BACKGROUNDMyopia is a common disorder and the incidence has increased yearly, but its pathogenesis remains unclear. The aim of this study was to investigate the possible role of hepatocyte growth factor (HGF) and its receptor c-Met in the development of lens-induced myopia in guinea pigs.

METHODSSixty one-week-old guinea pigs were chosen. The right eyes were treated with -10.0 diopters (D) lenses as the lens-induced myopia group; the left eyes remained untreated as the control group. Six weeks later, refractive status and axial length were determined by streak retinoscopy and A-scan ultrasonography, respectively. The guinea pigs were killed and both eyes collected. Morphological changes were observed by hematoxylin and eosin staining. The expression levels of HGF, c-Met, and matrix metalloproteinase 2 (MMP-2) mRNA and protein in the posterior sclera were analyzed by RT-PCR and Western blotting, respectively.

RESULTSThe lens-induced myopia group became myopic with a significant increase in axial length and a significant decrease in refraction. Compared with the control group, the posterior retina and sclera were thinner in the lens-induced myopia group. The expression levels of HGF and MMP-2 mRNA and protein and of phosphorylated c-Met protein were significantly higher in the posterior sclera of the lens-induced myopia group than in the control group (all P < 0.05). In the lens-induced myopia group, the expression level of MMP-2 in the posterior sclera positively correlated with the expression level of HGF (r = 0.902, P < 0.05) and phosphorylated c-Met (r = 0.885, P < 0.05).

CONCLUSIONHGF/c-Met might play a role in the development of lens-induced myopia in guinea pigs by upregulating the expression of MMP-2.

Animals ; Guinea Pigs ; Hepatocyte Growth Factor ; metabolism ; Myopia ; etiology ; metabolism ; Proto-Oncogene Proteins c-met ; metabolism

OBJECTIVE: To investigate the effect of form-deprivation on level of gelatinase in the posterior sclera in chicks. METHODS: Fifty 1-day-old chicks were monocularly deprived to establish the animal model of form-deprivation myopia (FDM). According to the duration of form-deprivation the experimental chicks were divided randomly and equivalently into 5 groups, which were deprived for 3, 7, 14, 21 and 30 days respectively. Meanwhile the other eyes of the deprived chicks were used as self-control groups and chicks of the same days were chosen randomly as the normal control groups for each FDM group. At each form-deprivation point the changes of degree of diopters and axial length of chicks in each group were recorded. The levels of gelatinase in posterior sclera of the experimental eyes were measured by gelatin enzymography. RESULTS: Compared with the normal and self-control groups, the levels of MMP-2 activity in FDM groups were much higher (P <0.01). With the increase of the time of monocular deprivation these changes became more significant and reached the top after 14 days' deprivation with an inter-group statistical difference (P <0.01). The dynamic changes of MMP-2 activity were the same as those of axial length and degree of diopters in each experimental groups. There was positive correlation between the MMP-2 activity and axial length (r = 0.989, P < 0.01). But there was a negative correlation between the MMP-2 activity and refractive degree. CONCLUSION Increase of MMP-2 activity in the posterior sclera of chicks would be a direct key factor to trigger sclera ECM remodeling process in chick FDM.
Animals ; Chickens ; Gelatinases ; metabolism ; Matrix Metalloproteinase 2 ; metabolism ; Myopia ; enzymology ; etiology ; Sclera ; enzymology

BACKGROUNDThe form deprivation (FD) reduces spatial contrasts and induces myopia. Nitric oxide and cyclic guanosine monophosphate (cGMP) are involved in visual signal transmission. This study investigated changes in nitric oxide synthase (NOS) activity and cGMP concentration in ocular tissues in acute and chronic form deprivation myopia.

METHODSGuinea pigs had one eye covered by translucent glass for 7, 14 or 21 days. Untreated litter mates were used as controls. NOS activity and cGMP concentrations in the retinal, choroidal and scleral tissues of FD eyes and control eyes were analyzed by radioimmunoassay after various durations of FD. The expression of NOS subtypes was identified by immunohistochemistry.

