Hypoxia in tissue repair and fibrosis.

Hypoxia and hypoxia signalling through the transcription factor hypoxia inducible factor-1 (HIF-1), play an important role in normal tissue repair processes. Tissue injury generally produces at least the transient loss of normal vascular perfusion and the resulting hypoxia induces the expression of many genes that allow the tissue to adapt to hypoxia, to start the repair process and, in time, to re-establish oxygen delivery to the tissue. In most cases, transient hypoxia and the activation of the HIF-1 pathway are beneficial and promote the repair process, producing tissue that might not perfectly reform its original architecture but that has its function substantially restored. However, in some cases of chronic injury, chronic hypoxia and pathological repair, the hypoxia pathway might be responsible for driving the process of fibrosis and can lead to excessive scarring and compromised organ function.