immune responses against infections while in space. Using an innovative mouse experimental
model, this set of experiments tests whether initial specific activation of T cells is intact and
whether memory T cell function is maintained during spaceflight.
RESULTS
Results indicate that the process of hematopoietic and mesenchymal stem cell differentiation in
bone marrow is profoundly altered under conditions of reduced mechanical load in
microgravity, with retention of stem cell characteristics and a broad down-regulation in marrow
differentiation capacity. This phenomenon is revealed in multiple cell types, including
osteoclasts and osteoblasts required for bone remodeling and mineral homeostasis,
erythrocytes required for the transport of oxygen and iron throughout the body, and
megakaryocytes required for the formation of platelets. These results also suggest that under
conditions of reduced gravitational mechanical load, such as physical inactivity, mechanical
disuse conditions, and spaceflight, it is likely that differentiation of somatic stem cells,
such as in bone and blood, may be inhibited, possibly resulting in serious regenerative health
effects (Blaber 2013).
PUBLICATION(S)
Mednieks M, Khatri A, Hand AR. Salivary gland protein expression after Bion-M1 and Space
Shuttle STS-135 missions. Gravitational and Space Research. July 2015;3:18.
Chang TT, Spurlock SM, Candelario TT, Grenon SM, Hughes-Fulford M. Spaceflight impairs
antigen-specific tolerance induction in vivo and increases inflammatory cytokines. FASEB:
Federation of American Societies for Experimental Biology Journal. 2015 June 17; 29: 4122-
- DOI: 10.1096/fj.15-275073.
Martinez EM, Yoshida MC, Candelario TT, Hughes-Fulford M. Spaceflight and simulated
microgravity cause a significant reduction of key gene expression in early T-cell activation.
American Journal of Physiology: Regulatory, Integrative, and Comparative Physiology. March
15, 2015; 308(6):R480-R488. doi: 10.1152/ajpregu.00449.2014.
Mednieks M, Khatri A, Rubenstein R, Burleson JA, Hand AR. Microgravity alters the expression
of salivary proteins. Oral Health and Dental Management. June 2014;13:6.
Blaber EA, Dvorochkin N, Lee C, et al. Microgravity induces pelvic bone loss through osteoclastic
activity, osteocytic osteolysis, and osteoblastic cell cycle inhibition by CDKN1a/p21. PLOS ONE.
April 18, 2013;8(4):e61372. doi: 10.1371/journal.pone.0061372.
Stabley JN, Dominguez JM, Dominguez CE, et al. Spaceflight reduces vasoconstrictor
responsiveness of skeletal muscle resistance arteries in mice. Journal of Applied Physiology.
November 1, 2012;113(9):1439-1445. doi: 10.1152/japplphysiol.00772.2012.