Objective: To observe the inhibitive effect of pirenzepine on form deprivation myopia in guinea pigs and to explore the mechanism of Smad3 signaling pathway and connective tissue growth factor (CTGF) in the inhibition of myopia by pirenzepine.
Methods: Forty 1-week-old guinea pigs of either sex were randomly divided into 4 groups: a control group (Group I), a form deprivation group (Group II), a pirenzepine ophthalmic solution group (Group III), and a sodium chloride ophthalmic solution group (Group IV). Translucent blinders were used in the right eyes of Group II, III and IV. The left eyes were not given any treatment as the normal control group. Covered eyes of Group III and IV were given 3% pirenzepine ophthalmic solution and 0.1% azone ophthalmic solution respectively twice every day. Six weeks later, refraction and axial length were measured at the end of the experiment, and immunohistochemistry and Western blot were used to analyze the expression levels of Smad3 and CTGF in the sclera of all 4 groups.
Results: There was no significant difference between Group III and I in relative refraction and changes of axial length (P>0.05). The difference of Group II and IV compared with Group I was statistically significant (P<0.05). The number of Smad3 and CTGF positive cells in the sclera between Group III and I was not significantly different (P>0.05), while the difference in Group II, IV and I was significant (P<0.05). Western blot showed that the expression levels of Smad3 and CTGF in Group II and IV were much lower than those in Group I (P<0.05), but not evident in Group III and I (P>0.05).
Conclusion: Pirenzepine ophthalmic solution can inhibit the development of form deprivation myopia. Pirenzepine may affect Smad3 signaling pathway in the sclera by inhibiting the development of form deprivation myopia.