The Effects Of TGF-β1 And INOS On FDM In The Chick

Objective We used a chick model to explore the effects of transforming growth factor-beta 1(TGF- 1) and inducible nitric oxide synthase (iNOS) on form-deprivation myipia(FDM) in the retina and choriod ,and the interaction between TGF-pl and iNOS,through detecting the expression of TGF-pl and iNOS protein and their mRNA in form-deprivation myipia(FDM).Methods FDM was established in 60 one-day-old white leghorn chicks by fixing translucent plastic goggles over one eye randomly,the other as control. The chicks were divided into A and B experimental groups. Chicks in A group were occluded for 3 weeks,chicks in B group occluded for 2 weeks and then unoccluded for 1 week. In each week of experimental period, the axial length was measured with A-mode ultrasound,and retinoscopic refraction was performed.After 2 or 3 weeks,the chicks were killed and both eyes enucleated. The concentration of NOx(nitrite and nitrate) from the control and form-deprivation chick retina and choroid was determined using NO detection kit. The expression of TGF- l mRNA and iNOS mRNA was detected by reverse transcription polymerase chain reaction (RT-PCR). TGF- 1 and iNOS protein was analysed with immunohistochemistry (modified strept avidin-biotin complex, SABC),and the histopathologic featurs of the posterior sclera were also observed under light microscopy.Results Form-deprivation eyes were significantly more myopic than control eyes. The axial length of occluded eyes were significantly longer than control eyes. Unocclusion attenuated the development of myopia and inhibited axial elongation. Expression of TGF- 1 and iNOS mRNA was higher in the control chick retina and choroid than that in FDM. The immunostaining of TGF- 1 and iNOS protein mainly was detected in the outer part of photoreceptor layer, and nonspecific immunostaining was found in the RPE and choroids. In the FDM chickretina and choroid,the concentration of NOx decreased,the immunostaining of TGF- 1 and iNOS protein and expression of TGF- 1 and iNOS mRNA decreased,while recovered 1 week after unocclusion. Except that the expression of iNOS mRNA was significantly higher than control eyes at 1 week after unocclusion. In the myopic eyes the cartilaginous sclera was thicker relatively,and the ratio of binucleate cells/chondrocytes was higher than that in control eyes. The morphological featurs of myopic sclera became similar to control eyes after unocclusion.Conslusion Form-deprivation caused myopia,eyeball enlargement,and the morphological changes of myopic sclera. TGF- 1 and iNOS may be involved in the positive regulation in the myopic development. Probably FDM is correlated with the reduction of TGF- 1 and iNOS in the retina. The similar expression of TGF- 1 and iNOS in FDM implied some interaction between the TGF- 1 and iNOS,probably other factors also involve in the regulation procedure in FDM. FDM increased production of extracellular matrix(ECM) and level of mitotic activity in the cartilaginous sclera as the consequence of scleral active remodelling. FDM is reversible before chick become mature.