss the biological mechanisms and the physio-pathological causes behind ADSC senescence and how they can impact cellular functionality. Moreover, we will examine the possible strategies to invert these processes, re-establishing the full regenerative potential of this progenitor population.

Results of the Phase 1 Open-Label Safety Study of Umbilical Cord Lining Mesenchymal Stromal/Stem Cells (Corlicyte®) to Heal Chronic Diabetic Foot Ulcers

BACKGROUND

Mesenchymal stromal/stem cells (MSCs) play a critical role in wound healing. Corlicyte® is an MSC product derived from allogeneic umbilical cord tissue donated under an institutional review board-approved protocol and processed in accordance with section 501(a)(2)(B) of the Federal Food, Drug, and Cosmetic Act. This open-label phase 1 trial was performed under a United States Food and Drug Administration Investigational New Drug Application to establish the safety and tolerability of Corlicyte® in patients with diabetes and chronic diabetic foot ulcer (DFU).

METHODS

Escalating doses were applied topically twice a week for up to 8 weeks after ulcer debridement, wound photography, and measurement. Subjects were followed for 4 weeks after the treatment phase. Adverse events were assessed at every visit.

RESULTS

Nine subjects in 2 dosing cohorts completed the trial. No subjects experienced a serious adverse reaction to Corlicyte® or the development of anti-human leukocyte antigen (HLA) antibodies. Sixty percentage of subjects in the lower dose cohort experienced ulcer closure by Day 70 of follow-up, while the mean ulcer size was reduced by 54-67% in the other subjects.

CONCLUSIONS

Topical administration of Corlicyte®, a novel biologic therapy consisting of allogeneic umbilical cord lining MSCs, appeared safe and tolerable and resulted in a significant decrease in ulcer area, demonstrating its potential as a therapy for healing of chronic DFU.

Culture-expanded mesenchymal stromal cell therapy: does it work in knee osteoarthritis? A pathway to clinical success

Osteoarthritis (OA) is a degenerative multifactorial disease with concomitant structural, inflammatory, and metabolic changes that fluctuate in a temporal and patient-specific manner. This complexity has contributed to refractory responses to various treatments. MSCs have shown promise as multimodal therapeutics in mitigating OA symptoms and disease progression. Here, we evaluated 15 randomized controlled clinical trials (RCTs) and 11 nonrandomized RCTs using culture-expanded MSCs in the treatment of knee OA, and we found net positive effects of MSCs on mitigating pain and symptoms (improving function in 12/15 RCTs relative to baseline and in 11/15 RCTs relative to control groups at study endpoints) and on cartilage protection and/or repair (18/21 clinical studies). We examined MSC dose, tissue of origin, and autologous vs. allogeneic origins as well as patient clinical phenotype, endotype, age, sex and level of OA severity as key parameters in parsing MSC clinical effectiveness. The relatively small sample size of 610 patients limited the drawing of definitive conclusions. Nonetheless, we noted trends toward moderate to higher doses of MSCs in select OA patient clinical phenotypes mitigating pain and leading to structural improvements or cartilage preservation. Evidence from preclinical studies is supportive of MSC anti-inflammatory and immunomodulatory effects, but additional investigations on immunomodulatory, chondroprotective and other clinical mechanisms of action are needed. We hypothesize that MSC basal immunomodulatory "fitness" correlates with OA treatment efficacy, but this hypothesis needs to be validated in future studies. We conclude with a roadmap articulating the need to match an OA patient subset defined by molecular endotype and clinical phenotype with basally immunomodulatory "fit" or engineered-to-be-fit-for-OA MSCs in well-designed, data-intensive clinical trials to advance the field.

In situ photo-crosslinking silk fibroin based hydrogel accelerates diabetic wound healing through antibacterial and antioxidant

Bacterial infection and excessive reactive oxygen species (ROS) in diabetic wounds lead to a prolonged inflammatory phase, and injuries are highly susceptible to developing into chronic wounds. Improving the poor microenvironment is vital to achieving effective diabetic wound healing. In this work, methacrylated silk fibroin (SFMA) was combined with ε-polylysine (EPL) and manganese dioxide nanoparticles (BMNPs) to form an SF@(EPL-BM) hydrogel with in situ forming, antibacterial and antioxidant properties. EPL imparted high antibacterial activity (>96 %) to the hydrogel. BMNPs and EPL showed good scavenging activity against a variety of free radicals. SF@(EPL-BM) hydrogel had low cytotoxicity and could alleviate H₂O₂-induced oxidative stress in L929 cells. In diabetic wounds infected with Staphylococcus aureus (S. aureus), the SF@(EPL-BM) hydrogel exhibited better antibacterial properties and reduced wound ROS levels more significantly than that of the control in vivo. In this process, the pro-inflammatory factor TNF-α was down-regulated, and the vascularization marker CD31 was up-regulated. H&E and Masson staining showed a rapid transition from the inflammatory to the proliferative phase of the wounds, with significant new tissue and collagen deposition. These results confirm that this multifunctional hydrogel dressing holds well potential for chronic wound healing.

A multifunctional sateen woven dressings for treatment of skin injuries

Cutaneous wounds with impaired healing such as diabetic ulcers and burns constitute major and rapidly growing threat to healthcare systems worldwide. Accelerating wound healing requires the delivery of biological factors that induce angiogenesis, support cellular proliferation, and modulate inflammation while minimizing infection. In this study, we engineered a dressing made by weaving of composite fibers (CFs) carrying mesenchymal stem cells (MSCs) and a model antibiotic using a scalable sateen textile technique. In this regard, two different sets of CFs carrying MSCs or an antimicrobial agent were used to generate a multifunctional dressing. According to cell viability and metabolic activity as CCK-8 and live/dead with qRT-PCR results, more than %90 the encapsulated MSCs remain viable for 28 days and their expression levels of the wound repair factors including ECM remodeling, angiogenesis and immunomodulatory maintained in MSCs post dressing manufacturing for 14 days. Post 10 days culture of the dressing, MSCs within CFs had 10-fold higher collagen synthesis (p < 0.0001) determined by hydroxyproline assay which indicates the enhanced healing properties. According to in vitro antimicrobial activity results determined by disk diffusion and broth microdilution tests, the first day and the total amount of release gentamicin loaded dressing samples during the 28 days were higher than determined minimal inhibition concentration (MIC) values for S. aureus and K. pneumonia without negatively impacting the viability and functionality of encapsulated MSCs within the dressing. The dressing is also flexible and can conform to skin curvatures making the dressing suitable for the treatment of different skin injuries such as burns and diabetic ulcers.

MicroRNA-139-5p mediates BMSCs impairment in diabetes by targeting HOXA9/c-Fos

The properties and functions of BMSCs were altered by the diabetic microenvironment, and its mechanism was not very clear. In recent years, the regulation of the function of BMSCs by microRNA has become a research hotspot, meanwhile, HOX genes also have been focused on and involved in multiple functions of stem cells. In this study, we investigated the role of miR-139-5p in diabetes-induced BMSC impairment. Since HOXA9 may be a target gene of miR-139-5p, we speculated that miR-139-5p/HOXA9 might be involved in regulating the biological characteristics and the function of BMSCs in diabetes. We demonstrated that the miR-139-5p expression was increased in BMSCs derived from STZ-induced diabetic rats. MiR-139-5p mimics were able to inhibit cell proliferation, and migration and promoted senescence and apoptosis in vitro. MiR-139-5p induced the down-regulated expression of HOXA9 and c-Fos in BMSCs derived from normal rats. Moreover, miR-139-5p inhibitors reversed the tendency in diabetic-derived BMSCs. Further, gain-and-loss function experiments indicated that miR-139-5p regulated the functions of BMSCs by targeting HOXA9 and c-Fos. In vivo wound model experiments showed that the downregulation of miR-139-5p further promoted the epithelialization and angiogenesis of diabetic BMSC-mediated skin. In conclusion, induction of miR-139-5p upregulation mediated the impairment of BMSCs through the HOXA9/c-Fos pathway in diabetic rats. Therefore, miR-139-5p/HOXA9 might be an important therapeutic target in treating diabetic BMSCs and diabetic complications in the future.

