Dynamic changes of activator protein 1 and collagen I expression in the sclera of myopia guinea pigs.

AIM: To investigate the dynamic changes of activator protein 1 (AP1) and collagen I expression in the sclera of form-deprivation myopic model in guinea pigs. METHODS: A form-deprivation myopic model in guinea pigs were established with the left eye covered for 2 to 6wk (FDM group). Normal control group (n=25) were untreated. Changes in refractive power and axial length (AL) were measured and recorded at different time points. Expressions of AP1 and collagen 1 of the sclera were measured with Western blotting and reverse transcription-polymerase chain reaction (RT-PCR). The relationship between AP1 and collagen I levels was analyzed. RESULTS: After 0, 2, 4, 6wk, and 4/-1wk of form-deprivation, the diopter in the FDM group was gradually changed (2.08±0.31, -1.23±0.68, -4.17±0.58, -7.07±0.55, and -2.67±0.59 D, respectively, P<0.05), and the AL was gradually increased (5.90±0.38, 6.62±0.37, 7.30±0.35, 7.99±0.31, and 6.97±0.32 mm, respectively, P<0.05). With the prolongation of covered time, the protein expressions of AP1 and collagen I in the FDM group were gradually down-regulated (all P<0.05); the mRNA expressions of them were also gradually down-regulated (all P<0.05); and there was positive correlation between them. The control group had no obvious change in each index (all P>0.05). CONCLUSION: AP1 may be an important transcription factor involved in the regulation of collagen I synthesis and degradation during myopic scleral remodeling.

TRPV4 regulates migration and tube formation of human retinal capillary endothelial cells.

BACKGROUND: Ca2+ entry plays an important role in modulating endothelial cell migration and tube formation. Transient receptor potential cation channel subfamily V member 4 (TRPV4) is a Ca2+-permeable channel that is widely expressed in endothelial cells. It has been reported that TRPV4 is expressed in HRCECs and regulates Ca2+ entry. However, the function of TRPV4 in human retinal capillary endothelial cells (HRCECs) remains unknown. METHODS: In this study we used western blot and immunostaining assay to verify TRPV4 expression in HRCECs. And then we pretreated HRCECs with HC067047 and transfected with specific shRNA of TRPV4. The functional presence of TrpV4 was determined by using fluorescence, migration and tube formation assay in TrpV4 knockdown cells or control cells. RESULTS: Using western blot and immunostaining, we confirmed TRPV4 expression in HRCECs. Moreover, inhibition of TRPV4 using the specific inhibitor HC067047 and the knockdown of TRPV4 with shRNA significantly suppressed tube formation and migration by HRCECs. CONCLUSIONS: TRPV4 is essential for HRCEC migration and tube formation, and maybe a potential therapeutic target for retinal vascular diseases.

Expression and role of specificity protein 1 in the sclera remodeling of experimental myopia in guinea pigs.

AIM: To study the expression of collagen I and transcription factor specificity protein 1 (Sp1), a transforming growth factor-ß1 (TGF-ß1) downstream target, and reveal the impact of the TGF-ß1-Sp1 signaling pathway on collagen remodeling in myopic sclera. METHODS: Seventy-five 1-week-old guinea pigs were randomly divided into normal control, form deprivation myopia (FDM), and self-control groups. FDM was induced for different times using coverage with translucent latex balloons and FDM recovery was performed for 1wk after 4wk treatment; then, changes in refractive power and axial length were measured. Immunohistochemistry and reverse transcription-polymerase chain reaction were used to evaluate dynamic changes in collagen I and Sp1 expression in the sclera of guinea pigs with emmetropia and experimental myopia, and the relationship between collagen I and Sp1 levels was analyzed. RESULTS: In the FDM group, the refractive power was gradually changed (from 2.09±0.30 D at week 0 to -1.23±0.69 D, -4.17±0.59 D, -7.07±0.56 D, and -4.30±0.58 D at weeks 2, 4, 6, and 1wk after 4wk, respectively; P<0.05), indicating deepening of myopia. The axial length was increased (from 5.92±0.39 mm at week 0 to 6.62±0.36 mm, 7.30±0.34 mm, 7.99±0.32 mm, and 7.41±0.36 mm at weeks 2, 4, 6, and 1wk after 4wk; P<0.05). The mRNA and protein expression of Sp1 and collagen I in the sclera of the FDM group was lower than that of the control groups (P<0.05), and the reduction was eye-coverage time-dependent. Furthermore, correlation between Sp1 and collagen I down-regulation in the myopic sclera was observed. CONCLUSION: Our data indicate that transcription factor Sp1 may be involved in the regulation of type I collagen synthesis/degradation during myopic sclera remodeling, suggesting that TGF-ß1 signaling plays a role in the development and progression of myopia.

[Clinical research of intraoperative floppy iris syndrome during operation].

Intraoperative floppy iris syndrome (IFIS) has been recently identified as a new small pupil syndrome during phacoemulsification. This syndrome is characterized by three intraoperative features: a flaccid iris stroma that undulates and bellows in response to intraocular fluid currents; a propensity for the floppy iris stroma to prolapse toward the tip of phacoemulsification and side-port incisions despite proper wound construction; and progressive intraoperative pupil constriction despite standard preventive preoperative pharmacologic measures designed to prevent this. It is now mostly considered that IFIS is associated with the use of tamsolusin, a highly selective alpha-1A receptor antagonist for the treatment of benign prostatic hypertrophy. It is recommended that a careful history of the use of alpha-1 blocking agents be taken before cataract surgery to anticipate the occurrence of IFIS. A combination of strategies could decrease the complications of IFIS. These procedures include preoperative use of atropine, intracameral injection of dilute phenylephrine or epinephrine, the use of super-cohesive ophthalmic viscosurgical devices, lower phacoemulsification vacuum and aspiration settings and various iris hooks or pupil dilators.