Retinal Pigment Epithelial Sheets Research Articles

Validation of iPS Cell-Derived RPE Tissue in Animal Models.

Previous work suggests that replacing diseased Retinal Pigment Epithelium (RPE) with a healthy autologous RPE sheet can provide vision rescue for AMD patients. We differentiated iPSCs into RPE using a directed differentiation protocol. RPE cells at the immature RPE stage were purified and seeded onto either electrospun poly(lactic-co-glycolic acid) (PLGA) scaffolds or non-biodegradable polyester cell culture inserts and compared the two tissues. In vitro, PLGA and polyester substrates produced functionally similar results. Following in vitro evaluation, we tested RPE tissue in animal models for safety and function. Safety studies were conducted in RNU rats using an injection composed of intact cells and homogenized scaffolds. To assess function and develop surgical procedures, the tissues were implanted into an acute RPE injury model pig eye and evaluated using optical coherence tomography (OCT), multifocal ERG (mfERG), and histology. Subretinal injection studies in rats demonstrated safety of the implant. Biodegradability and biocompatibility data from a pig model demonstrated that PLGA scaffold is safe, with the added benefit of being resorbed by the body over time, leaving no foreign material in the eye. We confirmed that biodegradable substrates provide suitable support for RPE maturation and transplantation.

Isolation and Culture of Primary Mouse Retinal Pigment Epithelial (RPE) Cells with Rho-Kinase and TGFβR-1/ALK5 Inhibitor.

BackgroundPrimary RPE cells could be a reliable model for representing in vivo status of RPE compared with cell lines. We present a protocol for in vitro isolation and culture of primary RPE cells from C57BL mice.Material/MethodsWe used C57BL mice ages 7 days to 4 months. The RPE layer was separated from the neural retina layer by digestion with 2% Dispase for 45 min and scraped off from the choroid after 25-min incubation in 37°C. Collected RPE sheets were gently pipetted up into smaller sheets. RPE sheets were transferred into well plates and cultured in vitro for 2 weeks. To inhibit epithelial-mesenchymal transition (EMT) of RPE cells, we used Y27632 and Repsox to treat cultured primary RPE cells.ResultsRPE cells isolated from C57BL mice maintained pigmented and hexagonal morphology in culture. However, long-term in vitro culture lead to the periphery cells of a RPE sheet becoming mesenchymal-like cells. In contrast to the control group, Y27632 and Repsox, which are inhibitors of Rho-kinase or TGFβR-1/ALK5, promoted primary RPE cells to maintain epithelial-like morphology and eventually become confluent.ConclusionsRPE cells isolated from C57BL mice could be a powerful cell model to study the biological function of RPE. Especially, C57BL mice with different defective genetic background resulting in ocular diseases, would expand the genome type of RPE cells. The method presented here could be an efficient and applicable technique to obtain large numbers of primary RPE cells that maintain some characteristics of in vivo RPE.

Fibrin hydrogels as a xenofree and rapidly degradable support for transplantation of retinal pigment epithelium monolayers

Stem cell-derived retinal pigment epithelial (RPE) cell transplantation is currently in phase 1 clinical trials for macular degeneration (MD). A major obstacle in these studies is delivering the RPE as a living, flat sheets without leaving behind foreign materials in the retina. Here we investigate the suitability of using hydrogels made from human blood-derived proteins for RPE transplant. Our data shows that these fibrin hydrogels are rigid enough for use in surgery, support growth of stem cell-derived RPE, and are easily degraded within hours without damage to the RPE sheet. These fibrin hydrogels offer a promising solution to transplant RPE for patients with MD.

