Mechanisms of action of mesenchymal stem cells in cutaneous wound repair and regeneration

Unveiling advanced strategies for therapeutic stem cell interventions in severe burn injuries: a comprehensive review

This comprehensive review explores the complex terrain of stem cell therapies as a potential therapeutic frontier in the healing of complicated burn wounds. Serious tissue damage, impaired healing processes, and possible long-term consequences make burn wounds a complex problem. An in-depth review is required since, despite medical progress, existing methods for treating severe burn wounds have significant limitations. Burn wounds are difficult to heal because they cause extensive tissue damage. The challenges of burn injury-induced tissue regeneration and functional recovery are also the subject of this review. Although there is a lot of promise in current stem cell treatments, there are also some limitations with scalability, finding the best way to transport the cells, and finding consistent results across different types of patients. To shed light on how to improve stem cell interventions to heal severe burn wounds, this review covers various stem cell applications in burn wounds and examines these obstacles. To overcome these obstacles, one solution is to enhance methods of stem cell distribution, modify therapies according to the severity of the burn, and conduct more studies on how stem cell therapy affects individual patients. Novel solutions may also be possible through the combination of cutting-edge technologies like nanotechnology and biotechnology. This review seeks to increase stem cell interventions by analyzing present challenges and suggesting strategic improvements. The goal is to provide a more effective and tailored way to repair serious burn wounds.

Exploring the therapeutic potential of allogeneic amniotic membrane for quality wound healing in rabbit model

BACKGROUND

The amniotic membrane (AM) has shown immense potential in repairing wounds due to its great regenerative qualities. Although the role of AM as a biological scaffold in repairing wounds has been studied well, the tissue regenerative potential of AM-derived mesenchymal stem cells (MSCs) and conditioned media (CM) derived from it remains to be discovered as of now. Here, we examined the wound healing abilities of fresh and frozen thawed rabbit AM (rAM) along with the MSCs and their lyophilised CM in rabbits challenged with skin wounds.

METHODS

To elucidate the role of rAM-MSCs and its CM in repairing the wound, we isolated it from the freshly derived placenta and characterised their differentiation potential by performing an in vitro tri-lineage differentiation assay besides other standard confirmations. We compared the wound repair capacities of rAM-MSCs and lyophilised CM with the fresh and cryopreserved AM at different timelines by applying them to excision wounds created in rabbits.

RESULTS

By monitoring wound contractions and tissue histology of wounded skin at different time points after the application, we observed that rAM-MSCs and rAM-MSC-derived CM significantly promoted wound closure compared to the control group. We also observed that the wound closure capacity of rAM-MSCs and rAM-MSC-derived CM is as efficient as fresh and cryopreserved rAM.

CONCLUSION

Our findings suggest that rAM-MSCs and rAM-MSC derived CM can be effectively used to treat skin wounds in animals and correctly delivered to the damaged tissue using AM as a bioscaffold, either fresh or frozen.

Sorting Technology for Mesenchymal Stem Cells from a Single Tissue Source

Mesenchymal stem cells (MSCs) are adult stem cells that can be obtained, enriched and proliferated in vitro. They owned enormous potential in fields like regenerative medicine, tissue engineering and immunomodulation. However, though isolated from the same origin, MSCs are still essentially heterogeneous cell populations with different phenotypes and functions. This heterogeneity of MSCs significantly affects their therapeutic efficacy and brings obstacles to scientific research. Thus, reliable sorting technology which can isolate or purify MSC subpopulations with various potential and differentiation pathways is urgently needed. This review summarized principles, application status and clinical implications for these sorting methods, aiming at improving the understanding of MSC heterogeneity as well as providing fresh perspectives for subsequent clinical applications.

Bone Marrow Mesenchymal Stem Cell-derived Exosomal microRNA-99b-5p Promotes Cell Growth of High Glucose-treated Human Umbilical Vein Endothelial Cells by Modulating THAP Domain Containing 2 Expression

INTRODUCTION

Bone marrow mesenchymal stem cell-derived exosomes (BMSC-exos) may function as novel candidates for treating diabetic wounds due to their ability to promote angiogenesis.

MATERIALS AND METHODS

This study investigated the effects of BMSC-exos on the growth and metastasis of human umbilical vein endothelial cells (HUVECs) treated with high glucose (HG). The exosomes were separated from BMSCs and identified. The cell phenotype was detected by 3-(4,5- dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide and 5-ethynyl-2'-deoxyuridine, wound healing, and transwell assays, while the number of tubes was measured via tube formation assay.

RESULT

The RNA and protein expression levels were studied using reverse transcription-quantitative polymerase chain reaction and western blotting, whereas integration of microRNA-99b-5p (miR-99b-5p) with THAP domain containing 2 (THAP2) was confirmed via dual-luciferase reporter and RNA pull-down assays. Results of transmission electron microscopy, nanoparticle tracking analysis, and laser scanning confocal microscopy revealed that exosomes were successfully separated from BMSCs and endocytosed into the cytoplasm by HUVECs. Similarly, BMSC-exos were found to promote the growth of HG-treated HUVECs, while their growth was inhibited by suppressing miR-99b-5p. THAP2 was found to bind to miR-99b-5p, where THAP2 inhibition reversed the miR-99b-5p-induced effects on cell growth, migration, and tube numbers.

CONCLUSION

In conclusion, miR-99b-5p in BMSC-exo protects HUVECs by negatively regulating THAP2 expression.

Bone marrow-derived mesenchymal stem cells: A promising therapeutic option for the treatment of diabetic foot ulcers

Chronic wounds fail to heal through the three normal stages of healing (inflammatory, proliferative, and remodelling), resulting in a chronic tissue injury that is not repaired within the average time limit. Patients suffering from type 1 and type 2 diabetes are prone to develop diabetic foot ulcers (DFUs), which commonly develop into chronic wounds that are non treatable with conventional therapies. DFU develops due to various risk factors, such as peripheral neuropathy, peripheral vascular disease, arterial insufficiency, foot deformities, trauma and impaired resistance to infection. DFUs have gradually become a major problem in the health care system worldwide. In this review, we not only focus on the pathogenesis of DFU but also comprehensively summarize the outcomes of preclinical and clinical studies thus far and the potential therapeutic mechanism of bone marrow-derived mesenchymal stem cells (BMSCs) for the treatment of DFU. Based on the published results, BMSC transplantation can contribute to wound healing through growth factor secretion, anti-inflammation, differentiation into tissue-specific cells, neovascularization, re-epithelialization and angiogenesis in DFUs. Moreover, clinical trials showed that BMSC treatment in patients with diabetic ulcers improved ulcer healing and the ankle-brachial index, ameliorated pain scores, and enhanced claudication walking distances with no reported complications. In conclusion, although BMSC transplantation exhibits promising therapeutic potential in DFU treatment, additional studies should be performed to confirm their efficacy and long-term safety in DFU patients.

LPS-pretreatment adipose-derived mesenchymal stromal cells promote wound healing in diabetic rats by improving angiogenesis

Mesenchymal stem cells (MSCs) play a key role in wound healing, and the advantages of pretreated MSCs in wound healing have previously been reported. In the present study, we investigated the impact of LPS pretreated human adipose-derived MSCs on skin wound healing in diabetic rats. We found that some improvements occurred through improving angiogenesis. Then, we scrutinized the impact of lipopolysaccharide (LPS) treatment on human adipose-derived MSCs in a high-glucose (HG) medium, as an in vitro diabetic model. In vivo findings revealed significant improvements in epithelialization and angiogenesis of diabetic wounds which received LPS pre-MSCs. Particularly, LPS pre-MSCs-treated diabetic wounds reached considerably higher percentages of wound closure. Also, the granulation tissue of these wounds had higher pronounced epithelialization and more vascularization compared with PBS-treated and MSCs-treated diabetic ones by CD31, VEGF, CD90, collagen 1, and collagen 3 immunostaining. Western-blots analyses indicated that LPS pre-MSCs led to the upregulation of vascular endothelial growth factor (VEGF) and DNMT1. In addition, significantly higher cell viability (proliferation/colonie), and elevated VEGF and DNMT1 protein expression were observed when MSCs were treated with LPS (10 ng/ml, 6 h) in HG culture media. Based on these findings, it is suggested that LPS pre-MSCs could promote wound repair and skin regeneration, in some major processes, via the improvement of cellular behaviors of MSCs in the diabetic microenvironment. The beneficial advantages of LPS treated with mesenchymal stem cells on wound healing may lead to establishing a novel approach as an alternative therapeutic procedure to cure chronic wounds in diabetic conditions.

