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Retracted: Cell Fate and Tissue Remodeling in Canine Urethral Repair Using a Bone Marrow Mesenchymal Stem Cell+Endothelial Progenitor Cell Amniotic Patch

In a previous study, a 3-cm-long circumferential urethral defect of the canine was repaired using bone marrow mesenchymal stem cell (BMSC)+endothelial progenitor cell (EPC) amniotic patch. To clarify the differentiation fate of BMSCs and EPCs as well as the tissue remodeling process during the repair, canine BMSCs and EPCs were respectively labeled with green and red fluorescent proteins, the labeled cells were used to construct a tissue-engineered amniotic membrane patch and the patch was used to repair a 3-cm-long circumferential urethral defect of the canine. Examination in 1-2 months after surgery showed that the dogs in test group urinated normally, the newly generated urethras were covered by a mucosal epithelium composed of five to six layers of columnar cells, similar to the epithelial structure of the normal urethra, and the submucosa was richly vascularized. In the area of newly generated urethral mucosal epithelium, green fluorescence and red fluorescence coexisted, and more cells emitting green fluorescence than cells emitting red fluorescence were present. In the submucosa, there were many cells emitting red fluorescence, they formed a large number of vascular structures, and there were few cells emitting green fluorescence. These results demonstrated that BMSCs mainly differentiated into urothelial cells, and EPCs mainly differentiated into vascular endothelial cells. Altogether, these cells participated in the repair of the urethral mucosal epithelium, and most of the submucosal tissues were formed by the growth of the adjacent recipient cells. The BMSC+EPC amniotic patch could completely repair the canine 3-cm-long circumferential urethral defect within 1-2 months, which is expected that it will be applied in clinical practice. Impact statement In the complete repair of a 3-cm-long circumferential urethral defect of the canine perineum using bone marrow mesenchymal stem cell (BMSC)+endothelial progenitor cell (EPC) amniotic membrane patch labeled with green and red fluorescent proteins, BMSCs mainly differentiated into urothelial cells, EPCs mainly differentiated into vascular endothelial cells, these two cells together participated in the repair of the urethral mucosal epithelium, and most of the submucosal tissues were formed by the growth of the adjacent recipient cells. Fluorescent protein labeling had no influence on stem cell proliferation and tissue repair ability.