Generation and phenotype of myeloid cell specific Clcn7-mutation osteopetrosis mouse model / 中华内分泌代谢杂志

ABSTRACT

Objective:To construct a myeloid cell specific Clcn7-G763R mutant mouse model and characterize its phenotype.Methods:A mouse conditional knocked in p. G763R mutation in Clcn7 gene was constructed and bred with LysM cre mice to obtain osteopetrosis mice with myeloid cell specific Clcn7-G763R mutation. The differences of bone mass in mice with different genotypes were analyzed using Micro CT and the changes of histology were observed with HE staining. Osteoclasts were cultured and the expression levels of osteoclasts differentiation and maturation-related genes were detected by real-time PCR. The functions of osteoclasts were examined through bone resorption assay.Results:The body weight of homozygous mutant mice at 4 weeks old was reduced compared with the wild type mice [(12.000±1.666)g vs(15.630±2.314)g, P=0.021], with shorter femur length [(1.160±0.096)cm vs (1.300±0.082)cm, P=0.037]. Micro CT showed that bone mineral density of homozygous mutant mice was remarkably increased at 4 weeks old [(0.753±0.002)g/cm 3vs(0.143±0.034)g/cm 3, P=0.003], while bone mineral density of heterozygous mutant mice increased significantly at 8 weeks old [(0.236±0.021)g/cm 3vs(0.180±0.020)g/cm 3, P=0.030]. HE staining revealed increased trabecula bone volume in the mutant mice, especially in homozygous mutant mice with narrow bone marrow cavity and wider hypertrophic zone of chondrocytes. There was no significant difference in the number of osteoclasts between wild type mice and heterozygous mice in vitro( P=0.358), while total area of osteoclasts increased in heterozygous mutant mice [(3.590×10 6±0.911×10 6)μm 2vs(1.352×10 6±0.260×10 6)μm 2, P=0.043]. Impaired function of resorption was unveiled by bone resorption assay. There were no significant differences in the expressions of osteoclast differentiation and maturity-related genes including NFATc1, c-fos, Ctsk, and Acp5 between the two groups. Conclusion:A myeloid cell specific Clcn7-G763R mutation mice with impaired osteoclasts and increased bone mass is successfully constructed.