TRACTIONAL FORCE GENERATION BY PORCINE MULLER CELLS - STIMULATION BY GROWTH-FACTORS IN HUMAN VITREOUS

Purpose. To examine the levels of Muller cell contraction-stimulating activity in human vitreous, correlate these levels with clinical prese ntation, and identify the causative growth factors. Methods. Human vit reous was collected from patients undergoing pars plana vitrectomy (n = 84). Muller cells were isolated from porcine retina and maintained i n tissue culture. Tractional forces generated by cells incubated on th ree-dimensional collagen gels were measured as changes in gel thicknes s. Contraction-stimulating activity in vitreous (VA) was calculated fr om the dose-response profiles of gel contraction to vitreous protein. The contributions of individual growth factors to vitreous activity (n = 10) were assessed by inhibition with specific neutralizing antibodi es. Results. The mean VA of patients with retinal detachment (3.65) an d proliferative vitreoretinopathy stages A, B, and C (2.06) were eleva ted above that of patients without retinal pathology (vitreous activit y = 0.23) or retinal defects alone (0.57). Mean activities in patients with epimacular proliferation (1.22) and vitreous hemorrhage (1.40) w ere also significantly elevated. The percentage of this activity attri butable to insulin-like growth factor 1 (IGF-1) varied from 9.2% to 84 .5% with a mean of 61.3%. Similarly, the percent contribution of plate let-derived growth factor (PDGF) ranged from 6.8% to 49.0% with a mean of 26.5%. Conclusions. The vitreous of patients with retinal detachme nt, proliferative retinal disease, and vitreous hemorrhage contain var ying amounts of growth factors that stimulate tractional force generat ion by Muller cells. The majority of the activity can be attributed to IGF-1 and a smaller proportion to PDGF.