UC San Diego

Hyaluronic acid (HA), an essential glycosaminoglycan of the extracellular matrix, exhibits molecular weight (MW)-specific biological activity through receptors such as CD44, RHAMM, and TLR2/4. Although these signaling functions are well characterized, the MW-specific effects of HA on cellular metabolism remain largely unexplored. This thesis used label-free multimodal optical imaging techniques to address this gap across three specific aims. First, spontaneous Raman spectroscopy of pure HA powders spanning 814 Da to 2.7 MDa established MW-dependent vibrational signatures independent of any biological context, consistent with differences in backbone conformation, hydrogen bonding, or chain packing. Second, deuterium oxide-probed stimulated Raman scattering (DO-SRS) and multiphoton redox imaging were applied to HA-treated HeLa cells across this MW range, revealing concentration-gated metabolic responses that were largely shared across molecular weights. Third, oral administration of HA in Drosophila melanogaster led to tissue- and molecular weight-dependent metabolic responses in the gut and fat body that cannot be attributed to canonical HA receptors. Together, these findings indicate that HA molecular weight shapes cellular metabolism in a concentration- and tissue-dependent manner across two distinct model systems.