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Purpose: To identify an effective method to prevent myopia progression by characterizing the regulation of matrix metalloproteinase- (MMP-) 2 expression and its secretion from scleral fibroblasts and retinal pigment epithelium (RPE) cells by miR-29a., Methods: The effects of miR-29a on the growth of scleral fibroblasts and RPE cells were assessed using the cell counting kit-8. The changes in MMP-2 mRNA levels in scleral fibroblasts and RPE cells after transfection with miR-29a mimics or inhibitor were measured by quantitative PCR. Enzyme-linked immunosorbent assays were used to determine the changes in MMP-2 secretion from scleral fibroblasts and RPE cells after transfection with miR-29a mimics or inhibitor., Results: The miR-29a mimics or inhibitor did not significantly alter the growth of scleral fibroblasts or RPE cells at 24, 48, or 72 hours after transfection. MMP-2 mRNA levels were significantly decreased in scleral fibroblasts and RPE cells transfected with the miR-29a mimics. The secretion of MMP-2 by scleral fibroblasts and RPE cells was significantly decreased in cells transfected with the miR-29a mimics., Conclusions: Suppression of scleral fibroblast and RPE cell expression and secretion of MMP-2 by miR-29a can be used as a therapeutic target for the prevention and treatment of myopia.

Purpose: Recently, we reported finding that circulating melatonin levels in age-related macular degeneration patients were significantly lower than those in age-matched controls. The purpose of this study was to investigate the hypothesis that melatonin deficiency may play a role in the oxidative damage of the retinal pigment epithelium (RPE) by testing the protective effect of melatonin and its receptor antagonist on RPE cells exposed to H(2)O(2) damage., Methods: Cultured human RPE cells were subjected to oxidative stress induced by 0.5 mM H(2)O(2). Cell viability was measured using the microculture tetrazoline test (MTT) assay. Cells were pretreated with or without melatonin for 24 h. Luzindole (50 μM), a melatonin membrane-receptor antagonist, was added to the culture 1 h before melatonin to distinguish direct antioxidant effects from indirect receptor-dependent effects. All tests were performed in triplicate., Results: H(2)O(2) at 0.5 mM decreased cell viability to 20% of control levels. Melatonin showed dose-dependent protective effects on RPE cells against H(2)O(2). Cell viability of RPE cells pretreated with 10(-10), 10(-8), 10(-6), and 10(-4) M melatonin for 24 h was 130%, 160%, 187%, and 230% of cells treated with H(2)O(2) alone (all p<0.05). Using cells cultured without H(2)O(2) as the control, cell viability of cells treated with H(2)O(2) after pretreatment with 10(-10)-10(-4) M melatonin was still significantly lower than that of the controls, suggesting that melatonin significantly decreased but did not completely abolish the in vitro cytotoxic effects of H(2)O(2). Luzindole completely blocked melatonin's protective effects at low concentrations of melatonin (10(-10)-10(-8) M) but not at high concentrations (10(-6)-10(-4) M)., Conclusions: Melatonin has a partial protective effect on RPE cells against H(2)O(2) damage across a wide range of concentrations (10(-10)-10(-4) M). This protective effect occurs through the activation of melatonin membrane receptors at low concentrations (10(-10)-10(-8) M) and through both the direct antioxidant and indirect receptor activation effects at high concentrations (10(-6)-10(-4) M).

Fullerol is a fullerene derivative that is extensively hydroxylated [nano-C(60)(OH)(24)] and this makes it water-soluble. These fullerene derivatives have shown promise as drug carriers that bypass ocular barriers but fullerols are also potentially phototoxic to human lens and retinal tissues. Fluorescence imaging is a powerful and non-invasive means of probing nanoparticles in biological systems. However, fullerol nanoparticles have a very low level of fluorescence and have not as yet been imaged in vitro and in vivo. Using specialized measurements including time-correlated single photon counting (TCSPC), fullerol fluorescence was determined in aqueous solutions and detected in both human lens and retinal pigment epithelial cells. Time-resolved fluorescence of fullerol (5-200 μM) was characterized in aqueous environment, where the fluorescence decay is best fitted with three lifetimes (3 ns, 0.7-0.9 ns and 0.2 ns). Time-resolved microspectrofluorimetry and time-gated fluorescence imaging were performed on both human lens and retinal pigment epithelial cells incubated with increasing fullerol doses (5-500 μM and 5-50 μM, respectively). Upon increasing concentration, we observe some shortening of the lifetimes, a reduction in the relative amplitude of the shortest-living component and a corresponding increase in the weight of the intermediate-living species. Time-gated imaging of fullerol fluorescence provided information on its intracellular distribution that correlates with progressive cell damage. Therefore time-gated imaging may potentially be used as a means to investigate fullerol distribution and toxicity in the human lens and retina in vivo.

