Transplantation of dermal multipotent cells promotes the hematopoietic recovery in sublethally irradiated rats

A Beginner's Introduction to Skin Stem Cells and Wound Healing

The primary function of the skin is that of a physical barrier against the environment and diverse pathogens; therefore, its integrity is essential for survival. Skin regeneration depends on multiple stem cell compartments within the epidermis, which, despite their different transcriptional and proliferative capacity, as well as different anatomical location, fall under the general term of skin stem cells (SSCs). Skin wounds can normally heal without problem; however, some diseases or extensive damage may delay or prevent healing. Non-healing wounds represent a serious and life-threatening scenario that may require advanced therapeutic strategies. In this regard, increased focus has been directed at SSCs and their role in wound healing, although emerging therapeutical approaches are considering the use of other stem cells instead, such as mesenchymal stem cells (MSCs). Given its extensive and broad nature, this review supplies newcomers with an introduction to SSCs, wound healing, and therapeutic strategies for skin regeneration, thus familiarizing the reader with the subject in preparation for future in depth reading.

Bone marrow-derived mesenchymal stem cells laden novel thermo-sensitive hydrogel for the management of severe skin wound healing

Bone marrow-derived mesenchymal stem cells (BMSCs) are easy to collect and culture, and it is identified that it has multi-directional differentiation potential, moreover it has low immunogenicity, hence it can be used as an allogeneic cell source for skin wound healing. Hydrogel has been widely used in skin wound healing own to it is able to mimic the 3D microenvironment of cells, which supports cell proliferation, migration and secretion. In this study, we created a novel biocompatible thermo-sensitive hydrogel to carry BMSCs for full-thickness skin wound healing. The thermo-sensitive hydrogel loaded with BMSCs can fast achieve sol-gel transition after implanting to the wound. Histological results confirmed that hydrogel-BMSCs combination group showed significant promotion of wound closure, epithelial cells' proliferation and re-epithelialization, and reduced inflammatory responses in the wounds and in the tissues surrounding the wounds. The combination therapy also can promote collagen deposition, TGF-β1 and bFGF secretion and tissue remodeling. The present study provides a promising strategy for the clinical treatment of skin wounds.

Non-cultured dermal-derived mesenchymal cells attenuate sepsis induced by cecal ligation and puncture in mice

Sepsis remains a threat to critically ill patients and carries a high morbidity and mortality. Cell-based therapies have risen in prominence in recent years. Dermal-derived mesenchymal cells (DMCs) are attractive as one of the abundant sources from which to isolate mesenchymal cells for therapeutic applications and can be easily accessed with minimal harm to the donor. In this study, we described for the first time the use of non-cultured DMCs for treating sepsis in a cecal ligation and puncture (CLP) mouse model and investigated their immunomodulatory effects. We found that non-cultured DMCs administration provides a beneficial effect to improve survival in CLP-induced sepsis. This effect is partly mediated by the ability of DMCs to home to sites of injury, to reduce the inflammatory response, to inhibit apoptosis, and to stimulate macrophage migration and phagocytosis. Our further findings suggest that DMCs treatment modulates the beneficial cytoprotective effects exhibited during sepsis, at least in part, by altering miRNA expression. These discoveries provide important evidence that non-cultured DMCs therapy has a specific anti-inflammatory effect on sepsis, and provide the basis for the development of a new therapeutic strategy for managing clinical sepsis.

Therapeutic Implications of Newly Identified Stem Cell Populations From the Skin Dermis

Skin, the largest organ of the body, is a promising reservoir for adult stem cells. The epidermal stem cells and hair follicle stem cells have been well studied for their important roles in homeostasis, regeneration, and repair of the epidermis and appendages for decades. However, stem cells residing in dermis were not identified until the year 2001, when a variety of stem cell subpopulations have been isolated and identified from the dermis of mammalian skin such as neural crest stem cells, mesenchymal stem cell-like dermal stem cells, and dermal hematopoietic cells. These stem cell subpopulations exhibited capabilities of self-renewing, multipotent differentiating, and immunosuppressive properties. Hence, the dermis-derived stem cells showed extensive potential applications in regenerative medicine, especially for wound healing/tissue repair, neural repair, and hematopoietic recovery. Here we summarized current research on the stem cell subpopulations derived from the dermis and aimed to provide a comprehensive review on their isolation, specific markers, differentiation capacity, and the functional activities in homeostasis, regeneration, and tissue repair.

