Role of CD14 and TLR4 in type I, type III collagen expression, synthesis and secretion in LPS-induced normal human skin fibroblasts

Objectives: The primary aim of this study was to investigate the role of CD14 and TLR4 in type I, type III collagen expression, synthesis and secretion in LPS-induced normal human skin fibroblasts. The secondary aim was to provide theoretical basis for the molecular mechanisms of scar formation induced by LPS. Methods: The normal skin fibroblasts cultured in vitro were randomly divided into four groups: 0.1 mu g/mL LPS reference group, CD14 pretreatment + LPS, TLR4 pretreatment + LPS, CD14 and TLR4 pretreatment + LPS. The collagen DNA synthesis was assessed by H-3-proline incorporation method. Real-time Quantitative PCR was used to detect type I, type III collagen mRNA expression. Results: Similar results were revealed for mRNA expression levels. The immunofluorescence staining suggested that type I and type III collagen were expressed in all investigated groups and that the expression was differentially downregulated in groups B, C, D. ELISA demonstrated markedly decreased levels in secreting type I, type III collagens and hydroxyproline in groups B, C, D (P< 0.05), and the lowest level was detected in group D (P< 0.01). Conclusion: Pretreatment with CD14 or TLR4 alone or their combination can significantly reduce the levels of type I and type III collagen expression, synthesis and secretion, with the most notable reduction detected in case of CD14 and TLR4 combined. We could thus conclude that both CD14 and TLR4 are involved in type I and type III collagen expression, synthesis and secretion in LPS-induced skin fibroblasts.