Hypoxia Upregulates the Synthesis of TGF-β1 by Human Dermal Fibroblasts

Abstract

In this report, we have investigated the secretion and synthesis of transforming growth factor-β1 (TGF–β1) by human dermal fibroblast cultures β1) response to hypoxia (2% oxygen), and have compared it to standard oxygen culture condition (15% oxygen at the cell surface). Sandwich enzyme-linked immunosorbent assay (SELISA) showed a selective and progressive increase in secretion of the TGF-β1 isoform in response to hypoxia, up to ninefold after cultures were exposed to low oxygen for 72 h; TGF-β2 peptide levels were not increased. We then investigated the transcriptional regulation of the TGF-β1 gene in response to low and standard oxygen tensions. In the first 24–48h TGF-β1 mRNA levels decreased steadily in both oxygen environments. This mRNA decline continued for up to 72h in standard oxygen but not in cultures exposed to low oxygen tension. At 72 h, steady-state TGF-β1 mRNA levels were 8 times greater in low compared to standard oxygen, and this increase was reversible upon re-exposure of fibroblast cultures to standard oxygen tension for 24h. Elevated TGF-β1 mRNA levels in both low and standard oxygen declined steadily and with the same half-life after the addition of actinomycin D, suggesting that hypoxia increased TGF-β1 transcription rather than mRNA stability. We conclude that low oxygen tension upregulates the synthesis of TGF-β1 by human dermal fibroblasts, and leads to increased secretion of this peptide