Publication Date

5-2021

Date of Final Oral Examination (Defense)

4-14-2021

Type of Culminating Activity

Thesis

Degree Title

Master of Science in Materials Science and Engineering

Department

Materials Science and Engineering

Major Advisor

Gunes Uzer, Ph.D.

Advisor

Danielle Wu, Ph.D.

Advisor

Clare Fitzpatrick, Ph.D.

Advisor

Trevor Lujan, Ph.D.

Advisor

David Estrada, Ph.D.

Abstract

Aged individuals and astronauts experience bone loss despite rigorous physical activity. Bone mechanoresponse is in part regulated by mesenchymal stem cells (MSCs). We reported that daily low intensity vibration (LIV) restores MSC proliferation in senescence and simulated microgravity models, suggesting reduced mechanical signal delivery to MSCs likely contributes to declining bone mechanoresponse. To this end, we have developed a 3D bone marrow analog which controls trabecular geometry, marrow mechanics and external stimuli.

Finite element (FE) models of hydrogels, representing bone marrow, were generated using instantaneous compression (1000% strain/s, 20% strain) and relaxation experiments (100s) of both gelatin and hyaluronin-based hydrogels. Experimental and in silico vibration experiments using molded-gelatin wells (widths= 4 , 5, 6 and 8 mm) were performed under 1g acceleration, 100 Hz for FE model calibration.

For MSC experiments, 0.25cmgyroid-based trabeculae of bone volume fractions (BV/TV) corresponding to adult (25%) and aged (13%) mice were printed using polylactic acid. MSCs encapsulated (1x106 cells/mL) in migration-permissive hydrogelswithin [sic] printed trabeculae were exposed to LIV (1g, 100 Hz, 1 hour/day). After 14 days, type-I collagen, Ki-67, f-actin (n=3/grp) were quantified for extracellular matrix composition, proliferation, and morphology and grouped with respect to the maximum von Mises strain for 13.5% and 25% BV/TV scaffolds using the calibrated FE models.

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