Oxidative Stress Response in Adipose Tissue-Derived Mesenchymal Stem/Stromal Cells

Reactive oxygen species (ROS) can irreversibly damage biological molecules, a process known as oxidative stress. Elevated ROS levels are associated with immune cell activation. Sustained immune system activation can affect many different cells in the environment. One cell type that has been detected in almost all tissues of the body is mesenchymal stem/stromal cells (MSC). MSC possess proliferation and differentiation potential, thus facilitating regeneration processes. However, the regenerative capacity of MSC might be impaired by oxidative stress, and the effects of long-term oxidative stress on MSC functions are sparsely described. The examination of oxidative stress is often performed by exposure to H2O2. Since H2O2 is rapidly degraded, we additionally exposed the cell cultures to glucose oxidase (GOx), resulting in sustained exposure to H2O2. Using these model systems, we have focused on the effects of short- and long-term oxidative stress on viability, migration, differentiation, and signaling. All cellular functions examined were affected by the applied oxidative stress. The differences that occur between pulsed and sustained oxidative stress indicated higher oxidative stress in MSC upon direct H2O2 exposure, whereas the GOx-induced prolonged exposure to H2O2 seems to allow for better cellular adaptation. The mechanisms underlying these different responses are currently unknown.

Applications of human amniotic fluid stem cells in wound healing

ABSTRACT

Complete wound regeneration preserves skin structure and physiological functions, including sensation and perception of stimuli, whereas incomplete wound regeneration results in fibrosis and scarring. Amniotic fluid stem cells (AFSCs) would be a kind of cell population with self-renewing and non-immunogenic ability that have a considerable role in wound generation. They are easy to harvest, culture, and store; moreover, they are non-tumorigenic and not subject to ethical restrictions. They can differentiate into different kinds of cells that replenish the skin, subcutaneous tissues, and accessory organs. Additionally, AFSCs independently produce paracrine effectors and secrete them in exosomes, thereby modulating local immune cell activity. They demonstrate anti-inflammatory and immunomodulatory properties, regulate the physicochemical microenvironment of the wound, and promote full wound regeneration. Thus, AFSCs are potential resources in stem cell therapy, especially in scar-free wound healing. This review describes the biological characteristics and clinical applications of AFSCs in treating wounds and provide new ideas for the treatment of wound healing.

Adipose-derived mesenchymal stem cells and wound healing: Potential clinical applications in wound repair

Delayed and chronic wounds result from the dysregulation of molecular and cellular events associated with wound healing, including migration, inflammation, angiogenesis, extracellular matrix (ECM) remodeling, and re-epithelialization. Adipose tissue is an abundant, easily accessible, and rich source of mesenchymal stem cells (MSCs) with high therapeutic potential. In addition to their capability to differentiate into various lineages with specialized functions, adipose-derived MSCs (AMSCs) can mediate to the wound repair process through the secretion of different growth factors and mediators rather than making structural contribution alone. Adipose-derived MSCs mediate the formation of blood vessels, recruit progenitor cells, stimulate cell differentiation and ECM formation, and promote wound healing by releasing immune mediators and exosomes. Herein, we discuss and review the therapeutic potential of AMSCs for wound repair via acceleration of wound closure, re-epithelialization, enhancement of angiogenesis and immunomodulation of prolonged inflammatory responses, as well as the current challenges in clinical implementation.

Measuring human mesenchymal stem cell remodeling in hydrogels with a step-change in elastic modulus

Human mesenchymal stem cells (hMSCs) are instrumental in the wound healing process. They migrate to wounds from their native niche in response to chemical signals released during the inflammatory phase of healing. At the wound, hMSCs downregulate inflammation and regulate tissue regeneration. Delivering additional hMSCs to wounds using cell-laden implantable hydrogels has the potential to improve healing outcomes and restart healing in chronic wounds. For these materials to be effective, cells must migrate from the scaffold into the native tissue. This requires cells to traverse a step-change in material properties at the implant-tissue interface. Migration of cells in material with highly varying properties is not well characterized. We measure 3D encapsulated hMSC migration and remodeling in a well-characterized hydrogel with a step-change in stiffness. This cell-degradable hydrogel is composed of 4-arm poly(ethylene glycol)-norbornene cross-linked with an enzymatically-degradable peptide. The scaffold is made with two halves of different stiffnesses separated by an interface where stiffness changes rapidly. We characterize changes in structure and rheology of the pericellular region using multiple particle tracking microrheology (MPT). MPT measures Brownian motion of embedded particles and relates it to material rheology. We measure more remodeling in the soft region of the hydrogel than the stiff region on day 1 post-encapsulation and similar remodeling everywhere on day 6. In the interface region, we measure hMSC-mediated remodeling along the interface and migration towards the stiff side of the scaffold. These results can improve materials designed for cell delivery from implants to a wound to enhance healing.

Stem Cell-Based Therapeutic Strategies in Diabetic Wound Healing

Impaired wound healing and especially the “all-too-common” occurrence of associated diabetic foot ulcers (DFU) are becoming an increasingly urgent and deteriorating healthcare issue, which drastically impact the quality of life and further heighten the risks of infection and amputation in patients with diabetes mellitus. Amongst the multifactorial wound healing determinants, glycemic dysregulation has been identified to be the primary casual factor of poor wound healing. Unfortunately, current therapeutic modalities merely serve as moderate symptomatic relieves but often fail to completely restore the wound site to its pre-injury state and prevent further recurrence. Stem cell-based therapeutics have been employed for its promising potential to address the root of the problem as they not only exhibit the capacity for self-renewal and differentiation towards multiple lineages, but also have been disclosed to participate in mediating variant growth factors and cytokines. Herein we review the current literatures on the therapeutic benefits of using various kinds of stem cells, including embryonic stem cells (ESCs), induced pluripotent stem cells (iPSCs), mesenchymal stem cells (MSCs), and adipose-derived stem cells (ASCs) in diabetic wound healing by searching on the PubMed® Database for publications. This study shall serve as an overview of the current body of research with particular focus on autologous ASCs and the laboratory expandable iPSCs in hope of shedding more light on this attractive therapy so as to elevate the efficacy of wound healing that is almost always compromised in diabetic patients.

Superior therapeutic activity of TGF-β-induced extracellular vesicles against interstitial cystitis

Interstitial cystitis/bladder pain syndrome (IC/BPS) is a chronic disease characterized by incapacitating pelvic pain. Mesenchymal stem cell-derived extracellular vesicles (MSC-EVs) are considered key mediators of the paracrine action of MSCs and show better biological activities than the parent MSCs, especially in the bladder tissue, which may be unfavorable for MSC survival. Here, we produced MSC-EVs using advanced three-dimensional (a3D) culture with exogenous transforming growth factor-β3 (TGF-β3) (T-a3D-EVs). Treatment with T-a3D-EVs led to significantly enhanced wound healing and anti-inflammatory capacities. Moreover, submucosal layer injection of T-a3D-EVs in chronic IC/BPS animal model resulted in restoration of bladder function, superior anti-inflammatory activity, and recovery of damaged urothelium compared to MSCs. Interestingly, we detected increased TGF-β1 level in T-a3D-EVs, which might be involved in the anti-inflammatory activity of these EVs. Taken together, we demonstrate the excellent immune-modulatory and regenerative abilities of T-a3D-EVs as observed by recovery from urothelial denudation and dysfunction, which could be a promising therapeutic strategy for IC/BPS.

Application of Electrospun Nanofiber Membrane in the Treatment of Diabetic Wounds

Diabetic wounds are complications of diabetes which are caused by skin dystrophy because of local ischemia and hypoxia. Diabetes causes wounds in a pathological state of inflammation, resulting in delayed wound healing. The structure of electrospun nanofibers is similar to that of the extracellular matrix (ECM), which is conducive to the attachment, growth, and migration of fibroblasts, thus favoring the formation of new skin tissue at the wound. The composition and size of electrospun nanofiber membranes can be easily adjusted, and the controlled release of loaded drugs can be realized by regulating the fiber structure. The porous structure of the fiber membrane is beneficial to gas exchange and exudate absorption at the wound, and the fiber surface can be easily modified to give it function. Electrospun fibers can be used as wound dressing and have great application potential in the treatment of diabetic wounds. In this study, the applications of polymer electrospun fibers, nanoparticle-loaded electrospun fibers, drug-loaded electrospun fibers, and cell-loaded electrospun fibers, in the treatment of diabetic wounds were reviewed, and provide new ideas for the effective treatment of diabetic wounds.

