Effect of type of dialysis membrane on bone in haemodialysis patients

Background, Uraemic bone disease is the result of a number of factors modul ating bone formation and resorption in a complex manner. In the present stu dy, the hypothesis tested was that the type of haemodialysis membrane used for renal replacement therapy might also play a role. Methods. We conducted a prospective, open study in 24 chronic haemodialysis patients who were randomized to dialysis treatment with either cellulosic (CELL group, n=11) or polyacrylonitrile (AN-69 group, n=13) membrane for 9 months. Repeated determinations of plasma parameters reflecting bone turnov er were done in all patients, and a bone biopsy in a subgroup at the start and end of study. Results, At the start. mean plasma intact parathyroid hormone levels were c omparable between the two groups and they did nut vary significantly at 9 m onths of treatment. Similarly, plasma bone-specific alkaline phosphatase an d osteocalcin (markers of bone formation), and cross-laps (marker of bone r esorption) remained unchanged. However, plasma insulin-like growth factor-I (IGF-I) progressively decreased from 169 to 119 ng/ml in AN-69 group (P < 0.01), whereas it remained unchanged in CELL group. In addition, the levels of IGF binding protein (IGFBP)-1 and IGFBP-2 were increased while the leve ls of IGFBP-5 were decreased in AN-69 group. In the five patients of each g roup who had repeat bone biopsies, histomorphometric analysis showed a decr ease in osteoblast surface, osteoclast surface and osteoclast number in AN- 69 group at 9 months, compared with baseline values measured at the start o f the study. In contrast, all three parameters significantly increased in t he CELL group at 9 months (P < 0.001 for the difference between each of the three parameters). Bone formation rate decreased by 31% in the AN-69 group , but increased by 50% in CELL group. However, this latter difference was n ot statistically significant. Plasma interleukin (IL)-6 and soluble IL-6 re ceptor levels did not change in the two groups of patients who had undergon e bone biopsy. Conclusion, Dialysis with CELL membrane was associated with increased bone turnover whereas the use of AN-69 membrane was associated with decreased bo ne turnover. suggesting a beneficial effect of the latter on high-turnover uraemic bone disease. However, as the number of patients with repeat bone b iopsies was small, these findings need to be confirmed in a larger study. F urther studies are also needed to evaluate whether or not the changes in IG F system components play a role in decreased bone cell activity in patients on dialysis using the AN-69 polyacrylonitrile membrane.