Effects of Chemically Induced Hypoxia on In Vitro Expression of Hypoxia Inducible Factor-l𝛂, Vascular Endothelial Growth Factor, Aggrecanase-1, and Tissue Inhibitor of Metalloproteinase-3 in Rat Mandibular Condylar Chondrocytes

Aims: To examine the expression of hypoxia inducible factor-lα (HIF-1α), vascular endothelial growth factor (VEGF), aggrecanase-1 (ADAMTS-4), and tissue inhibitor of metalloproteinase-3 (TIMP-3) in rat mandibular condylar chondrocytes under hypoxic conditions and examine the relationship of these expressed factors in early condylar cartilage growth. Methods: CoCl2 was used to mimic a hypoxic microenvironment by chemically inducing hypoxia. Chondrocytes, which were obtained from the mandibular condyles of 3-week-old female Sprague-Dawley rats, were treated with 125 μmol/L CoCl2 for 48 hours. The HIF-1α, VEGF, ADAMTS-4, and TIMP-3 mRNA levels in chondrocytes were detected using a semiquantitative polymerase chain reaction (PCR) at 12, 24, and 48 hours after the initiation of hypoxia and normoxia conditions. A univariate variance analysis (pairwise least significant difference t test) using a SPSS 13.0 software package was performed to test for differences between different groups. Results: PCR analysis of the chondrocytes showed that the expression of HIF-1α and VEGF mRNA increased at 12, 24, and 48 hours after induction of hypoxia. HIF-1α expression gradually increased throughout the study duration, while VEGF expression peaked at 12 hours. Compared to normoxia conditions, hypoxia resulted in constantly elevated expression levels of both. On the other hand, there was no significant difference in the ADAMTS-4 and TIMP-3 mRNA expression between hypoxic and normoxic conditions throughout the study (P > .05). Conclusion: An upregulated HIF-1α and VEGF mRNA expression indicates their important roles in cartilage vascularization and development in newly hypoxic microenvironments. Additionally, chemically induced hypoxia has little effect on the expressions of ADAMTS-4 and TIMP-3.

HIF-1α; VEGF; aggrecanase-1 (ADAMTS-4); TIMP-3; hypoxia; CoCl2; TMJ cartilage

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