The bone marrow provides inflammatory cells and endothelial progenitor cells to healing cutaneous wounds. To further explore the bone marrow contribution to skin and healing wounds, we used a chimeric mouse model in which the bone marrow from enhanced green fluorescent protein (EGFP) transgenic mice is transplanted into normal C57BL mice. We found that normal skin is a target organ for bone marrow–derived cells from both the hematopoietic and the mesenchymal stem cell pool. We present evidence that the bone marrow contribution to normal skin and the healing cutaneous wound is substantially greater than the previously recognized CD45+ subpopulation, where 15%–20% of the spindle‐shaped dermal fibroblasts were bone marrow–derived (EGFP+). Furthermore, the bone marrow–derived cells were able to contract a collagen matrix and transcribe both collagen types I and III, whereas the skin‐resident cells transcribed only collagen type I. Whereas endothelial progenitor cells were found early during the wound repair process, bone marrow–derived endothelial cells were not seen after epithelialization was complete. Our data show that wound healing involves local cutaneous cells for reconstituting the epidermis but distant bone marrow–derived cells and the adjacent uninjured dermal mesenchymal cells for reconstituting the dermal fibroblast population.

Background: Cutaneous wound repair in adult mammals does not regenerate the original epithelial architecture and results in altered skin function. We propose that lack of regeneration may be due to the absence of appropriate molecular signals to promote regeneration. In this study, we investigated the regulation of Wnt signaling during cutaneous wound healing and the consequence of activating either the beta-catenin-dependent or beta-catenin-independent Wnt signaling on epidermal architecture during wound repair.

Injury induces a flux in the cellular composition of tissues as part of the wound healing response. There is no reliable and rapid method to quantify and characterize the cellular composition of the matrix-rich wound. Our aim was to develop a rapid method to quantify the cellular composition in wounds by tissue dispersion and flow cytometry. Age- and weight-matched mice were wounded on the dorsum using a 1.5 x 1.5 cm2 template, and the wounds were excised at predetermined time points. Tissues were dispersed into single-cell suspensions and labeled with antibodies to cell surfaces and intracellular antigens. Flow cytometry was performed to quantify the percentage of each cell population and cell death. We found that our tissue dispersion protocol resulted in low cell death (4%-6%) and very high yield (80-220 x 10(6) cells/g). Furthermore, cell surfaces and intracellular antigens were preserved to provide accurate identification of the different cell populations. With the appropriate modifications, this protocol is likely to be applicable for the viable retrieval and identification of cells from skin and other collagen-dense tissues.