116
The bioengineered hair follicle germ can develop into a fully functional hair follicle
through the rearrangement of various stem cells and their niches (Toyoshima et al.
2012 ). The dissected bioengineered hair follicles can also restore fully physiologi-
cal hair functions in adult skin via ectopic transplantation of the bioengineered hair
follicle germs (Toyoshima et al. 2012 ). Future studies of in vitro culture systems
that can reproduce bioengineered hair follicles from bioengineered hair follicle
germs permit the promotion of therapeutic systems such as FUT in the clinic.
To successfully provide clinically useful and effective hair follicle regenerative
therapy, several issues persist, such as the optimization of human hair follicle-
derived stem cell sources and in vitro expansion for clinical applications (Ohyama
2007 ). There are significant variations in follicular stem cell marker expression
among species, hair types, skin surface regions, and individuals, although the clini-
cal definition of useful stem cell markers is maintained (Ohyama 2007 ). There is no
way to satisfactorily in vitro propagate human follicular stem cells using clinically
available culture systems. The organ germ method and functional hair regeneration
assay assist the development of a high-throughput system, which would facilitate
techniques leading to the clinical application of hair follicle regenerative therapy.
Recent biological and technical innovations have achieved substantial progress
in the development of a novel therapeutic model for hair follicle regenerative ther-
apy for alopecia and organ replacement regenerative therapy. Further studies
focused on the optimization of human hair follicle-derived stem cell sources for
clinical applications of stem cell niches will contribute to the development of hair
regenerative therapy as a prominent class of organ replacement regenerative therapy
in the future.
Acknowledgments This work was partially supported by Organ Technologies, Inc.
Conflict of Interest K. Toyoshima and T. Tsuji have no competing interests.
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