Induced Retro‐Differentiation of Human Retinal Pigment Epithelial Cells on PolyHEMA

Retinal pigment epithelium (RPE) cells represent a great potential to rescue degenerated cells of the damaged retina. Activation of the virtually plastic properties of RPE cells may aid in recovery of retinal degenerative disorders without the need for entire RPE sheet transplantation. Poly (2-hydroxyethyl methacrylate)(PolyHEMA) is one of the most important hydrogels in the biomaterials world. This hydrophobic polymer does not normally support attachment of mammalian cells. In the current study we investigated the effect of PolyHEMA as a cell culture substrate on the growth, differentiation, and plasticity of hRPE cells. hRPE cells were isolated from neonatal human globes and cultured on PolyHEMA and polystyrene substrates (as controls) in 24-well culture plates. DMEM/F12 was supplemented with 10% fetal bovine serum (FBS) and/or 30% human amniotic fluid (HAF) for cultured cells on polystyrene and PolyHEMA coated vessels. Morphology, rate of cell proliferation and cell death, MTT assay, immunocytochemistry and Real-Time RT-PCR were performed to investigate the effects of PolyHEMA on the growth and differentiation of cultured hRPE cells. Proliferation rate of the cells that had been cultured on PolyHEMA was reduced; PolyHEMA did not induce cell death in the hRPE cultures. hRPE cells cultured on PolyHEMA formed many giant spheroid colonies. The giant colonies were re-cultured and the presence of retinal progenitor markers and markers of hRPE cells were detected in cell cultures on PolyHEMA. PolyHEMA seems to be promising for both maintenance and de-differentiation of hRPE cells and expansion of the retinal progenitor cells from the cultures that are originated from hRPE cells. J. Cell. Biochem. 118: 3080-3089, 2017. © 2017 Wiley Periodicals, Inc.

Optimization of ultrastructure observation of human embryonic stem cell-derived retinal pigment epithelial cells

Background Normal ultrastructure is the anatomical basis of retinal pigment epithelial(RPE)cells to perform normal physiological function.At present the precipitation method is often used to detect the ultrastructure of RPE cells with transmission electron microscopy(TEM). Objective The aim of this study was to explore a simple and feasible approach to examine the ultrastructure of human embryonic stem cell-derived retinal pigment epithelial (hESC-RPE) cells. Methods hESCs were induced and differentiated into RPE cells by the spontaneous differentiation method, and the expressions of microphthalmia associated transcription factor MITF and paired-box gene 6 (PAX6), specific protein of RPE cells, in the cells were detected by immunofluorescence assay.hESC-RPE cells were inoculated into Transwell filter, and the ultrastructure of the cell sheet was examined under the TEM.Then the ultrastructure of the cell sheet specimens was compared with those of hESC-RPE cells from cell precipitation and RPE cell specimens of 90-day-old Long Evans rats. Results MITF and PAX6 were positively expressed in hESC-RPE cells.The normal ultrastructure were visible in the RPE cells of rats under the TEM, including apical microvilli, polarized melanin granules, cellular nucleus, basement membrane and intercellular junctions, and the ultrastructure of hESC-RPE cell sheet on Transwell was similar to the RPE cells in rats.However, only scatter melanin granules, nonpolar nucleus and scanty microvilli were observed under the TEM in the hESC-RPE cells by cell precipitation method. Conclusions Without digestion process, hESC-RPE cell sheet on Transwell can retain the normal ultrastructure of hESC-RPE cells under the TEM, with a more simple and reliable advantage. Key words: Retinal pigment epithelium/cytology; Embryonic stem cells; Microscopy, electron, transmission; Cell differentiation/physiology; Cells, cultured; Rats; Retinal pigment epithelial sheets, human

The progress of cell-replacement therapy for age-related macular degeneration

Based on the pathogenic mechanisms of age-related macular degeneration (AMD), tremendous preclinical and clinical trials have demonstrated that cell transplantation which aim to replace impaired retinal pigment epithelium (RPE) with healthy RPE cells is a promising approach to treat AMD. So far, choices of cell sources mainly are autologous RPE, iris pigment epithelium, fetal RPE, human embryonic stem cell-derived RPE and human induced pluripotent stem cell-derived RPE, and some of them are undergoing clinical researches. Grafting manners in cell-based therapies are various including RPE sheet or RPE-choroid complex transplantation, RPE cell suspension injection, and RPE sheet transplantation with scaffolds. This review is limited to cell-based therapies for RPE that damaged first in the progress of AMD and focus on recent advances in cell sources, transplantation methods, preclinical and clinical trials, and the obstacles that must be overcome. Key words: Macular degeneration/therapy; Retinal pigment epithelium; Cell transplantation; Review

RPE Cell and Sheet Properties in Normal and Diseased Eyes.