Adipose-Derived Stromal Cells Seeded in Pullulan-Collagen Hydrogels Improve Healing in Murine Burns

Burn scars and scar contractures cause significant morbidity for patients. Recently, cell-based therapies have been proposed as an option for improving healing and reducing scarring after burn injury, through their known proangiogenic and immunomodulatory paracrine effects. Our laboratory has developed a pullulan-collagen hydrogel that, when seeded with mesenchymal stem cells (MSCs), improves cell viability and augments their proangiogenic capacity in vivo. Concurrently, recent research suggests that prospective isolation of cell subpopulations with desirable transcriptional profiles can be used to further improve cell-based therapies. In this study, we examined whether adipose-derived stem cell (ASC)-seeded hydrogels could improve wound healing following thermal injury using a murine contact burn model. Partial thickness contact burns were created on the dorsum of mice. On days 5 and 10 following injury, burns were debrided and received either ASC hydrogel, ASC injection alone, hydrogel alone, or no treatment. On days 10 and 25, burns were harvested for histologic and molecular analysis. This experiment was repeated using CD26⁺/CD55⁺ FACS-enriched ASCs to further evaluate the regenerative potential of ASCs in wound healing. ASC hydrogel-treated burns demonstrated accelerated time to reepithelialization, greater vascularity, and increased expression of the proangiogenic genes MCP-1, VEGF, and SDF-1 at both the mRNA and protein level. Expression of the profibrotic gene Timp1 and proinflammatory gene Tnfa was downregulated in ASC hydrogel-treated burns. ASC hydrogel-treated burns exhibited reduced scar area compared to hydrogel-treated and control wounds, with equivalent scar density. CD26⁺/CD55⁺ ASC hydrogel treatment resulted in accelerated healing, increased dermal appendage count, and improved scar quality with a more reticular collagen pattern. Here we find that ASC hydrogel therapy is effective for treating burns, with demonstrated proangiogenic, fibromodulatory, and immunomodulatory effects. Enrichment for CD26⁺/CD55⁺ ASCs has additive benefits for tissue architecture and collagen remodeling postburn injury. Research is ongoing to further facilitate clinical translation of this promising therapeutic approach. Impact statement Burns remain a significant public health burden. Stem cell therapy has gained attention as a promising approach for treating burns. We have developed a pullulan-collagen biomimetic hydrogel scaffold that can be seeded with adipose-derived stem cells (ASCs). We assessed the delivery and activity of our scaffold in a murine contact burn model. Our results suggest that localized delivery of ASC hydrogel treatment is a promising approach for the treatment of burn wounds, with the potential for rapid clinical translation. We believe our work will have broad implications for both hydrogel therapeutics and regenerative medicine and will be of interest to the general scientific community.

Adeno-Associated Virus-Mediated Overexpression of Interleukin-10 Affects the Immunomodulatory Properties of Equine Bone Marrow-Derived Mesenchymal Stem Cells

Joint injury can cause posttraumatic inflammation, which if severe enough can lead to posttraumatic osteoarthritis (PTOA), a progressive and debilitating condition. Posttraumatic inflammation is characterized by an influx of T lymphocytes and upregulation of inflammatory cytokines and degradative enzymes by activated chondrocytes and synoviocytes. Intra-articular bone marrow-derived mesenchymal stem cell (BM-MSC) injection for the treatment of osteoarthritis (OA) has been of interest due to the immunomodulatory properties of these cells. Interleukin (IL)-10, a potent immunomodulatory cytokine, has also been investigated as an OA therapeutic. Therefore, the objective of this study was to evaluate the combinatorial effects of BM-MSCs and IL-10 in OA using a gene therapy approach. We hypothesized that BM-MSCs overexpressing IL-10 would have superior immunomodulatory effects leading to increased suppression of T cell proliferation and decreased production of proinflammatory cytokines, providing protection of the extracellular matrix (ECM) in a stimulated, co-culture OA model. Treatment groups included the following: untransduced BM-MSC, adeno-associated virus (AAV)-IL10-transduced BM-MSC, and AAV-null transduced BM-MSC, which were unstimulated or stimulated with IL-1β/tumor necrosis factor-α (TNF-α). T cell proliferation was significantly decreased by the presence of BM-MSCs, especially when these BM-MSCs were AAV transduced. There was no significant difference in T cell suppression when cells were cultured with AAV-IL10-transduced or AAV-null transduced BM-MSCs. AAV transduction itself was associated with decreased synthesis of IL-1β, IL-6, and TNF-α. Expression of IL-1β and MMP13 was downregulated in AAV-transduced BM-MSCs and MMP13 expression was downregulated in cartilage explants co-cultured with AAV-transduced BM-MSCs. Despite mitigation of some proinflammatory cascades, rescue of ECM loss, as determined by glycosaminoglycan quantification and histological evaluation, did not occur in either AAV-IL10-transduced or AAV-null transduced co-cultures. Although IL-10 overexpression may enhance BM-MSC-mediated T cell suppression, we did not observe significant modulation of inflammation-driven cartilage degradation in cultures containing AAV-IL10-transduced BM-MSCs. AAV transduction itself does appear to affect paracrine signaling by BM-MSCs, which warrants further investigation.

Mesenchymal stem cell-inspired microgel scaffolds to control macrophage polarization

There is a desire in regenerative medicine to create biofunctional materials that can control and direct cell function in a precise manner. One particular stem cell of interest, human mesenchymal stem cells (hMSCs), can function as regulators of the immunogenic response and aid in tissue regeneration and wound repair. Here, a porous hydrogel scaffold assembled from microgel subunits was used to recapitulate part of this immunomodulatory behavior. The scaffolds were used to culture a macrophage cell line, while cytokines were delivered exogenously to polarize the macrophages to either a pro-inflammatory (M1) or alternatively activated (M2a) phenotypes. Using a cytokine array, interleukin 10 (IL-10) was identified as one key anti-inflammatory factor secreted by hMSCs in pro-inflammatory conditions; it was elevated (125 ± 25 pg/ml) in pro-inflammatory conditions compared to standard medium (6 ± 10 pg/ml). The ability of hMSC laden scaffolds to reverse the M1 phenotype was then examined, even in the presence of exogenous pro-inflammatory cytokines. Co-culture of M1 and M2 macrophages with hMSCs reduced the secretion of TNFα, a pro-inflammatory cytokine even in the presence of pro-inflammatory stimulatory factors. Next, IL-10 was supplemented in the medium or tethered directly to the microgel subunits; both methods limited the secretion of pro-inflammatory cytokines of encapsulated macrophages even in pro-inflammatory conditions. Cumulatively, these results reveal the potential of biofunctional microgel-based scaffolds as acellular therapies to present anti-inflammatory cytokines and control the immunogenic cascade.

Development of Cutaneous Wound in Diabetic Immunocompromised Mice and Use of Dental Pulp-Derived Stem Cell Product for Healing

Chronic nonhealing wounds impact nearly 15% of Medicare beneficiaries (8.2 million) in the United States costing $28-$32 billion annually. Despite advancement in wound management, approximately 8% of diabetic Medicare beneficiaries have a foot ulcer and 1.8% will have an amputation. The development of a regenerative approach is warranted to save these before-mentioned amputations. To this extent, herein, we describe the detailed methods in generating a type 1 diabetes mellitus (T1DM) condition in immunocompromised mice, inducing cutaneous wound, and application of dental pulp stem cell-derived secretory products for therapeutic assessment. This model helps in evaluating the efficacy of stem cell-based therapy and helps with the investigation of involved mechanisms in impaired cutaneous wound healing caused by hyperglycemic stress due to type 1 diabetes.

