The effects of simulated microgravity on intervertebral disc degeneration

Background contextAstronauts experience back pain, particularly low back pain, during and after spaceflight. Recent studies have described histologic and biochemical changes in rat intervertebral discs after space travel, but there is still no in vitro model to investigate the effects of microgravity on disc metabolism.PurposeTo study the effects of microgravity on disc degeneration and establish an in vitro simulated microgravity study model.Study designDiscs were cultured in static and rotating conditions in bioreactor, and the characteristics of disc degeneration were evaluated.MethodsThe mice discs were cultured in a rotating wall vessel bioreactor where the microgravity condition was simulated. Intervertebral discs were cultured in static and microgravity condition. Histology, biochemistry, and immunohistochemical assays were performed to evaluate the characteristics of the discs in microgravity condition.ResultsIntervertebral discs cultured in rotating bioreactors were found to develop changes of disc degeneration manifested by reduced red Safranin-O staining within the annulus fibrosus, downregulated glycosaminoglycan (GAG) content and GAG/hydroxyproline ratio, increased matrix metalloproteinase 3 expression, and upregulated apoptosis.ConclusionsWe conclude that simulated microgravity induces the molecular changes of disc degeneration. The rotating bioreactor model will provide a foundation to investigate the effects of microgravity on disc metabolism.