Effect of gel re-organization and tensional forces on alpha 2 beta 1 integrin levels in dermal fibroblasts

Mechanical forces are known to play an important role in regulating cell fu nction in a wide range of biological systems. This is of particular relevan ce to dermal fibroblast function, given that the skin is known to be held u nder an intrinsic natural tension. To understand mon about the generation o f force by dermal fibroblasts and their ability to respond to changes in it , we have studied the role of the beta 1 integrin receptors expressed by de rmal fibroblasts in their ability to generate tensional forces within a col lagen type I matrix and the effect of altered tensional force on integrin e xpression by dermal fibroblasts. Using a purpose-built culture force monitor, function-blocking antibodies d irected towards the beta 1 receptors dramatically reduced the tensional for ces generated by dermal fibroblasts in a 3D collagen I matrix. However, the specific involvement of alpha 1 or alpha 2 subunits could not be demonstra ted. Analysis of cellular response demonstrated that cells isolated from contrac ting collagen gels expressed fourfold higher levels of alpha 2 mRNA than ce lls isolated from fully restrained gels. The levels of beta 1 messenger RNA were relatively unaffected by reductions in force, Cells exposed to single reductions in force. however, did not exhibit alterations in either alpha 1 or beta 1 mRNA levels. We propose, therefore that alpha 2 beta 1 integrin receptor levels in dermal fibroblasts are not altered in response to singl e reductions of gel tension, but do change following a continual change in force and associated matrix re-organization.