Purpose: To study the effect of subtoxic levels of hydrogen peroxide (H(2)O(2)) on the expression and release of interleukin-6 (IL-6) by cultured retinal pigment epithelial (RPE) cells and to explore the relevant signal pathways., Methods: Cultured human RPE cells were stimulated with various subtoxic concentrations of H(2)O(2) for different periods. Conditioned medium and cells were collected. IL-6 in the medium and IL-6 mRNA in the collected cells were measured using an IL-6 enzyme-linked immunosorbent assay kit and reverse transcriptase polymerase chain reaction, respectively. Nuclear factor-kappaB (NF-κB) in nuclear extracts and phosphorylated p38 mitogen-activated protein kinase (MAPK), extracellular signal-regulated kinase (ERK), and c-Jun N-terminal kinases (JNK) in cells cultured with and without H(2)O(2) were measured by NF-κB and MAPK enzyme-linked immunosorbent assay kits. Inhibitors of p38 (SB203580), ERK (UO1026), JNK (SP600125), and NF-κB (BAY11-7082) were added to the cultures before the addition of H(2)O(2) to test their effects(.), Results: Subtoxic levels of H(2)O(2) (100 µM and less) increased the IL-6 mRNA level and the release of IL-6 protein by the cultured human RPE cells in a dose- and time-dependent manner. This was accompanied by an increase of NF-κB in nuclear extracts and phosphorylated p38 MAPK, ERK, and JNK in cell lysates, particularly in the p38 and NF-κB. The NF-κB inhibitor decreased the H(2)O(2)-induced expression of IL-6. The p38 inhibitor, but not the ERK or JNK inhibitor, completely abolished H(2)O(2)-induced expression of IL-6 by RPE cells. The p38 inhibitor also abolished the increase of NF-κB in nuclear extracts in cells treated with H(2)O(2)., Conclusions: H(2)O(2) stimulated the production of IL-6, a key factor in the modulation of immune responses, inflammatory processes, and the occurrence of autoimmune diseases, which recently has been documented to be increased in age-related macular degeneration (AMD). This may be a molecular linkage for the oxidative stress and inflammatory/autoimmune reactions in AMD and may provide a novel target for the treatment of AMD.

The water-soluble nanoparticle hydroxylated fullerene [fullerol, nano-C60(OH)(22-26)] has several clinical applications including use as a drug carrier to bypass the blood ocular barriers. We have previously found that fullerol is both cytotoxic and phototoxic to human lens epithelial cells (HLE B-3) and that the endogenous antioxidant lutein blocked some of this phototoxicity. In the present study we have found that fullerol induces cytotoxic and phototoxic damage to human retinal pigment epithelial cells. Accumulation of nano-C60(OH)(22-26) in the cells was confirmed spectrophotometrically at 405 nm, and cell viability, cell metabolism and membrane permeability were estimated using trypan blue, MTS and LDH assays, respectively. Fullerol was cytotoxic toward hRPE cells maintained in the dark at concentrations higher than 10 microM. Exposure to an 8.5 J x cm(-2) dose of visible light in the presence of >5 microM fullerol induced TBARS formation and early apoptosis, indicating phototoxic damage in the form of lipid peroxidation. Pretreatment with 10 and 20 microM lutein offered some protection against fullerol photodamage. Using time resolved photophysical techniques, we have now confirmed that fullerol produces singlet oxygen with a quantum yield of Phi=0.05 in D2O and with a range of 0.002-0.139 in various solvents. As our previous studies have shown that fullerol also produces superoxide in the presence of light, retinal phototoxic damage may occur through both type I (free radical) and type II (singlet oxygen) mechanisms. In conclusion, ocular exposure to fullerol, particularly in the presence of sunlight, may lead to retinal damage.