RESULTSMyopia was successfully induced in FD eyes after 14 days. Compared with control groups, the retinal NOS activity and cGMP concentrations in the FD eyes significantly increased after 14 and 21 days while the retinal NOS activity in the FD eyes was transiently suppressed by 7 days of FD. The NOS activity and cGMP concentrations of choroid and sclera in the FD eyes were higher than in the control groups at 21 days. The three isoenzymes of nitric oxide synthase were detected in the ocular tissues of guinea pigs.

CONCLUSIONSThe NOS activity and cGMP concentrations were upregulated after chronic FD and the retinal NOS activity was transiently suppressed at acute FD. The function of elevated NOS activity may be mediated by cGMP.

Animals ; Cyclic GMP ; analysis ; Guinea Pigs ; Immunohistochemistry ; Myopia ; metabolism ; Nitric Oxide ; physiology ; Nitric Oxide Synthase ; metabolism ; Refractive Errors ; Retina ; metabolism

OBJECTIVETo observe the expressions of the collagen , matrix metalloproteases-2 (MMP-2), and tissue inhibitor of matrix metalloproteinase-2 (TIMP-2) in the posterior sclera of newborn guinea pigs with negative lens-defocused myopia.

METHODSNewborn guinea pigs were monocularly defocused by -10D lens. After 4 weeks of defocus, the eyes were removed to provide posterior scleral samples for detection. Expression of collagen was detected by immunohistochemistry on frozen sections of guinea pig sclera, and the protein levels of MMP-2 and TIMP-2 were evaluated by Western blot.

RESULTSImmunohistochemical analysis indicated that the expressions of collagen and TIMP-2 were significantly lower and the expression of MMP-2 was significantly higher in the posterior sclera in the defocused eyes than in the contralateral eyes (all P < 0.01). However, all these indicators were not significantly different between the contralateral eyes and normal control eyes (all P > 0.05). In the defocused animals, the refraction of defocused eyes was positively correlated with the expression levels of collagen (r = 0.79, P < 0.01) and TIMP-2 (r = 0.74, P < 0.05) and was negatively correlated with the expression level of MMP-2 (r = -0.78, P < 0.01) in posterior sclera.

CONCLUSIONAlteration of extracellular matrix in the posterior sclera, probably participated by MMP-2, may exist during the development of defocus-induced myopia.

Animals ; Animals, Newborn ; Collagen Type I ; metabolism ; Disease Models, Animal ; Guinea Pigs ; Matrix Metalloproteinase 2 ; metabolism ; Myopia ; metabolism ; Sclera ; metabolism ; Tissue Inhibitor of Metalloproteinase-2 ; metabolism

OBJECTIVETo investigate the expression of 5 muscarinic receptor subtypes in the scleral tissue of immature guinea pigs.

METHODSThe scleral tissue was collected from six 2-week-old pigmented guinea pigs to determine mRNA expressions of the muscarinic receptors with RT-PCR. Immunofluorescence was used to observe the protein expressions of the 5 muscarinic receptor subtypes.

RESULTSThe mRNAs of the 5 muscarinic receptor subtypes were all detected in the scleral tissue, and the mRNA expression was the highest for M1 subtype. Green fluorescence of M1 to M5 subtypes surrounding the fibroblast nuclei were found in the scleral matrix using laser confocal microscopy.

CONCLUSIONFive muscarinic receptor subtypes are present in the scleral tissues of immature guinea pigs, indicating the involvement of the muscarinic receptors in eye growth regulation.