The immunosuppressive properties of non-cultured dermal-derived mesenchymal stromal cells and the control of graft-versus-host disease

Mesenchymal stromal cells (MSCs) have been developed for the prevention and treatment of graft-versus-host disease (GVHD). Non-cultured natural MSCs are considered ideal, as they better maintain their biological and therapeutic properties. The skin is the largest organ in the body and constitutes an interesting alternative to bone marrow for the generation of MSCs. Large numbers of dermal-derived-MSCs (DMSCs) can be easily generated without culturing in vitro, but their therapeutic effects still remain unclear. In this study, we described for the first time the use of non-cultured DMSCs for controlling GVHD in an MHC-mismatched mouse model and investigated their immunomodulatory effects. Our results showed that non-cultured mouse DMSCs decreased the incidence and severity of acute GVHD during MHC-mismatched stem cell transplantation in mice. This effect was mediated by the inhibition of splenic cell (SPC) proliferation and the enhancement of Treg cells. Consistent with the results in vivo, the results in vitro showed that human DMSCs inhibited the proliferation of peripheral blood mononuclear cells (PBMCs) by inhibiting the proliferation of CD3(+) T cells. hDMSCs prevented PBMCs from entering S phase, suppressed the activation of CD3(+) T cells and increased Treg proportions. In conclusion, DMSCs should be considered as a novel MSC source for the control of refractory GVHD.

Isolation and characterization of two kinds of stem cells from the same human skin back sample with therapeutic potential in spinal cord injury

Backgrounds and Objective

Spinal cord injury remains to be a challenge to clinicians and it is attractive to employ autologous adult stem cell transplantation in its treatment, however, how to harvest cells with therapeutic potential easily and how to get enough number of cells for transplantation are challenging issues. In the present study, we aimed to isolate skin-derived precursors (SKPs) and dermal multipotent stem cells (dMSCs) simultaneously from single human skin samples from patients with paraplegia.

Methods

Dissociated cells were initially generated from the dermal layer of skin samples from patients with paraplegia and cultured in SKPs proliferation medium. Four hours later, many cells adhered to the base of the flask. The suspended cells were then transferred to another flask for further culture as SKPs, while the adherent cells were cultured in dMSCs proliferation medium. Twenty-four hours later, the adherent cells were harvested and single-cell colonies were generated using serial dilution method. [³H]thymidine incorporation assay, microchemotaxis Transwell chambers assay, RT-PCR and fluorescent immunocytochemistry were employed to examine the characterizations of the isolated cells.

Results

SKPs and dMSCs were isolated simultaneously from a single skin sample. SKPs and dMSCs differed in several respects, including in terms of intermediate protein expression, proliferation capacities, and differentiation tendencies towards mesodermal and neural progenies. However, both SKPs and dMSCs showed high rates of differentiation into neurons and Schwann cells under appropriate inducing conditions. dMSCs isolated by this method showed no overt differences from dMSCs isolated by routine methods.

Conclusions

Two kinds of stem cells, namely SKPs and dMSCs, can be isolated simultaneously from individual human skin sample from paraplegia patients. Both of them show ability to differentiate into neural cells under proper inducing conditions, indicating their potential for the treatment of spinal cord injury patients by autologous cell transplantation.

Effect of hBD2 genetically modified dermal multipotent stem cells on repair of infected irradiated wounds

Deficiencies in repair cells and infection are two of the main factors that can hinder the process of wound healing. In the present study, we investigated the ability of human beta-defensin-2 (hBD2) genetically modified dermal multipotent stem cells (dMSCs) to accelerate the healing irradiated wounds complicated by infections. An hBD2 adenovirus expression vector (Adv-hBD2) was firstly constructed and used to infect dMSCs. The antibacterial activity of the supernatant was determined by Kirby-Bauer method and macrodilution broth assay. Time to complete wound healing, residual percentage of wound area, and the number of bacteria under the scar were measured to assess the effects of Adv-hBD2-infected dMSC transplantation on the healing of irradiated wounds complicated by Pseudomonas aeruginosa infection. Results showed that the supernatant from Adv-hBD2-infected dMSCs had obvious antibacterial effects. Transplantation of Adv-hBD2-infected dMSCs killed bacteria in the wound. The complete wound healing time was 19.8 ± 0.45 days, which was significantly shorter than in the control groups (P < 0.05). From 14 days after transplantation, the residual wound area was smaller in the experimental group than in the control groups (P < 0.05). In conclusion, we found that transplantation of hBD2 genetically modified dMSCs accelerated the healing of wounds complicated by P. aeruginosa infection in whole body irradiated rats.