Previous studies of human retinal pigment epithelium (RPE) morphology found spatial differences in density: a high density of cells in the macula, decreasing peripherally. Because the RPE sheet is not perfectly regular, we anticipate that there will be differences between conditions and when and where damage is most likely to begin. The purpose of this study is to establish relationships among RPE morphometrics in age, cell location, and disease of normal human and AMD eyes that highlight irregularities reflecting damage. Cadaveric eyes from 11 normal and 3 age-related macular degeneration (AMD) human donors ranging from 29 to 82 years of age were used. Borders of RPE cells were identified with phalloidin. RPE segmentation and analysis were conducted with CellProfiler. Exploration of spatial point patterns was conducted using the "spatstat" package of R. In the normal human eye, with increasing age, cell size increased, and cells lost their regular hexagonal shape. Cell density was higher in the macula versus periphery. AMD resulted in greater variability in size and shape of the RPE cell. Spatial point analysis revealed an ordered distribution of cells in normal and high spatial disorder in AMD eyes. Morphometrics of the RPE cell readily discriminate among young vs. old and normal vs. diseased in the human eye. The normal RPE sheet is organized in a regular array of cells, but AMD exhibited strong spatial irregularity. These findings reflect on the robust recovery of the RPE sheet after wounding and the circumstances under which it cannot recover.

Role of Retinal Pigment Epithelial Cell β-Catenin Signaling in Experimental Proliferative Vitreoretinopathy

Proliferative vitreoretinopathy is caused by the contraction of fibrotic membranes on the epiretinal surface of the neurosensory retina, resulting in a traction retinal detachment and loss of visual acuity. Retinal pigment epithelial (RPE) cells play an important role in formation of such fibrotic, contractile membranes. We investigated the role of Wnt/β-catenin signaling, a pathway implicated in several fibrotic diseases, in RPE cells in proliferative vitreoretinopathy. In vitro culture of swine RPE sheets resulted in nuclear translocation of β-catenin in dedifferentiated RPE cells. FH535, a specific inhibitor of β-catenin signaling, reduced the outgrowth of cultured RPE sheets and prevented dedifferentiated RPE cell proliferation and migration. It also inhibited formation of contractile membranes by dedifferentiated RPE cells on collagen I matrices. Expression and function of the β-catenin signaling target connexin-43 were down-regulated by FH535, and functional blockade of connexins with carbenoxolone also prevented the in vitro formation of fibrotic, contractile membranes. Intravitreal injection of FH535 in swine also inhibited formation of dense, contractile membranes on the epiretinal surface and prevented development of traction retinal detachment. These findings demonstrate that β-catenin signaling is involved in formation of contractile membranes by dedifferentiated RPE cells and suggest that adjunctive treatment targeting this pathway could be useful in preventing proliferative vitreoretinopathy.

Tumorigenicity Studies of Induced Pluripotent Stem Cell (iPSC)-Derived Retinal Pigment Epithelium (RPE) for the Treatment of Age-Related Macular Degeneration

