Quantification of bone marrow interstitial pH and calcium concentration by intravital ratiometric imaging

• Published in: Nature communications Vol. 13; no. 1; p. 393
• Main Authors: Yeh, S-C. A., Hou, J., Wu, J. W., Yu, S., Zhang, Y., Belfield, K. D., Camargo, F. D., Lin, C. P.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 19.01.2022; Nature Publishing Group; Nature Portfolio
• Subjects: 631/1647/328/2235; 631/532/1542; 631/532/2139; 639/624/1107/328/2235; Aging; Aging - metabolism; Animals; Benzopyrans - chemistry; Bone imaging; Bone marrow; Bone Marrow - blood supply; Bone Marrow - diagnostic imaging; Bone Marrow - metabolism; Bone Remodeling; Calcium; Calcium (extracellular); Calcium - metabolism; Calcium ions; Cellular Microenvironment; Fluorescence; Hematopoietic stem cells; Hematopoietic Stem Cells - metabolism; Humanities and Social Sciences; Hydrogen-Ion Concentration; Intravital Microscopy; Ion concentration; Mice; Mice, Inbred C57BL; multidisciplinary; Naphthols - chemistry; pH effects; Rhodamines - chemistry; Science; Science (multidisciplinary); Spatial discrimination; Spatial resolution; Stem cell transplantation; Stem cells
• ISSN: 2041-1723; 2041-1723
• 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 2+ ] e ), but the local [Ca 2+ ] e around individual HSCs in vivo remains unknown. Here we develop intravital ratiometric analyses to quantify the absolute pH and [Ca 2+ ] e 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 2+ ] e 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 2+ ] e (1.5 ± 0.57 mM). With aging, a significant increase in [Ca 2+ ] e is found in M-type cavities that exclusively support clonal expansion of activated HSCs. This work thus establishes a tool to investigate [Ca 2+ ] e and pH in the HSC niche with high spatial resolution and can be broadly applied to other tissue types. The fate of hematopoietic stem cells can be controlled by factors such as calcium ion concentration. Here the authors report an intravital ratiometric analysis method to measure extracellular calcium ion concentrations and absolute pH in mouse bone marrow.