Neurotrophic activity of interphotoreceptor matrix on human Y79 retinoblastoma cells

Interphotoreceptor matrix based biomaterial: Impact on human retinal progenitor cell attachment and differentiation

While cell transplantation therapies show great promise as treatments for retinal degeneration, the challenge of low cell survival upon transplantation motivates exploration of materials that may serve as cell delivery vehicles and promote survival and differentiation. In this study, we explored the native matrix that surrounds the outer segments of photoreceptors and promotes their homeostasis, interphotoreceptor matrix (IPM), as a substrate for human retinal progenitor cells (hRPCs). Bovine IPM was characterized to determine its structure and biochemical composition, and processed to develop substrates for cells. Cell viability, morphology, proliferation and expression of photoreceptors marker genes were studied on IPM-based substrates in vitro. We explored different preparations of IPM as a scaffold. Lectin staining revealed that a distinct honeycomb structure of native IPM is lost during centrifugation to prepare a more concentrated suspension of matrix. Biochemical analysis of bovine IPM indicated presence of glycosaminoglycans and proteins. IPM mediated hRPC attachment and spreading with no signs of cytotoxicity. Cells proliferated more on native IPM substrates compared to IPM that was centrifuged to create a concentrated suspension. Cells cultured on IPM substrates expressed markers of photoreceptors: rhodopsin, NRL and ROM1. Together this data supports further exploration of IPM as a tool for retinal tissue engineering. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 891-899, 2018.

Interphotoreceptor Retinoid-Binding Protein Mitigates Cellular Oxidative Stress and Mitochondrial Dysfunction Induced by All-trans-Retinal

Purpose

Point and null mutations in interphotoreceptor retinoid-binding protein (IRBP) cause retinal dystrophy in affected patients and IRBP-deficient mice with unknown mechanism. This study investigated whether IRBP protects cells from damages induced by all-trans-retinal (atRAL), which was increased in the Irbp^−/− retina.

Methods

Wild-type and Irbp^−/− mice retinal explants in buffer with or without purified IBRP were exposed to 800 lux light for different times and subjected to retinoid analysis by high-performance liquid chromatography. Purity of IRBP was determined by Coomassie Brilliant Blue staining and immunoblot analysis. Cellular damages induced by atRAL in the presence or absence of IRBP were evaluated in the mouse photoreceptor-derived 661W cells. Cell viability and death were measured by 3-(4,5-dimethyl-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS) and TUNEL assays. Expression and modification levels of retinal proteins were determined by immunoblot analysis. Intracellular reactive oxygen species (ROS) and nitric oxide (NO) were detected with fluorogenic dyes and confocal microscopy. Mitochondrial membrane potential was analyzed by using JC-1 fluorescent probe and a flow cytometer.

Results

Content of atRAL in Irbp^−/− retinal explants exposed to light for 40 minutes was significantly higher than that in wild-type retinas under the same light conditions. All-trans-retinal caused increase in cell death, tumor necrosis factor activation, and Adam17 upregulation in 661W cells. NADPH oxidase-1 (NOX1) upregulation, ROS generation, NO-mediated protein S-nitrosylation, and mitochondrial dysfunction were also observed in 661W cells treated with atRAL. These cytotoxic effects were significantly attenuated in the presence of IRBP.

Conclusions

Interphotoreceptor retinoid-binding protein is required for preventing accumulation of retinal atRAL, which causes inflammation, oxidative stress, and mitochondrial dysfunction of the cells.

Differential expression of folate receptor-alpha, sodium-dependent multivitamin transporter, and amino acid transporter (B (0, +)) in human retinoblastoma (Y-79) and retinal pigment epithelial (ARPE-19) cell lines

PURPOSE

The overall objective of this study was to investigate the differential expression of folate receptor-alpha (FR-α), sodium-dependent multivitamin transporter (SMVT), and amino acid transporter [B ((0, +))] in retinoblastoma (Y-79) and retinal pigment epithelial (ARPE-19) cells.

METHODS

Polymerase chain reaction (PCR) analysis was performed to confirm the existence of FR-α, SMVT, and B ((0, +)) in Y-79 and ARPE-19 cell lines. Quantitative real-time PCR was also performed to determine the relative expression of FR-α, SMVT, and B ((0, +)) at mRNA level in these cell lines. Quantitative uptake of [(3)H] Folic acid, [(3)H] Biotin, and [(14)C] Arginine was studied in Y-79 and ARPE-19 cells. Further, saturation kinetics of [(3)H] Folic acid, [(3)H] Biotin, and [(14)C] Arginine was performed in the presence of various concentrations of respective cold substrates to determine the kinetic parameters (K(m) and V(max)) in Y-79 and ARPE-19 cells.