Cutaneous mesenchymal stem cells: status of current knowledge, implications for dermatopathology

Stem cell biology is currently making its impact on medicine, which will probably increase over the next decades. It not only influences our therapeutic thinking caused by the enormous plasticity of stem cells but also affects diagnostic and conceptual aspects of dermatopathology. Although our knowledge of the keratinocytic stem cells located within the follicular bulge has exploded exponentially since their discovery in 1990, the concept of cutaneous mesenchymal stem cells (MSCs) is new. Described initially in 2001 in mice, MSCs later were also found in the human dermis. The connective tissue sheath and the papilla of the hair follicle probably represent the anatomical niche for cutaneous MSCs. In line with the cancer stem cell hypothesis, mutations of these cells may be the underlying basis of mesenchymal skin neoplasms, such as dermatofibrosarcoma protuberans. Furthermore, research on cutaneous MSCs may impact our thinking on the interaction of the epithelial component of skin neoplasms with their surrounding stroma. We are only in the early stages to recognize the importance of the potential contributions of cutaneous MSC research to dermatopathology, but it is not inconceivable to assume that they could be tremendous, paralleling the early discovery of the follicular bulge as a stem cell niche.

CXCR4 gene transfer enhances the distribution of dermal multipotent stem cells to bone marrow in sublethally irradiated rats

Our previous study indicated that systemically transplanted dermal multipotent cells (DMCs) were recruited more frequently to bone morrow (BM) of rats with sublethal irradiation than that of normal rats, and the interactions between stromal-derived factor (SDF-1) and its receptor (CXC chemokine receptor 4, CXCR4) played an important role in this process. In the present study, we aimed to investigate whether CXCR4 gene transfer could promote the distribution of DMCs into irradiated BM and accelerate its function recovery. Firstly, adenovirus vector of CXCR4 (Adv-CXCR4) and green fluorescent protein (Adv-GFP) were constructed. Then male DMCs infected by Adv-CXCR4 (group A), or infected by Adv-GFP (group B), and non-infected DMCs (group C) were transplanted into irradiated female rats, and real-time polymerase chain reaction for the sex-determining region of Y chromosome was employed to determined the amount of DMCs in BM. The functional recovery of BM was examined by hematopoietic progenitor colonies assay. The results showed that the amount of DMCs in BM of group A was greater than that in group B and group C from day 5 after injury (P < 0.05), and the amount of CFU-F, CFU-E and CFU-GM were greater than that in group B and group C from day 14 after injury (P < 0.05). These findings suggest that DMCs infected by Adv-CXCR4 distributed more frequently to the bone marrow of sublethally irradiated rats and could accelerate hematopoiesis function recovery.

Progress in research on radiation combined injury in China

The significant feature of radiation combined injury is the occurrence of a combined effect. For decades our institute has focused on studying the key complications of radiation-burn injury, including shock, suppression of hematopoiesis and immunity, gastrointestinal damage and local refractory wound healing. Here we summarize recent advancements in elucidating the mechanisms of and potential treatments for radiation combined injury. Concerning the suppression and regeneration of hematopoiesis in radiation combined injury, mechanisms of megakaryocyte damage have been elucidated and a new type of fusion protein stimulating thrombopoiesis has been developed and is being tested in animals. With regard to the damage and repair of intestinal epithelium, the important molecular mechanisms of radiation combined injury have been clarified, and new measures to prevent and treat gastrointestinal tract injury are proposed. With respect to the difficulties encountered in wound healing, the underlying causes of radiation combined injury have been proposed, and some potential methods to accelerate wound closure are under study. Systemic experiments have been done to determine the appropriate time for eschar excision and skin grafting, and the results provided significant insight into clinical treatment of the injury. In the search for early therapeutic regimens for severe burns and radiation combined injury to prevent deterioration of injuries and to improve survival, cervical sympathetic ganglion block was used for the treatment of animals with radiation combined injury and had significant benefits. These research advancements have potential for application in on-site emergency rescue and in-hospital treatment of radiation combined injury.