Aims: Cyclin-dependent kinases (CDKs) play essential roles in the intracellular control of the cell cycle. It has been postulated that roscovitine, a potent CDK2, CDK5, and CDC2 inhibitor, might inhibit cellular proliferation by arresting the cell cycle. This in vitro study investigated the antiproliferative and apoptotic effects of roscovitine in cultured rabbit retinal pigment epithelial (RPE) cells., Methods: Experiments using rabbit RPE from young pigmented rabbits were carried out using roscovitine dissolved in dimethylsulfoxide at concentrations ranging from 1 to 100 micromol. Cell proliferation was measured by an MTT assay. The cell cycle response of RPE cells to roscovitine was analyzed by flow cytometry of propidium iodide-stained nuclei. Proteins related to DNA damage in the RPE cells were then assayed by Western blot., Results: Roscovitine inhibited proliferation of RPE cells in a dose-dependent manner. Cell cycle analysis after treatment demonstrated an accumulation of cells arrested in the S- and G2/M phases. Flow cytometry showed that 40 microM of roscovitine increased the cell population in the sub-G1 peak, which is considered a marker of cell death by apoptosis. Western blot analysis revealed Bcl-2 decreased and Bax increased after treatment of RPE cells with roscovitine., Conclusions: This study of the response of RPE cells to roscovitine demonstrated a bidirectional relationship between cell cycle control and apoptosis.

Aim: The aim of this study was to investigate the effect of membrane stretch on the activity of BK(Ca) channels and determine whether change in BK(Ca)-channel activity induced by membrane stretch can be altered in the presence of riluzole., Methods: The effect and mechanisms of membrane stretch on the activity of large-conductance Ca(2+)-activated K(+) (BK(Ca)) channels in human retinal pigment epithelial (RPE) cells were investigated using the patch-clamp technique., Results: In cell-attached patches, an increase in BK(Ca)-channel activity was induced by membrane stretch, which is mainly mediated by the increase in the number of long-lived openings. With inside-out patches, application of pipette suction did not modify single-channel conductance of BK(Ca) channels; however, it did enhance the channel activity. Membrane stretch-induced channel activity was found to be independent of the level of intracellular Ca(2+). Membrane stretch also potentiated riluzole-stimulated BK(Ca)-channel activity., Conclusions: BK(Ca) channel can be stimulated by membrane stretch in human RPE cells. During an increase in tensile strength of RPE, the BK(Ca) channel might exert a protective action against deleterious tension by promoting a hyperpolarizing outflow that forces the cell to rest.

Hypericin is the active ingredient of the off-the-shelf antidepressant St. John's Wort. It is an effective phototoxic agent and its systemic administration at therapeutic doses could induce particular damage in the eye due to continuous light exposure. Hypercin is strongly fluorescent and its fluorescence properties can be monitored to investigate noninvasively its localization and interactions. To this aim, time-resolved microspectrofluorimetry and fluorescence lifetime imaging were used to assess the spectral and temporal properties as well as the spatial distribution of the fluorescence emitted by retinal pigment epithelium (RPE) cells treated with Hyp at concentrations in the micromolar range (0.5-10 microM). In the presence of hypericin, the emission peaks at 600-605 nm and the fluorescence decay is best fitted with three lifetimes (5.5-7 ns, 1.9-2.5 ns and <0.8 ns). Spectral and temporal differences were observed between high (> or =5 microM) and low hypericin concentrations. In particular, upon increasing concentration, the emission spectrum of the slow component broadens and its lifetime shortens. The latter change is observed also when high concentrations are reached locally, due to more efficient localization within the cell.

Background Hypoxia is the most important stimulus leading to up-regulation of vascular endothelial growth factor (VEGF) in the retina via elevation of hypoxia-inducible factors-1α (HIF-1α) protein. The purpose of this study was to test the effects of melatonin on the expression of VEGF and HIF-1α in the cultured human retinal pigment epithelial (RPE) cells under normoxia and hypoxia. Method An in vitro RPE cell hypoxia model was established by placing cells under 1% oxygen pressure or by adding cobalt chloride (CoCl2) to the culture medium. RPE cells and conditioned media were collected from cultures treated with and without melatonin under normoxia and hypoxia. The protein and RNA levels of VEGF and HIF-1α were measured by ELISA kits and RT-PCR, respectively. Result Hypoxia induced a significant increase of expression and secretion of VEGF and accumulation of HIF-1α protein in RPE cells ( P < 0.05). Melatonin at 10−5 to 10−8 M significantly inhibited hypoxia-induced expression, the secretion of VEGF and the accumulation of HIF-1α protein ( P < 0.05), but not affected expression of VEGF and HIF-1α under normoxia ( P > 0.05). Conclusion This study suggests that melatonin may have potential value in the prevention and treatment of various retinal diseases associated with increase of VEGF, vascular leakage and angiogenesis. [ABSTRACT FROM AUTHOR]