RESULTS

PCR analysis had confirmed the existence of FR-α, SMVT, and B ((0, +)) in Y-79 and ARPE-19 cells. Quantitative real-time PCR analysis had shown significantly higher expression of FR-α, SMVT, and B ((0, +)) mRNA levels in Y-79 cells compared with ARPE-19 cells. Quantitative uptake of [(3)H] Folic acid, [(3)H] Biotin, and [(14)C] Arginine was found to be significantly higher in Y-79 cells relative to ARPE-19 cells. [(3)H] Folic acid uptake process followed saturation kinetics with apparent K(m) of 8.29 nM and V(max) of 393.47 fmol/min/mg protein in Y-79 cells and K(m) of 80.55 nM and V(max) of 491.86 fmol/min/mg protein in ARPE-19 cells. [(3)H] Biotin uptake process also displayed saturation kinetics with K(m) of 8.53 μM and V(max) of 14.12 pmol/min/mg protein in Y-79 cells and K(m) of 138.25 μM and V(max) of 38.85 pmol/min/mg protein in ARPE-19 cells. [(14)C] Arginine uptake process followed saturation kinetics with K(m) of 16.77 μM and V(max) of 348.27 pmol/min/mg protein in Y-79 cells and K(m) of 52.03 μM and V(max) of 379.21 pmol/min/mg protein in ARPE-19 cells.

CONCLUSIONS

This work demonstrated for the first time the higher expression and affinity of FR-α, SMVT, and B ((0, +)) mRNA levels in retinoblastoma (Y-79) cells compared with retinal pigment epithelial (ARPE-19) cells.

Pigment epithelium-derived factor associates with neuropathy and fibrosis in pancreatic cancer

OBJECTIVES

Pigment epithelium-derived factor (PEDF) is a noninhibitory member of the serine protease inhibitor gene family with neuroprotective, neuroproliferative, and anti-angiogenic functions. Its role in pancreatic fibrosis and neuropathy is unknown.

METHODS

The expression and localization of PEDF were assessed by quantitative real-time (RT)-PCR, immunohistochemistry, and quantitative image analysis and correlated with neural and microvessel densities (MVDs) in the normal pancreas (n=20) and pancreatic cancer (n=55). Primary human pancreatic stellate cells (PSCs), mouse neuroblastoma, and human Schwann cells were used for functional experiments. The effect of hypoxia on PEDF production in cancer cell lines and immortalized pancreatic ductal epithelial cells was assessed by quantitative RT-PCR and enzyme-linked immunosorbent assay. The effect of recombinant PEDF on PSCs was assessed by immunoblot analysis.

RESULTS

PEDF expression was homogeneous in epithelial cells of the normal pancreas where some acinar cells consistently displayed stronger staining. A higher expression was found in tubular complexes, PanIN lesions, and inflammatory cells in pancreatic cancer. Cancer cells expressed various levels of PEDF. In cancer cell lines and in human immortalized pancreatic ductal epithelial cells, hypoxia increased PEDF mRNA up to 132-fold. Higher expression of PEDF in cancer cells was significantly correlated with better patient survival (median survival 21.5 months vs. 17.5 months, P=0.043), increased neuropathy (P=0.0251), increased PSC activity, and extracellular matrix protein production.

CONCLUSIONS

PEDF increases PSC activity, thereby contributing to the desmoplasia of pancreatic cancer. PSC overactivation likely leads to periacinar fibrosis and degeneration of fine acinar innervation. Increased focal PEDF expression in cancer cells correlates with neuropathic changes and better patient survival.

Investigating maspin in breast cancer progression using mouse models

Clade B serpin family of proteins regulate a variety of cellular functions including cell adhesion and motility. One key member of the clade B serpin family is maspin (SERPINB5). Maspin is classified as a type II tumor suppressor that regulates cell adhesion and invasion. It is expressed in normal mammary epithelial cells but is reduced in benign breast tumors and absent in invasive breast carcinomas. Although maspin regulates cell apoptosis, cell adhesion, migration, and invasion in breast cancer cell culture systems, mouse models are necessary to verify this in vivo. In this chapter, we review the development of transgenic and syngeneic mouse models to study the role of maspin in mammary tumorigenesis and in normal mammary development.

