Autosomal Dominant Osteopetrosis type II (ADO2) is a rare bone disease of impaired osteoclastic bone resorption that usually results from heterozygous missense mutations in the chloride channel 7 (CLCN7) gene. We previously created mouse models of ADO2 (p.G213R) with one of the most common mutations (G215R) as found in humans and demonstrated that this mutation in mice phenocopies the human disease of ADO2. Previous studies have shown that roflumilast (RF), a selective phosphodiesterase 4 (PDE4) inhibitor that regulates the cAMP pathway, can increase osteoclast activity. We also observed that RF increased bone resorption in both wild-type and ADO2 heterozygous osteoclasts in vitro, suggesting it might rescue bone phenotypes in ADO2 mice. To test this hypothesis, we administered RF-treated diets (0, 20 and 100 mg/kg) to 8-week-old ADO2 mice for 6 months. We evaluated bone mineral density and bone micro-architecture using longitudinal in-vivo DXA and micro-CT at baseline, and 6-, 12-, 18-, and 24-week post-baseline time points. Additionally, we analyzed serum bone biomarkers (CTX, TRAP, and P1NP) at baseline, 12-, and 24-week post-baseline. Our findings revealed that RF treatment did not improve aBMD (whole body, femur, and spine) and trabecular BV/TV (distal femur) in ADO2 mice compared to the control group treated with a normal diet. Furthermore, we did not observe any significant changes in serum levels of bone biomarkers due to RF treatment in these mice. Overall, our results indicate that RF does not rescue the osteopetrotic bone phenotypes in ADO2 heterozygous mice.

常染色体显性骨石症 II 型 (ADO2) 是一种罕见的破骨细胞骨吸收受损的骨病，通常由氯离子通道 7 ( CLCN7 ) 基因的杂合错义突变引起。我们之前创建了 ADO2 (p.G213R) 小鼠模型，该模型具有人类中最常见的突变 (G215R) 之一，并证明小鼠中的这种突变表现出 ADO2 的人类疾病。先前的研究表明，罗氟司特 (RF) 是一种调节 cAMP 通路的选择性磷酸二酯酶 4 (PDE4) 抑制剂，可以增加破骨细胞活性。我们还在体外观察到 RF 增加了野生型和 ADO2 杂合破骨细胞的骨吸收，表明它可能挽救 ADO2 小鼠的骨表型。为了检验这一假设，我们给 8 周大的 ADO2 小鼠喂食 RF 处理的饮食（0、20 和 100 毫克/千克）6 个月。我们在基线以及基线后 6、12、18 和 24 周时间点使用纵向体内DXA 和显微 CT评估骨矿物质密度和骨微结构。此外，我们还分析了基线、基线后 12 周和 24 周时的血清骨生物标志物（CTX、TRAP 和 P1NP）。我们的研究结果表明，与正常饮食治疗的对照组相比，射频治疗并没有改善 ADO2 小鼠的 aBMD（全身、股骨和脊柱）和小梁 BV/TV（股骨远端）。此外，我们没有观察到这些小鼠因射频治疗而导致骨生物标志物血清水平发生任何显着变化。总体而言，我们的结果表明 RF 不能挽救 ADO2 杂合子小鼠的骨硬化骨表型。