Advanced Microscopy Program, Center for Systems Biology and Wellman Center for Photomedicine, Massachusetts General Hospital, Harvard Medical School, Boston, MA, 02114, USA.
Department of Chemistry and Environmental Science, New Jersey Institute of Technology, 323 Martin Luther King Jr. Blvd., Newark, NJ, 07102, USA.
Nat Commun. 2022 Jan 19;13(1):393. doi: 10.1038/s41467-022-27973-x.
The fate of hematopoietic stem cells (HSCs) can be directed by microenvironmental factors including extracellular calcium ion concentration ([Ca]), but the local [Ca] around individual HSCs in vivo remains unknown. Here we develop intravital ratiometric analyses to quantify the absolute pH and [Ca] in the mouse calvarial bone marrow, taking into account the pH sensitivity of the calcium probe and the wavelength-dependent optical loss through bone. Unexpectedly, the mean [Ca] in the bone marrow (1.0 ± 0.54 mM) is not significantly different from the blood serum, but the HSCs are found in locations with elevated local [Ca] (1.5 ± 0.57 mM). With aging, a significant increase in [Ca] is found in M-type cavities that exclusively support clonal expansion of activated HSCs. This work thus establishes a tool to investigate [Ca] and pH in the HSC niche with high spatial resolution and can be broadly applied to other tissue types.
造血干细胞 (HSCs) 的命运可以由包括细胞外钙离子浓度 ([Ca]) 在内的微环境因素决定，但体内单个 HSCs 周围的局部 [Ca] 仍不清楚。在这里，我们开发了活体比率分析方法，以量化小鼠颅盖骨骨髓中的绝对 pH 和 [Ca]，同时考虑了钙探针的 pH 敏感性和通过骨骼的波长相关光损耗。出乎意料的是，骨髓中的平均 [Ca]（1.0 ± 0.54mM）与血清没有显著差异，但 HSCs 存在于局部 [Ca] 升高的位置（1.5 ± 0.57mM）。随着年龄的增长，在仅支持激活 HSCs 克隆扩增的 M 型腔中发现 [Ca] 显著增加。因此，这项工作建立了一种具有高空间分辨率研究 HSC 龛位中 [Ca] 和 pH 的工具，并可以广泛应用于其他组织类型。
