IMMORTALIZED RAT WHISKER DERMAL PAPILLA CELLS COOPERATE WITH MOUSE IMMATURE HAIR FOLLICLE BUDS TO ACTIVATE TYPE-IV PROCOLLAGENASES IN COLLAGEN MATRIX COCULTURE - CORRELATION WITH ABILITY TO PROMOTE HAIR FOLLICLE DEVELOPMENT IN NUDE-MOUSE GRAFTS

An in vivo nude mouse graft model and an in vitro collagen matrix cult ure system were used to study interactions of immature hair follicle b uds from new-born mice with clonally derived AdE1A-12S-immortalized ra t whisker dermal papilla cell lines, Of the 19 available dermal papill a cell lines, four consistently supported good hair follicle developme nt and hair growth in grafts, Seven cell lines were clearly negative i n this assay, and the remaining eight cell lines yielded poor to moder ate hair growth, As a correlate to in vivo extracellular matrix remode ling accompanying hair follicle development, type IV collagenase activ ity in the medium from cocultures of dermal papilla cells and hair fol licle buds was analyzed by gelatin zymography, Hair follicle buds cult ured alone secrete primarily the 92-kDa type IV procollagenase, Cocult ivation of hair follicle buds with eight of the dermal papilla cell li nes resulted in activation of this proenzyme and activation of the 72- kDa and 92-kDa type IV procollagenases produced by the dermal papilla cells, Seven of these eight dermal papilla cell lines support hair gro wth in the graft system, In the absence of dermal papilla cells, sever al growth factors induced activation of the 92-kDa procollagenase secr eted by hair follicle buds cultured in serum-free medium: epidermal gr owth factor, transforming growth factor alpha, acidic fibroblast growt h factor, and keratinocyte growth factor, The current working hypothes is is that a) hair follicle epithelial cells interact with dermal papi lla cells in coculture by mutual induction of growth factors and cytok ines that stimulate the release and activation of matrix remodeling pr oteases; and b) the ability of dermal papilla cells to interact with h air follicle epithelial cells in this way may be crucial for controlle d dermal matrix remodeling during HF development.