Biomechanical Modification of the Sclera: An Ex Vivo Study on Porcine Eyes

Scleral biomechanics are altered in various ocular pathologies. Modification of sclera biomechanics has been proposed as a potential treatment strategy. This study characterizes the biomechanical effect of collagenase (COL), glyceraldehyde (GAD), microbial transglutaminase (mTG), transglutaminase 1 (TG1), transglutaminase 2 (TG2), and lysyl oxidase (LOX) on ex vivo porcine sclera.

Tissue biomechanics were assessed by uniaxial tensile testing. Tangent modulus (ET) was calculated from the stress-strain curve. The biomechanical response was analyzed based on dose-response curves. Locally applied treatments to the intraocular, extraocular, and combined intra- and extraocular scleral surface were compared with incubated tissue strips. Treatment safety was investigated on human adult retinal pigment epithelium cells (ARPE19) and mouse retinal ganglion cells.

GAD 0.1 M and mTG 1 U/mL led to a 10.53-fold (P = 0.0011) and 4.71-fold (P = 0.0210) increase in ET, respectively. COL 0.05 mg/mL decreased tissue stiffness by 2.33-fold (P < 0.0001). Incubation with TG1, TG2, and LOX did not lead to significant changes in tissue ET. The effect of strip incubation was significantly higher for GAD (P < 0.0001) and mTG (P < 0.01) compared with local applications, with no quantitative difference for COL. Viability assays showed a relatively safe application of mTG and COL on retinal ganglion cells and ARPE19, but increased cytotoxicity at higher GAD concentrations.

COL, GAD, and mTG induced dose-responsive biomechanical changes in ex vivo scleral biomechanics with acceptable safety. Locally applied treatments showed reduced biomechanical impact compared with strip incubation. Further experiments need to confirm these findings in vivo and determine its role in diseased eyes.