The contributions of skeletal cells to the processes of B cell development in the bone marrow (BM) have not been completely described. The von-Hippel Lindau protein (VHL) plays a key role in cellular responses to hypoxia. Previous work showed that Dmp1-Cre;Vhl conditional knockout mice (VhlcKO), which delete Vhl in late osteoblasts and osteocytes, display dysregulated bone growth and reduction in B cells. Here, we investigated the mechanisms underlying the B cell defects using flow cytometry and high-resolution imaging. In the VhlcKO BM, B cell progenitors were increased in frequency and number, whereas Hardy Fractions B-F were decreased. VhlcKO Fractions B-C cells showed increased apoptosis and quiescence. Reciprocal BM chimeras confirmed a B cell-extrinsic source of the VhlcKO B cell defects. In support of this, VhlcKO BM serum contained reduced CXCL12 and elevated EPO levels. Staining of VhlcKO B cells with an intracellular hypoxic marker indicated the natural existence of distinct B cell microenvironments that differ in local oxygen tensions. Additionally, intravital and ex vivo imaging revealed VhlcKO BM blood vessels with increased diameter, frequency, volume, and a diminished blood-BM barrier. Our studies identify novel mechanisms linking altered bone homeostasis with drastic BM microenvironmental changes that dysregulate B cell development.

中文翻译：

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Dmp1 表达细胞中 Vhl 的缺失导致 B 细胞淋巴细胞生成的微环境损伤

骨骼细胞对骨髓 (BM) 中 B 细胞发育过程的贡献尚未完全描述。von-Hippel Lindau 蛋白 (VHL) 在细胞对缺氧的反应中起关键作用。以前的工作表明Dmp1 -Cre; Vhl条件性敲除小鼠 ( Vhl cKO)在晚期成骨细胞和骨细胞中删除Vhl，显示出骨骼生长失调和 B 细胞减少。在这里，我们使用流式细胞术和高分辨率成像研究了 B 细胞缺陷的潜在机制。在Vhl cKO BM 中，B 细胞祖细胞的频率和数量增加，而 Hardy Fractions BF 减少。电压cKO Fractions BC 细胞显示出增加的细胞凋亡和静止状态。相互的 BM 嵌合体证实了Vhl cKO B 细胞缺陷的 B 细胞外源。为了支持这一点，Vhl cKO BM 血清含有降低的 CXCL12 和升高的 EPO 水平。用细胞内缺氧标记对Vhl cKO B 细胞进行染色表明自然存在不同的局部氧张力不同的 B 细胞微环境。此外，活体和离体成像显示Vhl cKO BM 血管具有增加的直径、频率、体积和减少的血 BM 屏障。我们的研究确定了将改变的骨稳态与导致 B 细胞发育失调的剧烈 BM 微环境变化联系起来的新机制。