The Fetal Dermal but Not Loose Fascial Mesenchymal Cells Possess Regenerative Activity of Dermal Structure

Fetal Fibroblast Transplantation via Ablative Fractional Laser Irradiation Reduces Scarring

Scar treatments include fractional laser treatment, cell transplantation, surgery, skin needling, and dermal fillers. Fractional laser treatments are used to reduce scarring and blurring. Cell transplantation is promising, with mature fibroblasts and adipose-derived stem cells being used clinically, while embryonic fibroblasts are used experimentally. Herein, we developed a combination of ablative CO₂ (carbon dioxide) fractional laser and cell transplantation for the treatment of scars. Eight-week-old male C57Bl/6 mice were used to create a full-layer skin defect in the back skin and create scars. The scar was then irradiated using a CO₂ fractional laser. The cells were then transplanted onto the scar surface and sealed with a film agent. The transplanted cells were GFP-positive murine fetal fibroblasts (FB), fetal fibroblasts with a long-term sphere-forming culture (LS), and fetal skin with a short-term sphere-forming culture (SS). After transplantation, green fluorescent protein (GFP)-positive cells were scattered in the dermal papillary layer and subcutis in all the groups. LS significantly reduced the degree of scarring, which was closest to normal skin. In conclusion, the combination of ablative fractional laser irradiation and fetal fibroblast transplantation allowed us to develop new methods for scar treatment.

Actin cable formation and epidermis-dermis positional relationship during complete skin regeneration

Up to a certain developmental stage, a fetus can completely regenerate wounds in the skin. To clarify the mechanism of fetal skin regeneration, identifying when the skin switches from fetal-type wound regeneration to adult-type wound repair is necessary. We hypothesized that this switch occurs at several time points and that complete skin regeneration requires epidermal–dermal interactions and the formation of actin cables. We compared normal skin and wound morphology at each developmental stage. We examined two parameters: epidermal texture and dermal structure. We found that the three-dimensional structure of the skin was completely regenerated in full-thickness skin incisions made before embryonic day (E) 13. However, the skin texture did not regenerate in wounds made after E14. We also found that the dermal structure regenerates up to E16, but wounds created after E17 heal as scars with dermal fibrosis. By controlling the activity of AMP-activated protein kinase and altering actin cable formation, we could regulate scar formation in utero. These findings may contribute to therapies that allow complete skin regeneration without scarring.

Downregulation of Lhx2 Markedly Impairs Wound Healing in Mouse Fetus

Multiple transitions occur in the healing ability of the skin during embryonic development in mice. Embryos up to embryonic day 13 (E13) regenerate completely without a scar after full-thickness wounding. Then, up to E16, dermal structures can be formed, including skin appendages such as hair follicles. However, after E17, wound healing becomes incomplete, and scar formation is triggered. Lhx2 regulates the switch between maintenance and activation of hair follicle stem cells, which are involved in wound healing. Therefore, we investigated the role of Lhx2 in fetal wound healing. Embryos of ICR mice were surgically wounded at E13, E15, and E17, and the expression of Lhx2 along with mitotic (Ki67 and p63) and epidermal differentiation (keratin-10 and loricrin) markers was analyzed. The effect of Lhx2 knockdown on wound healing was observed. Lhx2 expression was not noticed in E13 due to the absence of folliculogenesis but was evident in the epidermal basal layer of E15 and E17 and at the base of E17 wounds, along with Ki67 and p63 expression. Furthermore, Lhx2 knockdown in E15 markedly prolonged wound healing and promoted clear scar formation. Therefore, Lhx2 expression is involved in cell division associated with wound healing and may contribute to scar formation in late embryos.

Decorin Inhibits Dermal Mesenchymal Cell Migration and Induces Scar Formation

Background

Variations in skin healing capacities are observed during different murine embryonic developmental stages. Through embryonic day 16 (E16), embryos are able to regenerate dermal architecture following flank skin wounding; however, after E17, wounds heal incompletely, inducing scar formation. The regenerative ability of the E16 fetal dermis depends on the migration of dermal mesenchymal cells. Decorin is a small molecule known to affect tissue tensile strength, cell phenotype, and tissue repair, including skin wound healing. In the current study, we evaluated the expression and roles of decorin in wound healing.

Methods

Surgical injury was induced at E16 and E17 in ICR mouse embryos. Decorin expression was evaluated in tissue samples from these embryos using immunohistochemistry and reverse transcription quantitative polymerase chain reaction. Cell migration assays were used to evaluate wound healing capability of separated dermal and fascial tissues.

Results

Our results showed that decorin exhibited distinct expression patterns during wound healing at E16 versus E17. Additionally, decorin expression altered cell migration in vitro. Dermal and fascial mesenchymal cells were found to exhibit distinct migration patterns concomitant with altered decorin expression. Specifically, decorin inhibited migration and favored scar formation.

Conclusion

Decorin expression may contribute to scar formation in the late stage of mouse embryos by inhibiting the migration of dermal mesenchymal cells.

Transplanted mesenchymal stem cells are effective for skin regeneration in acute cutaneous wounds of pigs

Introduction

We investigated the effects of mesenchymal stem cells (MSCs) on cutaneous wound healing in pigs in order to develop new therapies to enhance wound healing in humans.

Methods

We cultured bone marrow cells from the femurs of male pigs, and the multipotency of these cells were then confirmed. The characteristics of the cultured cells were determined by flow cytometric analyses. The MSCs were injected intradermally into the skin of pigs as auto-transplantation, and linear full-thickness incisional wounds were made through the injected area immediately afterward.