Basic studies of human pluripotential stem cells have advanced rapidly and stem cell products are now seeing therapeutic applications. However, questions remain regarding the tumorigenic potential of such cells. Here, we report the tumorigenic potential of induced pluripotent stem cell (iPSC)-derived retinal pigment epithelium (RPE) for the treatment of wet-type, age-related macular degeneration (AMD). First, immunodeficient mouse strains (nude, SCID, NOD-SCID and NOG) were tested for HeLa cells’ tumor-forming capacity by transplanting various cell doses subcutaneously with or without Matrigel. The 50% Tumor Producing Dose (TPD50 value) is the minimal dose of transplanted cells that generated tumors in 50% of animals. For HeLa cells, the TPD50 was the lowest when cells were embedded in Matrigel and transplanted into NOG mice (TPD50 = 101.1, n = 75). The TPD50 for undifferentiated iPSCs transplanted subcutaneously to NOG mice in Matrigel was 102.12; (n = 30). Based on these experiments, 1×106 iPSC-derived RPE were transplanted subcutaneously with Matrigel, and no tumor was found during 15 months of monitoring (n = 65). Next, to model clinical application, we assessed the tumor-forming potential of HeLa cells and iPSC 201B7 cells following subretinal transplantation of nude rats. The TPD50 for iPSCs was 104.73 (n = 20) and for HeLa cells 101.32 (n = 37) respectively. Next, the tumorigenicity of iPSC-derived RPE was tested in the subretinal space of nude rats by transplanting 0.8–1.5×104 iPSC-derived RPE in a collagen-lined (1 mm×1 mm) sheet. No tumor was found with iPSC-derived RPE sheets during 6–12 months of monitoring (n = 26). Considering the number of rodents used, the monitoring period, the sensitivity of detecting tumors via subcutaneous and subretinal administration routes and the incidence of tumor formation from the iPSC-derived RPE, we conclude that the tumorigenic potential of the iPSC-derived RPE was negligible.

Functional Principal Component Analysis Reveals Discriminating Categories of Retinal Pigment Epithelial Morphology in Mice

To determine whether multivariate, functional principal component analysis of the size and shape of retinal pigment epithelial (RPE) cell morphology allows discrimination of mouse RPE genotypes and age. Flatmounts of RPE sheets obtained from C57BL/6J (n = 50) and rd10 (n = 61) mice at postnatal days 30 to 720 were stained for zonula occludens-1 (ZO-1) and imaged with confocal microscopy. A total of 111 flatmounts were prepared. Twenty-one morphometric measurements were made on tiled, composite images of complete flatmounts, including cell location, area, and eccentricity, using automated image analysis software for quantitatively measuring cell phenotypes. In young (≤61-day-old) C57BL/6J mice, the RPE morphology resembled a regular hexagonal array of cells of uniform size throughout the retina, except near the ciliary body, where the shapes of RPE resembled a soft network. Old (≥180-day-old) C57BL/6J eyes had a subpopulation of large cells. A clear disruption of the regular cell size and shape appeared in rd10 mutants. Aspect ratio and cell area gave rise to principal components that predictively classified mouse age and genotype. Quantitative differences in the RPE sheet morphology allowed discrimination of rd10 from C57BL/6J strains despite the confounding effect of aging. This has implications for RPE sheet morphology as a potential early biomarker for diagnosis of eye disease and prognosis of the eye at early stages when disease is subtle. We conclude that an RPE cell's area and aspect ratio are very early quantitative indicators that predict progression to advanced RPE disease as manifested in rd10.

Pigment Epithelium-Derived Factor Secreted from Retinal Pigment Epithelium Facilitates Apoptotic Cell Death of iPSC

We show that pigment epithelium-derived factor (PEDF), which is secreted from primary or iPSC-derived retinal pigment epithelium (RPE), dramatically inhibits the growth of iPSCs. PEDF is detected abundantly in culture supernatants of primary or iPSC-derived RPE. Apoptotic cell death is induced in iPSC when co-cultured with RPE, a process that is significantly blocked by addition of antibody against PEDF. Indeed, addition of recombinant PEDF to the iPSC cell culture induces apoptotic cell death in iPSCs, but the expression of pluripotency related-genes is maintained, suggesting that PEDF causes cell death, not differentiation, of iPSCs. To recapitulate this event in vivo, we examined tumor formation in NOG mice after subcutaneous injection of iPSCs with or without an iPSC-derived RPE sheet (2.5 × 105 RPE cells). We observed that the tumor forming potential of iPSCs was significantly suppressed by simultaneous transplantation with an iPSC-derived RPE sheet.

