OSTEOBLASTIC PROLIFERATION IN BONE BIOPSIES FROM PATIENTS WITH END-STAGE CHRONIC-RENAL-FAILURE

Osteoblasts have traditionally been considered to be terminally differ entiated cells and therefore unable to divide, Data in recent years, h owever, indicate that cellular differentiation does not usually preclu de preservation of proliferative ability and that most differentiated cells are able to divide under adequate stimuli. The aim of this study was to assess whether cubic osteoblasts undergo proliferation during the formation phase of the remodeling cycle under a stimulus that incr eased bone turnover, For that purpose, the osteoblastic proliferation index (OPI) was analyzed by DNA image cytometry in transiliac bone bio psies from 33 patients with chronic renal failure (23 men, 10 women; m ean age 50.4 +/- 15.1 years) who have been classified into low (n = 13 ), normal (n = 15), and high (II = 15) bone turnover according to acti vation frequency (Ac.f). OPI was significantly higher (p < 0.002) in t he high bone turnover group (13.90 +/- 4.72%) compared with the low (2 .38 +/- 4.13%) and normal turnover groups (2.84 +/- 4.04%), There was a positive correlation between OPI and the following histomorphometric parameters: bone formation rate, surface referent (r = 0.76, p = 0.00 001), activation frequency (r = 0.73,p = 0.00001), mineral apposition rate (r = 0.73, p = 0.00001), bone formation rate, volume referent (r = 0.71, p = 0.00001), and mineralizing surface (r = 0.62, p = 0.0001). This study shows that a rise in bone turnover is associated with a ma rked increase of bone-forming cell proliferation in patients with end- stage chronic renal failure, From this finding, it may be concluded th at cubic osteoblasts do not behave as ''terminally differentiated'' ce lls in vivo, because a high proportion of them are still able to divid e.