INTERLEUKIN-10 IS A MESANGIAL CELL-GROWTH FACTOR IN-VITRO AND IN-VIVO

Macrophages are involved in the pathogenesis of mesangioproliferative glomerulonephritis. As macrophages are known to produce interleukin-10 (IL-10), we investigated the effect of recombinant murine IL-10 (rIL- 10) on mesangial cell growth. In vitro studies were performed using th e rat 1097 mesangial cell line. These cells exhibited a dose-dependent proliferative response to rIL-10 (23% to 70% up arrow at 80 ng/mL; p < 0.01), as assessed by both H-3-thymidine uptake and cell count. This effect was inhibited by preincubation of rIL-10 with a neutralizing a nti-IL-10 antibody. When added to cultures of growth-arrested 1097 cel ls, IL-10 induced dose-dependent proliferation that paralleled the eff ects of platelet-derived growth factor. Incubation with a neutralizing anti-IL-10 Ab for 48 hours reduced H-3-thymidine uptake (median, 27% down arrow; range, 2% to 56% down arrow)versus a control Ab; p < 0.05) . Rat mesangial cells were also shown to express IL-10 mRNA and protei n, as determined by Northern Plotting and immunostaining, thereby sugg esting a role for IL-10 in autocrine mesangial cell growth. To examine the effects of IL-10 in vivo, inbred male Sprague-Dawley rats were gi ven subcutaneous rIL-10 (0.5 mg/kg) for 3 (n = 6), 7 (n = 3), or 14 da ys (n = 4), or vehicle control, then killed. IL-10 administration indu ced a transient reduction in creatinine clearance of 35% at Day 3 (p < 0.01). Following IL-10 administration, an increase in glomerular cell ularity was seen, which was maximal at Day 3 (82.7 +/- 5.9 nuclei/glom erular cross section versus control 64.6 +/- 4.6, 28% up arrow; p < 0. 001) and maintained at Day 14 (23% up arrow; p < 0.01). Immuno-histoch emical staining for proliferating cell nuclear antigen demonstrated an increased number of proliferating cells per glomerular cross section at day 3 (48% up arrow versus controls; p < 0.05). Staining for or-smo oth-muscle actin showed significant labeling only in the glomeruli of IL-10-treated animals; double-labeling with an anti- proliferating cel l nuclear antigen Ab demonstrated that some of these mesangial cells w ere proliferating. Collectively, these results suggest that IL-10 is a growth factor for rat mesangial cells both in vitro and in vivo.