Freezing Hair Follicles Keeps Stem Cells Thriving
The use of stem cell therapy to treat or prevent disease has greatly expanded in the last few years, as biotechnology begins to offer practical solutions to many of the technical hurdles the industry faced early on. The initial stigma of using embryonic stem cells has faded, as researchers discover new sources of stem cells, including bone marrow, umbilical cord blood, fat tissue, and even skin cells. Now, in a collaborative work published by scientists from Sagamihara in Japan and San Diego, in the U.S., the prospect of using stem cells derived from hair follicles is being investigated. 
Hair follicle-associated pluripotent stem cells, or HAP cells, as they are called, have an impressive potential for clinical use in regenerative medicine. The cells, found at the base of the hair shaft, are easily accessible, and can differentiate into a number of different cell types, including keratinocytes, neurons, glial cells, and smooth muscle cells. The neuronal stem cell marker, nestin, is expressed by these cells, suggesting that they have features in common with neural stem cells. In fact, one of the main reasons they are considered so promising is that both mouse and human HAP cells have been shown to promote peripheral nerve and spinal cord repair.
For most stem cell regenerative medicine applications, it is necessary to be able to cryopreserve the cells in question. Freezing the cells allows them to be stored for any number of downstream applications, including their potential use in clinical trials. Naturally, the cryopreservation method must preserve HAP cell function and multipotent status, and so the authors sought to uncover the most suitable cryopreservation method for achieving this outcome.
Whole hair follicles were cryopreserved by slow-rate cooling and stored in liquid nitrogen. Slow-rate cooling is often considered the best way to maximize stem cell viability. The follicles were later thawed and cultured until cells from the upper portion of the follicle grew out. The growing cells were transferred to serum-free medium, where a week later they had formed “hair spheres” containing HAP stem cells.
The researchers were pleased to discover that cryopreserved hair follicles produced as many hair spheres as freshly isolated follicles. Stem cell marker genes were as abundant in these follicles as in freshly isolated hair follicles, and HAP cells contained within the hair spheres generated from the follicles were as pluripotent as those from fresh hair follicles. By contrast, whole hair follicles cryopreserved by rapid cooling (vitrification) failed to thrive. Stem cell marker genes in these follicles were greatly reduced, as was the pluripotency of the stem cells derived from these follicles. When hair spheres alone were cryopreserved, by either slow or rapid cooling, much of their pluripotency was lost. The authors concluded that the best way to preserve HAP cell function is to cryopreserve whole hair follicles by slow cooling.
Stored HAP stem cells could be very promising for personalized regenerative medicine applications. Who knows? They could even help us get to the root of the age-old problem of preventing hair loss.
 Kajiura S. et al., Cryopreservation of the Hair Follicle Maintains Pluripotency of Nestin-Expressing Hair Follicle-Associated Pluripotent Stem Cells. Tissue Engineering Part C: Methods. 21(8): 825-831. doi:10.1089/ten.tec.2014.0500. August 2015.