Hypoxia-induced irreversible up-regulation of type I collagen and transforming growth factor-β1 in human peritoneal fibroblasts

Objective: To determine whether restoration of normoxia after a hypoxic insult returns the molecular expression of type I collagen and TGF-β1 to baseline levels. Design: Prospective experimental study. Setting: University medical center. Patient(s): Primary cultures of fibroblasts established from peritoneal tissues of five patients. Intervention(s): Hypoxia treatment of the primary cultured fibroblasts. Main Outcome Measure(s): Cultured human peritoneal fibroblasts (HPF) were maintained under hypoxic conditions (2% oxygen) for 24 hours and then transferred into normal culture conditions (normoxia) for another 24 hours. Total cellular RNA from cells was collected and subjected to multiplex reverse transcription polymerase chain reaction to quantitate type I collagen and transforming growth factor (TGF)-β1 mRNA levels in response to these treatments. Result(s): Hypoxia treatment resulted in 30% and 50% increases in type I collagen and TGF-β1 expression, respectively. Restoration of normoxia after hypoxia treatment failed to restore type I collagen and TGF-β1 expression to their baseline levels. Conclusion(s): These data support the hypothesis that hypoxia induces irreversible molecular changes in peritoneal fibroblasts that produce a phenotype that increases extracellular matrix expression and thereby would promote adhesion development. Thus once a phenotype consistent with increased adhesion development is manifested, restoration of oxygen supply does not reverse the stimulation of HPF type I collagen and TGF-β1 expression. This observation may in part explain the clinical observation that adhesion reformation is more difficult to prevent than de novo adhesion formation.