Animals ; Female ; Gene Expression Regulation ; Guinea Pigs ; Immunohistochemistry ; Male ; Myopia ; metabolism ; pathology ; RNA, Messenger ; genetics ; metabolism ; Receptors, Muscarinic ; genetics ; metabolism ; Sclera ; cytology ; metabolism

OBJECTIVE: To explore the underlying mechanism of inhibition by Jinkui Shenqi Pills (JKSQP) on glucocorticoid-enhanced axial length elongation in experimental lens-induced myopia (LIM) guinea pigs. METHODS: Sixty 2-week old male guinea pigs were randomly divided into 4 groups with 15 guinea pigs in each group, according to the random numbers generated by SPSS software: control, LIM, saline and JKSQP groups. The control group includes animals with no treatment, while the guinea pigs in the other 3 groups received lens-induced myopization on the right eyes throughout the experiment (for 8 weeks). The saline and JKSQP groups were given daily intraperitoneal injections of 10 mg/kg hydrocortisone for 2 consecutive weeks at the same time, and then orally administered either saline or JKSQP [13.5 g/(kg•d) for 6 consecutive weeks. Body weight, anal temperature and animal appearance were observed and recorded to evaluate the GC-associated symptoms. The ocular parameters, including refraction and axial length, were measured by streak retinoscopy and A-scan ultrasonography, respectively. The levels of plasma hormones associated with the hypothalamic-pituitary-adrenal axis (HPAA), including free triiodothyronine, free thyroxine, estradiol and testosterone, were measured by radioimmunoassay, and cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate were measured by enzyme-linked immunosorbent assay. In addition, the mRNA and protein expressions of retinal amphiregulin (AREG) was measured by quantitative real-time polymerase chain reaction and Western blotting, respectively. RESULTS: JKSQP effectively increased body weight and anal temperature, improved animal appearance and suppressed axial length elongation in glucocorticoid-enhanced myopic guinea pigs with normalization of 4 HPAA-associated plasma hormones (all P<0.05). The plasma level of cAMP was significantly increased, whereas the plasma level of cGMP and the mRNA and protein expressions of retinal AREG were decreased after treatment with JKSQP (all P<0.05). CONCLUSION JKSQP exhibited a significant inhibitory effect on axial length elongation with decreased expression of AREG in the retina, and normalized 4 HPAA-associated plasma hormones and the expression of cAMP and cGMP in GC-enhanced myopic guinea pigs.
Guinea Pigs ; Male ; Animals ; Glucocorticoids ; Hypothalamo-Hypophyseal System ; Pituitary-Adrenal System ; Myopia/metabolism* ; Body Weight ; RNA, Messenger ; Disease Models, Animal

OBJECTIVE: To investigate the dynamic expression and significance of vasoactive intestinal peptide receptor 2 (VIPR2) on retina-choroid-clera in high myopia. METHODS: Twenty-one yellow chicks of 1 day old were used in the research. The right eyes were the experimental group, covered continuously for 1 week, 2 weeks and 4 weeks respectively. The left eyes were not covered as the normal control group. Both groups were detected diopter degrees using retinoscopic refraction, determinated eyeball axis using ophthalmology ultra-A, and investigated VIPR2 expression on retina-choroid-sclera in both groups at three stages by SP immunohistochemical staining. RESULTS: The experimental eyes changed from hypermetropia at pre-experiment to high myopia during the experiment stages, and the diopter degrees were deeper and eyeball axis was longer along with the period of being covered. Both groups had strong expression of VIPR2 on photoreceptor-outer segment of the retina and choroids. The expression was down-regulated with the time in both groups. Compared with the control group, VIPR2 expression of the experimental group was significantly up-regulated (P < 0.05). CONCLUSION Form deprivation could induce high myopia. The expression of VIPR2 existed on photoreceptor-outer segment of the retina and choroids. VIPR2 may play an important role on the formation and development of myopia.
Animals ; Animals, Newborn ; Chickens ; Choroid ; metabolism ; Female ; Male ; Myopia ; etiology ; metabolism ; Receptors, Vasoactive Intestinal Peptide, Type II ; biosynthesis ; genetics ; Retina ; metabolism