Subacromial bursa increases the failure force in a mouse model of supraspinatus detachment and repair

BACKGROUND

It has been shown that subacromial bursa (SAB) harbors connective tissue progenitor cells. The purpose of this study was to evaluate the effects of implantation of SAB-derived cells (SBCs) suspended in a fibrin sealant bead and implantation of SAB tissue at rotator cuff repair site on biomechanical properties of the repair in a mouse (C57Bl/6) model of supraspinatus tendon (ST) detachment and repair.

METHODS

Part 1: Murine SAB tissue was harvested and cultured. Viability of SBCs suspended in 10 μL of fibrin sealant beads was confirmed in vitro and in vivo. Eighty mice underwent right ST detachment and repair augmented with either fibrin sealant bead (control group) or fibrin sealant bead with 100,000 SBCs (study group) applied at the repair site. Part 2: 120 mice underwent right ST detachment and repair and were randomized equally into 4 groups: (1) a tissue group, which received a piece of freshly harvested SAB tissue; (2) a cell group, which received SBCs suspended in fibrin sealant bead; (3) a fibrin sealant group, which received plain fibrin sealant bead without cells; and (4) a control group, which received nothing at the ST repair site. An equal number of mice in each group were killed at 2 and 4 weeks. Specimens underwent biomechanical testing to evaluate failure force (part 1 and 2) and histologic analysis of the repair site (part 1 only).

RESULTS

Part 1: The mean failure force in the study group was significantly higher than controls at 2 and 4 weeks (3.25 ± 1.03 N vs. 2.43 ± 0.56 N, P = .01, and 4.08 ± 0.99 N vs. 3.02 ± 0.8 N, P = .004, respectively). Mean cell density of the ST at the repair site was significantly lower in the study group at 2 weeks than in controls (18,292.13 ± 1706.41 vs. 29,501.90 ± 3627.49, P = .001). Study group specimens had lower proteoglycan contents than controls, but this difference was not statistically significant. Part 2: There was no difference in failure force between cell and tissue groups at the 2- and 4-week time points (P = .994 and P = .603, respectively). There was no difference in failure force between fibrin sealant bead and control groups at the 2- and 4-week time points (P = .978 and P = .752, respectively).

CONCLUSION

This study shows that the application of SBCs and SAB tissue at the rotator cuff repair site increases the strength of repair in a murine model of rotator cuff detachment and repair.

Stem Cells and Organs-on-chips: New Promising Technologies for Human Infertility Treatment

Having biological children remains an unattainable dream for most couples with reproductive failure or gonadal dysgenesis. The combination of stem cells with gene editing technology and organ-on-a-chip models provides a unique opportunity for infertile patients with impaired gametogenesis caused by congenital disorders in sex development or cancer survivors. But how will these technologies overcome human infertility? This review discusses the regenerative mechanisms, applications, and advantages of different types of stem cells for restoring gametogenesis in infertile patients, as well as major challenges that must be overcome before clinical application. The importance and limitations of in vitro generation of gametes from patient-specific human-induced pluripotent stem cells (hiPSCs) will be discussed in the context of human reproduction. The potential role of organ-on-a-chip models that can direct differentiation of hiPSC-derived primordial germ cell-like cells to gametes and other reproductive organoids is also explored. These rapidly evolving technologies provide prospects for improving fertility to individuals and couples who experience reproductive failure.

Oral administration of sea cucumber (Stichopus japonicus) protein exerts wound healing effects via the PI3K/AKT/mTOR signaling pathway

This study aimed to investigate the effect of the oral administration of sea cucumber protein (SCP) on wound healing. SCP was isolated and purified from the body wall of Stichopus japonicus. A mouse skin incision model was operated on to evaluate the wound repair effect of SCP. The histological changes in the skin at the wound sites of BALB/c mice were observed by staining with haematoxylin and eosin (H&E) and Masson's trichrome. The enzyme-linked immunosorbent assay (ELISA) was used to analyze the expression of inflammatory cytokines in BALB/c mice. The boost cell migration ability was detected by a scratch assay after HaCaT cells were cultured with digested SCP (dSCP). Western blotting and RT-PCR assays were performed to determine the mechanism of SCP promoting wound healing. As a result, the wound healing rate in the SCP high dose group was 1.3-fold, compared to that in the blank group on day 14. Also, increased epidermal thickness and 1.79-fold collagen deposition contrasted with the blank group. Additionally, SCP could up-regulate the levels of pro-inflammatory factors (IL-1β, IL-6, TNF-α) from day 3 to 7 firstly and decreased from day 7 to 14. IL-8 expression continuously decreased while the level of anti-inflammatory factor (IL-10) increased during the healing stage. Furthermore, the cell closure area reached 67% after being treated with 50 μg mL^-1 of dSCP for 48 h. Cell proliferation was associated with the dSCP-activated PI3K/AKT/mTOR pathway. Taken together, SCP can be orally used as an effective agent for wound repair.

Bone Marrow Aspirate Concentrate for the Treatment of Knee Osteoarthritis: A Systematic Review

BACKGROUND

Bone marrow aspirate concentrate (BMAC) has emerged as a therapeutic option for symptomatic knee osteoarthritis (OA).

PURPOSE

To systematically review the literature to evaluate the efficacy of isolated BMAC injection in the treatment of OA of the knee joint.

STUDY DESIGN

Systematic review; Level of evidence, 4.

METHODS

A systematic review was performed by searching the PubMed, Embase, and Cochrane Library databases up to July 2020 to identify human studies that assessed the clinical outcomes of isolated BMAC injection for the treatment of knee OA. The electronic search strategy used was "bone marrow aspirate concentrate knee osteoarthritis."

RESULTS

Eight studies met the inclusion criteria, including a total of 299 knees with a mean follow-up of 12.9 months (range, 6-30 months). Of all patient-reported outcomes assessed across studies, 34 of 36 (94.4%) demonstrated significant improvement from baseline to latest follow-up (P < .05). Five studies evaluating numerical pain scores (visual analog scale and Numeric Rating Scale) reported significant improvements in pain level at final follow-up (P < .01). However, 3 comparative studies evaluating BMAC in relation to other therapeutic injections failed to demonstrate the clinical superiority of BMAC.

CONCLUSION

The BMAC injection is effective in improving pain and patient-reported outcomes in patients with knee OA at short- to midterm follow-up. Nevertheless, BMAC has not demonstrated clinical superiority in relation to other biologic therapies commonly used in the treatment of OA, including platelet-rich plasma and microfragmented adipose tissue, or in relation to placebo. The high cost of the BMAC injection in comparison with other biologic and nonoperative treatment modalities may limit its utility despite demonstrable clinical benefit.

Role of mesenchymal stromal cells derivatives in diabetic foot ulcers: a controlled randomized phase 1/2 clinical trial

BACKGROUND

Diabetes-related foot complications have been identified as the most common isolated cause of morbidity among patients with diabetes and the leading cause of amputation. Therefore, new strategies to stimulate skin regeneration may provide a novel therapeutic approach to reduce non-healing ulcer disease. Recently, we demonstrated in proof-of-concept in humans that administration of allogeneic bone marrow mesenchymal stromal cellss derivatives (allo-hBM-MSCDs) is effective in a similar way to the use of allogeneic bone marrow mesenchymal stromal cellss (allo-hBM-MSCs) in grade 2 diabetic foot ulcers (DFUs).

AIM

To assess the safety and efficacy profile of the allo-hBM-MSCDs relative to the conventional approach (PolyMen® dressing) in 1/2 clinical trial phases in patients with grade 1 and 2 DFUs.

