The wound-healing and antioxidant effects of adipose-derived stem cells

Human gingiva-derived mesenchymal stem cells elicit polarization of m2 macrophages and enhance cutaneous wound healing

Increasing evidence has supported the important role of mesenchymal stem cells (MSCs) in wound healing, however, the underlying mechanism remains unclear. Recently, we have isolated a unique population of MSCs from human gingiva (GMSCs) with similar stem cell-like properties, immunosuppressive, and anti-inflammatory functions as human bone marrow-derived MSCs (BMSCs). We describe here the interplay between GMSCs and macrophages and the potential relevance in skin wound healing. When cocultured with GMSCs, macrophages acquired an anti-inflammatory M2 phenotype characterized by an increased expression of mannose receptor (MR; CD206) and secretory cytokines interleukin (IL)-10 and IL-6, a suppressed production of tumor necrosis factor (TNF)-α, and decreased ability to induce Th-17 cell expansion. In vivo, we demonstrated that systemically infused GMSCs could home to the wound site in a tight spatial interaction with host macrophages, promoted them toward M2 polarization, and significantly enhanced wound repair. Mechanistically, GMSC treatment mitigated local inflammation mediated by a suppressed infiltration of inflammatory cells and production of IL-6 and TNF-α, and an increased expression of IL-10. The GMSC-induced suppression of TNF-α secretion by macrophages appears to correlate with impaired activation of NFκB p50. These findings provide first evidence that GMSCs are capable to elicit M2 polarization of macrophages, which might contribute to a marked acceleration of wound healing.

Epithelial-mesenchymal interactions as a working concept for oral mucosa regeneration

Oral mucosa consists of two tissue layers, the superficial epithelium and the underlying lamina propria. Together, oral mucosa functions as a barrier against exogenous substances and pathogens. In development, interactions of stem/progenitor cells of the epithelium and mesenchyme are crucial to the morphogenesis of oral mucosa. Previous work in oral mucosa regeneration has yielded important clues for several meritorious proof-of-concept approaches. Tissue engineering offers a broad array of novel tools for oral mucosa regeneration with reduced donor site trauma and accelerated clinical translation. However, the developmental concept of epithelial-mesenchymal interactions (EMIs) is rarely considered in oral mucosa regeneration. EMIs in postnatal oral mucosa regeneration likely will not be a simple recapitulation of prenatal oral mucosa development. Biomaterial scaffolds play an indispensible role for oral mucosa regeneration and should provide a conducive environment for pivotal EMIs. Autocrine and paracrine factors, either exogenously delivered or innately produced, have rarely been and should be harnessed to promote oral mucosa regeneration. This review focuses on a working concept of epithelial and mesenchymal interactions in oral mucosa regeneration.

Enhanced healing of diabetic wounds by topical administration of adipose tissue-derived stromal cells overexpressing stromal-derived factor-1: biodistribution and engraftment analysis by bioluminescent imaging

Chronic ulcers represent a major health problem in diabetic patients resulting in pain and discomfort. Conventional therapy does not guarantee adequate wound repair. In diabetes, impaired healing is partly due to poor endothelial progenitor cells mobilisation and homing, with altered levels of the chemokine stromal-derived factor-1 (SDF-1) at the wound site. Adipose tissue-associated stromal cells (AT-SCs) can provide an accessible source of progenitor cells secreting proangiogenic factors and differentiating into endothelial-like cells. We demonstrated that topical administration of AT-SCs genetically modified ex vivo to overexpress SDF-1, promotes wound healing into diabetic mice. In particular, by in vivo bioluminescent imaging analysis, we monitored biodistribution and survival after transplantation of luciferase-expressing cells. In conclusion, this study indicates the therapeutic potential of AT-SCs administration in wound healing, through cell differentiation, enhanced cellular recruitment at the wound site, and paracrine effects associated with local growth-factors production.

The pivotal role of VEGF in adipose-derived-stem-cell-mediated regeneration

IMPORTANCE OF THE FIELD

Several lines of evidence suggest that VEGF is a key regulator of the paracrine effects of adipose-derived stem cells (ASCs), but the mechanism of action remains to be identified.

AREAS COVERED IN THIS REVIEW

This brief review discusses the following research questions: i) Does VEGF increase the proliferation/migration and differentiation of ASCs?; ii) Does VEGF mediate the paracrine effects of ASCs?; and iii) How is VEGF synthesized, and which factors regulate VEGF secretion?

WHAT THE READER WILL GAIN

External stimuli such as hypoxia may activate receptor tyrosine kinases in the membrane of ASCs, which, in turn, phosphorylate extracellular signal regulated kinase (ERK) and members of the Akt signaling pathway, stabilizing hypoxia inducible factor 1α (HIF-1α) that are primary regulators of VEGF expression. Secreted VEGF directly stimulates ASCs via VEGF receptors in an autocrine manner and regenerates damaged neighboring cells in a paracrine manner.

TAKE HOME MESSAGE

Most studies of stem cell regeneration have focused on differentiation of ASCs and their building block function; however, the paracrine effects of ASCs should also be the focus of attention.

