Targeting Wnt Signaling To Reduce Fibrosis
Britta A. Kuehlmann, Clark A. Bonham, Geoffrey C. Gurtner.
Stanford University, Stanford, CA, USA.
BACKGROUND- Wnt signaling plays a central role in various forms of fibrotic diseases, including skin fibrosis. Activation of the Wnt pathway increases excessive collagen deposition. Foreign body responses around implants mediate remodeling of the extracellular matrix (ECM) resulting in a surrounding capsule of fibrotic tissue.
METHODS- Fibrosis was induced by inserting implants in Bl6-mice and Wnt11-knockout mice. H&E staining was done to qualitatively assess the morphology and density of the fibrotic tissues. Cells were isolated and characterized by fluorescence-activated cell scanning (FACS), single cell quantitative polymerase chain reaction (qPCR) and single cell RNA sequencing to determine their impact on fibrotic responses. Additionally, SEM, TEM and 3D confocal imaging were performed.
RESULTS- FACS and immunohistochemistry stains revealed that collagen-depositing macrophages are responsible for the development of implant fibrosis. qPCR revealed that the majority of cells in the fibrotic tissue expressed macrophage genes and were found to significantly increase Col1a1 and Wnt11. Therefore, we looked at an intervention to reduce these macrophages by using Wnt11-knockout mice and subsequent induction of fibrosis. Using transcriptional analysis we found distinct markers to differentiate three macrophage subgroups (Group 1=Cd36, Group 2= Cd209, Group 3= Ccr2). FACS revealed that Cd36 and Ccr2 were significantly reduced in the fibrotic tissue of Wnt11-knockout mice compared to Bl6-mice. Wnt11-knockout mice displayed significantly thinner capsules with loosely arranged fibers after 3 months.
CONCLUSIONS- For the first time, we identify macrophage subgroups that are essential to fibrotic development around implants and we use a methodology to decrease fibrosis in an animal model. These findings have promising therapeutic implications for the treatment of fibrosis around implants.
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