Ion transport across the murine retinal pigment epithelium

The retinal pigment epithelium (RPE) is important for the normal transport of ions and water from the subretinal space. Due to the small size of mice, ion transport across fresh murine RPE has not been studied in vitro. Sheets of RPE with the retina attached from normal mice were mounted in EasyMount Ussing chambers with an aperture of 0.031 cm2 (Physiological Instruments Inc) with aireated 38°C Krebs. The short‐circuit current, ISC, and the transepithelial resistance, TER, was recorded with a voltage clamp apparatus. Initial ISC (n=7) was −17,6 ±4,5 μA/cm2, with apical side negative, and TER was 82,8 ±7,6 Ohm*cm2. The following substances were tested (30 min each, both apical and basolateral sides): ATP (100 μM) had no effect on the ISC. Epinephrine (100 μM) increased the ISC by 5%. Bumetanide (100 μM) inhibited the ISC from −16.1 ± 5.2 to −14.5 ± 5.4 μA/cm2. Ouabain (1 mM) induced a biphasic response, a rapid 6 min increase to −17.4 ± 2.6 μA/cm2, and a slower 30 min decrease to 36% of pre‐addition ISC. The Isc was reduced by low Cl− Krebs. Reducing the K+ concentration on the apical side decreased the Isc, which was inhibited by 1 mM BaCl2. The mouse RPE preparation was stable for 2–3 hours. The results indicate that adrenergic but not purinergic receptors affect murine RPE ion transport as measured by the ISC. The ion transport is likely due to Cl− transport with some K+ involvement, with the NaK‐ATPase serving as an important driving force.

Perspectives on human clinical trials of therapies using iPS cells in Japan: Reaching the forefront of stem-cell therapies

A research project involving sheets of retinal pigment epithelium constructed from iPS cells derived from patients with age-related maculopathy is one step closer to being approved for clinical trials by the Japanese Government. Now is the time to make therapies using iPS cells clinically available.

Morphologic Features and Viability Analysis of Human Detached Retinal Pigment Epithelium in Age-Related Macular Degeneration

To evaluate the morphologic features and viability of human retinal pigment epithelium (RPE) cells captured from the pigment epithelium detachment (PED) region outside the choroidal neovascular membrane lesion in eyes with hemorrhagic age-related macular degeneration. Prospective, observational case series. Five specimens of the RPE sheet were obtained from the PED region after choroidal neovascular membrane excision in 5 eyes of 5 patients during RPE transplantation for hemorrhagic age-related macular degeneration. The specimens were stained with hematoxylin and eosin and with periodic acid-Schiff. Immunohistochemistry analysis for RPE-65 and zonula occludens-1 also was performed. RPE cells from the PED region were cultured and passaged 5 times. Scanning and transmission electron microscopy were performed to analyze the specimens. The RPE cells of the specimens contained brownish pigment and were autofluorescent in vitro. Periodic acid-Schiff staining revealed that the Bruch membrane below the RPE monolayer was not intact. The specimens demonstrated positive results for both zonula occludens-1 and RPE-65 staining. The RPE basement membrane in the specimen was observed by both scanning and transmission electron microscopy. Intercellular tight junctions among RPE cells of the specimen also were observed. RPE cells captured from the PED region were cultured successfully and were passaged 5 times. The RPE sheet developed from the PED region outside the choroidal neovascular membrane lesion had tight intercellular junctions, a simple RPE basement membrane, and active cellular viability. This monolayer RPE sheet may be considered as a substitution for subfoveal RPE loss in eyes with hemorrhagic age-related macular degeneration.

Toxicity of endogenous peroxynitrite and effects of puerarin on transplanted retinal pigment epithelial sheets in the subretinal space in mice.