Keratinocyte proximity and contact can play a significant role in determining mesenchymal stem cell fate in human tissue

Bone marrow-derived human mesenchymal stem cells (hMSCs) possess multipotent differentiation capabilities and are a potent source of paracrine factors. We show how the epidermal keratinocyte can direct hMSC differentiation selectively. Keratinocytes and hMSCs were either cocultured in physical contact (contact cocultures), or separated without physical contact using a transwell insert (noncontact cocultures). We also delivered hMSCs into an ex vivo human excisional wound where subpopulations of the hMSCs were either in contact or were physically separated from the epidermal keratinocytes. In comparison to control hMSCs that were not cocultured, contact cocultured hMSCs adopted an epithelial morphology and expressed keratinocyte markers while noncontact cocultured hMSCs, surprisingly, adopted phenotypes that resembled myofibroblast and early neural lineage, both of which are of dermal origin. Cell fusion was not a requirement in in vitro contact cocultures, as determined by fluorescence-activated cell sorting (FACS) and fluorescence in situ hybridization analysis (FISH). To the best of our knowledge, this work provides the first example of hMSC differentiation into different lineages depending on their proximity to a single cell type.

Potential application of adipose-derived stem cells and their secretory factors to skin: discussion from both clinical and industrial viewpoints

IMPORTANCE OF THE FIELD

Adipose tissue is one of the richest sources of mesenchymal stem cells. Even more interesting is the fact that adipose-derived stem cells (ASCs) show an outstanding ability to regenerate damaged skin. Thus, ASCs are a popular and feasible treatment in clinical dermatology.

AREAS COVERED IN THIS REVIEW

This review discusses the potential applications of ASCs and conditioned medium of ASC (ASC-CM) to skin, and briefly touches on the mechanisms by which ASCs promote skin regeneration.

WHAT THE READER WILL GAIN

Clinically, processed lipo-aspirated (PLA) cells are commonly used for treatment of aged skin; however, the use of PLA cells for cosmetic purposes is not convenient, because PLA cells are prepared from patients. Alternatively, cosmetics that contain ASC-CM can be pre-made from healthy volunteers such that they are immediately available for clinical treatment of aged skin. Cell-based therapies are adequate for improvement of wrinkles or for soft tissue augmentation, whereas ASC-CM has merit for amelioration of skin tone. When culturing ASCs for the production of cosmetic raw materials, hypoxic culture conditions and transduction of specific genes into ASCs may increase the regenerative protein content of the conditioned medium.

TAKE HOME MESSAGE

Application of ASCs and ASC-CM to dermatology shows promising results for skin regeneration.

Human adipose-derived stromal cells accelerate diabetic wound healing: impact of cell formulation and delivery

Human adipose-derived stromal cells (ASCs) have been shown to possess therapeutic potential in a variety of settings, including cutaneous wound healing; however, it is unknown whether the regenerative properties of this cell type can be applied to diabetic ulcers. ASCs collected from elective surgical procedures were used to treat full-thickness dermal wounds in leptin receptor-deficient (db/db) mice. Cells were delivered either as multicellular aggregates or as cell suspensions to determine the impact of cell formulation and delivery methods on biological activity and in vivo therapeutic effect. After treatment with ASCs that were formulated as multicellular aggregates, diabetic wounds experienced a significant increase in the rate of wound closure compared to wounds treated with an equal number of ASCs delivered in suspension. Analysis of culture supernatant and gene arrays indicated that ASCs formulated as three-dimensional aggregates produce significantly more extracellular matrix proteins (e.g., tenascin C, collagen VI alpha3, and fibronectin) and secreted soluble factors (e.g., hepatocyte growth factor, matrix metalloproteinase-2, and matrix metalloproteinase-14) compared to monolayer culture. From these results, it is clear that cell culture, formulation, and delivery method have a large impact on the in vitro and in vivo biology of ASCs.

Responses of adipose-derived stem cells during hypoxia: enhanced skin-regenerative potential

Mesenchymal stem cells within the stromal-vascular fraction of subcutaneous adipose tissue (i.e., adipose-derived stem cells (ASCs)), have been used for tissue engineering. In addition to serving a building-block function, ASCs are reported to secrete growth factors that are essential for their function. Increasing evidence indicates that ASCs play a significant role in skin regeneration, a function that is enhanced by hypoxia through upregulating secretion of growth factors. Although the anatomical sites of ASCs in the body are relatively oxygen-deficient, ASCs are usually cultured under normoxic conditions (i.e., atmospheric oxygen levels). Culturing ASCs under physiologically relevant low-oxygen-tension conditions may uniquely benefit the expansion, differentiation, adhesion, growth factor secretion and regenerative potential of ASCs. Therefore, understanding the response and adaptation of ASCs to hypoxia may be invaluable for developing novel cell- and cyto-therapy strategies. This review highlights our current understanding of cellular and molecular responses of ASCs to hypoxia, focusing on the enhancement of ASC function and secretory activity by hypoxic culture conditions.