Results

The MSCs were found to be positive for SWC3a, CD44, SLA class I, CD29, CD44H, and CD90. At 28 days post-surgery, wounds treated with MSCs had healed well, with only very fine scars visible macroscopically. Histologically, collagen architecture was thick and elastic fibers appeared in the wounds. Histomorphologic scale analysis demonstrated that the wounds treated with MSCs scored better than the controls. Significantly larger fibroblasts were observed in the wounds treated with MSCs than controls.

Conclusion

These results indicate that transplantation of MSCs causes wounds to heal almost completely, possible indicating regeneration to normal skin. We hypothesize that the transplantation protocol described in this study may also be applicable to human wound healing.

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MSCs contribute to skin regeneration in acute cutaneous wounds of pigs.

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Cutaneous wounds of pig transplanted with bone marrow-derived MSCs healed with very fine scars, and collagen architectures were similar to normal dermis.

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We hypothesize that the transplantation of MSCs may also be applicable to human wound healing, because cutaneous of pigs are an excellent model for human skin.

Article Commentary: Stem Cell Research in Cell Transplantation: An Analysis of Geopolitical Influence by Publications

One of the fastest growing fields in researching treatments for neurodegenerative and other disorders is the use of stem cells. These cells are naturally occurring and can be obtained from three different stages of an organism's life: embryonic, fetal, and adult. In the US, political doctrine has restricted use of federal funds for stem cells, enhancing research towards an adult source. In order to determine how this legislation may be represented by the stem cell field, a retrospective analysis of stem cell articles published in the journal Cell Transplantation over a 2-year period was performed. Cell Transplantation is considered a translational journal from preclinical to clinical, so it was of interest to determine the publication outcome of stem cell articles 6 years after the US regulations. The distribution of the source of stem cells was found to be biased towards the adult stage, but relatively similar over the embryonic and fetal stages. The fetal stem cell reports were primarily neural in origin, whereas the adult stem cell ones were predominantly mesenchymal and used mainly in neural studies. The majority of stem cell studies published in Cell Transplantation were found to fall under the umbrella of neuroscience research. American scientists published the most articles using stem cells with a bias towards adult stem cells, supporting the effect of the legislation, whereas Europe was the leading continent with a bias towards embryonic and fetal stem cells, where research is “controlled” but not restricted. Japan was also a major player in the use of stem cells. Allogeneic transplants (where donor and recipient are the same species) were the most common transplants recorded, although the transplantation of human-derived stem cells into rodents was the most common specific transplantation performed. This demonstrates that the use of stem cells is an increasingly important field (with a doubling of papers between 2005 and 2006), which is likely to develop into a major therapeutic area over the next few decades and that funding restrictions can affect the type of research being performed.

Hair Induction by Cultured Mesenchymal Cells Using Sphere Formation

Isolated dermal cells possess the capacity to induce hair growth. The cells cannot be expanded while they retain the capacity for hair induction, and lose their potential immediately after cultivation. Sphere-forming multipotent cells derived from the dermis (skin-derived precursors [SKPs]) possess hair-inducing activity. These observations provide two possibilities for the determination of the capacity for hair induction: capacity is dependent on either identity as a dermal cell or on the process of sphere formation. We developed a method that demonstrates cultivated mesenchymal cells derived from dermis and lung tissue possess in vivo hair-inducing capacity via sphere formation.

Recruited minced skin grafting for improving the skin appearance of the donor site of a split-thickness skin graft

OBJECTIVE

To improve skin appearance at the donor site of a split-thickness skin graft, part of the harvested skin was minced and grafted back onto the site in a process we named "recruited minced skin grafting."

MATERIALS AND METHODS

Thirteen Japanese patients who needed split-thickness skin grafts were treated with recruited minced skin grafting. Five patients were used as controls, in whom donor sites were treated with the traditional method. Part of the split-thickness skin was minced using two surgical blades (number 24) to an approximate particle size of less than 0.5 mm. Minced skin was spread and transplanted onto the donor site and covered with polyurethane foam. Twelve months after the operation, donor sites were scored for hypopigmentation, hyperpigmentation, redness, and disruption of skin texture. Gross appearance was evaluated according to total score.

RESULTS

Donor sites treated with recruited minced skin grafts had significantly better appearance than those of controls. Donor sites that had more than 5% of the total area treated tended to have better results.

CONCLUSION

Recruited minced skin grafting is a good method of improving the appearance of the donor site.

Sphere formation restores and confers hair-inducing capacity in cultured mesenchymal cells

Interactions between epithelial and dermal cells are essential for hair follicle morphogenesis and maintenance. In experimental trials of hair regeneration, isolated dermal cells have been shown to possess hair-inducing capacity. However, dermal cells lose this potential immediately after cultivation. Sphere-forming multipotent cells derived from the dermis possess hair-inducing capacity. These previous findings raise the question of whether hair-inducing capacity depends on the identity as dermal cells or the process of sphere formation. To address this issue, we compared the in vitro and in vivo characteristics of two-dimensionally cultured or thereafter sphere formation-induced dermal and lung mesenchymal cells. We show that sphere-forming mesenchymal cells exhibited higher expression of Wnt signalling genes. Sphere-forming cells but not two-dimensionally cultured cells possessed in vivo hair-inducing capacity. These data suggest that various mesenchymal cells attain hair-inducing capacity through the process of sphere formation.