Pigment epithelium-derived factor (PEDF) as a therapeutic target in cardiovascular disease

In this review we discuss the role of pigment epithelium-derived factor (PEDF) as a possible new target molecule to therapeutically influence cardiovascular disease. PEDF is a multifunctional, pleiotropic protein with antiangiogenic, antitumorigenic, antioxidant, anti-inflammatory, antithrombotic, neurotrophic and neuroprotective properties. First identified in retinal pigment epithelium cells, it is expressed in various tissues throughout the body such as the eye, liver and adipose tissue. Recently PEDF has also been characterized in the heart. PEDF has been suggested to have a protective role in atherosclerosis, the main cause of coronary heart disease, myocardial infarction and heart failure due to its anti-inflammatory, antioxidant and antithrombotic effects in the vessel wall and platelets. Additionally PEDF has strong antiangiogenic effects by inducing apoptosis in endothelial cells and by regulating the expression of other angiogenic factors. Therefore blocking of PEDF locally for example in ischemic tissue in the heart might favour angiogenesis, induce neovascularization and lead to increased perfusion of the injured tissue. On the other hand, local overexpression of PEDF restricted to atherosclerotic lesions might block angiogenesis, inflammation and thrombosis at these sites and thus counteract destabilization and rupture of the lesion otherwise caused by inflammatory activation and excessive angiogenesis and inhibit subsequent thrombus formation.

Folic acid transport via high affinity carrier-mediated system in human retinoblastoma cells

The primary objective of this study was to investigate the expression of a specialized carrier-mediated system for folic acid and to delineate its uptake mechanism and intracellular trafficking in a human derived retinoblastoma cell line (Y-79). Uptake of [3H]Folic acid was determined at various concentrations, pH, temperatures, in the absence of sodium and chloride ions and in the presence of structural analogs, methyltetrahydro folate (MTF) and methotrexate (MTX), vitamins, membrane transport and metabolic inhibitors to delineate the mechanism of uptake. Kinetics of uptake was studied in the presence of various intracellular regulatory pathways; protein kinases A and C (PKA and PKC), protein tyrosine kinase (PTK) and calcium-calmodulin modulators. Reverse transcription polymerase chain reaction (RT-PCR) was performed to confirm the molecular identity of folate carrier systems. The uptake was found to be linear up to 30min. The rate of uptake followed saturation kinetics with apparent Km of 8.29+/-0.74nM, 17.03+/-1.98nM and 563.23+/-115.2nM and Vmax of 393.47+/-9.33, 757.58+/-26.21 and 653.17+/-31.7fmol/(minmg) protein for folic acid, MTF and MTX, respectively. The process was chloride, temperature and energy dependent but sodium and pH independent; inhibited by the structural analogs MTF and MTX but not by structurally unrelated vitamins. Membrane transport inhibitors did not affect the uptake of [3H]Folic acid, however endocytic inhibitor, colchicine, significantly inhibited the [3H]Folic acid uptake indicating the involvement of receptor mediated endocytosis process. PKC, PTK and Ca2+/calmodulin pathways appeared to play important roles in the regulation of folic acid uptake. Molecular evidence of the presence of folate receptor (FR) precursor was identified by RT-PCR analysis. This research work demonstrated, for the first time, the functional and molecular existence of a specialized high affinity carrier-mediated system for folic acid uptake, in human retinoblastoma cells.

Biotin uptake and cellular translocation in human derived retinoblastoma cell line (Y-79): A role of hSMVT system

The objective of this research was to investigate the presence of a specialized carrier-mediated system for biotin and delineate uptake mechanism and intracellular trafficking of biotin in the human derived retinoblastoma cell line (Y-79). Human derived retinoblastoma cell line, Y-79, was used for uptake studies. Uptake of [3H]Biotin was determined at various concentrations, pH, temperatures, in the absence of sodium and in the presence of other vitamins and metabolic inhibitors to delineate the mechanism of uptake. Uptake was determined in the presence of various intracellular regulatory pathways (protein kinase A & C, protein tyrosine kinase and calcium-calmodulin) modulators. Reverse transcription polymerase chain reaction (RT-PCR) was performed to confirm the molecular identity of human sodium-dependent multivitamin transporter (hSMVT). Uptake of [3H]Biotin in Y-79 cells were found to be saturable at micromolar concentration range, with apparent Km of 8.53 microM and Vmax of 14.12 pmol/min/mg protein, but linear at nanomolar concentration range. Uptake was sodium, pH, temperature and energy-dependent, but chloride independent; inhibited by the structural analogue desthiobiotin, pantothenic acid and lipoic acid at milimolar concentrations and not at nanomolar concentrations. Uptake of [3H]Biotin was trans-stimulated by the intracellular biotin. Ca2+/calmodulin pathways appeared to play important roles in the regulation of riboflavin uptake in Y-79 cells via significant reduction in Vmax (66%) and Km (28%) of the uptake process. A human sodium-dependant multivitamin transporter, hSMVT, was identified by RT-PCR in Y-79. These studies demonstrated for the first time the existence of a human sodium dependant multivitamin transporter (hSMVT), a specialized carrier-mediated system for biotin uptake, in human derived retinoblastoma cells.

