Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana, USA.
Department of Orthopaedic Surgery, Indiana University School of Medicine, Indianapolis, Indiana, USA.
FASEB J. 2022 Sep;36(9):e22471. doi: 10.1096/fj.202200678R.
Autosomal dominant osteopetrosis type II (ADO2) is a heritable bone disease of impaired osteoclastic bone resorption caused by missense mutations in the chloride channel 7 (CLCN7) gene. Clinical features of ADO2 include fractures, osteomyelitis of jaw, vision loss, and in severe cases, bone marrow failure. Currently, there is no effective therapy for ADO2, and patients usually receive symptomatic treatments. Theoretically, bone marrow transplantation (BMT), which is commonly used in recessive osteopetrosis, could be used to treat ADO2, although the frequency of complications related to BMT is quite high. We created an ADO2 knock-in (p.G213R mutation) mouse model on the 129 genetic background, and their phenotypes mimic the human disease of ADO2. To test whether BMT could restore osteoclast function and rescue the bone phenotypes in ADO2 mice, we transplanted bone marrow cells from 6-8 weeks old male WT donor mice into recipient female ADO2 mice. Also, to determine whether age at the time of transplant may play a role in transplant success, we performed BMT in young (12-week-old) and old (9-month-old) ADO2 mice. Our data indicate that ADO2 mice transplanted with WT marrow achieved more than 90% engraftment up to 6 months post-transplantation at both young and old ages. The in-vivo DXA data revealed that young ADO2 mice transplanted with WT marrow had significantly lower whole body and spine areal bone mineral density (aBMD) at month 6 post-transplantation compared to the ADO2 control mice. The old ADO2 mice also displayed significantly lower whole body, femur, and spine aBMD at months 4 and 5 post-transplantation compared to the age-matched control mice. The in-vivo micro-CT data showed that ADO2 experimental mice transplanted with WT marrow had significantly lower BV/TV at months 2 and 4 post-transplantation compared to the ADO2 control mice at a young age. In contrast, ADO2 control and experimental mice displayed similar BV/TV values for all post-transplantation time points at old age. In addition, serum CTX was significantly higher at month 2 post-transplantation in both young and old ADO2 experimental mice compared to the ADO2 control mice. Serum P1NP levels in young ADO2 experimental mice were significantly higher at baseline and month 2 post-transplantation compared to the ADO2 control mice. These data suggest that BMT may provide, at least, some beneficial effect at both young and adult ages.
常染色体显性遗传骨硬化症 2 型（ADO2）是一种遗传性骨骼疾病，由氯离子通道 7（CLCN7）基因突变引起破骨细胞骨吸收受损。ADO2 的临床特征包括骨折、颌骨骨髓炎、视力丧失，在严重的情况下，还会出现骨髓衰竭。目前，尚无针对 ADO2 的有效治疗方法，患者通常接受对症治疗。骨髓移植（BMT）常用于治疗隐性骨硬化症，理论上也可以用于治疗 ADO2，尽管与 BMT 相关的并发症发生率相当高。我们在 129 遗传背景下创建了 ADO2 基因敲入（p.G213R 突变）小鼠模型，其表型模拟了人类 ADO2 疾病。为了测试 BMT 是否可以恢复破骨细胞功能并挽救 ADO2 小鼠的骨骼表型，我们将来自 6-8 周龄雄性 WT 供体小鼠的骨髓细胞移植到受体雌性 ADO2 小鼠中。此外，为了确定移植时的年龄是否会影响移植的成功率，我们在年轻（12 周龄）和老年（9 月龄）ADO2 小鼠中进行了 BMT。我们的数据表明，年轻和老年 ADO2 小鼠在移植后 6 个月内，接受 WT 骨髓移植的小鼠的嵌合率超过 90%。体内 DXA 数据显示，年轻 ADO2 小鼠在移植后 6 个月时，与 ADO2 对照组相比，全身和脊柱面积骨矿物质密度（aBMD）显著降低。老年 ADO2 小鼠在移植后 4 个月和 5 个月时，与年龄匹配的对照组相比，全身、股骨和脊柱 aBMD 也显著降低。体内 micro-CT 数据显示，年轻 ADO2 实验小鼠在移植后 2 个月和 4 个月时，与 ADO2 对照组相比，BV/TV 显著降低。相比之下，在老年时，ADO2 对照组和实验组的所有移植后时间点的 BV/TV 值相似。此外，年轻和老年 ADO2 实验组在移植后 2 个月时的血清 CTX 明显高于 ADO2 对照组。年轻 ADO2 实验组的血清 P1NP 水平在基线和移植后 2 个月时均明显高于 ADO2 对照组。这些数据表明，BMT 至少在年轻和成年时都能提供一些有益的效果。