METHODS

In the present study, we used 2 doses of allo-hBM-MSCDs (1 mL) or 1 dose of allo-hBM-MSCs (1 × 106 cells) intradermally injected around wounds and assessed their safety and effectiveness, relative to the conventional approach (PolyMem dressing). Allo-hBM-MSCDs and allo-hBM-MSCs were produced in a certified Good Manufacturing Practice-type Laboratory. Patients with grade 1 and 2 DFUs were randomized to receive allo-hBM-MSCDs (n=12), allo-hBM-MSCs (n=6) or conventional treatment (PolyMem dressing) (n=10). The wound-healing process was macroscopically evaluated until the complete closure of the ulcers.

RESULTS

No adverse events were reported. Patients with grade 1 and 2 DFUs treated with either allo-hBM-MSCDs or allo-hBM-MSCs, achieved greater percentages of wound closure, enhanced skin regeneration in shorter times and a greater ulcer-free survival relative to the patients who received conventional treatment. Finally, through proteomic analysis, we elucidated the proteins and growth factors that are secreted by allo-hBM-MSCs and relevant to the wound-healing process. In addition, by combining proteomics with Gene Ontology analysis, we comprehensively classified secreted proteins on both biological process and molecular function.

CONCLUSIONS

In this phase 1/2 trial, our cumulative results suggest that 2 doses of allo-hBM-MSCDs combined with a wound dressing are a safe and effective treatment for grade 1 and 2 DFUs.

Research update of adipose tissue-based therapies in regenerative dermatology

Mesenchymal stromal/stem cells (MSCs) have a spontaneous propensity to support tissue homeostasis and regeneration. Among the several sources of MSCs, adipose-derived tissue stem cells (ADSCs) have received major interest due to the higher mesenchymal stem cells concentration, ease, and safety of access. However, since a significant part of the natural capacity of ADSCs to repair damaged tissue is ascribable to their secretory activity that combines mitogenic factors, cytokines, chemokines, lipids, and extracellular matrix components, several studies focused on cell-free strategies. Furthermore, adipose cell-free derivatives are becoming more attractive especially for non-volumizing purposes, such as most dermatological conditions. However, when keratinocytes, fibroblasts, melanocytes, adipocytes, and hair follicle cells might not be locally sourced, graft of materials containing concentrated ADSCs is preferred. The usage of extracellular elements of adipose tissue aims to promote a self-autonomous regenerative microenvironment in the receiving area restoring physiological homeostasis. Hence, ADSCs or their paracrine activity are currently being studied in several dermatological settings including wound healing, skin fibrosis, burn, and aging.The present work analyzing both preclinical and clinical experiences gives an overview of the efficacy of adipose tissue-derivatives like autologous fat, the stromal vascular fraction (SVF), purified ADSCs, secretome and extracellular matrix graft in the field of regenerative medicine for the skin.

The application of mesenchymal stromal cells (MSCs) and their derivative exosome in skin wound healing: a comprehensive review

Recently, mesenchymal stromal cells (MSCs) and also their exosome has become a game-changing tool in the context of tissue engineering and regenerative medicine. MSCs due to their competencies to establish skin cells, such as fibroblast and keratinocyte, and also their unique attribute to suppress inflammation in wound site has attracted increasing attention among scholars. In addition, MSC's other capabilities to induce angiogenesis as a result of secretion of pro-angiogenic factors accompanied with marked anti-fibrotic activities, which mainly mediated by the releases matrix metalloproteinase (MMPs), make them a rational and effective strategy to accelerate wound healing with a small scar. Since the chief healing properties of the MSCs depend on their paracrine effects, it appears that MSCs-derived exosomes also can be an alternative option to support wound healing and skin regeneration as an innovative cell-free approach. Such exosomes convey functional cargos (e.g., growth factor, cytokine, miRNA, etc.) from MSCs to target cells, thereby affecting the recipient skin cells' biological events, such as migration, proliferation, and also secretion of ECM components (e.g., collagen). The main superiorities of exosome therapy over parental MSCs are the diminished risk of tumor formation and also lower immunogenicity. Herein, we deliver an overview of recent in vivo reports rendering the therapeutic benefits of the MSCs-based therapies to ease skin wound healing, and so improving quality of life among patients suffering from such conditions.

Small Intestinal Submucosa Membrane Modified by Fusion Peptide-Mediated Extracellular Vesicles to Promote Tissue Regeneration

Tissue injury, which often occurs in daily life, remains challenging in clinical medicine. Developing a novel biomaterial with the capability to provide an ideal microenvironment and homeostasis around the wound is highly desirable for effective tissue regenerative medicine. The small intestinal submucosa (SIS) membrane possesses a precise spatial structure with excellent biocompatibility. Extracellular vesicles (EVs) derived from umbilical cord mesenchymal stem cells can achieve rapid cell proliferation and migration with little immune response by creating a satisfactory microenvironment. In this study, fusion peptide-mediated EVs are able to modify the surface of the SIS membrane via specific combination. In vitro studies prove that modified SIS membranes can promote cell migration and spreading. This phenomenon may be because of the activation of TEADs, which regulate cell behavior. By constructing a rat abdominal wall defect model, it is further demonstrated that the modified SIS membrane is more conducive to tissue regeneration. Collectively, these results suggest that SIS membranes modified by fusion peptide-mediated EVs achieve excellent biofunction and provide promising prospects for tissue regeneration.

Simulated Microgravity Inhibits Rodent Dermal Fibroblastic Differentiation of Mesenchymal Stem Cells by Suppressing ERK/β-Catenin Signaling Pathway

Studies have shown that bone marrow-derived mesenchymal stem cells (BMSCs) can differentiate into dermal fibroblasts to participate in skin-repairing. However, at present, little is known about how microgravity affects dermal fibroblastic differentiation of BMSCs in space. The aim of this study was to investigate the effect of simulated microgravity (SMG) on the differentiation of BMSCs into dermal fibroblasts and the related molecular mechanism. Here, using a 2D-clinostat device to simulate microgravity, we found that SMG inhibited the differentiation and suppressed the Wnt/β-catenin signaling and phosphorylation of extracellular regulated protein kinases 1/2 (ERK1/2). After upregulating the Wnt/β-catenin signaling with lithium chloride (LiCl) treatment, we found that the effect of the differentiation was restored. Moreover, the Wnt/β-catenin signaling was upregulated when phosphorylation of ERK1/2 was activated with tert-Butylhydroquinone (tBHQ) treatment. Taken together, our findings suggest that SMG inhibits dermal fibroblastic differentiation of BMSCs by suppressing ERK/β-catenin signaling pathway, inferring that ERK/β-catenin signaling pathway may act as a potential intervention target for repairing skin injury under microgravity conditions.

Advantages and challenges of stem cell therapy for osteoarthritis (Review)

Osteoarthritis (OA) is a degenerative disorder of the cartilage and is one of the leading causes of disability, particularly amongst the elderly, wherein patients with advanced-stage OA experience chronic pain and functional impairment of the limbs, thus resulting in a significantly reduced quality of life. The currently available treatments primarily revolve around symptom management, and is thus palliative rather than curative. The aim of the present review is to briefly discuss the limitations of some of the currently available treatments for patients with OA, and highlight the value of the potential use of stem cells in cellular therapy, which is widely regarded as the breakthrough that can address the present unmet medical needs for treatment of degenerative diseases, such as OA. The advantages of stem cell therapy, particularly mesenchymal stem cells, and the challenges involved are also discussed in this review.

Bone Marrow Aspirate Matrix: A Convenient Ally in Regenerative Medicine

The rise in musculoskeletal disorders has prompted medical experts to devise novel effective alternatives to treat complicated orthopedic conditions. The ever-expanding field of regenerative medicine has allowed researchers to appreciate the therapeutic value of bone marrow-derived biological products, such as the bone marrow aspirate (BMA) clot, a potent orthobiologic which has often been dismissed and regarded as a technical complication. Numerous in vitro and in vivo studies have contributed to the expansion of medical knowledge, revealing optimistic results concerning the application of autologous bone marrow towards various impactful disorders. The bone marrow accommodates a diverse family of cell populations and a rich secretome; therefore, autologous BMA-derived products such as the “BMA Matrix”, may represent a safe and viable approach, able to reduce the costs and some drawbacks linked to the expansion of bone marrow. BMA provides —it eliminates many hurdles associated with its preparation, especially in regards to regulatory compliance. The BMA Matrix represents a suitable alternative, indicated for the enhancement of tissue repair mechanisms by modulating inflammation and acting as a natural biological scaffold as well as a reservoir of cytokines and growth factors that support cell activity. Although promising, more clinical studies are warranted in order to further clarify the efficacy of this strategy.