Mesenchymal Stromal Cells in Viral Infections: Implications for COVID-19

Mesenchymal stromal cells (MSCs) constitute a heterogeneous population of stromal cells with immunomodulatory and regenerative properties that support their therapeutic use. MSCs isolated from many tissue sources replicate vigorously in vitro and maintain their main biological properties allowing their widespread clinical application. To date, most MSC-based preclinical and clinical trials targeted immune-mediated and inflammatory diseases. Nevertheless, MSCs have antiviral properties and have been used in the treatment of various viral infections in the last years. Here, we revised in detail the biological properties of MSCs and their preclinical and clinical applications in viral diseases, including the disease caused by the severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) infection (COVID-19). Notably, rapidly increasing numbers of MSC-based therapies for COVID-19 have recently been reported. MSCs are theoretically capable of reducing inflammation and promote lung regeneration in severe COVID-19 patients. We critically discuss the rationale, advantages and disadvantages of MSC-based therapies for viral infections and also specifically for COVID-19 and point out some directions in this field. Finally, we argue that MSC-based therapy may be a promising therapeutic strategy for severe COVID-19 and other emergent respiratory tract viral infections, beyond the viral infection diseases in which MSCs have already been clinically applied.

Comparative Proteomic Analysis of the Mesenchymal Stem Cells Secretome from Adipose, Bone Marrow, Placenta and Wharton's Jelly

Mesenchymal stem cells (MSCs) have the potential to be a viable therapy against various diseases due to their paracrine effects, such as secretion of immunomodulatory, trophic and protective factors. These cells are known to be distributed within various organs and tissues. Although they possess the same characteristics, MSCs from different sources are believed to have different secretion potentials and patterns, which may influence their therapeutic effects in disease environments. We characterized the protein secretome of adipose (AD), bone marrow (BM), placenta (PL), and Wharton’s jelly (WJ)-derived human MSCs by using conditioned media and analyzing the secretome by mass spectrometry and follow-up bioinformatics. Each MSC secretome profile had distinct characteristics depending on the source. However, the functional analyses of the secretome from different sources showed that they share similar characteristics, such as cell migration and negative regulation of programmed cell death, even though differences in the composition of the secretome exist. This study shows that the secretome of fetal-derived MSCs, such as PL and WJ, had a more diverse composition than that of AD and BM-derived MSCs, and it was assumed that their therapeutic potential was greater because of these properties.

Cranial Suture Regeneration Mitigates Skull and Neurocognitive Defects in Craniosynostosis

Craniosynostosis results from premature fusion of the cranial suture(s), which contain mesenchymal stem cells (MSCs) that are crucial for calvarial expansion in coordination with brain growth. Infants with craniosynostosis have skull dysmorphology, increased intracranial pressure, and complications such as neurocognitive impairment that compromise quality of life. Animal models recapitulating these phenotypes are lacking, hampering development of urgently needed innovative therapies. Here, we show that Twist1+/- mice with craniosynostosis have increased intracranial pressure and neurocognitive behavioral abnormalities, recapitulating features of human Saethre-Chotzen syndrome. Using a biodegradable material combined with MSCs, we successfully regenerated a functional cranial suture that corrects skull deformity, normalizes intracranial pressure, and rescues neurocognitive behavior deficits. The regenerated suture creates a niche into which endogenous MSCs migrated, sustaining calvarial bone homeostasis and repair. MSC-based cranial suture regeneration offers a paradigm shift in treatment to reverse skull and neurocognitive abnormalities in this devastating disease.

Cryogel/hydrogel biomaterials and acupuncture combined to promote diabetic skin wound healing through immunomodulation

Unhealed chronic wounds often deteriorate into multiple infection with several kinds of bacteria and excessive proteolytic wound exudate and remains one of the common healthcare issues. Here, the functional and antimicrobial hydrogel and cryogel biomaterials were prepared from glycol chitosan and a novel biodegradable Schiff base crosslinker difunctional polyurethane (DF-PU). The cryogel exhibited ~2730 ± 400% of water absorption with abundant macropores and 86.5 ± 1.6% of porosity formed by ice crystal as well as ~240% cell proliferation effect; while the hydrogel demonstrated considerable antimicrobial activity and biodegradability. As an optimized procedure to treat the diabetic skin wound in a rat model, the combined application of adipose stem cell-seeded cryogel/hydrogel biomaterials on the wound and acupuncture surrounding the wound may attain 90.34 ± 2.3% of wound closure and secure the formation of granulation tissue with sufficient microvessels and complete re-epithelialization in 8 days. The average increases in the superficial temperature of wounded animals after acupuncture were about 1-2 °C. Through the activation of C3a and C5a, the increased secretion of cytokines SDF-1 and TGFβ-1, as well as the down-regulation of proinflammatory cytokines TNF-α and IL-1β, the combined treatment of stem cell-seeded cryogel/hydrogel biomaterials and acupuncture on wounds produced synergistic immunomodulatory effects. The strategy using the combined treatment of biomaterials, stem cells, and acupuncture reveals a perspective new approach to accelerate the tissue regeneration.

Mesenchymal Stem Cell/Multipotent Stromal Cell Augmentation of Wound Healing: Lessons from the Physiology of Matrix and Hypoxia Support

Cutaneous wounds requiring tissue replacement are often challenging to treat and result in substantial economic burden. Many of the challenges inherent to therapy-mediated healing are due to comorbidities of disease and aging that render many wounds as chronic or nonhealing. Repeated failure to resolve chronic wounds compromises the reserve or functioning of localized reparative cells. Transplantation of mesenchymal stem cells/multipotent stromal cells (MSCs) has been proposed to augment the reparative capacity of resident cells within the wound bed to overcome stalled wound healing. However, MSCs face a variety of challenges within the wound micro-environment that curtail their survival after transplantation. MSCs are naturally pro-angiogenic and proreparative, and thus numerous techniques have been attempted to improve their survival and efficacy after transplantation, many with little impact. These setbacks have prompted researchers to re-examine the normal wound bed physiology, resulting in new approaches to MSC transplantation using extracellular matrix proteins and hypoxia preconditioning. These studies have also led to new insights on associated intracellular mechanisms, particularly autophagy, which play key roles in further regulating MSC survival and paracrine signaling. This review provides a brief overview of cutaneous wound healing with discussion on how extracellular matrix proteins and hypoxia can be utilized to improve MSC retention and therapeutic outcome.

Homing and Engraftment of Intravenously Administered Equine Cord Blood-Derived Multipotent Mesenchymal Stromal Cells to Surgically Created Cutaneous Wound in Horses: A Pilot Project

Limb wounds on horses are often slow to heal and are prone to developing exuberant granulation tissue (EGT) and close primarily through epithelialization, which results in a cosmetically inferior and non-durable repair. In contrast, wounds on the body heal rapidly and primarily through contraction and rarely develop EGT. Intravenous (IV) multipotent mesenchymal stromal cells (MSCs) are promising. They home and engraft to cutaneous wounds and promote healing in laboratory animals, but this has not been demonstrated in horses. Furthermore, the clinical safety of administering >1.00 × 10⁸ allogeneic MSCs IV to a horse has not been determined. A proof-of-principle pilot project was performed with two horses that were administered 1.02 × 10⁸ fluorescently labeled allogeneic cord blood-derived MSCs (CB-MSCs) following wound creation on the forelimb and thorax. Wounds and contralateral non-wounded skin were sequentially biopsied on days 0, 1, 2, 7, 14, and 33 and evaluated with confocal microscopy to determine presence of homing and engraftment. Results confirmed preferential homing and engraftment to wounds with persistence of CB-MSCs at 33 days following wound creation, without clinically adverse reactions to the infusion. The absence of overt adverse reactions allows further studies to determine effects of IV CB-MSCs on equine wound healing.

