Contraction and relaxation of cultured mesangial cells on a silicone rubber surface

Abstract

Glomerular mesangial cells (MC) in culture are believed to contract or relax in response to agents such as angiotensin II and cyclic AMP. However, cells grown on glass or plastic surfaces are limited in their response to vasoactive agents because of the rigid surfaces to which they adhere; thus, interpretation of a change in shape as contraction, relaxation, or detachment is difficult. We have grown MC on a flexible silicone rubber (dimethylpolysiloxane) substrate (DMPS), and studied with sequential photographs several models of cell contraction, relaxation, and detachment. When the cells contracted, the DMPS became wrinkled; when the cells relaxed, the DMPS lost wrinkles. In contrast, if the cells detached, the sheet lost wrinkles as the cells became smaller and rounder. Angiotensin II (5 X 10(-7) M), and calcium ionophore A23187 (2 X 10(-6) M) increased wrinkles in more than 30% of cells at 22 degrees C and more than 40% of the cells at 36 degrees C. The earliest effect was visible within five to 10 minutes at 22 degrees C and within one minute at 36 degrees C and increased until 40 minutes; thereafter, the cells relaxed and wrinkles were reduced. 10(-1) M Na azide prevented the increase in wrinkles produced by angiotensin II. Seventy-two percent of the angiotensin II-treated cells whose margins could be seen in their entirety, and 78% of the calcium ionophore-treated cells showed a reduction in surface area at a time when new wrinkles were appearing or wrinkles were increasing in size. Dibutyryl cyclic AMP, a known smooth muscle relaxant, produced a decrease or loss of wrinkles in 90% of the cells, and an accompanying increase in surface area. Untreated control cells, observed in conjunction with the above series, showed little change in wrinkles. Ten percent DMSO, an actin-translocating agent, produced a reversible disappearance of wrinkles. These models of contraction and relaxation could be distinguished from cell detachment; EDTA, for example, in the presence of zero calcium, diminished both cell size and wrinkles, with an accompanying lifting of cells from the surface. Similar results were obtained with cytochalasin B and chlorpromazine. Thus, the silicone rubber system accurately reflects the contraction, relaxation and detachment of cultured mesangial cells in response to a variety of agents.