Author:
Lewis Karl J.,Frikha-Benayed Dorra,Louie Joyce,Stephen Samuel,Spray David C.,Thi Mia M.,Seref-Ferlengez Zeynep,Majeska Robert J.,Weinbaum Sheldon,Schaffler Mitchell B.
Abstract
Osteocytes are considered to be the major mechanosensory cells of bone, but how osteocytes in vivo process, perceive, and respond to mechanical loading remains poorly understood. Intracellular calcium (Ca2+) signaling resulting from mechanical stimulation has been widely studied in osteocytes in vitro and in bone explants, but has yet to be examined in vivo. This is achieved herein by using a three-point bending device which is capable of delivering well-defined mechanical loads to metatarsal bones of living mice while simultaneously monitoring the intracellular Ca2+ responses of individual osteocytes by using a genetically encoded fluorescent Ca2+ indicator. Osteocyte responses are imaged by using multiphoton fluorescence microscopy. We investigated the in vivo responses of osteocytes to strains ranging from 250 to 3,000 𝝁ϵ and frequencies from 0.5 to 2 Hz, which are characteristic of physiological conditions reported for bone. At all loading frequencies examined, the number of responding osteocytes increased strongly with applied strain magnitude. However, Ca2+ intensity within responding osteocytes did not change significantly with physiological loading magnitudes. Our studies offer a glimpse into how these critical bone cells respond to mechanical load in vivo, as well as provide a technique to determine how the cells encode magnitude and frequency of loading.
Funder
HHS | NIH | National Institute of Arthritis and Musculoskeletal and Skin Diseases
HHS | NIH | National Institute of Diabetes and Digestive and Kidney Diseases
Publisher
Proceedings of the National Academy of Sciences
Cited by
73 articles.
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