Biofat grafts as an orthobiologic tool in osteoarthritis: An update and classification proposal

Among degenerative musculoskeletal disorders, osteoarthritis remains one of the main causes of pain and disability in the adult population. Current available alternatives to alleviate symptoms include conservative treatments such as physical therapy, anti-inflammatory drugs and an educational approach to lifestyle modification. The use of certain analgesics, such as opiates and corticosteroids offer short-term results but does not address the etiological source of pain and disability. In addition, prolonged use of such medications can cause additional complications. Therefore, the demand for regeneration of joint cartilage has led to an alternative approach called "orthobiologics". This alternative is based on cellular and molecular components capable of inducing and promoting tissue repair. Products derived from adipose tissue have been studied as an excellent source of orthobiologics in an attempt to promote joint cartilage repair. However, the lack of standardization regarding collection and processing protocols presents a challenge for the generalization of study results and determination of effectiveness. To the best of our knowledge, orthobiologics derived from fat have not yet been classified. Therefore, this manuscript proposes the HGS classification system which aims to describe certain parameters that are relevant to the quality of organic products regarding harvesting techniques (H), graft type (G), and number of centrifugations (S). The more parameters used would imply greater characterization and complexity of the evaluation of the biological product used. The HGS classification may provide a valuable contribution to the understanding of clinical procedures and research results, aiming to ultimately usher in a standardization of optimal practice.

Unlocking mammalian regeneration through hypoxia inducible factor one alpha signaling

Historically, the field of regenerative medicine has aimed to heal damaged tissue through the use of biomaterials scaffolds or delivery of foreign progenitor cells. Despite 30 years of research, however, translation and commercialization of these techniques has been limited. To enable mammalian regeneration, a more practical approach may instead be to develop therapies that evoke endogenous processes reminiscent of those seen in innate regenerators. Recently, investigations into tadpole tail regrowth, zebrafish limb restoration, and the super-healing Murphy Roths Large (MRL) mouse strain, have identified ancient oxygen-sensing pathways as a possible target to achieve this goal. Specifically, upregulation of the transcription factor, hypoxia-inducible factor one alpha (HIF-1α) has been shown to modulate cell metabolism and plasticity, as well as inflammation and tissue remodeling, possibly priming injuries for regeneration. Since HIF-1α signaling is conserved across species, environmental or pharmacological manipulation of oxygen-dependent pathways may elicit a regenerative response in non-healing mammals. In this review, we will explore the emerging role of HIF-1α in mammalian healing and regeneration, as well as attempts to modulate protein stability through hyperbaric oxygen treatment, intermittent hypoxia therapy, and pharmacological targeting. We believe that these therapies could breathe new life into the field of regenerative medicine.

Adipose mesenchymal stem cell exosomes promote wound healing through accelerated keratinocyte migration and proliferation by activating the AKT/HIF-1α axis

Accelerating wound healing is a key consideration for surgeons. The three stages of wound healing include the inflammatory response, cell proliferation and tissue repair, and much research has focused on the migration and proliferation of epidermal cells, since this is one of the most important steps in wound healing. Studies have shown that adipose mesenchymal stem cells (ADSCs) can promote wound healing by releasing exosomes, although the specific mechanism remains unclear. To clarify the role of adipose mesenchymal stem cell exosomes (ADSCs-exo), we constructed a HaCaT cells model and a mouse wound healing model to examine the effects of ADSCs-exo on wound healing. CCK8 assays and the scratch test showed that ADSCs-exo could promote the proliferation and migration of HaCaT cells. Western blotting and real-time PCR showed that ADSCs-exo upregulated the phosphorylation of AKT and the expression of HIF-1α in HaCaT cells. HIF-1α expression was reduced by inhibiting AKT phosphorylation,and the migration of HaCaT cells simultaneously slowed. These results were also confirmed in vivo. In conclusion, we confirmed that ADSCs-exo promote the proliferation and migration of HaCaT cells by regulating the activation of the AKT/HIF-1α signaling pathway, thus promoting wound healing.

Mesenchymal Stem Cells for Chronic Wound Healing: Current Status of Preclinical and Clinical Studies

Healing skin wounds with anatomic and functional integrity, especially under chronic pathological conditions, remain an enormous challenge. Due to their outstanding regenerative potential, mesenchymal stem cells (MSCs) have been explored in many studies to determine the healing ability for difficult-to-treat diseases. In this article, we review current animal studies and clinical trials of MSC-based therapy for chronic wounds, and discuss major challenges that confront future clinical applications. We found that a wealth of animal studies have revealed the versatile roles and the benefits of MSCs for chronic wound healing. MSC treatment results in enhanced angiogenesis, facilitated reepithelialization, improved granulation, and accelerated wound closure. There are some evidences of the transdifferentiation of MSCs into skin cells. However, the healing effect of MSCs depends primarily on their paracrine actions, which alleviate the harsh microenvironment of chronic wounds and regulate local cellular responses. Consistent with the findings of preclinical studies, some clinical trials have shown improved wound healing after transplantation of MSCs in chronic wounds, mainly lower extremity ulcers, pressure sores, and radiation burns. However, there are some limitations in these clinical trials, especially a small number of patients and imperfect methodology. Therefore, to better define the safety and efficiency of MSC-based wound therapy, large-scale controlled multicenter trials are needed in the future. In addition, to build a robust pool of clinical evidence, standardized protocols, especially the cultivation and quality control of MSCs, are recommended. Altogether, based on current data, MSC-based therapy represents a promising treatment option for chronic wounds. Impact statement Chronic wounds persist as a significant health care problem, particularly with increasing number of patients and the lack of efficient treatments. The main goal of this article is to provide an overview of current status of mesenchymal stem cell (MSC)-based therapy for chronic wounds. The roles of MSCs in skin wound healing, as revealed in a large number of animal studies, are detailed. A critical view is made on the clinical application of MSCs for lower extremity ulcers, pressure sores, and radiation burns. Main challenges that confront future clinical applications are discussed, which hopefully contribute to innovations in MSC-based wound treatment.

Bone marrow-derived products: A classification proposal - bone marrow aspirate, bone marrow aspirate concentrate or hybrid?

Degenerative musculoskeletal disorders are one of the top causes of pain and disability in the adult population. Current available alternatives to mitigate symptoms include conservative treatments such as the administration of pharmacological agents and an educative approach towards lifestyle modification. The use of certain analgesics, such as opiates and corticosteroids, delivers short term results but do not address the etiological source of pain and disability. Also, prolonged use of such medications may cause additional complications. Therefore, the demand for musculoskeletal tissue regeneration has led to an alternative approach referred to as "orthobiologics". This alternative is based on cellular and molecular components capable of inducing and promoting tissue repair. Bone marrow (BM) aspirate (BMA) and concentrate are well-known orthobiologics used to treat musculoskeletal conditions. Orthobiologics derived from the BM have been discussed in the literature; however, the lack of standardization regarding collection and processing protocols presents a challenge for generalization of study outcomes and determination of efficacy. Since BM-derived orthobiologics have not yet been classified, to our knowledge, this manuscript proposes the ACH classification system, which speaks to BMA (A), BMA and concentrate (C) and hybrid (H), which combines A and C. This classification proposes and describes 8 parameters that are relevant for the quality of biological products. The more parameters used would imply greater characterization and complexity of the evaluation of the biological product used. The ACH classification envisages a necessary contribution to the comprehension of both clinical procedures and research outcomes, ultimately ushering in a standardization of best practice.

