HYALURONIC-ACID STIMULATES HUMAN FIBROBLAST PROLIFERATION WITHIN A COLLAGEN MATRIX

Human dermal fibroblasts suspended in a collagen matrix exhibit a 4-da y delay in cell division, while the same cells in monolayer divided by day 1. The initial rates of H-3-thymidine incorporation by cells in m onolayer or suspended in collagen were not significantly different. Wh en suspended in collagen, there was a threefold increase in the propor tion of cells in a tetraploidal (4N) DNA state compared to the same ce lls in monolayer. Flow cytometry analysis and H-3-thymidine incorporat ion studies identified the delay of cell division as a consequence of a block in the G2/M of the cell cycle and not an inhibition of DNA syn thesis. The inclusion of 150 mu g/ml of hyaluronic acid (HA) in the ma nufacture of fibroblast populated collagen lattices (FPCL) caused a st imulation of cell division, as determined by cell counting; increased the expression of tubulin, as determined by Western blot analysis; and reduced the proportion of cells in a 4N state, as determined by flow cytometry. HA added to the same cells growing in monolayer produced a minimal increase in the rate of cell division or DNA synthesis. HA sup plementation of FPCLs stimulated cell division as well as tubulin conc entrations, but it did not enhance lattice contraction. The introducti on of tubulin isolated from pig brain or purchased tubulin into fibrob lasts by electroporation prior to their transfer into collagen lattice s promoted cell division in the first 24 hours and enhanced FPCL contr action. It is proposed that tubulin protein, the building blocks of mi crotubules, is limited in human fibroblasts residing within a collagen matrix. When human fibroblasts are suspended in collagen, one effect of added HA may be to stimulate the synthesis of tubulin which assists cells through the cell cycle. (C) 1998 Wiley-Liss, Inc.