Cytokine Expression and Biomechanical Characteristics after Posterior Scleral Reinforcement Using Demineralized Bone Matrix and Allogeneic Sclera.

ABSTRACT

Background: Myopia is associated with scleral weakness and thinness, leading to visual impairment. Currently, posterior scleral reinforcement (PSR) remains the primary treatment for this condition. However, clinical practice commonly faces challenges such as insufficient donor availability and inadequate strength of allogeneic sclera materials. Therefore, in this study, we evaluated the cytokine expression and biomechanical characteristics of two types of scleral reinforcement materials (demineralized bone matrix (DBM) and allogeneic sclera) to identify the optimal material for PSR. Methods: Seventy-two two-week-old New Zealand rabbits were utilized in this study. Each rabbit eye was assigned to either an experimental group or an untreated group (no surgical intervention), which were further divided into DBM, allogenic sclera, and control groups (surgery without implantation). Samples were analyzed during different postoperative periods including the inflammatory response period at week 2, angiogenesis period at week 4, collagen formation period at week 12, and connective tissue proliferation period at week 24. Refractive power and axial length of the experimental eyes were measured at 2, 4, 12,and 24 weeks postoperatively while implanted slices with attached sclera from the DBM and Sclera group experimental eyes were collected. The same area of sclera was obtained from the sham group for immunohistochemical analysis and western blot detection to analyze levels of bFGF (Basic Fibroblast Growth Factor), CTGF (Connective Tissue Growth Factor), TGF-ß (Transforming Growth Factor ß),and Collagen I along with respective elasticity modulus and ultimate strength of the implant slice taken. Results: There were no significant differences (P > .05) in axial length and refractive power between the DBM and allogenic groups before 24 weeks, while a significant difference (P < .05) was observed compared to the control group. The levels of bFGF, CTGF, and TGF-ß in the DBM and sclera groups were significantly higher than those in the control group (P < .05). After 24 weeks, histological analyses revealed a strong connection between the implants and sclera with collagen formation. The elasticity modulus and ultimate strength of both DBM and scleral groups were significantly higher than those of the control group (P < .05). Furthermore, the DBM group exhibited a higher elastic modulus and ultimate strength compared to the scleral group (P < .05). The synthesis of collagen can be effectively promoted by bFGF, CTGF, and TGF-ß, leading to increased elastic modulus and ultimate strength which helps prevent posterior scleral expansion, thereby controlling further axial growth delay complications occurrence. Conclusion: The cytokine expression profile along with biomechanical characteristics make DBM an ideal material for posterior scleral reinforcement due to its low antigenicity, excellent biocompatibility without obvious postoperative rejection reaction as well as its ability to closely associate with autologous sclera making it widely available from various sources.