Regeneration of skin appendages and nerves: current status and further challenges

Tissue-engineered skin (TES), as an analogue of native skin, is promising for wound repair and regeneration. However, a major drawback of TES products is a lack of skin appendages and nerves to enhance skin healing, structural integrity and skin vitality. Skin appendages and nerves are important constituents for fully functional skin. To date, many studies have yielded remarkable results in the field of skin appendages reconstruction and nerve regeneration. However, patients often complain about a loss of skin sensation and even cutaneous chronic pain. Restoration of pain, temperature, and touch perceptions should now be a major challenge to solve in order to improve patients’ quality of life. Current strategies to create skin appendages and sensory nerve regeneration are mainly based on different types of seeding cells, scaffold materials, bioactive factors and involved signaling pathways. This article provides a comprehensive overview of different strategies for, and advances in, skin appendages and sensory nerve regeneration, which is an important issue in the field of tissue engineering and regenerative medicine.

Cellular Senescence as the Pathogenic Hub of Diabetes-Related Wound Chronicity

Diabetes is constantly increasing at a rate that outpaces genetic variation and approaches to pandemic magnitude. Skin cells physiology and the cutaneous healing response are progressively undermined in diabetes which predisposes to lower limb ulceration, recidivism, and subsequent lower extremities amputation as a frightened complication. The molecular operators whereby diabetes reduces tissues resilience and hampers the repair mechanisms remain elusive. We have accrued the notion that diabetic environment embraces preconditioning factors that definitively propel premature cellular senescence, and that ulcer cells senescence impair the healing response. Hyperglycemia/oxidative stress/mitochondrial and DNA damage may act as major drivers sculpturing the senescent phenotype. We review here historical and recent evidences that substantiate the hypothesis that diabetic foot ulcers healing trajectory, is definitively impinged by a self-expanding and self-perpetuative senescent cells society that drives wound chronicity. This society may be fostered by a diabetic archetypal secretome that induces replicative senescence in dermal fibroblasts, endothelial cells, and keratinocytes. Mesenchymal stem cells are also susceptible to major diabetic senescence drivers, which accounts for the inability of these cells to appropriately assist in diabetics wound healing. Thus, the use of autologous stem cells has not translated in significant clinical outcomes. Novel and multifaceted therapeutic approaches are required to pharmacologically mitigate the diabetic cellular senescence operators and reduce the secondary multi-organs complications. The senescent cells society and its adjunctive secretome could be an ideal local target to manipulate diabetic ulcers and prevent wound chronification and acute recidivism. This futuristic goal demands harnessing the diabetic wound chronicity epigenomic signature.

Novel trends in application of stem cells in skin wound healing

The latest findings indicate the huge therapeutic potential of stem cells in regenerative medicine, including the healing of chronic wounds. Main stem cell types involved in wound healing process are: epidermal and dermal stem cells, mesenchymal stem cells (MSCs), endothelial progenitor cells (EPCs) and hematopoietic stem cells (HSCs). In the therapy of chronic wounds, they can be administrated either topically or using different matrix like hydrogels, scaffolds, dermal substitutes and extracellular matrix (ECM) derivatives. Stem cells are proven to positively influence wound healing by different direct and indirect mechanisms including residing cells stimulation, biomolecules release, inflammation control and ECM remodelling. MSCs are especially worth mentioning as they can be easily derived from bone-marrow or adipose tissue. Apart from traditional approach of administering living stem cells to wounds, new trends have emerged in recent years. Good healing results are obtained using stem cell secretome alone, for example exosomes or conditioned media. There are also attempts to improve healing potential of stem cells by their co-culture with other cell types as well as by their genetic modifications or pretreatment using different chemicals or cell media. Moreover, stem cells have been tested for novel therapeutic purposes like for example acute burns and have been used in experiments on large animal models including pigs and sheep. In this review we discuss the role of stem cells in skin wound healing acceleration. In addition, we analyse possible new strategies of stem cells application in treatment of chronic wounds.

Effectiveness of a single intra-articular bone marrow aspirate concentrate (BMAC) injection in patients with grade 3 and 4 knee osteoarthritis

Aim

To evaluate the clinical efficacy and safety of an intra-articular injection of bone marrow aspirate concentrate (BMAC) as a treatment option for osteoarthritis (OA) of the knee.

Materials and methods

Between June 2014 and February 2017, data from 233 patients with knee osteoarthritis treated with BMAC injection at a single center, were retrospectively evaluated. Only patients with idiopathic osteoarthritis were included. Exclusion criteria were post-traumatic osteoarthritis, previous knee surgery, age less than 50 years old or more than 85 years old, active infection, uncontrolled diabetes mellitus, rheumatological or other systemic disease, malignancy, or treatment with immunosuppressive drugs. Bone marrow from the iliac crest was aspirated/concentrated with a standardized technique using a single-spin manual method. Patients were evaluated before and after the procedure, using the numeric pain scale (NPS) and Oxford knee score (OKS). Mean follow-up period was 11 months, range (6–30 months).

Results

A total of 121 of 233 patients had completed data as previously defined and were included in the statistical analysis. There were 85 females and 36 males, with mean age 70 years (range 50–85). Compared to baseline, the mean NPS decreased from 8.33 to 4.49 (p < 0.001) and the mean OKS increased from 20.20 to 32.29 (P < 0.001) at final follow-up. There were no complications.

Conclusion

A single intra-articular injection of BMAC is a safe and reliable procedure that results in clinical improvement of knee OA.

Differentiation Potential of Human Wharton's Jelly-Derived Mesenchymal Stem Cells and Paracrine Signaling Interaction Contribute to Improve the In Vitro Maturation of Mouse Cumulus Oocyte Complexes

In vitro maturation (IVM) in cumulus oocyte complexes (COCs) can be improved by the presence of human Wharton's jelly-derived MSCs (hWJ-MSCs), under specific culture conditions. COCs were cultured in twelve different culture systems, composed of four stock media, stock media conditioned with hWJ-MSCs, and stock media in which the oocytes were indirectly cocultured with the hWJ-MSCs. The rates of maturation to meiosis II were compared among the groups. G2-PLUS and coculture with DMEM-F12 were the most efficient systems for the maturation of COCs. The fertilization rate and rate of development to the blastocyst stage were compared between these two groups. Moreover, hWJ-MSC-conditioned media showed no benefits for the COC-IVM. The analysis of OCT4 expression of hWJ-MSCs in G1-PLUS, TYH, and G2-PLUS showed a downregulation of OCT4 by 25.9, 24.7, and 6.6%, respectively, compared to that in hWJ-MSCs cultured in DMEM-F12. Finally, we have demonstrated that two prerequisites appeared to be necessary for the hWJ-MSCs to improve the IVM of COCs: hWJ-MSCs' differentiation potential and the presence of coordinated paracrine interaction between the stem cells and COCs. Under the appropriate conditions, the paracrine factors produced in the coculture system with DMEM-F12 may help to develop synthetic media for successful in vitro culture of COCs.

Regenerative potential of partially differentiated mesenchymal stromal cells in a mouse model of a full-thickness skin wound

Mesenchymal stromal cells (MSCs, known as mesenchymal stem cells) are considered to be a promising therapeutic tool for many diseases. But it is still unclear which cells are more efficient and safe for wound healing and tissue regeneration for clinical applications: undifferentiated, partially differentiated stem cells or differentiated cells. In this study, we modified MSCs with keratinocyte-conditioned medium (KCM) and examined MSCs, partially differentiated MSCs (PMSCs) and differentiated cell migration, accumulation in the wounded area as well as cell regenerative efficiency in a full-thickness skin wound model. In addition to that, the impact of intradermal and intravenous cell delivery methods of wound healing was evaluated. C57BL/6J mouse compact bone MSCs were treated with a KCM for 14 days. Flow cytometry analysis showed the appearance of keratinocyte surface markers which were absent in MSCs, whereas the specific markers for MSCs were lost. Cells were injected either intravenously or intradermally in C57BL/6J mice. Wound closure, cell migration and accumulation in the wounded area were further analysed. Wound healing was assessed by the rate of wound closure and by histological evaluation. Cells were monitored using optical imaging. We demonstrated that PMSCs showed morphology similar to keratinocyte cells, had enhanced migration and increased survival at the site of injury. PMSCs had a beneficial effect on wound healing and tissue regeneration. This effect was reinforced when these cells were injected intravenously. Due to their partial differentiation status, we assume that PMSCs can differentiate more rapidly into epidermal cell lineages thus causing faster and qualitatively improved wound healing.