Diabetes-induced glucolipotoxicity impairs wound healing ability of adipose-derived stem cells-through the miR-1248/CITED2/HIF-1α pathway

Despite being an attractive cell type for mesenchymal stem cell (MSC) transplantation therapy for wound healing, human adipose-derived stem cells (hADSCs) from diabetes mellitus (DM) patients result in remarkable retention of stem cell activity due to diabetes-induced glucolipotoxicity. We explored the effect of diabetes and medium containing AGEs on the cell activity, phenotype, multipotency, angiogenic potential, and the therapeutic effect of hADSCs. Then, miRNA-1248 was selected by miRNA microarray analysis to further study the core molecular pathways that regulate the wound healing ability of hADSCs. hADSCs isolated from DM patients or cultured in medium containing AGEs in vitro exhibited decreased effectiveness in stem cell therapy. The expression of miRNA-1248 was decreased in the hADSCs of DM patients and hence failed to positively regulate stem cell activity, differentiation functions, and angiogenesis promotion effect. This concomitantly increased the expression of CITED2, an inhibitor of HIF-1α, thus influencing growth factors that promote angiogenesis, cellular proliferation, and wound healing. Overall, our data demonstrated that the glucolipotoxicity-impaired wound healing ability of hADSCs might occur through the miR-1248/CITED2/HIF-1α pathway. MiRNA-1248 may have potential to be used as a novel therapeutic target for wound healing in DM patients or restoring the wound healing ability of diabetic hADSCs.

Exosome laden oxygen releasing antioxidant and antibacterial cryogel wound dressing OxOBand alleviate diabetic and infectious wound healing

Lack of oxygen, reduced vascularization, elevated oxidative stress, and infection are critical clinical hallmarks of non-healing chronic diabetic wounds. Therefore, delivering oxygen, inducing angiogenesis, and management of oxidative stress and infection may provide newer and improved therapeutic avenues for better clinical outcomes in diabetic wound healing. Here, we report the development and evaluation of an exosome laden oxygen releasing antioxidant wound dressing OxOBand to promote wound closure and skin regeneration in diabetic wounds. OxOBand is composed of antioxidant polyurethane (PUAO), as highly porous cryogels with sustained oxygen releasing properties and supplemented with adipose-derived stem cells (ADSCs) exosomes. Exosomes engulfed by the cells enhanced the migration of human keratinocytes and fibroblasts and increased the survival of human neuroblastoma cells under hyperglycemic conditions. OxOBand facilitated faster wound closure, enhanced collagen deposition, faster re-epithelialization, increased neo-vascularization, and decreased oxidative stress within two weeks as compared to untreated diabetic control wounds. The dressing promoted the development of mature epithelial structures with hair follicles and epidermal morphology similar to that of healthy skin. In clinically challenging infected diabetic wounds, these dressings prevented infection and ulceration, improved wound healing with increased collagen deposition, and re-epithelialization. Altogether, OxOBand is a remarkably newer treatment strategy for enhanced diabetic wound healing and may lead to novel therapeutic interventions for the treatment of diabetic ulcers.

The Equine Hoof: Laminitis, Progenitor (Stem) Cells, and Therapy Development

The equine hoof capsule, composed of modified epidermis and dermis, is vital for protecting the third phalanx from forces of locomotion. There are descriptions of laminitis, defined as inflammation of sensitive hoof tissues but recognized as pathologic changes with or without inflammatory mediators, in the earliest records of domesticated horses. Laminitis can range from mild to serious, and signs can be acute, chronic, or transition from acute, severe inflammation to permanently abnormal tissue. Damage within the intricate dermal and epidermal connections of the primary and secondary lamellae is often associated with lifelong changes in hoof growth, repair, and conformation. Decades of research contribute to contemporary standards of care that include systemic and local therapies as well as mechanical hoof support. Despite this, consistent mechanisms to restore healthy tissue formation following a laminitic insult are lacking. Endogenous and exogenous progenitor cell contributions to healthy tissue formation is established for most tissues. There is comparably little information about equine hoof progenitor cells. Equine hoof anatomy, laminitis, and progenitor cells are covered in this review. The potential of progenitor cells to advance in vitro equine hoof tissue models and translate to clinical therapies may significantly improve prevention and treatment of a devastating condition that has afflicted equine companions throughout history.

Effect of Collagen Scaffold With Bcl-2-Modified Adipose-Derived Stem Cells on Diabetic Mice Wound Healing

This study aimed at evaluating the effects of collagen scaffold with Bcl-2-modified adipose-derived stem cells (ADSCs) on wound repair in streptozotocin-induced diabetic mice. A round full thickness skin defect with a diameter of 7 mm was made in the mice model. The experimental mice were divided into 4 groups (n = 12 each): group A (control group), group B (scaffold group), group C (ADSCs-scaffold group), and group D (Bcl-2-ADSCs-scaffold group). On days 3, 7, 10, and 14 after surgery, characteristics of wound healing was observed, and wound tissues were sampled for histology characteristics via hematoxylin-eosin staining and immunohistochemical staining. Compared with other groups, the wound healing rate was significantly higher in group D a week after operation (P < .05). On the seventh day postoperation, group D exhibited higher blood vessel in the wounds granulation tissue than other groups according to results of hematoxylin-eosin staining and immunohistochemistry. In conclusion, these findings demonstrated that collagen scaffold with Bcl-2 modified ADSCs may effectively improve the wound healing process in diabetic mice.

Fate of systemically and locally administered adipose-derived mesenchymal stromal cells and their effect on wound healing

There is increasing interest in the use of adipose‐derived mesenchymal stromal cells (ASCs) for wound repair. As the fate of administered cells is still poorly defined, we aimed to establish the location, survival, and effect of ASCs when administered either systemically or locally during wound repair under physiological conditions. To determine the behavior of ASCs, a rat model with wounds on the dorsal aspect of the hind paws was used and two treatment modes were assessed: ASCs administered systemically into the tail vein or locally around the wound. ASCs were transduced to express both firefly luciferase (Fluc) and green fluorescent protein to enable tracking by bioluminescence imaging and immunohistological analysis. Systemically administered ASCs were detected in the lungs 3 hours after injection with a decrease in luminescent signal at 48 hours and signal disappearance from 72 hours. No ASCs were detected in the wound. Locally administered ASCs remained strongly detectable for 7 days at the injection site and became distributed within the wound bed as early as 24 hours post injection with a significant increase observed at 72 hours. Systemically administered ASCs were filtered out in the lungs, whereas ASCs administered locally remained and survived not only at the injection site but were also detected within the wound bed. Both treatments led to enhanced wound closure. It appears that systemically administered ASCs have the potential to enhance wound repair distally from their site of entrapment in the lungs whereas locally administered ASCs enhanced wound repair as they became redistributed within the wound bed.

Mesenchymal Stem Cells From Bone Marrow, Adipose Tissue, and Lung Tissue Differentially Mitigate Lung and Distal Organ Damage in Experimental Acute Respiratory Distress Syndrome

OBJECTIVES

Mesenchymal stem cells-based therapies have shown promising effects in experimental acute respiratory distress syndrome. Different mesenchymal stem cells sources may result in diverse effects in respiratory diseases; however, there is no information regarding the best source of mesenchymal stem cells to treat pulmonary acute respiratory distress syndrome. We tested the hypothesis that mesenchymal stem cells derived from bone marrow, adipose tissue, and lung tissue would lead to different beneficial effects on lung and distal organ damage in experimental pulmonary acute respiratory distress syndrome.

DESIGN

Animal study and primary cell culture.

SETTING

Laboratory investigation.

SUBJECTS

Seventy-five Wistar rats.

INTERVENTIONS

Wistar rats received saline (control) or Escherichia coli lipopolysaccharide (acute respiratory distress syndrome) intratracheally. On day 2, acute respiratory distress syndrome animals were further randomized to receive saline or bone marrow, adipose tissue, or lung tissue mesenchymal stem cells (1 × 10 cells) IV. Lung mechanics, histology, and protein levels of inflammatory mediators and growth factors were analyzed 5 days after mesenchymal stem cells administration. RAW 264.7 cells (a macrophage cell line) were incubated with lipopolysaccharide followed by coculture or not with bone marrow, adipose tissue, and lung tissue mesenchymal stem cells (10 cells/mL medium).