To evaluate the toxicity of endogeneous peroxynitrite on transplanted retinal pigment epithelial (RPE) sheets and the effect of puerarin on their survival in the C57BL/6 mice after RPE sheets have been transplanted into SD rats' subretinal space . C57BL/6 mice eyes were used to culture RPE cells. Ninety-six SD rats were involved in the experiment. They were divided into control (block control), streptozotocin (STZ, negative control), untransplanted RPE (positive control) and transplanted RPE groups respectively. Diabetes was induced in SD rats by intra-peritoneal STZ injection in the latter three groups. Saline was injected into the subretinal space of 24 SD rats in the untransplanted RPE group and primary RPE sheets were injected into the subretinal space of 24 SD rats in the transplanted RPE group. Puerarin (45mg/kg) was administrated into both untransplanted RPE and transplanted RPE groups of diabetic rats through intra-peritoneal injection route after RPE sheets transplantation. At 20, 40, 60 days after surgery, Western blotting analysis, DNA ladder and RT-PCR were used for determining the differences in expression of nitrotyrosine (NT, the foot print of peroxynitrite ), apoptosis and iNOS mRNA in the control, STZ, untransplanted RPE and transplanted RPE groups respectively. HE staining was used for determining the RPE survival in the subretinal space of the transplanted RPE group. Apoptosis and expression of NT and iNOS mRNA were observed in STZ, untransplanted RPE and transplanted RPE groups, but were delayed in untransplanted RPE and transplanted RPE groups in a time-dependent manner compared with control and STZ groups (P<0.01). There were no differences between the two groups (P>0.01). NT, DNA ladder, iNOS mRNA were down-regulated, which were associated with the decrease of expression of peroxynitrite. Numerous pigmented cells emerged and increased in number in the subretinal space during the 60-day observation period after transplantation. On day 20, heavily pigmented cells were visible at the transplant site; On day 40, monolayer and multilayered transplant was visible in the subretinal space; On day 60, heavily pigmented monolayer and multilayered transplants with round apical profile were present along Bruch's membrane. Puerarin increased the 60-day survival of C57BL/6 mice RPE xenografts in the SD rats' subretinal space, which may be related to its direct inhibition of apoptosis of RPE cells and antagnism of damage of peroxynitrite to RPE cells.

Nicotine Increases the VEGF/PEDF Ratio in Retinal Pigment Epithelium: A Possible Mechanism for CNV in Passive Smokers with AMD

Cigarette smoking is the strongest environmental risk factor for wet age-related macular degeneration (AMD). Inappropriate expression of proangiogenic vascular endothelial growth factor (VEGF) and antiangiogenic pigment epithelium derived factor (PEDF) may cause choroidal neovascularization (CNV), a key event in wet AMD, resulting in vision loss. Nicotine (NT), a potent angiogenic agent abundant in second-hand smoke, may play a major role in the pathogenesis of wet AMD. The purpose of this study was to evaluate the expression of nicotinic acetylcholine receptors (nAchR) in retinal pigment epithelium (RPE) and determine the effects of NT on RPE-derived VEGF and PEDF expression in the context of passive smoking. Human RPE cells were treated with NT (10(-8) M), with or without the nAchR-nonspecific antagonist hexamethonium (HXM) (10(-5) M) for 72 hours. RPE sheets were microdissected from rats exposed to NT in drinking water (100 μg/mL), with or without HXM (40 mg/kg/d, intraperitoneally), for 72 hours. Cell death was determined by cell count and proliferation by Western blot for proliferating cell nuclear antigen (PCNA). nAchR expression was examined by real-time PCR and Western blot. ERK activation was evaluated by Western blot analysis. VEGF and PEDF expression was assessed by ELISA, Western blot, and real-time PCR. Cultured RPE cells constitutively expressed the nAchR α3, α10, and β1 subunits, with β1 being the most prevalent. The nAchR α4, α5, α7, and β2 subunits were detected in RPE sheets from rats, among which α4 is the predominant subtype. NT, which did not result in either cell death or proliferation, induced β1 nAchR, upregulated VEGF, and downregulated PEDF expression through nAChR in ARPE-19 cells. Transcriptional activation of the nAchR α4 subunit and nAChR-mediated upregulation of VEGF and PEDF were observed in RPE from rats exposed to NT. NT increased the VEGF-to-PEDF ratio in the RPE through nAchR in vitro and in vivo. This alteration in the ratio may play a key role in the progression to wet AMD in passive smokers.

Effect of 308 nm excimer laser irradiation on retinal pigment epithelium cell viability in vitro

Background:Translocation of an autologous retinal pigment epithelium (RPE) sheet under the macula is currently under investigation as a treatment for exudative AMD. Excimer laser-assisted RPE sheet translocation (EST) employs intraocular...

