The effects of hyperuricemia on the differentiation and proliferation of osteoblasts and vascular smooth muscle cells are implicated in the elevated risk of osteopenia and vascular calcification in gout: An in vivo and in vitro analysis.

BACKGROUND

In this study, we established both an animal model and a cellular model of hyperuricemia (HUC). Subsequently, we treated these models with allopurinol (ALLO) to study the effect of uric acid (UA) and ALLO on the differentiation and proliferation of osteoblasts and vascular smooth muscle cells (VSMC).

METHODS

Western Blot, immunohistochemistry assay, and real-time polymerase chain reaction were conducted to measure the changes in the expression of differentiation-related factors in osteoblasts and VSMCs in HUC and HUC+ALLO groups. MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay and flow cytometry were utilized to observe the changes in the proliferation of osteoblasts in HUC and HUC+ALLO groups. Von Kossa staining was performed along with calcium content measurement to investigate the effect of HUC/ALLLO on vascular calcification.

RESULTS

In this study, the levels of Wnt3a and differentiation-related factors, including Runx2, Sp7, Ibsp, Bglap, Dmp1, and Col1a1, were all evidently decreased in HUC rats, while the presence of ALLO increased the levels of above factors. In addition, the viability of osteoblasts was reduced while their apoptosis was elevated in the HUC group, and ALLO treatment reduced the apoptosis and increased the viability of osteoblasts to a certain extent. Moreover, HUC elevated the levels of Wnt3a, Runx2, Sp7, Bglap, Col1a1, SM22a, and Acta2 in VSMCs of HUC rats, leading to greatly increased calcium content and obvious vascular calcification. In contrary, ALLO treatment reduced the effect of HUC. Furthermore, the effect of UA and ALLO on osteoblasts and VSMCs was also validated in cellular models treated with monosodium urate (MSU) crystals or MSU+ALLO.

CONCLUSIONS

HUC can suppress the differentiation and proliferation of osteoblasts while promoting the differentiation of VSMCs both in vivo and in vitro. The treatment by ALLO exhibited a therapeutic effect on HUC by promoting the differentiation and proliferation of osteoblasts while reducing vascular calcification.