MEASUREMENTS AND MAIN RESULTS

Regardless of mesenchymal stem cells source, cells administration improved lung function and reduced alveolar collapse, tissue cellularity, collagen, and elastic fiber content in lung tissue, as well as decreased apoptotic cell counts in liver. Bone marrow and adipose tissue mesenchymal stem cells administration also reduced levels of tumor necrosis factor-α, interleukin-1β, keratinocyte-derived chemokine, transforming growth factor-β, and vascular endothelial growth factor, as well as apoptotic cell counts in lung and kidney, while increasing expression of keratinocyte growth factor in lung tissue. Additionally, mesenchymal stem cells differently modulated the secretion of biomarkers by macrophages depending on their source.

CONCLUSIONS

Mesenchymal stem cells from different sources led to variable responses in lungs and distal organs. Bone marrow and adipose tissue mesenchymal stem cells yielded greater beneficial effects than lung tissue mesenchymal stem cells. These findings may be regarded as promising in clinical trials.

Engineered delivery strategies for enhanced control of growth factor activities in wound healing

Growth factors (GFs) are versatile signalling molecules that orchestrate the dynamic, multi-stage process of wound healing. Delivery of exogenous GFs to the wound milieu to mediate healing in an active, physiologically-relevant manner has shown great promise in laboratories; however, the inherent instability of GFs, accompanied with numerous safety, efficacy and cost concerns, has hindered the clinical success of GF delivery. In this article, we highlight that the key to overcoming these challenges is to enhance the control of the activities of GFs throughout the delivering process. We summarise the recent strategies based on biomaterials matrices and molecular engineering, which aim to improve the conditions of GFs for delivery (at the 'supply' end of the delivery), increase the stability and functions of GFs in extracellular matrix (in transportation to target cells), as well as enhance the GFs/receptor interaction on the cell membrane (at the 'destination' end of the delivery). Many of these investigations have led to encouraging outcomes in various in vitro and in vivo regenerative models with considerable translational potential.

Tissue engineering strategies combining molecular targets against inflammation and fibrosis, and umbilical cord blood stem cells to improve hampered muscle and skin regeneration following cleft repair

Cleft lip with or without cleft palate is a congenital deformity that occurs in about 1 of 700 newborns, affecting the dentition, bone, skin, muscles and mucosa in the orofacial region. A cleft can give rise to problems with maxillofacial growth, dental development, speech, and eating, and can also cause hearing impairment. Surgical repair of the lip may lead to impaired regeneration of muscle and skin, fibrosis, and scar formation. This may result in hampered facial growth and dental development affecting oral function and lip and nose esthetics. Therefore, secondary surgery to correct the scar is often indicated. We will discuss the molecular and cellular pathways involved in facial and lip myogenesis, muscle anatomy in the normal and cleft lip, and complications following surgery. The aim of this review is to outline a novel molecular and cellular strategy to improve musculature and skin regeneration and to reduce scar formation following cleft repair. Orofacial clefting can be diagnosed in the fetus through prenatal ultrasound screening and allows planning for the harvesting of umbilical cord blood stem cells upon birth. Tissue engineering techniques using these cord blood stem cells and molecular targeting of inflammation and fibrosis during surgery may promote tissue regeneration. We expect that this novel strategy improves both muscle and skin regeneration, resulting in better function and esthetics after cleft repair.

Stem cell therapies for wound healing

INTRODUCTION

Aberrant wound healing is a significant healthcare problem, posing a substantial burden on patients, their families, and the healthcare system. Existing treatment options remain only moderately effective and often fail to promote the closure of non-healing wounds in susceptible populations, such as aging and diabetic patients. Stem cell therapy has emerged as a promising treatment modality, with the potential to restore tissue to its pre-injured state. Of particular interest are mesenchymal stromal cells, which have been shown to accelerate wound healing by modulating the immune response and promoting angiogenesis.

AREAS COVERED

This review provides an overview of wound healing and current methods for the management of chronic wounds, as well as the current state and considerations for optimizing stem cell therapy. Considerations include stem cell types, tissue source, donor selection, cell heterogeneity, delivery methods, and genetic engineering.

EXPERT OPINION

A growing body of evidence has shown that delivery of stem cells, particularly mesenchymal stromal cells, has the potential to effectively improve the rate and quality of wound healing. However, significant additional basic and clinical research must be performed to optimize cell therapy, such as further elucidation of the therapeutic mechanisms of stem cells and standardization of clinical trial guidelines.

Potential of Allogeneic Adipose-Derived Stem Cell-Hydrogel Complex for Treating Diabetic Foot Ulcers

Mesenchymal stem cells (MSCs) may hold great promise for treating diabetic wounds. However, it is difficult for a clinician to use MSCs because they have not been commercialized. Meanwhile, a new commercial drug that contains adipose-derived stem cells (ASCs) has been developed. The purpose of this study was to examine the potential of allogeneic ASC sheets for treating diabetic foot ulcers. Fifty-nine patients with diabetic foot ulcers were randomized to either the ASC treatment group (n = 30) or a control group treated with polyurethane film (n = 29). Either an allogeneic ASC sheet or polyurethane film was applied on diabetic wounds weekly. These wounds were evaluated for a maximum of 12 weeks. Complete wound closure was achieved for 73% in the treatment group and 47% in the control group at week 8. Complete wound closure was achieved for 82% in the treatment group and 53% in the control group at week 12. The Kaplan-Meier median times to complete closure were 28.5 and 63.0 days for the treatment group and the control group, respectively. There were no serious adverse events related to allogeneic ASC treatment. Thus, allogeneic ASCs might be effective and safe to treat diabetic foot ulcers.

Adipose-derived mesenchymal stem cell exosomes: a novel pathway for tissues repair

The well-characterized curative effect of transplanted mesenchymal stem cells has been mainly attributed to their homing and subsequent differentiation for the repair and regeneration of damaged tissue. Adipose-derived mesenchymal stem cells (ADMSCs) are not only multipotent and plastic, but also abundant as they can be easily harvested with minimally invasive surgical techniques. This makes ADMSCs conducive for clinical applications. Recently, the secretory function of ADMSCs has been regarded as the primary mediator of MSC-based therapy. Exosomes are one kind of small cell extracellular membrane vesicles, which are primarily used to deliver cell-specific proteins, as well as nucleic acids secreted by various cell types. This review will introduce and characterize exosomes-derived ADMSCs (ADMSCs-Exo) and look at new therapies and prospective, including the limitations and outlook for therapeutic strategy. We will describe the latest research progress on myocardial repair, neuroprotection and neurotrophic effects, hepatic repair, renal repair, cutaneous repair, regeneration and other aspects using these cells.

A gelatin/collagen/polycaprolactone scaffold for skin regeneration

Background

A tissue-engineered skin substitute, based on gelatin (“G”), collagen (“C”), and poly(ε-caprolactone) (PCL; “P”), was developed.

Method

G/C/P biocomposites were fabricated by impregnation of lyophilized gelatin/collagen (GC) mats with PCL solutions, followed by solvent evaporation. Two different GC:PCL ratios (1:8 and 1:20) were used.

Results

Differential scanning calorimetry revealed that all G/C/P biocomposites had characteristic melting point of PCL at around 60 °C. Scanning electron microscopy showed that all biocomposites had similar fibrous structures. Good cytocompatibility was present in all G/C/P biocomposites when incubated with primary human epidermal keratinocytes (PHEK), human dermal fibroblasts (PHDF) and human adipose-derived stem cells (ASCs) in vitro. All G/C/P biocomposites exhibited similar cell growth and mechanical characteristics in comparison with C/P biocomposites. G/C/P biocomposites with a lower collagen content showed better cell proliferation than those with a higher collagen content in vitro. Due to reasonable mechanical strength and biocompatibility in vitro, G/C/P with a lower content of collagen and a higher content of PCL (GC_LP_H) was selected for animal wound healing studies. According to our data, a significant promotion in wound healing and skin regeneration could be observed in GC_LP_H seeded with adipose-derived stem cells by Gomori’s trichrome staining.

Conclusion

This study may provide an effective and low-cost wound dressings to assist skin regeneration for clinical use.

