Characterization of vibrissa germinative cells: transition of cell types

Germinative cells, small cell masses attached to the stalks of dermal papil lae that are able to differentiate into the hair shaft and inner root sheat h, form follicular bulb-like structures when co-cultured with dermal papill a cells. We studied the growth characteristics of germinative cells to dete rmine the cell types in the vibrissa germinative tissue. Germinative tissue s, attaching to dermal papillae, were cultured on 3T3 feeder layers. The cu ltured keratinocytes were harvested and transferred, equally and for two pa ssages, onto lined dermal papilla cells (LDPC) and/or 3T3 feeder layers. Th e resulting germinative cells were classified into three types in the prese nt experimental condition. Type 1 cells grow very well on either feeder lay er, whereas Type 3 cells scarcely grow on either feeder layer. Type 2 cells are very conspicuous and are reversible. They grow well on 3T3 but growth is suppressed on LDPC feeder layers. The Type 2 cells that grow well on 3T3 feeder layers, however, are suppressed when transferred onto LDPC and the Type 2 cells that are suppressed on LDPC begin to grow again on 3T3. The tr ansition of one cell type to another in vitro and the cell types that these germinative cell types correspond to in vivo is discussed. It was conclude d that stem cells or their close progenitors reside in the germinative tiss ues of the vibrissa bulb except at late anagen-early catagen.