Search

The alteration of normal dermal fibroblast function that leads to the development of hypertrophic scar after thermal injury is unknown. To determine functional differences that might explain this process, fibroblasts were cultured from biopsies of post-thermal injury mature hypertrophic scars and patient-matched normal skin. The mitogenic responses of scar cells to fetal bovine serum, epidermal growth factor (EGF), platelet-derived growth factor (PDGF), and tumor necrosis factor α (TNFα) were determined and compared to normal skin cells. Collagen synthetic rate was also compared in the presence and absence of transforming growth factor β1 (TGFβ1). Whereas both scar and normal cells responded with increased thymidine uptake to serum and cytokines, the stimulation to EGF and serum was significantly lower in scar cells. In contrast, synthesis of collagen, but not of non-collagenous proteins, was increased in scar relative to normal cells, both basally and when stimulated with low doses of TGFβ1. Additionally, the fraction of protein synthesized as collagen was significantly higher in scar fibroblasts. These results suggest that fibroblasts from hypertrophic scars demonstrate stable phenotypic differences in cytokine responsiveness in comparison to cells from unaffected skin. The increased rate of collagen synthesis and decreased responsiveness to mitogens are consistent with the increased extracellular matrix content and decreased cellularity of hypertrophic scars. [ABSTRACT FROM AUTHOR]

An excessive amount of matrix metalloproteinase-9 (MMP-9) has been well documented in inflammatory diseases, including chronic wounds and cancers. Secreted as a zymogen, proMMP-9 can be irreversibly converted to a mature form through cleavage of the N-terminal propeptide domain. Although the converting enzyme for proMMP-9 in human tissues is unknown, we previously found that tumor necrosis factor-α (TNF-α) promotes activation of proMMP-9 in human skin, and characterized the converting activities as tissue-associated chymotrypsin-like proteinases. On the other hand, the pathophysiologic inhibitor to prevent proMMP-9 maturation also remains elusive. In this regard, we observed the presence of the inhibitory property in burn blister fluid that abrogates the skin extract–mediated activation of proMMP-9. Then we determined that α-1-antichymotrypsin (α-ACT), an acute-phase factor abundantly present in the blister, effectively inhibited proMMP-9 activation in human and rodent skin. In contrast, the aminophenylmercuric acetate-induced “cysteine switch” and activation of proMMP-9 were not affected by α-ACT. TNF-α-induced activation of proMMP-9 by the explants of human skin was inhibited by α-ACT but not by related α-1-antitrypsin. α-ACT specifically attenuated maturation of proMMP-9 but not proMMP-2 or proMMP-13. Furthermore, short peptides that mimic the reactive center loop (RCL) of α-ACT were sufficient to inhibit the conversion. Mutation analysis demonstrated that a conserved leucine within the RCL was critical for α-ACT-exerted inhibition. In chronic wounds, a large amount of mature MMP-9 was associated with fragmentation and inactivation of α-ACT. Taken together, these results demonstrate that, to the best of our knowledge, α-ACT is a previously unreported pathophysiologic inhibitor that controls proMMP-9 activation in skin tissue.Journal of Investigative Dermatology (2008) 128, 2334–2342; doi:10.1038/jid.2008.77; published online 10 April 2008 [ABSTRACT FROM AUTHOR]

Abnormal wound healing encompasses a wide spectrum, from chronic wounds to hypertrophic scars. Both conditions are associated with an abnormal cytokine profile in the wound bed. In this study, we sought to understand the dynamic relationships between myofibroblast differentiation and mechanical performance of the collagen matrix under tissue growth factor–β (TGF-β) and tumor necrosis factor–α (TNF-α) stimulation. We found TGF-β increased α-smooth muscle actin (α-SMA) and TNF-α alone decreased the basal α-SMA expression. When TGF-β1 and TNF-α were both added, the α-SMA expression was suppressed below the baseline. Real-time PCR showed that TNF-α suppresses TGF-β1-induced myofibroblast (fibroproliferative) phenotypic genes, for example, α-SMA, collagen type 1A, and fibronectin at the mRNA level. TNF-α suppresses TGF-β1-induced gene expression by affecting its mRNA stability. Our results further showed that TNF-α inhibits TGF-β1-induced Smad-3 phosphorylation via Jun N-terminal kinase signaling. Mechanical testing showed that TNF-α decreases the stiffness and contraction of the lattices after 5 days in culture. We proposed that changes in α-SMA, collagen, and fibronectin expression result in decreased contraction and stiffness of collagen matrices. Therefore, the balance of cytokines in a wound defines the mechanical properties of the extracellular matrix and optimal wound healing.Journal of Investigative Dermatology (2007) 127, 2645–2655; doi:10.1038/sj.jid.5700890; published online 31 May 2007 [ABSTRACT FROM AUTHOR]