Hyperbaric oxygen promotes proximal bone regeneration and organized collagen composition during digit regeneration

Oxygen is critical for optimal bone regeneration. While axolotls and salamanders have retained the ability to regenerate whole limbs, mammalian regeneration is restricted to the distal tip of the digit (P3) in mice, primates, and humans. Our previous study revealed the oxygen microenvironment during regeneration is dynamic and temporally influential in building and degrading bone. Given that regeneration is dependent on a dynamic and changing oxygen environment, a better understanding of the effects of oxygen during wounding, scarring, and regeneration, and better ways to artificially generate both hypoxic and oxygen replete microenvironments are essential to promote regeneration beyond wounding or scarring. To explore the influence of increased oxygen on digit regeneration in vivo daily treatments of hyperbaric oxygen were administered to mice during all phases of the entire regenerative process. Micro-Computed Tomography (μCT) and histological analysis showed that the daily application of hyperbaric oxygen elicited the same enhanced bone degradation response as two individual pulses of oxygen applied during the blastema phase. We expand past these findings to show histologically that the continuous application of hyperbaric oxygen during digit regeneration results in delayed blastema formation at a much more proximal location after amputation, and the deposition of better organized collagen fibers during bone formation. The application of sustained hyperbaric oxygen also delays wound closure and enhances bone degradation after digit amputation. Thus, hyperbaric oxygen shows the potential for positive influential control on the various phases of an epimorphic regenerative response.