INTRODUCTION: The study evaluates the effect of hypoxia on the synthesis (i.e. quantity and quality) of collagen. Collagen is the most abundant protein present in animals, representing more than a quarter by weight of body protein tissue. Oxygen is involved in the synthesis and stabilisation (via cross‐linking) of this protein. We hypothesise that oxygen deprivation, as may be present in hypoxic tissues under repair, leads to the synthesis of inferior collagen that is unstable in nature.
METHODS: Monolayer cell culture medium was used to culture normal human dermal fibroblasts for 72 hours in two culture conditions. Hypoxic culture was incubated in a humidified chamber filled with special gas mixture (0% O2). Normoxic culture was incubated at atmospheric O2 levels. The production of the newly synthesized procollagen was measured by spectrophotomeric determination of hydroxyproline and molecular stability (enthalpy) of collagen was measured using differential scanning calorimetry.
RESULTS: Collagen production was significantly higher in normoxic culture (72.74 ± 45.26 μg/ml), when compared to the hypoxic (58.40 ± 34.16 μg/ml), P<0.001. In addition, molecular stability of the collagen produced under low oxygen tension (11.35 ± 1.56 J/g) was less than that produced with normal oxygenation (12.35 ± 1.58 J/g), P<0.01. (cont'd)
DISCUSSION: We have demonstrated that collagen biosynthesis is significantly depending on the oxygen tension, with lack of it leading to reduced production and unstable collagen, probably due to poor hydroxylation and abnormal cross‐linking. Most vertebrate cells respond to hypoxia by the stabilisation of hypoxia inducible factors (HIF) 1α and 2α, which both perform multiple and crucial roles in cell survival and function at low oxygen pressure. Our study is the first to provide clear evidence of the critical role of oxygen on collagen stability, and the potential this may have on degenerative processes in tissues such as cartilage and intervertebral disc.