Downregulation of gene expression in the ageing lens: a possible contributory factor in senile cataract

PURPOSE

To study the molecular characteristics of lens epithelial cells from patients with senile cataract by cDNA microarray technique.

METHODS

Lens epithelial cells adhering to anterior capsules taken during cataract surgery collected from 108 patients, aged 56-92 years (senile cataract group), were pooled. Pooled epithelial cells of normal, noncataractous lenses from one patient with ocular trauma, one patient with lens subluxation, and 25 cadaveric eyes, all under the age of 55 years, served as a control. Total RNA was extracted by conventional methods from the two groups of cells, and a fluorescent probe was prepared for each group. The probes were hybridized on 9700 known human cDNA clones. Hybridized clones were analysed using a scanning laser and the results were processed by GEMTools (Incyte Genomics) software.

RESULTS

A total of 1827 clones hybridized with the two probes. Of these, 400 showed differences of more than two-fold in gene expression between the two probes. Relative to controls, gene expression in the senile cataract lenses was upregulated in 318 clones and downregulated in 82. Three genes-filensin, inwardly rectifying potassium channel (IRPC), and pigment epithelium-derived factor (PEDF) were strongly downregulated (by 41.3-, 6.8-, and 5.9-fold, respectively) in senile cataract.

CONCLUSIONS

Cataractogenesis is associated with numerous changes in the genetic profile of the lens epithelial cells. Since filensin, IRPC, and PEDF genes are known to have important roles in the physiology and morphology of the transparent lens, substantial downregulation of their expression might contribute to the formation of senile cataract.

Maspin plays an important role in mammary gland development

Maspin is a unique member of the serpin family, which functions as a class II tumor suppressor gene. Despite its known activity against tumor invasion and motility, little is known about maspin's functions in normal mammary gland development. In this paper, we show that maspin does not act as a tPA inhibitor in the mammary gland. However, targeted expression of maspin by the whey acidic protein gene promoter inhibits the development of lobular-alveolar structures during pregnancy and disrupts mammary gland differentiation. Apoptosis was increased in alveolar cells from transgenic mammary glands at midpregnancy. However, the rate of proliferation was increased in early lactating glands to compensate for the retarded development during pregnancy. These findings demonstrate that maspin plays an important role in mammary development and that its effect is stage dependent.

RPE secreted proteins and antibody influence photoreceptor cell survival and maturation

Proteins in media conditioned by retinal pigment epithelial cells (RPE-CM) and an antibody against these proteins (RPE-SP) were tested for their respective effects on rat retinal development in vitro and in vivo. Proteins of RPE-CM were separated in denaturing gels and evaluated by Western blot analysis. Retinal explants from postnatal day 2 (P2) rats were cultured in RPE-CM only or CM diluted with the RPE-SP antibody and, after 7 days, the explants were dissociated into single cells that were immunostained for opsin. RPE-CM or antibody was also injected into the vitreous of postnatal day 7 (P7) Long-Evans rats and analyzed 7 and 21 days later. Electrophoretic analysis of RPE-CM predominantly showed 60-70 kDa proteins; when these proteins were probed with RPE-SP antibody by Western blot, immunoreactive proteins were restricted to this narrow molecular weight range. In P2 retinal explant cultures supplemented with RPE-CM, long ganglion cell-like neurites were detected in 3 days. This activity was nullified in explant cultures grown in RPE-CM titrated with antibody, and these explants appeared to degenerate within 5 days. Over 80% of dissociated retinal cells from explants 7 days after treatment with RPE-CM expressed opsin, compared to only 20% of cells from explants grown in defined medium or serum. Retinas of P14 rats injected intravitreally with RPE-CM at P7 had increased numbers of ectopic photoreceptor cells within the inner nuclear layer when compared to retinas of sham-injected eyes. In contrast, retinas of eyes injected intravitreally with RPE-SP antibody exhibited shorter outer (OS) and inner (IS) segments and thinner outer nuclear (ONL) and outer plexiform (OPL) layers than retinas of sham-injected eyes. In conclusion, proteins in RPE-CM appeared to accelerate and maximize the development of rat photoreceptor cells in vitro, while intravitreal injections of its antibody caused an apparent retardation of outer segment maturation. These results suggest that a protein(s) secreted by RPE plays a key role in normal retinal development, particularly in photoreceptor cell survival and outer segment maturation.