Effect of substrate stiffness on proliferation and differentiation of periodontal ligament stem cells

OBJECTIVES

The aim of this study was to understand the effect of substrate stiffness (a mechanical factor of the extracellular matrix) on periodontal ligament stem cells (PDLSCs) and its underlying mechanism.

MATERIALS AND METHODS

Elastic substrates were fabricated by mixing 2 components, a base and curing agent in proportions of 10:1, 20:1, 30:1 or 40:1. PDLSC morphology was observed using scanning electron microscopy (SEM). Cell proliferation and differentiation were assessed after PDLSCs was cultured on various elastic substrates. Data were analysed using one-way ANOVA.

RESULTS

SEM revealed variations in the morphology of PDLSCs cultured on elastic substrates. PDLSC proliferation increased with substrate stiffness (P < .05). Osteogenic differentiation of PDLSCs was higher on stiff substrates. Notch pathway markers were up-regulated in PDLSCs cultured on stiff substrates.

CONCLUSIONS

Results suggested that the osteogenic differentiation of PDLSCs might be promoted by culturing them in a stiffness-dependent manner, which regulates the Notch pathway. This might provide a new method of enhancing osteogenesis in PDLSCs.

The Combined Effects of Bone Marrow-Derived Mesenchymal Stem Cells and Microporous Porcine Acellular Dermal Matrices on the Regeneration of Skin Accessory Cells In Vivo

We investigated the effects of microporous porcine acellular dermal matrices (MPADM)-containing bone marrow-derived mesenchymal stem cells (BMMSCs) on accessory skin cell regeneration in vivo. Two kinds of the porcine acellular dermal matrices were prepared: one with microsized pores (the MPADM) and another without pores (the PADM). BMMSC populations from a Sprague-Dawley (SD) rat were seeded on both PADMs and MPADMs and cultured in vitro for 5 days. These rats were randomly divided into four groups: BMMSCs on an MPADM and covered with a PADM layer (group A), MPADM without cells and covered with a split-thickness skin graft (SSG) (group B), BMMSCs on an MPADM and covered with an SSG (group C), and BMMSCs on a PADM and covered with an SSG (group D). On post-surgery day (PSD) 5, all groups survived, except for group D. On PSD 7, there was no significant difference in the functional vascularization between groups A, B, and C. On PSD 14, large quantities of new capillaries, a larger rough endoplasmic reticulum in fibroblasts, and de novo unmyelinated nerve endings could be observed at the junction between the skin graft and the dermal matrix in group C; however, these structures were absent in groups A and B. The experimental results showed that MPADM could induce exogenous differentiation of BMMSCs in vivo and promote reconstruction of skin accessory cells.

Delivery systems of current biologicals for the treatment of chronic cutaneous wounds and severe burns

While wound therapy remains a clinical challenge in current medical practice, much effort has focused on developing biological therapeutic approaches. This paper presents a comprehensive review of delivery systems for current biologicals for the treatment of chronic wounds and severe burns. The biologicals discussed here include proteins such as growth factors and gene modifying molecules, which may be delivered to wounds free, encapsulated, or released from living systems (cells, skin grafts or skin equivalents) or biomaterials. Advances in biomaterial science and technologies have enabled the synthesis of delivery systems such as scaffolds, hydrogels and nanoparticles, designed to not only allow spatially and temporally controlled release of biologicals, but to also emulate the natural extracellular matrix microenvironment. These technologies represent an attractive field for regenerative wound therapy, by offering more personalised and effective treatments.

Human umbilical cord Wharton jelly cells promote extra-pancreatic insulin formation and repair of renal damage in STZ-induced diabetic mice

BACKGROUND

We evaluated the therapeutic effect and fate of high doses of human umbilical cord Wharton jelly cells (hUCWJCs) after IP administration to streptozotocin (STZ)-induced diabetic mice.

METHODS

Type 1 diabetes (T1D) was induced in Kunming mice via IP injection of STZ. hUCWJCs were labeled with 1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate (DiI). Diabetic animals with sustained hyperglycemia for at least 2 weeks were administered 1 × 10⁷ Dil-hUCWJCs via intraperitoneal injection. Insulin, glucagon and PDX-1 were detected by immunofluorescence with confocal microscopy. Serum mouse and human C-peptide was assayed in blood collected via intracardiac puncture. Specific β-cell differentiation markers and human DNA were assessed using qPCR performed with 200 ng of target DNA.

RESULTS

hUCWJCs migrated to the STZ-damaged organs and contributed to lower blood glucose levels in 30% of the treated mice. Confocal microscopy revealed the presence of resident insulin-positive cells in the liver and kidneys. hUCWJC-treated mice with restored hyperglycemia also showed increased serum mouse C-peptide levels. The qPCR results, particularly in the liver, revealed that after transplantation hUCWJCs upregulated genes of endocrine precursors but failed to express endocrine stage markers. Mice with restored hyperglycemia had reduced urinary volume and lacked glomerular hypertrophy, exhibiting a morphology resembling that of normal glomeruli. Moreover, we also verified that one of the possible mechanisms by which hUCWJCs exert immunosuppressive effects is through down-regulation of the cell surface receptor HLA-1.

CONCLUSIONS

We confirmed the potential of IP administration of hUCWJCs and the capability of these cells to migrate to damaged tissues and promote insulin secretion from non-pancreatic local cells and to improve renal damage. These findings confer unique therapeutic properties to hUCWJCs, suggesting a promising future in the treatment of diabetes mellitus.

Bioinformatics analysis of fibroblasts exposed to TGF‑β at the early proliferation phase of wound repair

The aim of the current study was to identify gene signatures during the early proliferation stage of wound repair and the effect of TGF-β on fibroblasts and reveal their potential mechanisms. The gene expression profiles of GSE79621 and GSE27165 were obtained from GEO database. Differentially expressed genes (DEGs) were identified using Morpheus and co-expressed DEGs were selected using Venn Diagram. Gene ontology (GO) function and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis of DEGs were performed using the Database for Annotation, Visualization and Integrated Discovery (DAVID) online tool. Protein-protein interaction (PPI) networks of the DEGs were constructed using Cytoscape software. PPI interaction network was divided into subnetworks using the MCODE algorithm and the function of the top one module was analyzed using DAVID. The results revealed that upregulated DEGs were significantly enriched in biological process, including the Arp2/3 complex-mediated actin nucleation, positive regulation of hyaluronan cable assembly, purine nucleobase biosynthetic process, de novo inosine monophosphate biosynthetic process, positive regulation of epithelial cell proliferation, whereas the downregulated DEGs were enriched in the regulation of blood pressure, negative regulation of cell proliferation, ossification, negative regulation of gene expression and type I interferon signaling pathway. KEGG pathway analysis showed that the upregulated DEGs were enriched in shigellosis, pathogenic Escherichia coli infection, the mitogen-activated protein kinase signaling pathway, Ras signaling pathway and bacterial invasion of epithelial cells. The downregulated DEGs were enriched in systemic lupus erythematosus, lysosome, arachidonic acid metabolism, thyroid cancer and allograft rejection. The top 10 hub genes were identified from the PPI network. The top module analysis revealed that the included genes were involved in ion channel, neuroactive ligand-receptor interaction pathway, purine metabolism and intestinal immune network for IgA production pathway. The functional analysis revealed that TGF-β may promote fibroblast migration and proliferation and defend against microorganisms at the early proliferation stage of wound repair. Furthermore, these results may provide references for chronic wound repair.

Wound Healing Effect of Conditioned Media Obtained From Adipose Tissue on Human Skin Cells: A Comparative in Vitro Study

BACKGROUND

Split-thickness skin grafting is the gold standard to cover extensive acute and chronic wounds with a well-vascularized wound bed. Although some headway has been made in developing biological agents to speed up healing, there is still no treatment that sufficiently replaces skin grafts to date. The use of secretory factors of adipose tissue may be a feasible approach to developing topical wound applications for faster wound healing.

