Regulation of Collagen I and Collagen III in Tissue Injury and Regeneration

Figures

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  Figure 1:. Collagen synthesis, distribution, and ECM remodeling. Collagen is synthesized by crosslinking of amino acids hydroxyproline, proline, and glycine, Crosslinking of these amino acids results in the formation of collagen fibrils and finally collagens. Collagens are differentially expressed in various body parts and pertain stability, elasticity, and strength along with the involvement in various physiological processes. Changes in collagen distribution during wound healing and ECM remodeling during injury where the ratio of collagen I and collagen III is altered with a higher amount of collagen III during healing while increased collagen I in a healed wound.

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  Figure 2:. Regulation of collagen degradation: Collagen degradation is regulated by matrix metalloproteinases (MMPs) which in turn are regulated by tissue inhibitors of matrix metalloproteinases (TIMPs) and membrane type 1 matrix metalloproteinase (MT1-MMP). MMPs are secreted by lymphocytes and granulocytes and their secretion is regulated by cytokines, transcription factors, and epigenetic factors. Collagenases are secreted in an inactive form and get activated via stromelysin. This suggests that the activation and secretion of MMPs are tightly regulated processes.

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  Figure 3:. Different phases of an injury and wound healing process. A. Normal skin having epi- dermis and dermis. B. Injury and blood flow to the site of injury. C. After injury, a clot is formed to prevent blood loss. The macrophages promote tissue remodeling and col III level starts increasing at this stage. D. Contraction of wound and scab formation. E. The maturation of tissue results in formation of scar tissue because of remodeling of the ECM where col III is replaced by col I. F. Restoration of normal skin after wound healing.