Fig. 4A–D.

(A) Type I collagen stain for the repair tissue of 16 weeks. Deep-stained brown granules deposited in the matrix of GETE group (Stain, type I collagen immunohistochemistry; original magnification,  × 200), and the coloration was deeper than the BMSCs group (Stain, Type I collagen immunohistochemistry; original magnification,  × 200) (B). (C) Scanning electron microscopic observation for the repair tissue in GETE group of 16 weeks demonstrated regular fibers in similar diameters arranged superficially with matrix filled between the fibers and covered the surface of some fibers. (D) Transmission electron microscope analysis of samples from 16 weeks confirmed round and oval chondrocyte-like cells in differently oriented fibers with multiple cell processes and abundant rough endoplasmic reticulum and ribosomes. GETE = gene-enhanced tissue engineering; BMSCs = bone marrow stromal cells.