Transient exposure to tumor necrosis factor-alpha inhibits collagen accumulation by cultured hypertrophic scar fibroblasts

Background. Hypertrophic scars (HS) are frequent consequences of deep derma l injury, such as deep partial-thickness burns and abrasions, and are chara cterized by overproduction of collagen. In vitro studies have shown that cu ltured HS fibroblasts produce elevated levels of collagen and insulin-like growth factor-binding protein 3 (IGFBP-3). Additionally, histological studi es have indicated HS contain fewer tumor necrosis factor alpha (TNF-alpha)- positive infiltrating cells and express lower levels of TNF-alpha mRNA, sug gesting TNF-alpha, which can inhibit collagen expression in some systems, m ay function to deactivate the wound healing process in scars. HS also exhib it increased levels of transforming growth factor beta (TGF-beta), a facts that stimulates collagen and extracellular matrix deposition by fibroblasts and also stimulates IGFBP-3 expression. In some systems, IGFBP-3 mediates the effects of TGF-beta. The present study sought to determine the effects of continuous and transient TNF-alpha exposure on collagen and IGFBP-3 expr ession by cultured;Hg fibroblasts and to investigate the role of IGFBP-3 in collagen accretion by HS fibroblasts. Materials and Methods. Superficial and deep dermal HS fibroblasts from four patients were cultured. Fibroblasts were cultured in serum-free medium and exposed to 0-2 ng/ml TNF-alpha for 0, 1, 4, or 72 h. After 72 h of culture , medium samples were processed for Western blot analysis of type I collage n accumulation or for ligand blot analysis of IGFBP-3 accumulation. The eff ects of an anti-IGFBP-3 neutralizing antibody on collagen accumulation were also assessed. Results. Treatment of superficial and deep HS fibroblasts with TNF-alpha re sulted in dose-dependent decreases in accumulation of both type I collagen and IGFBP-3 in the culture medium (P < 0.01). However, using the anti-IGFBP -3 neutralizing antibody, a causal relationship between decreased IGFBP-3 a nd decreased collagen accumulation could not be demonstrated. Transient exp osure of cultured HS fibroblasts to TNF-alpha for as little as 1 h was as e ffective as continuous exposure to TNF-alpha for 72 h in inhibiting collage n accumulation. Conclusions. These results support the hypothesis that TNF-alpha functions as a wound healing deactivation signal that is deficient in HS. Although TN F-alpha inhibited accretion of both collagen and IGFBP-3, the role of IGFBP -3 in HS remains unresolved. This study suggests that transient TNF-alpha e xposure may be used to inhibit collagen overaccumulation in HS and that the timing of TNF-alpha exposure following dermal injury may not be critical f or this inhibition. (C) 1999 Academic Press.