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

ABSTRACT: The fate of hematopoietic stem cells (HSCs) can be directed by microenvironmental factors including extracellular calcium ion concentration ([Ca²⁺]_e), but the local [Ca²⁺]_e around individual HSCs in vivo remains unknown. Here we develop intravital ratiometric analyses to quantify the absolute pH and [Ca²⁺]_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 [Ca²⁺]_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 [Ca²⁺]_e (1.5 ± 0.57 mM). With aging, a significant increase in [Ca²⁺]_e is found in M-type cavities that exclusively support clonal expansion of activated HSCs. This work thus establishes a tool to investigate [Ca²⁺]_e and pH in the HSC niche with high spatial resolution and can be broadly applied to other tissue types.

SUBMITTER: Yeh SA 

PROVIDER: S-EPMC8770570 | biostudies-literature | 2022 Jan

REPOSITORIES: biostudies-literature