Effects of retinal pigment epithelial cell-secreted factors on neonatal rat retinal explant progenitor cells

This study demonstrates the effects of conditioned media from transformed neonatal rat retinal pigment epithelial cells (tnrRPE-CM) in a culture system consisting of neonatal rat retinal explants. For this study, retinal explants from postnatal day 2 (PN2) normal rats were cultured for over 3 weeks on a poly-D-L-ornithine-coated surface in RPE-CM only, 10% serum, or a serum-free defined media, and then examined by phase-contrast and scanning electron microscopy and immunocytochemistry. After 2 days in vitro, long ganglion cell-like neurites projected from retinal explants grown in tnrRPE-CM. These neurites increased in number and length with prolonged time in culture. In addition, by 5 days, round cells were observed adjacent to neonatal explants grown in tnrRPE-CM. By day 10, these round cells had increased in number and were seen along the neurites, in massive clusters immediately adjacent to these explants and dispersed throughout the culture-plate surface. Media conditioned by primary cultures of normal neonatal rat RPE cells caused a similar, but less robust, cellular response in retinal explants when compared to tnrRPE-CM. At 10 days, retinal explants grown in 10% serum showed only a few short processes, but no round cells, while those explants grown in defined media appeared to be degenerating. The round migrating cells are classified as retinal progenitor cells since they immunostained for opsin and interphotoreceptor retinoid-binding protein (IRBP), two photoreceptor cell markers, and a few for cellular retinaldehyde binding protein (CRALBP), a Muller cell marker. Neurite outgrowth and retinal progenitor cell production from explants were eliminated when the tnrRPE-CM was subjected to trypsin or heat treatment, indicating that the factor(s) responsible for promoting these cellular events was most likely proteinaceous. Growth factors, including basic fibroblast growth factor, were unable to generate long neurite outgrowth or progenitor cell production as observed in RPE-CM-supplemented explant cultures. We report that CM from cultures of primary and transformed neonatal rat RPE cells promoted ganglion cell-like neurites and the production of migrating retinal progenitor cells that primarily expressed photoreceptor-specific markers, from neonatal rat retinal explants. This evidence further confirms the important role of RPE in retinal development. The production of large numbers of progenitor cells by an RPE-secreted factor(s) may have important implications for possible therapeutic approaches to help correct retinal disease states by replacing lost cells through transplantation technology.

Differentiation of Y79 retinoblastoma cells with pigment epithelial-derived factor and interphotoreceptor matrix wash: effects on tumorigenicity

We investigated the in vivo differentiation potential of Y79 human retinoblastoma cells following pre-treatment with two novel neurotrophic agents: PEDF (human recombinant pigmented-epithelial derived factor) or IPM (interphotoreceptor matrix) wash. These agents were able to induce a significant degree of morphological differentiation in vitro. However, 48 days after subretinal transplantation of pre-treated cells, massive tumor formation was apparent. In contrast, Y79 cells pre-treated with retinoic acid/sodium butyrate, which attain a lesser degree of morphological differentiation, did not produce tumors over a 30 to 60 day-survival time (del Cerro et al., Brain Research, 12-22, 1992). We conclude that for PEDF and IPM, the degree of in vitro differentiation and the degree of mitotic arrest are independent features.

Pigment epithelium-derived factor: neurotrophic activity and identification as a member of the serine protease inhibitor gene family

Cultured pigment epithelial cells of the fetal human retina secrete a protein, pigment epithelium-derived factor (PEDF), that induces a neuronal phenotype in cultured human retinoblastoma cells. Morphological changes include the induction of an extensive neurite meshwork and the establishment of corona-like cellular aggregates surrounding a central lumen. The differentiated cells also show increases in the expression of neuron-specific enolase and the 200-kDa neurofilament subunit. Amino acid and DNA sequence data demonstrate that PEDF belongs to the serine protease inhibitor (serpin) family. The PEDF gene contains a typical signal-peptide sequence, initiator methionine codon, and polyadenylylation signal and matches the size of other members of the serpin superfamily (e.g., alpha 1-antitrypsin). It lacks homology, however, at the putative serpin reactive center. Thus, PEDF could exert a paracrine effect in the embryonic retina, influencing neuronal differentiation by a mechanism that does not involve classic inhibition of serine protease activity.