No abstract

Unilateral nephrectomy results in compensatory renal growth, in which both the size and the functional capacity of the remaining kidney are increased. The functional adaptation to the removal of the contralateral kidney consists mostly of an increase in the glomerular filtration rate of the remaining kidney, and hypertrophy of cells comprising the nephron, mainly of the proximal tubular cells. Although the phenomenon of single kidney hypertrophy has been known for the past thousand years and despite intensive research over the past century, the mechanism of this process still remains unclear. The present article reviews the role of mesangial cells in compensatory renal hypertrophy.

SUMMARY1. Twenty 7-week female mice underwent right nephrectomy and twenty others were sham operated. A week later all animals were made pregnant. Pregnancy was repeated five more times consecutively and various renal parameters were assessed in the pups.2. Fractional fresh kidney weight (relative to body weight) was significantly increased in the pups of nephrectomized mothers while percentage renal water and protein content expressed as mg/g kidney weight were not statistically different in the two groups of pups. Thus dry kidney weight and amount of protein per kidney were increased in the experimental group. This was true for the newborns of all six pregnancies.3. Renal morphometric studies performed in newborns of first pregnancies showed that the mean number of glomeruli per microscopic field, mean fractional cumulative glomerular area (relative to microscopic field area) and the mean number of cells per glomerulus were significantly greater in the experimental group. Mean glomerular radius was not statistically different in the two groups.4. The results indicate that: (1) the renotrophic factor(s) crosses the placenta in mice; (2) its activity in maternal circulation following uninephrectomy is sustained for a relatively long period; and (3) fetal response to enhanced maternal renotrophin stimulation consists of increased renal dry weight and renal protein, formation of super-physiological numbers of glomeruli and cellular hyperplasia of the glomeruli.

Rat kidney mesangial cells were procured from 5 sham-operated and 10 previously uninephrectomized rats. They were grown in cell culture medium supplemented with 20% fetal calf serum. Cell free conditioned medium was collected on the 10th day. Tubular cell cultures were then prepared from 18 normal unoperated 3-week-old rats. Tubular cells from each separate kidney sample were grown in pooled-mesangium conditioned medium from sham-operated or from nephrectomized rats, supplied with 20% pooled serum from either sham-operated or nephrectomized animals, ³H-thymidine incorporation of normal tubular cell cultures grown in nephrectomy mesangium conditioned medium supplemented with sera from nephrectomized animals proved to be significantly greater than that of any of the other three experimental variations. No statistically significant difference was evident when either preconditioned medium of postnephrectomy mesangial cells or postnephrectomy serum were used alone.