OBJECTIVE: To explore the expression of cyclic guanine monophosphate (cGMP) and the ultrastructure change in retina of guinea pig with form-deprivation myopia and the underlying mechanisms. METHODS: Three-weeks-old guinea pigs were distributed in 3 groups: an untreated group (Group I), a myopia 2-weeks group (Group II) and a myopia 3-weeks group (Group III), animals underwent monocular form-deprivation by facemask for 2 and 3 weeks. The right eyes were deprived and the left eyes were self-controlled. The refraction and axial length of the eyes was measured. Retina was observed by electron microscope. The expression of cGMP was detected by radioimmunochemistry. RESULTS: Deprived eyes in guinea pig showed significant development of myopia, the refraction and axial length was increased. The pathological changes in ultrastructure of retina were aggravated with the development of myopia. The expression of cGMP was significantly up-regulated in the deprived eyes compared with self-control eyes(P<0.05). CONCLUSION Form-deprivation can up-regulate the expression of cyclic GMP, which might play an important role in the development of myopia.
Animals ; Cyclic GMP ; metabolism ; Disease Models, Animal ; Female ; Guinea Pigs ; Male ; Myopia ; etiology ; metabolism ; pathology ; Random Allocation ; Retina ; metabolism ; ultrastructure ; Sensory Deprivation ; Vision, Monocular ; physiology

OBJECTIVE: To study the apoptosis of retina and the expression of c-myc protein in form-deprivation myopia. METHODS: Two-day-old chickens were sutured with right eyelid for 4, 8 and 12 weeks. After measurement of refracation, the eyeballs were observed by light microscope and taken photos. Retinal apoptotic cells were measured by TUNEL staining and flow cytometry. C-myc protein were examined by immunohistochemistry and flow cytometry. RESULTS: Lacquer crack lesions were found in sutured eyes at 12 weeks. Apoptotic cells were observed in retinal outer and inner nuclear layer of the sutured eyes at 12 weeks and obvious peak of apoptosis was observed in sutured eyes at 12 weeks. The expression of c-myc protein was significantly more than control eyes at 8 and 12 weeks. CONCLUSION The apoptosis of retinal was present in form-deprivation myopia with the degeneration of retina. C-myc protein plays an important role in retinal apoptosis of myopia.
Animals ; Animals, Newborn ; Apoptosis ; physiology ; Chickens ; Flow Cytometry ; Myopia ; metabolism ; pathology ; Proto-Oncogene Proteins c-myc ; biosynthesis ; genetics ; Random Allocation ; Retina ; metabolism ; pathology

OBJECTIVE: To explore the relationship between melanin synthesis and the congenital high myopia of albino guinea-pigs. METHODS: Twelve albino guinea-pigs and 12 pigmented guinea-pigs of 220~250 grams (aged 5~6 weeks) were chosen at random. The eyes were examined with retinoscopy, A-scan ultrasonography and vernier caliper. The retinal structures were examined with light and electronic microscope. RESULTS: The diopter was -19.17 D in albino guinea-pigs and +0.63 D in pigmented guinea-pigs on average. Compared with the pigmented guinea-pigs, the axial dimensions of the albino guinea-pigs were elongated. There was significant difference between the albino guinea-pigs and the pigmented guinea-pigs. The retinal thickness, pigment granules and membrane disc of the outer segment of the visual cells decreased in the albino guinea-pigs, and the membrane disc space became narrow. The normal retinal thickness, plenty of pigment granules , membrane disc and wide membrane disc space could be observed in the pigmented guinea-pigs. CONCLUSION Albino guinea-pigs have high myopia, and pigmented guinea pigs have light hyperopia. There are structural differences in the retina between albino guinea-pigs and pigmented guinea-pigs. The abnormity of albino guinea-pigs provides optical foundation for its high myopia.
Albinism ; complications ; Animals ; Guinea Pigs ; Melanins ; biosynthesis ; Microscopy, Electron, Scanning ; Myopia ; congenital ; etiology ; metabolism ; Random Allocation ; Retina ; metabolism ; pathology ; ultrastructure ; Skin Pigmentation