Non-epithelial oral mucosal progenitor cell populations

This review considers the potential existence and role of stem or progenitor cell populations within the non-epithelial tissues of the oral mucosa. Currently, there is little published evidence supporting this hypothesis; however, because of the similarities in structure and function of the oral mucosa and skin, findings within the dermis of the skin may potentially reflect the situation within the oral mucosa. Over recent years, the identification of the skin as a local reservoir of adult stem cell populations and the idea that multipotent cell populations exist within the dermal tissues of skin has gained increasing credibility. Indeed, numerous multipotent progenitor cells have been identified within the dermis and resident appendages, all capable of differentiating into multiple cell lineages. Furthermore, a number of these cell populations have been implicated in the repair of these tissues following injury. There is increasing evidence suggesting that such populations of progenitor cells may also reside within the lamina propria. In this respect, the ability to isolate large numbers of multipotent progenitor cells from a tissue which when biopsied heals without a scar would be of great interest scientifically and commercially, particularly with respect to future therapeutic applications and the developing discipline of tissue engineering.

Crucial role of SDF-1/CXCR4 interaction in the recruitment of transplanted dermal multipotent cells to sublethally irradiated bone marrow

Our previous study indicated that dermal multipotent cells (DMCs) could engraft into bone morrow (BM) of rats with sublethal irradiation and promote hematopoietic recovery after being transplanted systemically, but the mechanisms determining the recruitment of DMCs to the irradiation injured BM remain unclear. In the present study, we investigated the role of stromal cellderived factor-1 (SDF-1)/CXCR4 interaction in this process. Male DMCs were isolated and transplanted into female rats systemically, and by employing quantitative real-time TaqMan polymerase chain reaction for the sex-determining region of Y chromosome, it was found that the amount of DMCs in BM of rats with sublethal irradiation was about 3 times more than that of normal rats (P < 0.01). Incubation of DMCs with AMD3100 before transplantation, which specifically blocks binding of SDF-1 to its endogenous receptor CXCR4, diminished recruitment of DMCs to the injured BM by 57.2 +/- 5.5% (P < 0.05). In addition, it was confirmed that the expression of SDF-1 in injured BM was up-regulated when compared with that in normal BM, and in vitro analysis revealed that BM extracts from irradiated rats had a strong chemotactic effect on DMCs, which decreased significantly when DMCs were pre-incubated with AMD3100 (P < 0.05). These data suggest that transplanted DMCs were recruited more frequently to irradiation-injured BM than normal BM and the interactions of SDF-1/CXCR4 played an important role in this process.

Stem cells and their applications in skin-cell therapy

Skin stem cell biology is a rapidly advancing field in the life sciences. There is increasing evidence that skin represents a larger reservoir for adult stem cells (including mesenchymal, hematopoietic and neural stem cells) than the epidermis. Given that skin is easily accessible and immune privileged, skin stem cells will not only provide hope for the functional repair of the skin itself but will also offer a potential source of adult stem cells for the cell-based therapy of injuries and diseases throughout the body. This article reviews the current status of research in this area and discusses the occurrence, plasticity and potential uses of skin stem cells.

Skin: a promising reservoir for adult stem cell populations

Plasticity of adult cells has been identified in several post-natal tissues in the past few years and has attracted special attention in regenerative medicine. Skin is the biggest organ in the body. Adult skin consists of epidermis, dermis and appendages such as hairs and glands which are linked to the epidermis but project deep into the dermal layer. Skin stem cell biology has been a focus of increasing interest in current life science. Committed stem cells with limited differentiation potential for regeneration and repair of epidermis have been known for decades. Recent studies further report that adult skin tissues contain cell populations with pluripotent characteristics. Multipotent stem cells from hair follicle and non-follicular skin, both in epidermal and dermal tissues, are found to have the differentiation capacity to generate multiple cell lineages. Basing on the present data, our hypothesis is that skin may serve as a local reservoir of various adult stem cell populations, including committed stem cell populations and pluripotent stem cell populations both in epidermal and dermal tissues. Given its easy accessibility, stem cells in skin will not only provide an experimental model for skin biology, but also may provide an experimental model for studying the epithelial-mesenchymal interactions of several other organs outside of skin. The stem cell populations in skin tissues may also have extensive therapeutic implications in the replacement of skin and may serve as an alternative source of stem cells for several other organs outside of skin. The in situ activation and mobilization of stem cell populations in the skin is an ideal way to renew and repair epidermis and dermis, even appendages.