(A.1-A.2). Low and high magnification (100×, 200×) of axial section through anastomosis in syngeneic tracheal replacement. (A.3). K5+ basal cells represent an intact epithelium. (B.1-B.2). Low and high magnification (100×, 200×) of axial section through anastomosis in resorbable graft implantation with (B.3) redemonstration of epithelium. (C.1-C.2). Low and high magnification (100×, 200×) of coronal section through anastomosis of resorbable scaffold; (C.3) anastomoses demonstrated evidence of respiratory epithelialization (black arrow) and K5+. (D.1-D.2). Nonresorbable grafts with dilated vessels, inflammatory cell infiltrate, and thickened sub-epithelium (*) leading to graft stenosis when compared to syngeneic grafts (open arrow). (C.1–C.2). Graft resorption and collapse in resorbable scaffolds (double open arrow). (C.3, D.3). Immunostaining demonstrates incomplete migration of epithelium onto the scaffold. Example suture artifact = red arrow. Scale bars: Low magnification (A.1–D.1): 200 µm. High magnification (A.2–D.2) and K5+ basal cells (A.3–D.3): 50 µm.