As increases in hepatocyte growth factor/scatter factor (HGF/SF) induce retinal pigment epithelial (RPE) migration and proliferation into the vitreous cavity and contribute to proliferative vitreoretinopathy (PVR) development, we determined if changes in miR-182 expression affect such behavioral changes. We found that miR-182 expression was less in PVR clinical samples than in primary RPE cells whereas c-Met was upregulated. Ectopic miR-182 inhibited RPE cell proliferation, cell cycle, and migration. Bioinformatic analysis identified c-Met as a miR-182 target, which was confirmed with the luciferase reporter assay. Transfection of miR-182 into RPE cells induced c-Met downregulation, which led to reduced cell proliferation and migration through declines in p-Akt formation. MiR-182 downregulation along with c-Met upregulation in PVR tissues suggest that these two opposing effects play important roles in PVR development. As ectopic miR-182 expression suppressed RPE cell proliferation and migration, strategies to selectively upregulate miR-182 expression in a clinical setting may provide a novel option to treat this disease. [ABSTRACT FROM AUTHOR]

Dry eye is a common disorder characterized by deficiency of tear. Hyperosmoticity of tear stimulates inflammation and damage of ocular surface tissues and plays an essential role in the pathogenesis of dry eye. Cultured human corneal epithelial (CE) cells were used for the study of effects of lutein and hyperosmoticity on the secretion of IL-6 by CE cells. Cell viability of CE cells was not affected by lutein at 1–10 μM as determined by MTT assay. Hyperosmoticity significantly elevated the secretion of IL-6 by CE cells as measured by ELISA analysis. The constitutive secretion of IL-6 was not affected by lutein. Lutein significantly and dose-dependently inhibited hyperosmoticity-induced secretion of IL-6. Phosphorylated- (p)- p38 MAPK, p-JNK levels in cell lysates and NF-κB levels in cell nuclear extracts were increased by being exposed to hyperosmotic medium. JNK, p38, and NF-κB inhibitors decreased hyperosmoticity-induced secretion of IL-6. Lutein significantly inhibited hyperosmoticity-induced elevation of NF-κB, p38, and p-JNK levels. We demonstrated that lutein inhibited hyperosmoticity-induced secretion of IL-6 in CE cells through the deactivation of p38, JNK, and NF-κB pathways. Lutein may be a promising agent to be explored for the treatment of dry eye. [ABSTRACT FROM AUTHOR]

Purpose: To study the cytotoxic effects and related signaling pathways of butein on human uveal melanoma cells in vitro. Materials and Methods: Three human uveal melanoma cell lines (M17, SP6.5, and C918), retinal pigment epithelial (RPE) cells and scleral fibroblasts were treated with butein at different dosages. The effects of butein on cell viability were assessed by using the MTT assay. Cell apoptosis was determined using annexin V-FITC/ethidium homodimer III flow cytometry. Mitochondrial transmembrane potential changes were assessed by using the JC-1 fluorescent reader, cytosol cytochrome c levels, and the activities of caspase-3, -8, and -9 were measured by using an enzyme-linked immunosorbent assay or colorimetric assay. Results: Butein reduced the cell viability of cultured human uveal melanoma cells in a dose-dependent manner (10, 30, and 100 μM), with IC50 at 13.3 μM and 15.8 μM in SP6.5 and M17 cell lines, respectively. Similar effects were also found in a highly aggressive and metastatic C918 cell line (IC50 16.7 μM). Butein at lower concentrations (10-30 μM) selectively reduced the cell viability of uveal melanoma cells, without affecting cell viability of RPE cells and fibroblasts. Butein-induced apoptosis of melanoma cells, increased mitochondrial permeability and the level of cytosol cytochrome c, caspase-9 and -3 activities (but not caspase-8) in a dose-dependent manner. Conclusions: Butein has selectively potent pro-apoptotic effects on cultured human uveal melanoma cells via the intrinsic mitochondrial pathway. [ABSTRACT FROM AUTHOR]

