Healing and Muscular Restoration of the Ureteral Wall Following Balloon-Induced Rupture: An Experimental Animal Model with Light Microscopic and Ultrastructural Observations

Abstract

Ureteral regrowth following balloon-induced rupture was studied using an animal model, with emphasis on the pattern and cellular events of self-reconstitution in the late phase of healing. At 4 weeks, the ureteral healing/remodeled region included a wedge-shaped muscular component which pointed toward a fibrous central zone, was continuous with the adjacent muscularis propria, and abutted on a thin-lining epithelium. Progressive enlargement, aggregation, and bundle formation of myogenic cells was observed along the centrifugal axis. At 7 weeks, there was near-total muscular continuity, a rudimentary lamina propria, and partial periluminal folding. Muscular restoration was unaffected by the use of a stent, but epithelial metaplastic changes were observed. The intermediate zone showed admixed fibroblasts, immature and mature myogenic cells, and myofibroblasts. Frequent plasmalemmal appositions and junctions were observed between different cell types, whereas myofibroblasts were not associated with cell-to-stroma attachments. Myofibroblasts might play more than a contractile role in this phase of ureteral healing, possibly having an induction role and/or representing a transient form in myogenic differentiation.