P#29  Expression and activation of matrix metalloproteinases in cultured human dermal papilla cells

Hiram de Almeida Jr., Felix B. Müller, Paola Zigrino, Thomas Krieg, Bernhard P. Korge and Cornelia Mauch. Dept of Dermatology and Venereolgy, University of Cologne

The dermal papilla (DP) represents a cluster of specialised mesenchymal cells at the bottom of the hair follicle, embedded in a loose extracellular matrix (ECM). These DP cells (DPC) have the capability to induce and support hair growth via close epithelial-mesenchymal interactions with the surrounding hair matrix keratinocytes. The ECM composition of the DP differs markedly from interfollicular dermal ECM and plays a key role in the maintenance of hair growth. In this study we investigated if matrix degrading proteins in DPC such as matrix metalloproteinases (MMP) and their inhibitors (TIMP) may contribute to the unique composition of the ECM in the DP. Human DPC were cultured in type I collagen lattices or as monolayer for 48 hours before collection of supernatants. Dermal fibroblasts (DF) from the same donors were used as controls. The supernatants were subsequently analysed by western blots and zymography to assess MMP expression and activation. DPC and DF both expressed strongly MMP-1 but weakly TIMP-2 and MT1-MMP. Also MMP-2 expression and activation was strong in DPC and DF cultured in collagen lattices. MMP-9 revealed always strong expression and activity in DF, whereas in DPC expression was very weak or absent. Expression of MMP-3 was exclusive in DF. In addition to a series of reported morphological and functional characteristics the here described differences in MMP expression support the idea that DPC represent a specialised subpopulation of mesenchymal cells. The functional consequences of the differential expression of MMPs for the composition of the ECM in the DP and for the hair cycle are currently under investigation.