Autologous bone marrow-derived cells for venous leg ulcers treatment: a pilot study

BACKGROUND

Chronic venous leg ulcers (VLUs) are a common problem in clinical practice and available treatments are not satisfactory. The use of adjuvant therapies in combination with lower limb compression may lead to improved healing rates. Chronic wounds are candidates for new strategies in the emergent field of regenerative medicine. Bone marrow-derived cells (BMDCs) contain cells and secrete cytokines known to participate in wound healing. Thus, BMDC therapy seems a logical strategy for the treatment of chronic wounds. Our objective was to evaluate feasibility, safety and initial clinical outcome of autologous BMDC therapy associated with standard treatment in patients with VLUs.

METHODS

We conducted an open-label, single-arm, prospective pilot clinical trial in four patients with six chronic VLUs. The study protocol was approved by the institutional and national review boards and ethics committees. Bone marrow was harvest, processed and then administered by multiple injections into the ulcers. All patients received standard treatment and non-healing characteristics of the VLUs were confirmed at study entry.

RESULTS

Ulcer size and wound pain evaluated 12 months after BMDC treatment were significantly reduced (P < 0.05). BMDC treatment was safe and well tolerated in long-term follow-up.

DISCUSSION

Despite the low number of patients studied, our results showed that autologous BMDC treatment could be a useful, feasible and safe procedure to enhance ulcer healing. However, randomized controlled trials with more patients are needed to address this question and translate this approach into clinical practice.

Novel non-angiogenic role for mesenchymal stem cell-derived vascular endothelial growth factor on keratinocytes during wound healing

With chronic wounds remaining a substantial healthcare issue, new therapies are sought to improve patient outcomes. Various studies have explored the benefits of promoting angiogenesis in wounds by targeting proangiogenic factors such as Vascular Endothelial Growth Factor (VEGF) family members to improve wound healing. Along similar lines, Mesenchymal Stem Cell (MSC) secretions, usually containing VEGF, have been used to improve angiogenesis in wound healing via a paracrine mechanism. Recent evidence for keratinocyte VEGF receptor expression, as well as proliferative and chemotactic responses by keratinocytes to exogenous VEGFA in vitro implies distinct non-angiogenic actions for VEGF during wound healing. In this review, we discuss the expression of VEGF family members and their receptors in keratinocytes in relation to the potential for wound healing treatments. We also explore recent findings of MSC secreted paracrine wound healing activity on keratinocytes. We report here the concept of keratinocyte wound healing responses driven by MSC-derived VEGF that is supported in the literature, providing a new mechanism for cell-free therapy of chronic wounds.

Potent laminin-inspired antioxidant regenerative dressing accelerates wound healing in diabetes

The successful treatment of chronic dermal wounds, such as diabetic foot ulcers (DFU), depends on the development of safe, effective, and affordable regenerative tools that the surgeon can rely on to promote wound closure. Although promising, strategies that involve cell-based therapies and the local release of exogenous growth factors are costly, require very long development times, and result in modest improvements in patient outcome. We describe the development of an antioxidant shape-conforming regenerative wound dressing that uses the laminin-derived dodecapeptide A5G81 as a potent tethered cell adhesion-, proliferation-, and haptokinesis-inducing ligand to locally promote wound closure. A5G81 immobilized within a thermoresponsive citrate-based hydrogel facilitates integrin-mediated spreading, migration, and proliferation of dermal and epidermal cells, resulting in faster tissue regeneration in diabetic wounds. This peptide-hydrogel system represents a paradigm shift in dermoconductive and dermoinductive strategies for treating DFU without the need for soluble biological or pharmacological factors.

Two Transcripts of FBXO5 Promote Migration and Osteogenic Differentiation of Human Periodontal Ligament Mesenchymal Stem Cells

OBJECTIVES

Enhanced migration and osteogenic differentiation of mesenchymal stem cells (MSCs) are beneficial for MSC-mediated periodontal tissue regeneration, a promising method for periodontitis treatment. FBXO5, a member of the F-box protein family, is involved in the osteogenic differentiation of MSCs. Here, we investigated the effect of FBXO5 on human periodontal ligament stem cells (hPDLSCs).

MATERIALS AND METHODS

hPDLSCs were isolated from periodontal ligament tissue. Lentivirus FBXO5 shRNA was used to silence FBXO5 expression. Two transcripts of FBXO5 were overexpressed and transduced into hPDLSCs via retroviral infection. Migration and osteogenic differentiation of hPDLSCs were evaluated using the scratch migration assay, alkaline phosphatase (ALP) activity, ALP staining, alizarin red staining, western blotting, and real-time polymerase chain reaction.

RESULTS

The expression of FBXO5 was upregulated after osteogenic induction in hPDLSCs. FBXO5 knockdown attenuated migration, inhibited ALP activity and mineralization, and decreased RUNX2, OSX, and OCN expression, while the overexpression of two transcript isoforms significantly accelerated migration, enhanced ALP activity and mineralization, and increased RUNX2, OSX, and OCN expression in hPDLSCs.

CONCLUSIONS

Both isoforms of FBXO5 promoted the migration and osteogenic differentiation potential of hPDLSCs, which identified a potential target for improving periodontal tissue regeneration.

Regenerative potential of tonsil mesenchymal stem cells on surgical cutaneous defect

As tissue engineering and regenerative medicine have evolved recently, stem cell therapy has been investigated in the field of impaired wound healing. Several studies have reported that mesenchymal stem cells derived from various tissues including bone marrow and adipose tissue can exert the regenerative efficacy in the wound healing. Previously, we have demonstrated the isolation and characterization of tonsil-derived mesenchymal stem cells (TMSCs) with excellent proliferative property. In the present study, we aimed to evaluate the regenerative efficacy of TMSCs in the wound healing process. Two distinct cutaneous surgical defects were generated in the dorsum of mice. Each wound was treated with TMSCs or phosphate-buffered saline (PBS), respectively. After sacrifice, the skin and subcutaneous tissues around the surgical defect were harvested and assessed for inflammation, re-epithelialization, dermal regeneration, and granulation tissue formation. The administration of TMSCs into wound beds significantly promoted the repair of surgical defects in mice. Especially, TMSCs efficiently contributed to the attenuation of excessive inflammation in the surgical lesion, as well as the augmentation of epidermal and dermal regeneration. To elucidate the underlying mechanisms, TMSCs were analyzed for their potency in immunomodulatory ability on immune cells, stimulatory effect on the proliferation of keratinocytes, and fibroblasts, as well as the regulation of fibroblast differentiation. TMSCs inhibited the non-specific or T-cell-specific proliferation of peripheral blood mononuclear cells, as well as the M1 polarization of macrophage-like cells. Moreover, TMSCs augmented the proliferation of skin-constituting fibroblasts and keratinocytes while they suppressed the differentiation of fibroblasts into myofibroblasts. Taken together, our findings demonstrate the regenerative potential of TMSCs in wound healing process through the regulation on inflammation, proliferation, and remodeling of various skin cells, implying that TMSCs can be a promising alternative for wound repair.

Engineered mesenchymal stem-cell-sheets patches prevents postoperative pancreatic leakage in a rat model

Post-operative pancreatic fistula (POPF) following pancreatic resection is a life-threatening surgical complication. Cell sheets were prepared and harvested using temperature-responsive culture dishes and transplanted as patches to seal POPF. Two different mesenchymal stem cell (MSC) sheets were compared in terms of the preventative ability for pancreatic leakage in a rat model. Both rat adipose-derived stem cell (rADSC) and bone marrow-derived stem cell (rBMSC) sheets were transplanted. Those rADSC and rBMSC sheets are created without enzymes and thus maintained their cell-cell junctions and adhesion proteins with intact fibronectin on the basal side, as well as characteristics of MSCs. The rats with post-pancreatectomy rADSC- or rBMSC-sheet patches had significantly decreased abdominal fluid leakage compared with the control group, demonstrated by MR image analysis and measurement of the volume of abdominal fluid. Amylase level was significantly lower in the rats with rADSC-sheet and rBMSC-sheet patches compared with the control groups. The rADSC sheet patches had increased adhesive and immune-cytokine profiles (ICAM-1, L-selectin, TIMP-1), and the rBMSC sheets had reduced immune reactions compared to the control. This is first project looking at the feasibility of tissue engineering therapy using MSC-sheets as tissue patches preventing leakage of abdominal fluid caused by POPF.