Subtype specific estrogen receptor action protects against changes in MMP-2 activation in mouse retinal pigmented epithelial cells

Eyes with age-related macular degeneration (AMD) demonstrate accumulation of specific deposits and extracellular matrix (ECM) molecules under the retinal pigment epithelium (RPE). AMD is about two times more prevalent in aging postmenopausal women. Therefore we studied whether 17β-estradiol (E2) modulates the expression and activity of the trimolecular complex (MMP-2, TIMP-2 and MMP-14), molecules which are of major importance for ECM turnover in RPE. We used cell lines isolated from estrogen receptor knockout mice (ERKO) to determine which ER (estrogen receptor) subtype was important for ECM regulation in RPE cells. We found that mouse RPE sheets had higher baseline MMP-2 activity in the presence of ERβ. This correlated with higher MMP-2 activity in RPE cell lines isolated from ERKOα mice. Exposure to E2 increased MMP-2 activity in mouse RPE cell lines. In addition E2 increased transcriptional activation of the MMP-2 promoter through a functional Sp1 site which required the presence of ERβ, but not ERα. E2 also maintained levels of pro MMP-2, and MMP-14 and TIMP-2 activity after oxidant injury. Since the direct effects of E2 on MMP-2 transcriptional activation and the regulation of the trimolecular complex after oxidant-induced injury requires ERβ, this receptor subtype may have a role as a potential therapeutic target to prevent changes in activation of MMP-2.

Effects of Exogenous Extracellular Matrix Proteins on the Reattachment of Retinal Pigment Epithelial Cells

Purpose: To evaluate the effect of adding exogenous extracellular matrix (ECM) proteins on the reattachment of retinal pigment epithelium (RPE) to the damaged surface of Bruch's membrane (BM). Methods: Porcine BM explants were divided into six groups: BMs with an intact basal lamina (bl-BM) and five damaged BMs (d-BM: bare & four ECM-coated). The d-BM was coated with ECM proteins (either fibronectin, laminin, collagen IV, or all). Primary RPE sheets were plated and cultured for each group of BM explants. The attached live cells were counted and examined with a scanning electron microscope after three days, as well as at 1, 2 and 4 weeks. Results: The RPE reattachment rate was highest in bl-BM and lowest in uncoated d-BM. ECM-coated groups showed a lower reattachment rate than bl-BM, but when compared with the uncoated group, the reattachment rate was significantly increased (p

Myosin II and Rho kinase activity are required for melanosome aggregation in fish retinal pigment epithelial cells

In the retinal pigment epithelium (RPE) of fish, melanosomes (pigment granules) migrate long distances through the cell body into apical projections in the light, and aggregate back into the cell body in the dark. RPE cells can be isolated from the eye, dissociated, and cultured as single cells in vitro. Treatment of isolated RPE cells with cAMP or the phosphatase inhibitor, okadaic acid (OA), stimulates melanosome aggregation, while cAMP or OA washout in the presence of dopamine triggers dispersion. Previous studies have shown that actin filaments are both necessary and sufficient for aggregation and dispersion of melanosomes within apical projections of isolated RPE. The role of myosin II in melanosome motility was investigated using the myosin II inhibitor, blebbistatin, and a specific rho kinase (ROCK) inhibitor, H-1152. Blebbistatin and H-1152 partially blocked melanosome aggregation triggered by cAMP in dissociated, isolated RPE cells and isolated sheets of RPE. In contrast, neither drug affected melanosome dispersion. In cells exposed to either blebbistatin or H-1152, then triggered to aggregate using OA, melanosome aggregation was completely inhibited. These results demonstrate that (1) melanosome aggregation and dispersion occur through different, actin-dependent mechanisms; (2) myosin II and ROCK activity are required for full melanosome aggregation, but not dispersion; (3) partial aggregation that occurred despite myosin II or ROCK inhibition suggests a second component of aggregation that is dependent on cAMP signaling, but independent of ROCK and myosin II.