METHODS

In this study, the effect of conditioned media (CMs) of human adipose-derived stem cells (ASCs), adipocytes, or adipose tissue on human skin cells was evaluated for viability, proliferation, and migration in vitro. Differentiation potential of stem cells treated with CM was monitored by AdipoRed staining and qualitative real-time polymerase chain reaction. Angiogenic potential of human endothelial cells treated with CM was tested via sprouting assay.

RESULTS

The CM of adipose tissue significantly enhanced ASC proliferation (P < 0.01). Treatment with CM showed no inductive effect on ASC differentiation into adipocytes but, at the same time, significantly induced cell sprouting of endothelial cells (P < 0.001). We show for the first time that CM of adipose tissue is a potent inducer of proliferation of ASCs and angiogenesis, with comparable effects with those of stem cell-enriched CM.

CONCLUSIONS

We suggest the use of the secretome of adipose tissue to produce CM for topical application on wounds, rather than working with adipose tissue or including the difficult process of enriching the patients' stem cells in vitro.

Effects of Mesenchymal Stem Cell Derivatives on Hematopoiesis and Hematopoietic Stem Cells

Hematopoiesis is a balance among quiescence, self-renewal, proliferation, and differentiation, which is believed to be firmly adjusted through interactions between hematopoietic stem and progenitor cells (HSPCs) with the microenvironment. This microenvironment is derived from a common progenitor of mesenchymal origin and its signals should be capable of regulating the cellular memory of transcriptional situation and lead to an exchange of stem cell genes expression. Mesenchymal stem cells (MSCs) have self-renewal and differentiation capacity into tissues of mesodermal origin, and these cells can support hematopoiesis through release various molecules that play a crucial role in migration, homing, self-renewal, proliferation, and differentiation of HSPCs. Studies on the effects of MSCs on HSPC differentiation can develop modern solutions in the treatment of patients with hematologic disorders for more effective Bone Marrow (BM) transplantation in the near future. However, considerable challenges remain on realization of how paracrine mechanisms of MSCs act on the target tissues, and how to design a therapeutic regimen with various paracrine factors in order to achieve optimal results for tissue conservation and regeneration. The aim of this review is to characterize and consider the related aspects of the ability of MSCs secretome in protection of hematopoiesis.

The biological and clinical basis for the use of adipose-derived stem cells in the field of wound healing

Worldwide, hard-to-heal lower limb wounds are estimated to affect 1.5–3% of the adult population with a treatment-related annual cost of $10 billion. Thus, chronic skin ulcers of the lower limb are a matter of economic and public concern. Over the years, multiple medical and surgical approaches have been proposed but they are still inadequate, and no effective therapy yet exists. Regenerative medicine and stem cell-based therapies hold great promise for wound healing. Recently, many plastic surgeons have studied the potential clinical application of adipose-derived stem cells (ASCs), which are a readily available adult stem cell population that can undergo multilineage differentiation and secrete growth factors that can enhance wound-healing processes by promoting angiogenesis, and hence increase local blood supply. ASCs have been widely studied in vitro and in vivo in animal models. However, there are few randomized clinical trials on humans, and these are still ongoing or recruiting patients. Moreover, there is no consensus on a common isolation protocol that is clinically feasible and which would ensure reproducible results. The authors aim to provide readers with an overview of the biological properties of ASCs as well as their clinical application, to help better understanding of present and future strategies for the treatment of hard-to-heal wounds by means of stem cell-based therapies.

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Worldwide, hard-to-heal wounds are a matter of economic and public concern.

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The emerging fields of regenerative medicine and stem cell-based therapies hold great promise for wound healing.

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ASCs can potentially give the support necessary for recovery of hard-to-heal wounds.

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ASCs can be easily harvested from adipose tissue by means of standard wet liposuction technique.

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ASCs have been widely studied in vitro and in vivo to demonstrate their potential and safety.

Trauma and Stem Cells: Biology and Potential Therapeutic Implications

Trauma may cause irreversible tissue damage and loss of function despite current best practice. Healing is dependent both on the nature of the injury and the intrinsic biological capacity of those tissues for healing. Preclinical research has highlighted stem cell therapy as a potential avenue for improving outcomes for injuries with poor healing capacity. Additionally, trauma activates the immune system and alters stem cell behaviour. This paper reviews the current literature on stem cells and its relevance to trauma care. Emphasis is placed on understanding how stem cells respond to trauma and pertinent mechanisms that can be utilised to promote tissue healing. Research involving notable difficulties in trauma care such as fracture non-union, cartilage damage and trauma induced inflammation is discussed further.

Comparative study on characterization and wound healing potential of goat (Capra hircus) mesenchymal stem cells derived from fetal origin amniotic fluid and adult bone marrow

Caprine amniotic fluid (cAF) and bone marrow cells (cBM) were isolated, expanded and phenotypically characterized by mesenchymal stem cells (MSCs) specific cell surface markers. Both cell types were compared for multilineage differentiation potential by flow cytometry using specific antibodies against lineage specific markers. Furthermore, in vitro expanded cAF-MSCs showed higher expression of trophic factors viz. VEGF and TGF-β1 as compared to cBM-MSCs. Full-skin thickness excisional wounds created on either side of the dorsal midline (thoracolumbar) of New Zealand White rabbits were randomly assigned to subcutaneous injection of either fetal origin cAF-MSCs (n=4) or adult cBM-MSCs (n=4) or sterile PBS (control, n=4). The rate of wound closure was found faster (p<0.05) in cAF-MSCs treated wounds as compared with cBM-MSCs and PBS treated wounds especially on 21st day post-skin excision. Histomorphological examination of the healing tissue showed that wound healing was improved (p<0.05) by greater epithelialization, neovascularization and collagen development in cAF-MSCs as compared to cBM-MSCs and PBS treated wounds.

Restoration of miR-1305 relieves the inhibitory effect of nicotine on periodontal ligament-derived stem cell proliferation, migration, and osteogenic differentiation

BACKGROUND

Nicotine hinders the regenerative potentials of human periodontal ligament-derived stem cells (PDLSCs) and delays the healing process of periodontal diseases, but the underlying mechanism remains unclear. miR-1305 upregulation and its potential target RUNX2 downregulation exist in the PDLSCs exposed to nicotine. In this study, we aimed to investigate whether nicotine inhibits PDLSC proliferation, migration, and osteogenic differentiation by increasing miR-1305 level and decreasing RUNX2 level.

METHODS

Quantitative real-time PCR (qRT-PCR) and Western blot assays were performed to detect the expression levels of miR-1305 and RUNX2 in the PDLSCs exposed to nicotine, respectively. PDLSCs with miR-1305 overexpression, low expression, or RUNX2 overexpression were constructed by lipofectin transfection. MTT, migration, and Western blot assays were applied to assess the effect of miR-1305 on PDLSC proliferation, migration, and osteogenic differentiation, respectively. Target prediction and luciferase reporter assays were performed to investigate the targets of miR-1305.

RESULTS

Nicotine promoted miR-1305 expression and inhibited RUNX2 expression in PDLSCs. Cell proliferation, migration, and differentiation detection showed that nicotine suppressed proliferation, migration, and osteogenic differentiation of PDLSCs, and restoration of miR-1305 relieved the inhibitory effect of nicotine on PDLSCs. Moreover, we identified and validated that RUNX2 was a direct target of miR-1305, and upregulation of RUNX2 had similar effects with the downregulation of miR-1305 on relieving the inhibitory effect of nicotine on PDLSCs.

CONCLUSION

Nicotine suppresses proliferation, migration, and osteogenic differentiation of PDLSCs, and restoration of miR-1305 relieves the inhibitory effect of nicotine on PDLSCs depending on its target RUNX2.

Bone Marrow Aspirate in the Treatment of Chondral Injuries

The ability of mesenchymal stem cells (MSCs) to transdifferentiate into a desired cell lineage has captured the imagination of scientists and clinicians alike. The limited ability for chondrocytes to regenerate in chondral injuries has raised the concept of using MSCs to help regenerate and repair damaged tissue. The expansion of cells in a laboratory setting to be delivered back to the patient is too costly for clinical use in the present tough economic climate. This process is slow with due to the complexity of trying to imitate the natural environment and biological stimulation of chondral cell replication and proliferation. Bone marrow aspirate concentrate (BMAC) has the potential to provide an easily accessible and readily available source of MSCs with key growth factors that can be used in treating chondral injuries. This review summarizes the underlying basic science of MSCs and the therapeutic potential of BMAC.

