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Updated: May 4, 2026
A Novel in vivo Gene Transfer Technique and in vitro Cell Based Assays for the Study of Bone Loss in Musculoskeletal Disorders
Published on: June 8, 2014
Elevated serum soluble CD200 and CD200R as surrogate markers of bone loss under bed rest conditions
O Kos1, R L Hughson2, D A Hart3
1Transplant Research Division, Toronto Hospital and University Health Network, 101 College St., Toronto, ON M5G1L7, Canada.
Insights
Soluble CD200 (sCD200) levels decrease and soluble CD200 receptor 1 (sCD200R1) levels increase during simulated microgravity. Continuous centrifugation countermeasure attenuated these changes, suggesting potential for monitoring bone loss risk.
Area of Science:
- Immunology
- Bone Biology
- Space Medicine
Background:
- CD200, an immunoglobulin family protein, regulates immune responses via its receptor CD200R.
- CD200:CD200R signaling is implicated in osteoclastogenesis and bone metabolism.
- Microgravity conditions are known to promote osteoclastogenesis and bone loss.
Purpose of the Study:
- To investigate alterations in soluble CD200 (sCD200) and soluble CD200R1 (sCD200R1) levels during simulated microgravity (head-down tilt bed rest).
- To assess the impact of a continuous centrifugation countermeasure on these soluble marker levels.
- To evaluate the potential of sCD200 and sCD200R1 as biomarkers for bone loss risk and treatment efficacy.
Main Methods:
- Volunteers underwent 6° head-down tilt bed rest to simulate microgravity.
- Blood samples were collected to measure sCD200 and sCD200R1 levels.
- A subset of volunteers underwent a continuous centrifugation protocol as a countermeasure.
Main Results:
- sCD200 levels decreased, while sCD200R1 levels increased during bed rest.
- Continuous centrifugation attenuated or abolished these observed changes in sCD200 and sCD200R1 levels.
- These findings suggest a correlation between CD200/CD200R1 dynamics and microgravity-induced bone loss.
Conclusions:
- sCD200 and sCD200R1 levels change predictably under simulated microgravity conditions.
- Continuous centrifugation may mitigate microgravity-associated alterations in these markers.
- Monitoring sCD200 and sCD200R1 could offer a rapid method for assessing bone loss risk and treatment effectiveness.
Abstract:
CD200 is a transmembrane protein that belongs to the immunoglobulin family of proteins and is ubiquitously expressed on a variety of cell types. Upon interaction with its receptors (CD200Rs) expressed on myeloid-derived cells and T lymphocytes, an immunoregulatory signal is delivered to receptor-expressing cells. Previous studies have implicated a role for CD200:CD200R in the regulation of the expression of mRNA markers of osteoclastogenesis/osteoblastogenesis, following interaction of CD200 (on osteoblast precursors) with CD200R1 (on osteoclast precursors). Signaling of CD200R1 is hypothesized to attenuate osteoclastogenesis. We have investigated whether levels of soluble forms of CD200 and/or CD200R1 (sCD200, sCD200R1) are altered in volunteers undergoing 6° head down tilt bed rest to mimic conditions of microgravity known to be associated with preferential osteoclastogenesis and whether countermeasures, reported to be beneficial in attenuation of bone loss under microgravity conditions, would lead to altered sCD200 and sCD200R1 levels. Our data suggest that, as predicted, sCD200 levels fall under bed rest conditions while sCD200R1 levels rise. In subjects undergoing 30-minute per day continuous centrifugation protocols, as a countermeasure to attenuate changes which may lead to bone loss, these alterations in sCD200 and sCD200R1 levels seen under conditions of bed rest were abolished or attenuated. Our results suggest that measurement of sCD200 and/or sCD200R1 may prove a useful and rapid means of monitoring subjects at risk of bone loss and/or accessing the efficacy of treatment regimes designed to counter bone loss.
