Efficacy and safety of microbial transglutaminase-induced scleral stiffening in vivo

The purpose of this study was to investigate the efficacy and safety of microbial transglutaminases (mTGases) during scleral collagen cross-linking (CXL) in vivo. Sixteen New Zealand white albino rabbits were treated with sub-Tenon's injections of 2 ml of 1 U/ml mTGases in the right eye and 2 ml of phosphate buffer saline (PBS) in the left eye. The rabbits were killed 2 weeks after the injection, and all eyeballs, including some scleral strips, were processed. The elastic modulus was measured with a biomaterials tester. Histopathological analysis and transmission electron microscopy (TEM) were used for the morphological observations. The elastic modulus of the mTGase-treated sclera was 15.79 ± 2.93 MPa, and that of the control was 6.91 ± 2.23 MPa, indicating an increase of 129% after the mTGases treatment (P < 0.05). The density of the scleral collagen bundles and diameter of the collagen fibrils increased compared with those in the control group. No apoptosis was detected in the retina or posterior sclera by TUNEL staining, and no histological damage was observed on the TEM scan. This study is based on a short-term study on animal models. These results indicate that mTGase-mediated scleral CXL is a promising approach to effectively stiffen the sclera and safe enough for retina, and may be a useful treatment modality for strengthening scleral tissue.