INTRODUCTION: Human mesenchymal stem cells (hMSCs) from the bone marrow represent a potential source of pluripotent cells for musculoskeletal tissue engineering. Glucose transporter‐1 (GLUT‐1) expression is upregulated in a variety of cells under hypoxic condition, which is mediated by the transcription factor hypoxia induced factor (HIF)‐1α. HIF‐1α and GLUT‐1 proved to be phenotypical signature of nucleus pulposus. Therefore, the objective of this study is to evaluate possibility that hMSCs induce the IVD in hypoxia condition.
MATERIALS AND METHODS: Human bone marrows were collected during surgery from patients (age range 45‐67 years) with lumbar spinal stenosis. hMSCs were purified by density gradient centrifugation in Ficoll/Hypaque and maintained in the condition medium until one passage. The hMSCs were seeded in collagen type I sponge at a cell density of 5 x 105 cell per each one for protein and RNA isolation in hypoxia condition (1% O2, 5% CO2, 37°C) and normal condition (5% CO2, 37°C) for three days. Human disc cells were used as a control. For expression of HIF‐1a and GLUT‐1 at the mRNA and protein level, RT‐PCR and western blot were performed according to the manufacturing protocol.
RESULTS: The expression of aggrecan mRNA was upregulated in hypoxia condition as compared to normoxic condition. In hypoxic condition, the expression of GLUT‐1 mRNA disc cells is higher than that of MSCs. MSCs under hypoxia revealed rendered increase in aggrecan and GLUT‐1 mRNA expression compared to those of normoxic condition. (cont'd)
DISCUSSION: Hypoxia provided phenotypical stabilization in disc cells upregulating GLUT‐1 and aggrecan mRNA expression. MSCs under hypoxic condition exhibited GLUT‐1 and aggrecan mRNA expression higher than normoxic condition, however the intensity of GLUT‐1 expression is lower than that of disc cells. In conclusion, hypoxia and its intracellular mediator GLUT‐1 might induce discogenic phenotypical differentiation of MSC.