Renal mononuclear cells secrete a factor triggering mesangial cell proliferation.

Thirty-six Charles River rats underwent left unilateral nephrectomy and 18 counterparts had sham nephrectomy. After 48 h the kidneys of all animals were removed, and renal mononuclear cells (RMNC) harvested. The RMNC were cultured in RPMI 1640 medium supplemented with either 20% fetal calf serum or sera procured from sham operated rats, or from nephrectomized animals. Ten days later the conditioned media of RMNC cultures were collected. Peripheral blood mononuclear cells (PBMC) from sham-operated or nephrectomized rats were also grown in RPMI 1640 supplemented with 20% fetal calf serum, sham serum or post-nephrectomy serum. The conditioned media of PBMC cultures were also collected after 10 days. Mesangial cells procured from kidneys of different normal animals were cultured in DMEM/F12HAM cell culture medium supplemented with 50% of the various RMNC- or PBMC-conditioned media. Proliferation of mesangial cells grown in conditioned medium of post-nephrectomy RMNC which had been precultured with post-nephrectomy serum was significantly augmented compared with control or any other experimental situation. There was no statistically-significant difference between proliferation rates of mesangial cells cultured in any other medium of control or experimental RMNC or PBMC. We conclude that following unilateral nephrectomy, RMNC of the remaining kidney are activated to secrete, under a sustained signal of post-nephrectomy serum, a growth factor(s) stimulating proliferation of normal mesangial cells.