Therapeutic effect of bone marrow mesenchymal stem cells pretreated with acetylsalicylic acid on experimental periodontitis in rats

Periodontitis is a local inflammatory environment with dysregulation of host responses, which results in destruction of periodontal tissues. Mesenchymal stem cells (MSCs) have been proven to play important roles in tissue regeneration by serving as progenitor cells, but its therapeutic outcomes are yet, evaluated variable and unpredictable because of the influence of local inflammation. Acetylsalicylic acid (ASA) has been reported to benefit for MSCs in terms of inflammation control and tissue regeneration. In this study, we aimed to explore the effect of bone marrow mesenchymal stem cells (BMMSCs) pretreated with ASA (ASA-BMMSCs) on periodontal bone repair in a ligature and bacteria-induced periodontitis model in rats. We show herein that, ASA-BMMSCs treatment reduced inflammatory infiltration and alveolar bone loss in periodontitis rats, reflected by immunohistochemistry staining of OPG/RANK-L and Micro-CT. Levels of TNF-α and IL-17 decreased while IL-10 increased after the treatment of ASA-BMMSCs in periodontitis rats. In addition, less osteoclasts number was detected in ASA-BMMSCs treated group. In vitro study showed that ASA facilitated BMMSCs proliferation and differentiation, which might explain the reduced bone loss in periodontitis. These results together suggest that local application of ASA-BMMSCs in periodontal lesion sites is capable of improving inflammatory microenvironment, promoting alveolar bone regeneration, thus leading to a recovery of periodontal homeostasis. Besides, this study also provides us a new idea that a combined application of ASA and BMMSCs may be a novel approach for periodontitis treatment and periodontal bone regeneration.

Efficacy, safety and influencing factors of intra-calf muscular injection of bone marrow mononuclear cells in the treatment of type 2 diabetes mellitus-induced lower extremity vascular disease

The efficacy, safety and impact of vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF) associated with the intra-calf muscular injection of bone marrow mononuclear cells (BMMCs) in the treatment of type 2 diabetes mellitus (T2DM)-induced lower extremity vascular disease (LEVD) were evaluated. Patients with T2DM-LEVD were randomly divided into a control group and BMMCs group to assess the efficacy and safety of the treatment; serum VEGF and bFGF levels were detected. The BMMCs group was divided into superior genicular artery (SGA) and inferior genicular artery (IGA) subgroups as well as low-dose and high-dose subgroups for the comparison of efficacy indices. The BMMCs group exhibited significantly improved indices (P<0.05) compared with the control group and no fatalities or cancer occurred. There were no significant changes in serum VEGF and bFGF levels (P>0.05). The claudication distance in the IGA subgroup was significantly greater that in the SGA subgroup (P<0.05); the low-dose subgroup and the high-dose subgroup did not demonstrate any significant differences in each index (P>0.05). BMMC treatment for T2DM-LEVD was found to be safe and effective and had no significant impact on serum VEGF and bFGF levels in the short term; However, the degree of LEVD may affect its efficacy.

Creation and Transplantation of an Adipose-derived Stem Cell (ASC) Sheet in a Diabetic Wound-healing Model

Artificial skin has achieved considerable therapeutic results in clinical practice. However, artificial skin treatments for wounds in diabetic patients with impeded blood flow or with large wounds might be prolonged. Cell-based therapies have appeared as a new technique for the treatment of diabetic ulcers, and cell-sheet engineering has improved the efficacy of cell transplantation. A number of reports have suggested that adipose-derived stem cells (ASCs), a type of mesenchymal stromal cell (MSC), exhibit therapeutic potential due to their relative abundance in adipose tissue and their accessibility for collection when compared to MSCs from other tissues. Therefore, ASCs appear to be a good source of stem cells for therapeutic use. In this study, ASC sheets from the epididymal adipose fat of normal Lewis rats were successfully created using temperature-responsive culture dishes and normal culture medium containing ascorbic acid. The ASC sheets were transplanted into Zucker diabetic fatty (ZDF) rats, a rat model of type 2 diabetes and obesity, that exhibit diminished wound healing. A wound was created on the posterior cranial surface, ASC sheets were transplanted into the wound, and a bilayer artificial skin was used to cover the sheets. ZDF rats that received ASC sheets had better wound healing than ZDF rats without the transplantation of ASC sheets. This approach was limited because ASC sheets are sensitive to dry conditions, requiring the maintenance of a moist wound environment. Therefore, artificial skin was used to cover the ASC sheet to prevent drying. The allogenic transplantation of ASC sheets in combination with artificial skin might also be applicable to other intractable ulcers or burns, such as those observed with peripheral arterial disease and collagen disease, and might be administered to patients who are undernourished or are using steroids. Thus, this treatment might be the first step towards improving the therapeutic options for diabetic wound healing.

Matrix-Embedded Endothelial Cells Attain a Progenitor-Like Phenotype

Culture of endothelial cells (ECs) embedded in 3D scaffolds of denatured collagen has shown tremendous therapeutic potential in clinical trials of tissue repair. It is postulated that these matrix-embedded ECs (MEECs) attain a differential phenotype similar to early progenitor forms, which cannot be attained in 2D culture. MEECs are compared to 2D-ECs and endothelial progenitor cells (EPCs) by secretome, phenotype, and genetic fingerprint, and are found to be altered from 2D-ECs on all levels, adopting an EPC-like phenotype. This manifests in elevation of CD34 expression-a progenitor cell marker-and protein secretion and gene expression pro-files that are similar to EPCs. Even more striking is that EPCs in 2D lose their phenotype, evident by the loss of CD34 expression, but are able to regain expression over time when embedded in the same 3D matrices, suggesting that future in vitro EPC work should use ME-EPCs to recapitulate in vivo phenotype. These findings elucidate the relationship between EPCs and the substratum-dependent regulation imparted by ECs which is critical to understand in order to optimize MEEC therapy and propel it into the clinic.

Paracrine Effects of Mesenchymal Stromal Cells Cultured in Three-Dimensional Settings on Tissue Repair

Mesenchymal stromal cells (MSCs) are a promising cell source for promoting tissue repair, due to their ability to release growth, angiogenic, and immunomodulatory factors. However, when injected as a suspension, these cells suffer from poor survival and localization, and suboptimal release of paracrine factors. While there have been attempts to overcome these limitations by modifying MSCs themselves, a more versatile solution is to grow them in three dimensions, as aggregates or embedded into biomaterials. Here we review the mechanisms by which 3D culture can influence the regenerative capacity of undifferentiated MSCs, focusing on recent examples from the literature. We further discuss how knowledge of these mechanisms can lead to strategic design of MSC therapies that overcome some of the challenges to their effective translation.

Engineered stem cell niche matrices for rotator cuff tendon regenerative engineering

Rotator cuff (RC) tears represent a large proportion of musculoskeletal injuries attended to at the clinic and thereby make RC repair surgeries one of the most widely performed musculoskeletal procedures. Despite the high incidence rate of RC tears, operative treatments have provided minimal functional gains and suffer from high re-tear rates. The hypocellular nature of tendon tissue poses a limited capacity for regeneration. In recent years, great strides have been made in the area of tendonogenesis and differentiation towards tendon cells due to a greater understanding of the tendon stem cell niche, development of advanced materials, improved scaffold fabrication techniques, and delineation of the phenotype development process. Though in vitro models for tendonogenesis have shown promising results, in vivo models have been less successful. The present work investigates structured matrices mimicking the tendon microenvironment as cell delivery vehicles in a rat RC tear model. RC injuries augmented with a matrix delivering rat mesenchymal stem cells (rMSCs) showed enhanced regeneration over suture repair alone or repair with augmentation, at 6 and 12-weeks post-surgery. The local delivery of rMSCs led to increased mechanical properties and improved tissue morphology. We hypothesize that the mesenchymal stem cells function to modulate the local immune and bioactivity environment through autocrine/paracrine and/or cell homing mechanisms. This study provides evidence for improved tendon healing with biomimetic matrices and delivered MSCs with the potential for translation to larger, clinical animal models. The enhanced regenerative healing response with stem cell delivering biomimetic matrices may represent a new treatment paradigm for massive RC tendon tears.