PhD Thesis Defense: Afton Limberg

"The Effects of Hyperbaric Oxygen on Achilles Tendon Healing"

Abstract

Tendon injuries represent a significant and growing clinical burden, particularly in the aging population where impaired healing capacity and limited effective therapeutic strategies remain a critical unmet need. Hyperbaric oxygen therapy (HBOT) has emerged as a promising regenerative intervention; however, its biological and biomechanical effects on tendon healing remain poorly understood. This thesis aimed to elucidate the effects of HBOT on tendon healing across three novel experimental models.
 
In vitro studies using murine Achilles tenocytes demonstrated that HBOT significantly increased cellular metabolic activity, transiently elevated reactive oxygen species (ROS) immediately following treatment, and decreased HIF-1α expression over a 24-hour period, collectively suggesting that HBOT shifts tenocytes towards a more metabolically active and oxidatively regulated phenotype. Assessment of an ex vivo murine Achilles tendon explant model demonstrated that while no significant structural or biomechanical differences were observed between HBOT-treated and control tendons, HBOT did not adversely affect tendon viability, and cytokine dynamics were responsive to treatment, confirming the safety of HBOT in tendon tissue and highlighting the importance of physiological mechanical loading in ex vivo culture models. In an aged in vivo murine partial tenotomy model, HBOT-treated animals demonstrated significantly accelerated skin wound closure, reduced inflammatory cell infiltration, decreased proteoglycan deposition, and significantly increased COL1A1 expression at day 14 post-injury, alongside altered expression of hypoxia- and metabolism-related genes.
 
Together, these findings suggest that HBOT modulates the wound healing cascade by reducing the duration of the inflammatory phase and promoting collagen deposition during the proliferative stage. While further pre-clinical investigation with larger sample sizes and extended follow-up periods is warranted, the wide clinical availability of hyperbaric chambers and HBOT's established non-invasive safety profile position it as a promising and readily translatable adjunct therapeutic strategy for tendon repair in the aging population.

Thesis Committee:

• Doug Van Citters (co-chair)
• Katie Hixon (co-chair)
• Jay Buckey Jr.
• Frances Faro
• Spencer Lake (Washington University in St. Louis)

Contact

For more information, contact Thayer Registrar at thayer.registrar@dartmouth.edu .