B3.2 THE HAIR PATCH ASSAY: A SIMPLE AND RAPID SCREEN  TO MEASURE AND  CHARACTERIZING TRICHOGENIC CELLS  

Y Zheng, X Du, W Wang, M Boucher, S Parimoo, K Stenn

Aderans Research Institute, Philadelphia , PA

In studying new follicle formation there is a need for a rapid, simple assay for cells with trichogenic properties.  Currently published assays, which include the organoid growth of cells under the kidney capsule (Ihara et al. Cell Tiss Res 266:65, 1991) and the Lichti/Prouty Cap assay (Lichti et al. J Invest Dermatol 101:124S, 1993; Prouty etc.; Amer J Path148:147, 1996), are complex to set-up and long (4 weeks) to assess.  Reported here is an assay which uses dissociated epithelial and mesenchymal cells from mouse pelage skin and then injects the cells within the hypodermis of immunoincompetent or immunocompetent mice. Trichogenic cells, properly prepared and placed, will form follicular organoids as early as 4 days after injection and form mature follicles with full length shafts within 14 days under the skin. The newly formed follicles show the morphology of different hair types found in the mouse pelage and the histology of the mature pilosebaceous apparatus; moreover, the newly formed follicles appear to cycle in a time frame equivalent to the first hair cycle of the newborn pup. The assay is dependent on epithelial and mesenchymal cells both of which are trichogenic. When an opening is created the regenerated hair shafts can grow and exit to the skin surface. This assay is simple, rapid, and efficient with minimal trauma to the recipient host.