Culture of human dermal fibroblasts in collagen gels: Modulation of interleukin 1-induced prostaglandin E 2 synthesis by an extracellular matrix

Abstract

Human dermal fibroblasts, cultured as suspensions in collagen gels and as monolayers, were stimulated with recombinant human interleukin-1β (rIL 1β) at 72 h, and prostaglandin E 2 (PGE 2) was assayed 24 h later. Fibroblasts in gels were less responsive to rIL 1β than monolayers, PGE 2 synthesis increasing from <1 ng/μg DNA without rIL 1β to maxima of 11.3 and 32.9 ng/βg DNA, with half maximal release occurring at 7.47 and 0.75 p M rIL 1β for the gel and monolayer cultures, respectively. Increased PGE 2 was first detected 4 h after addition of rIL 1β to gels and was inhibited by 10 −5 M indomethacin. The amount of PGE 2 synthesized per fibroblast increased with the time the gels had been in culture when stimulated with rIL 1β and was proportional to the number of flbroblasts in the gels, but inversely related to the collagen concentration. A common feature of these experiments was significantly greater induction of PGE 2 synthesis at higher cell densities in collagen gels. Exogenous 10 −4 M arachidonic acid further increased PGE 2 synthesis by rIL 1β-stimulated flbroblasts, but the differential in the amount of PGE 2 released from fibroblasts at high and low population densities in the gels was maintained. These results are consistent with interleukin 1 (IL 1) stimulating PGE 2 synthesis in dermal fibroblasts by increasing cyclooxygenase activity. Furthermore, the results show that dermal fibroblasts have an additional regulatory mechanism, related to the cell population densities or their interactions with an extracellular matrix, to finely modulate the amount of PGE 2 synthesized in response to IL 1.