Will stem cells bring hope to pathological skin scar treatment?

Pathological skin scars, such as keloids, aesthetically and psychosocially affect patients. The quest for scar reduction and the increasing recognition of patient satisfaction has led to the continued exploration of scar treatment. Stem cells are a promising source for tissue repair and regeneration. The multi-potency and secretory functions of these cells could offer possible treatments for pathological scars and have been examined in recent studies. Here, we analyze the factors that influence the formation of pathological skin scars, summarize recent research on pathological scar treatment with stem cells and elaborate on the possible mechanisms of this treatment. Additionally, other effects of stem cell treatments are also presented while evaluating potential side effects of stem cell-based pathological scar treatments. Thus, this review may provide meaningful guidance in the clinic for scar treatments with stem cells.

EDTA soluble chemical components and the conditioned medium from mobilized dental pulp stem cells contain an inductive microenvironment, promoting cell proliferation, migration, and odontoblastic differentiation

Background

The critical challenge in tissue engineering is to establish an optimal combination of stem cells, signaling morphogenetic molecules, and extracellular matrix scaffold/microenvironment. The extracellular matrix components of teeth may be reconstituted as an inductive microenvironment in an ectopic tooth transplantation bioassay. Thus, the isolation and identification of the chemical components of the inductive microenvironment in pulp/dentin regeneration will accelerate progress towards the goal of tissue engineering of the tooth.

Methods

The teeth demineralized in 0.6 M hydrochloric acid were sequentially extracted by 4.0 M guanidine hydrochloride (GdnHCl), pH 7.4, and 0.5 M ethylenediaminetetraacetic acid (EDTA), pH 7.4. The extracted teeth were transplanted into an ectopic site in severe combined immunodeficiency (SCID) mice with mobilized dental pulp stem cells (MDPSCs). The unextracted tooth served as a positive control. Furthermore, the soluble components for the inductive microenvironment, the GdnHCl extracts, or the EDTA extracts together with or without MDPSC conditioned medium (CM) were reconstituted systematically with autoclaved teeth in which the chemical components were completely inactivated and only the physical microenvironment was preserved. Their pulp/dentin regenerative potential and angiogenic potential were compared 28 days after ectopic tooth transplantation by histomorphometry and real-time RT-PCR analysis.

Results

Expression of an odontoblastic marker, enamelysin, and a pulp marker, thyrotropin-releasing hormone degrading enzyme (TRH-DE), was lower, and expression of a periodontal cell marker, anti-asporin/periodontal ligament-associated protein 1 (PLAP-1), was higher in the transplant of the EDTA-extracted teeth compared with the GdnHCl-extracted teeth. The autoclaved teeth reconstituted with the GdnHCl extracts or the EDTA extracts have weak regenerative potential and minimal angiogenic potential, and the CM significantly increased this potential. Combinatorial effects of the EDTA extracts and the CM on pulp/dentin regeneration were demonstrated in vivo, consistent with their in-vitro effects on enhanced proliferation, migration, and odontoblastic differentiation.

Conclusions

The EDTA-extracted teeth demonstrated significantly lower pulp/dentin regenerative potential compared with the GdnHCl-extracted teeth. The EDTA soluble chemical components when reconstituted with the physical structure of autoclaved teeth serve as an inductive microenvironment for pulp/dentin regeneration, promoting cell proliferation, migration, and odontoblastic differentiation.

Electronic supplementary material

The online version of this article (doi:10.1186/s13287-016-0334-z) contains supplementary material, which is available to authorized users.

Stromal cell-derived factor-1 promotes human adipose tissue-derived stem cell survival and chronic wound healing

Adipose tissue-derived stem cells (ADSCs) hold great potential for the stem cell-based therapy of cutaneous wound healing. Stromal cell-derived factor-1 (SDF-1) activates CXC chemokine receptor (CXCR)4⁺ and CXCR7⁺ cells and plays an important role in wound healing. Increasing evidence suggests a critical role for SDF-1 in cell apoptosis and the survival of mesenchymal stem cells. However, the function of SDF-1 in the apoptosis and wound healing ability of ADSCs is not well understood. The aim of this study was to analyze the effect of SDF-1 on the apoptosis and therapeutic effect of ADSCs in cutaneous chronic wounds in vitro and in vivos. By flow cytometric analysis, it was found that hypoxia and serum free promoted the apoptosis of ADSCs. When pretreated with SDF-1, the apoptosis of ADSCs induced by hypoxia and serum depletion was partly recovered. Furthermore, in vivo experiments established that the post-implantation cell survival and chronic wound healing ability of ADSCs were increased following pretreatment with SDF-1 in a diabetic mouse model of chronic wound healing. To explore the potential mechanism underlying the effect of SDF-1 on ADSC apoptosis, western blot analysis was employed and the results indicate that SDF-1 may protect against cell apoptosis in hypoxic and serum-free conditions through activation of the caspase signaling pathway in ADSCs. This study provides evidence that SDF-1 pretreatment can increase the therapeutic effect of ADSCs in cutaneous chronic wounds in vitro and in vivo.

Mesenchymal Stem Cells in Chronic Wounds: The Spectrum from Basic to Advanced Therapy

Significance: Almost 7 million Americans have chronic cutaneous wounds and billions of dollars are spent on their treatment. The number of patients with nonhealing wounds keeps increasing worldwide due to an ever-aging population, increasing number of obese and diabetic patients, and cardiovascular disease. Recent Advances: Advanced treatments for difficult wounds are needed. Therapy with mesenchymal stem cells (MSCs) is attractive due to their differentiating potential, their immunomodulating properties, and their paracrine effects. Critical Issues: New technologies (including growth factors and skin substitutes) are now widely used for stimulating wound healing. However, in spite of these advances, the percentage of complete wound closure in most clinical situations is around 50-60%. Moreover, there is a high rate of wound recurrence. Future Directions: Recently, it has been demonstrated that MSCs speed up wound healing by decreasing inflammation, by promoting angiogenesis, and by decreasing scarring. However, there are some potential limitations to successful MSC therapy. These limitations include the need to improve cell delivery methods, cell viability, heterogeneity in MSC preparations, and suboptimal wound bed preparation. Further large, controlled clinical trials are needed to establish the safety of MSCs before widespread clinical application.

Secretory factors of human chorion-derived stem cells enhance activation of human fibroblasts

BACKGROUND AIMS

Wound healing remains a principal challenge in modern medical science. Chorion-dervied stem cells (CDSCs), isolated from human placenta, have largely been overlooked, and few studies on their potential in wound healing have been conducted. In this study, we investigated the functional characteristics of CDSCs compared with adipose-derived stem cells (ASCs) on human fibroblasts (HFs).

METHODS

We analyzed CDSCs by means of flow cytometry to confirm their mesenchymal stromal cell characteristics. We then evaluated the paracrine effects of CDSCs on HFs in a co-culture system and focused on fibroblast proliferation, migration and collagen synthesis. To explore the potential of CDSCs in wound healing, CDSC- and ASC-secreted factors were compared by use of a cytokine antibody array.

RESULTS

CDSCs had morphology similar to MSCs and expressed a mesenchymal stromal cell phenotype. HF proliferation and migration increased more than 5-fold when co-cultured with CDSCs. Furthermore, Western blot and reverse transcription-polymerase chain reaction analysis showed that expression of collagen (types I and III) in fibroblasts was upregulated 2-fold when co-cultured with CDSCs. Cytokine array results of CDSC-conditioned medium and ASC-conditioned medium revealed the presence of growth factors known to influence wound healing, including interleukin -6, interleukin -8, monocyte chemotactic protein 1 and regulated on activation, normal T cells expressed and secreted.

CONCLUSIONS

Our data demonstrated that CDSCs are functionally similar to ASCs, promote HF activation, and secrete growth factors that influence wound healing. Therefore, we suggest that CDSCs are potentially applicable in wound healing.