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Analysis of Complex Biomarkers of Musculoskeletal Atrophy and Stress in Preserved Mouse Urine for the Mars Gravity Biosatellite. V.Y. Chang^1,2, E.B. Wagner^3,4, MIT Departments of ¹Biology, ²Chemistry, ³Aeronautics and Astronautics; ⁴Harvard-MIT Division of Health Sciences and Technology, Cambridge, MA.

  The Mars Gravity Biosatellite Program is developing an uncrewed partial gravity research platform capable of carrying fifteen mice in a 0.38-g environment for periods of up to five weeks. In order to understand the timecourse of adaptation to a partial gravity environment, we have developed a method for autonomously collecting and preserving rodent urine. Time-stamped weekly samples will be analyzed post-flight for evidence of musculoskeletal atrophy and systemic stress. Earlier research with this system examined preservation of urea and simple ionic moieties. We have since advanced to more robust and specific biomarkers, selecting a combination of ELISA and HPLC for small-sample reliability and high-specificity detection of these analytes.

  Corticosterone measurements using ELISA confirm the degree to which musculoskeletal degradation is due to low gravity conditions, rather than acute and chronic stresses of flight. Muscle atrophy is measured with a combination ELISA/HPLC method to determine the Creatine/Creatinine ratio, which increases with muscle breakdown. ELISA kits are currently being evaluated for deoxypyridinoline and n-telopeptides, bone-specific collagen components whose presence indicates an increase in bone turnover.

  Five week validation studies used pure urine adsorbed on a polyvinylidene difluoride microporous membrane (Durapore, Millipore Corp.) with and without applied Chlorhexidine n-Propyl-Gallate (CPG) preservative. The biomarker analysis method provides feedback on preservation while minimizing conflicts resulting from major urinary protein effects, Durapore absorption, chlorhexidine-protein binding, and dilution factors. (Supported by NASA SBIR NNA05CP01C)