Abstract:

Objective   To evaluate the morphometry changes of adult rabbit extraocular muscle after direct injection of nerve growth factor（NGF）. Methods   In a self-control study, the left eyes of 10 adult rabbits were selected as the experimental group, and the right eyes as the control group.  5μg(0.05mL) NGF was injected into the superior rectus muscle of each experimental eye, and the identical volume of sterilized saline into each control eyes. One week after injection, muscle wet weight and muscle fiber cross-sectional areas were examined. The morphology of the muscles both in the experimental group and the control group was studied by hematoxylin-eosin staining and Van Gieson staining under a light microscope，and the proliferating cell nuclear antigen （PCNA） positive cells in the superior rectus muscle were determined by immunohistochemistry. Results   There was no significant difference in wet weight between the experimental group［(0.14±0.02)g］ and the control group［(0.12±0.02)g］. The myofibers mean cross-sectional area of the superior rectus muscle was (9.67±1.82) mm2 in the experimental group,  and (6.97±1.90) mm2 in the control group, with a significant difference between them(t=2.79,P=0.02). No obvious infiltration of inflammatory cells was seen in the muscles after injection. The perimeter of the superior rectus muscle was (167.20±35.55) μm in the experimental group and (127.44±33.64) μm in the control group, with a significant difference between them(t=3.06, P<0.001).The frequencies of large and middle fibers in the muscles were higher in the experimental group than in the control group (χ2=64.16，P<0.001).The proportion of PCNA positive cells was higher in the experimental group than in the control group(χ2=54.61，P<0.001 ). Conclusion   Single direct injection of NGF into extraocular muscles is an effective and safe procedure. NGF can increase myofibers cross-sectional area of the extraocular muscle and promote the proliferation of extraocular muscle fibers.

Key words: Extraocular muscle; Nerve growth factor; Proliferating cell nuclear antigen； Rabbits; Strabismus