Purpose: To study the cytotoxic effects and related signaling pathways of curcumin on human uveal melanoma cells in vitro. Materials and Methods: Two human uveal melanoma cell lines (M21 and SP6.5), scleral fibroblasts, and choroidal melanocytes were treated with curcumin. The effects of curcumin on cell viability were assessed by using the MTT (3-[4,5-dimethylthiazol-2-yl]2,5-diphenyltetrazolium bromide) assay. Cytosol cytochrome c levels and the activities of caspase-9 and caspase-3 were measured by using an enzyme-linked immunosorbent assay. Results: Curcumin induced cell death of cultured human uveal melanoma cells in a dose-dependent manner (10, 30, and 100 μM) and time-dependent manner (3–48 hr), with IC50 at 19.05 μM and 22.39 μM in M21 and SP6.5 cell lines, respectively. Curcumin at lower concentrations (10–30 μM) selectively reduced the cell viability of uveal melanoma cells, without affecting cell viability of fibroblasts and choroidal melanocytes. Curcumin significantly increased the level of cytosol cytochrome c (2-fold greater than the controls after 2 hr treatment), caspase-9 and caspase-3 activities (approximately 4.5- and 6-fold greater than the controls after 2–6 hr treatment, respectively) in a dose-dependent manner. Conclusions: Curcumin has selectively potent cytotoxic effects on cultured human uveal melanoma cells. This effect is associated with the release of cytochrome c from the mitochondria and the activation of caspase-9 and caspase-3 in uveal melanoma cells after treatment with curcumin. [ABSTRACT FROM AUTHOR]

Abstract: Increased tear osmolarity is an essential feature of dry eye disease. Curcumin, a natural polyphenol extracted from herb turmeric, has recently been reported to have anti-inflammatory effects. However, its anti-inflammatory effects have not been investigated in dry eye disease. It has been reported that elevated osmolarity achieved by adding sodium chloride to the culture medium of corneal epithelial cells increased the production of IL-1β, a proinflammation cytokine. This in vitro dry eye model was used to test the anti-inflammatory effects of curcumin. In the present study, a 450 mOsM hyperosmotic medium was produced by adding sodium chloride to the culture medium to reach a final concentration of 90mM. Human corneal epithelial cells cultured in this hyperosmotic medium for 24h showed an increase of IL-1β, IL-6 and TNF-α levels in the conditioned medium. IL-1β was also upregulated at mRNA levels. Activation of p38 MAP kinase (p38), JNK MAP kinase (JNK) and NF-κB in cultured corneal epithelial cells were also induced by hyperosmotic conditions. Curcumin at concentrations of 1–30μM did not affect the cell viability of cultured corneal epithelial cells. Pretreatment of curcumin (5μM) completely abolished the increased production of IL-1β induced by the hyperosmotic medium. Increased phosphorylation of p38 caused by high osmolarity was also completely abolished by curcumin, whereas the phosphorylation of JNK was only partially inhibited. SB 203580 (p38 inhibitor), but not SP 600125 (JNK inhibitor), completely suppressed hyperosmoticity-induced IL-1β production, indicating that the inhibition of production of IL-1β by curcumin may be achieved through the p38 signal pathway. Curcumin completely abolished a hyperosmoticity-induced increase of NF-κB p65. NF-κB inhibitor suppressed hyperosmoticity-induced IL-1β production. p38 inhibitor suppressed hyperosmoticity-induced NF-κB activation, indicating that NF-κB activation was dependent on p38 activation. The present study suggests that curcumin might have therapeutic potential for treating dry eye disease. [Copyright &y& Elsevier]

Melanin has a photo-screening, a biophysical/biochemical and a cosmetic effect. Melanin content of cultured pigmented cells can be measured by spectrophotometry and expressed either as melanin content per cell or melanin content per culture (area). Melanin production can be calculated from melanin content and cell number at the beginning and at the end of a culture using various formulas and expressed as melanin production per cell per day or melanin production per culture per day. Melanin content or production per cell have been used widely to compare melanin content in various cell lines or to compare the melanin content during different stages in the culture ( e.g. growing stage and senescent stage). For the evaluation of changes in melanin content and production in a given pigment cell line after treatment with a special chemical, physical or biological stimulator or inhibitor, different parameters used for the evaluation of experimental data can lead to conflicting results. Melanin content per area is determined by melanin content per cell and the number of cells in this area. The biological and cosmetic effects of melanin in vivo are determined mainly by melanin content per area, not melanin content per cell. For example, if melanin content per cell is the same, but the number of cells in a given area is increased after the treatment, then the melanin content per area is also increased. Under this circumstance, the color of skin turns darker and the total antioxidant activity provided by melanin in this area is increased even though the melanin content per cell measured remains the same; therefore, melanin content or production per culture is more important than melanin content or production per cell under this circumstance. [ABSTRACT FROM AUTHOR]

