| Background and ObjectiveMyopia is a very common ocular problem, affecting perhaps one billion people worldwide. It is very important to study the pathogenesy of myopia for delaying the development,preventing the complication and exploring the treatment of it. The research on mammal animal myopia model and high myopia in humans has found most myopia is produced by lengthening of the vitreous chamber of the ocular globe. The sclera undergoes initiative remodeling process during the development of myopia. The changes of it in pathology are the decline of cell components and the change of content of extracelluar matrix (ECM). A series of research strongly suggest under the action of abnormal visual signal messages, the expression of lots of neurotransmitters and growth factors in the retina and choroid changed, the proliferation and metabolism of the scleral fibroblasts and ECM changed during a series of signal transduction process. It has been proved many substances attending this signal transmitter, such as dopamine(DA), vasoactive intestinal peptide(VIP), nitrogen monoxidum(NO). During the procedure abnormal visual message leading to pathological change in sclera, the action of these substance dose not produce on cells or ECM in sclera. They are just the upper signaling molecule. So, the key is to explore the bioactive substance changing in the sclera and elucidate the mechanism of these substance.Insulin-Like growth factors (IGF) are multifunction cell proliferation regulatory factors, they take promotion part in cell differentiation, proliferation and individual growth and development. There are there kinds of ligand of them: insulin,IGF- I,IGF-II. IGF- I and IGF- II , homologizing 70% , the structure and function of them are about 50% similar to the human insulin. They take action by binding with the receptors of IGF- I,IGF- II and with the IGF/Ins heterozygotic receptors, and have homoplastic structure and vitro activity, but do not all have same biological effect in vivo. The content and effect of IGF- I and IGF- II in different tissue and different periods of growth and development are different. Lots of histiocytes autocrine and paracrine secrete IGF- I . Depending on the chondrotropic hormone, IGF- I can stimulate the proliferation of various cells cultured in vitro and the synthesis of protein and DNA. We have detected a significant decrease in the amount of IGF- I mRNA in the guinea pig sclera, during the form deprived myopia(FDM) model of guinea pig, suggesting IGF- I may act as a direct factor inducing remodeling of sclera.The present study that observed the influence of IGF- I on guinea pig scleral fibroblast(GSF), aimed at clarifying the mechanism of IGF-I on the development of myopia.Material and methods1～3 days old guinea pigs were selected, weight between 80 to 200 gramma. GSF was cultured in vitro, the morphology of the primary GSF was observed, and using immunohistochemical method to identify vimentin and keratin. Using the 3～6 generation of GSF and MTT method to observe the time-dose effect of IGF- I on GSF proliferation. Using Chloramines T method to observe the effect of IGF- I on GSF collagen protein synthesis. Adding IGF-I to GSF, to explore the influence of IGF-I on formation and the expression ofMMP-2/TIMP-2.Results1. The cell cultured was identified as GSF for positive in vimentin and negative in keratin . The GSF of primary and serial subcultivation generation growed well.2. From 10.00 ng·ml-1～200.00 ng·ml-1, the proliferative of IGF-I is dose-depended, comparing with the control group(P<0.05). When the concentration of IGF- I is 100.00 ng·ml-1～200.00 ng·ml-1, the proliferative effect is the most significant(P <0.01).3. From the 2rd day,comparing with the control group, IGF-I can promote proliferation of the GSF significantly (P<0.05). 4. From 10.00 ng·ml-1～200.00 ng·ml-1, IGF-I can stimulate collagen protein synthesis of GSF. This effect is also dose-depended.5. When the concentration of IGF- I is 10.00 ng·ml-1, the expression of MMP-2 protein of the GSF is significant less than that in the control group(P<0.05). When the concentration is between 50.00 ng·ml-1～200.00 ng·ml-1, the decrease of the MMP-2 protein is more significant comparing with control group(P<0.01). While the expression of TIMP-2 protein has no significant changes at the concentration of IGF-1 from 5.00 ng·ml-1～200.00 ng·ml-1.Conclusion1. IGF- I can stimulate the proliferation of GSF significantly. This effect is dose-dependent.2. IGF-I can increase the collagen protein synthesis in viro. This effect is dose-dependent too.3. IGF- I can suppress the expression of MMP-2, and it has no evident influence on the expression of TIMP-2.4. During FDM sensitive period, supplying ectogenic IGF-I may delay the development of FDM.
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