Phagocytosis of Collagen Fibrils by Fibroblasts In Vivo Is Independent of the uPARAP/Endo180 Receptor. Issue 6 (11th January 2017)

• Record Type: Journal Article
• Authors: Sprangers, Sara; Behrendt, Niels; Engelholm, Lars; Cao, Yixuan; Everts, Vincent
• Is Part Of: Journal of cellular biochemistry. Volume 118:Issue 6(2017)
• Page Start: 1590
• Page End: 1595
• Publication Date: 2017-01-11
• Subjects: COLLAGEN PHAGOCYTOSIS -- uPARAP -- FIBROBLAST -- TRANSMISSION ELECTRON MICROSCOPY; Cytochemistry -- Periodicals; 572
• DOI: 10.1002/jcb.25821
• Languages: English
• ISSNs: 0730-2312

Abstract

ABSTRACT: As a crucial step in ECM remodeling, collagen degradation occurs through different processes, including both extracellular and intracellular degradation. The extracellular pathways of collagen degradation require secretion of collagenolytic proteases, whereas intracellular collagen degradation occurs in the lysosomal compartment after uptake, involving either pre‐cleaved or intact fibrillar collagen. The endocytic collagen receptor uPARAP/Endo180 plays an important role in internalization of large collagen degradation products, whereas its role in the phagocytosis of fibrillar collagen has been debated. In fact, the role of this receptor in regular collagen phagocytosis in vivo has not been established. In this study, we have studied the role of uPARAP in the phagocytosis of collagen fibrils in vivo by analyzing different connective tissues of mice lacking uPARAP. Using transmission electron microscopy (TEM), we found that fibroblasts in the periosteum of tibia and calvaria, as well as in the periodontal ligament of molar and incisor, phagocytosed collagen fibrils independently of uPARAP. Quantification of phagocytosed collagen in the periodontal ligament of uPARAP‐deficient mice and controls revealed no difference in the amount of fibrillar collagen taken up by uPARAP‐deficient mice. The findings show that under in vivo conditions uPARAP does not play a role in the phagocytic uptake of collagen fibrils by fibroblasts. Consequently, the cellular uptake of collagen fibrils and collagen cleavage products probably occurs through fundamentally different pathways. J. Cell. Biochem. 118: 1590–1595, 2017. © 2016 Wiley Periodicals, Inc. Abstract : The collagen receptor uPARAP is essential in the uptake of pre‐cleaved collagen fragment, but not in phagocytosis of collagen fibrils. This indicates that distinct different mechanisms are involved in the turnover of the most abundant matrix component in the body.