Abstract
Microgravity, characterized by a weak gravitational pull, poses physiological risks to astronaut health and performance. While its impact on muscle and bone is well documented, effects on connective tissue, such as tendon, remain understudied. PURPOSE: This study aimed to 1) quantify the effects of 37 days of microgravity on the compressive nanomechanics of individual collagen fibrils and 2) compare these findings to existing literature and previously collected lab data. We hypothesized that spaceflight (SF) fibrils would exhibit a lower Young’s Modulus (YM) than ground controls (GC). METHODS: Female C57BL/6J mice were exposed to 37 days of spaceflight aboard the International Space Station. Tendon (n = 9) from the gastrocnemius (GT) and quadricep (QU) was processed to isolate individual collagen fibrils (GC = 55; SF = 55), preserving native structure. Hydrated fibrils were imaged via atomic force microscopy (AFM) to assess morphology and YM. Micrographs were analyzed with JPK, Gwyddion, and SPSS softwares. RESULTS: SF fibrils had a 35% lower average YM than GC (2.10 ± 0.62 vs. 3.26 ± 0.97 MPa; p < 0.01). SF fibrils were also wider than GC (222 ± 61 nm vs. 168 ± 44 nm), revealing an inverse relationship between width and YM (r = -0.58). ANCOVA with Bonferroni correction confirmed significant group differences after controlling for width (p < 0.01), with adjusted YM means of 3.08 ± 0.11 MPa (GC) and 2.28 ± 0.11 MPa (SF). When grouped by tendon origin, both GT and QU fibrils showed reduced YM in the SF group. However, GT fibrils exhibited a larger decline (3.41 to 1.86 MPa, 46%) compared to QU (3.02 to 2.53 MPa, 16%). CONCLUSION: Sustained microgravity significantly reduces the stiffness (YM) of tendon-derived collagen fibrils. Although fibril width correlated inversely with YM, it did not fully explain differences between groups. The greater decline observed in GT fibrils may reflect baseline and tissue-specific loading differences or mechanical roles during spaceflight. These findings highlight the need for further investigation into collagen level mechanisms behind tendon deconditioning in microgravity. Future studies should consider the role of hydration and fibril alignment, as well as explore alternative imaging techniques such as Small-angle X-ray scattering (SAXS) to gain deeper structural insight.
Recommended Citation
Bialy, Patrick; Ichimura, Andrew S.; Lorenz, Kent A.; Scott, Ryan T.; and Bagley, James R.
(2025)
"Nanomechanical Effects of Microgravity on Murine Tendon Fibrils,"
International Journal of Exercise Science: Conference Proceedings: Vol. 14:
Iss.
5, Article 19.
Available at:
https://digitalcommons.wku.edu/ijesab/vol14/iss5/19
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