St. John’s wort (SJW), an over-the-counter antidepressant, contains hypericin, which absorbs light in the UV and visible ranges. In vivo studies have determined that hypericin is phototoxic to skin and our previous in vitro studies with lens tissues have determined that it is potentially phototoxic to the human lens. To determine if hypericin might also be phototoxic to the human retina, we exposed human retinal pigment epithelial (hRPE) cells to 10−7 to 10−5 M hypericin. Fluorescence emission detected from the cells ( λex = 488 nm; λem = 505 nm) confirmed hypericin uptake by human RPE. Neither hypericin exposure alone nor visible light exposure alone reduced cell viability. However when irradiated with 0.7 J cm−2 of visible light (λ > 400 nm) there was loss of cell viability as measured by MTS and lactate dehydrogenase assays. The presence of hypericin in irradiated hRPE cells significantly changed the redox equilibrium of glutathione and a decrease in the activity of glutathione reductase. Increased lipid peroxidation as measured by the thiobarbituric acid reactive substances assay correlated to hypericin concentration in hRPE cells and visible light radiation. Thus, ingested SJW is potentially phototoxic to the retina and could contribute to retinal or early macular degeneration. [ABSTRACT FROM AUTHOR]

Abstract: The purpose of the present study was to develop methods for isolation, purification and cultivation of human conjunctival melanocytes. Conjunctiva excised from donor eyes or corneal rims was subjected with various enzyme digestion methods or by the enzyme-microdissection method. Cells were cultured with F12 medium supplemented by fetal bovine serum, basic fibroblast growth factor, isobutylmethylxanthine and cholera toxin. Contaminant cells were eliminated by a selective cytotoxic agent, geneticin. Both trypsin digestion and dispase-microdissection methods provided pure conjunctival melanocyte cultures with high cell yields, good viability and rapid growth rate. Melanocytes isolated with dispase-microdissection method showed better viability and growth capacity. Cells grew well, could be passaged for 5–10 generations and divided 20 times in vitro. They maintained a constant melanin content per cell and produced measurable amounts of melanin in vitro. Melanogenesis correlated with the degree of pigmentation of the eyes (iris color). This method provides a valuable source of large numbers of human conjunctival melanocytes, which can be used to study their biological behavior, to compare with the epidermal and uveal melanocytes; and to compare them to their malignant counterparts in the exploration of the pathogenesis of conjunctival melanoma. [Copyright &y& Elsevier]

The article describes the case of a 22-year-old woman with progressive white spots on her face. She was diagnosed to have vitiligo with repigmentation of leukotrichia. It also discusses the transplantation of autologous cultured melanocytes in liquid media, retrograde migration with the use of a fibrin matrix, and the effectiveness of hair follicle grafting.

Abstract: All-trans retinoic acid (atRA) has been reported to inhibit the proliferation of retinal pigment epithelial (RPE) cells and used in treatment of proliferative vitreoretinopathy (PVR) in animal model. This study aimed at examining the effectiveness of atRA in inhibiting the extracellular matrix (ECM) biosynthesis by RPE cells and the RPE cell-mediated collagen gel contraction. Cultured RPE cells were treated with atRA and the expression of four ECM proteins (collagen types I, III, IV and laminin β1) was profiled. The results indicated that atRA treatment up-regulated de novo synthesis of collagen type I, but decreased that of laminin β1 in a dose-dependent manner. Moreover, the effect of atRA on RPE cell contraction was evaluated by measuring the area of collagen gel where RPE cells populated. Treatment with atRA significantly inhibited RPE cell-mediated collagen gel contraction. Addition of exogenous laminin nonapeptide into gels promoted RPE cell contraction, while atRA reversed the laminin-enhanced contractility. atRA treatment significantly suppressed the gene expression of integrin β3 but not αV subunit, and effectively inhibited the tyrosine phosphorylation of integrin β3 at residue 747 in RPE cells grown on laminin-coated dish, suggesting that atRA may suppress the RPE contractility through either inhibiting integrin β3 expression or abrogating the integrin β3-mediated signaling. In conclusion, atRA pharmacologically possesses a tissue-remodeling capacity and inhibits contractility of RPE cells. Therefore, atRA might be potentially a therapeutic agent for certain ocular disorders such as PVR. [Copyright &y& Elsevier]