Microfluidic Isolation of CD34‐Positive Skin Cells Enables Regeneration of Hair and Sebaceous Glands In Vivo

This paper describes a two‐stage microfluidic system to enrich CD34‐positive (CD34+) stem cells from mouse skin with high purity. Microfluidic devices minimize the processing time of stem cells in the starting population, are easily accessible, and can be multiplexed to separate large amounts of cell mixture. The released CD34+ stem cells were transplanted into full‐thickness skin defects in nude mice. Follicles and hairs were regenerated, and sebaceous glands were formed in the graft sites. Skin stem cells resident in the bulge area of hair follicles and at the basal layer of the epidermis are multipotent and able to self‐renew when transplanted into full‐thickness defects in nude mice. Based on cell surface markers such as CD34 and the α6‐integrin, skin stem cells can be extracted from tissue‐derived cell suspensions for engraftment using the gold standard cell separation technique of fluorescence‐activated cell sorting (FACS). This paper describes an alternative separation method using microfluidic devices coated with degradable antibody‐functionalized hydrogels. The microfluidic method allows direct injection of tissue digestate (no preprocessing tagging of cells is needed), is fast (45 minutes from injected sample to purified cells), and scalable. This method is used in this study to isolate CD34‐positive (CD34+) cells from murine skin tissue digestate, and the functional capability of these cells is demonstrated by transplantation into nude mice using protocols developed by other groups for FACS‐sorted cells. Specifically, the transplantation of microfluidic isolated CD34+ cells along with dermal and epidermal cells was observed to generate significant levels of hair follicles and sebaceous glands consistent with those observed previously with FACS‐sorted cells.