生长因子对培养人眼视网膜色素上皮细胞增的调控作用

探讨生长因子对人眼视网膜色素上皮细胞增殖的调控作用。方法建立人眼ＲＰＥ细胞的培养体系，利用＾３Ｈ－ＴｄＲ掺入法和细胞计数观察表皮生长因子、碱性成纤维细胞生长因子胰岛素样生长因子对培养ＲＰＥ细胞的作用。     

Synthesized TGF-beta s in RPE regulates cellular proliferation

Retinal pigment epithelial (RPE) cells transdifferentiate in culture, a transition which is accompanied by a shift in biological activity. The present study investigates whether transforming growth factor (TGF)-beta has the same effects on morphologically transformed RPE cells that it has on primary RPE cells. It also evaluates the autocrine and paracrine activities of TGF-beta s synthesized by RPE cells as well as the anti-TGF-beta effect of mannose-6-phosphate (M-6-P). RPE cells were subcultured at the sixth passage to induce morphological change. The effect of second passaged RPE-conditioned medium (CM) on DNA synthesis was evaluated by the incorporation of 3H-thymidine in rabbit subconjunctival fibroblasts (SCFs) and primary RPE cells. The presence of TGF-beta in RPE-CM was determined using immunoblotting analysis. And the inhibitory effect of M-6-P on cell proliferation mediated by RPE-CM was also analyzed using 3H-thymidine incorporation into DNA. TGF-beta 1, TGF-beta 2, and TGF-beta 3 inhibited the proliferation of the primary cultures of RPE cells in a dose-dependent manner, but the spindle-shaped sixth passaged RPE cells were not inhibited by these growth factors. The medium conditioned by RPE cells stimulated the proliferation of SCFs and inhibited the proliferation of primary RPE cells, in a manner similar to TGF-beta. When this medium was precipitated with either anti-TGF-beta 1, anti-TGF-beta 2, or anti-TGF-beta 3 antibodies, all three TGF-beta s, with an apparent molecular size of 25 kDa, were detected. Mannose-6-phosphate significantly blocked the effect of RPE-CM on cell proliferation. These findings indicate that RPE cells produce biologically functional TGF-beta s and that M-6-P can block the inhibitory effect of RPE-CM on cell proliferation.     

Retinoic acid promotes density-dependent growth arrest in human retinal pigment epithelial cells.

After retinal detachment the retinal pigment epithelium (RPE) undergoes a striking phenotypic change. It becomes dedifferentiated, proliferates to form multilayered colonies, and migrates into the subretinal space. These processes are important because they have been implicated in proliferative vitreoretinopathy and poor visual recovery after retinal reattachment; however the mechanisms by which they occur are unknown. In this study, the effect of retinoic acid on RPE cell morphology and growth in culture was examined. Cells grown in the presence of 1 microM retinoic acid do not exhibit cellular overgrowth and maintain characteristics associated with the morphologic appearance of mature RPE cells in vivo. Growth curves and 3H-thymidine incorporation suggest that retinoic acid inhibits RPE cell growth primarily after the cells have reached confluence. It may act by promoting density-dependent growth arrest. Dibutryl cyclic adenosine monophosphate also inhibits RPE cell growth and 3H-thymidine incorporation, but has little effect on cell morphology. However, in combination with retinoic acid it appears to have an additive effect on inhibition of cell growth and maintenance of a morphology like RPE in vivo. Retinoids have been demonstrated to modulate the growth and differentiation of several cell types. They are usually present in high levels in RPE cells. They become depleted in RPE in culture and such depletion may also occur in vivo after retinal detachment. This could play a role in the phenotypic alteration of RPE that occurs in association with retinal detachment.     

Stimulation of DNA synthesis in human and bovine RPE by peptide growth factors: the response to TNF-alpha and EGF is dependent upon culture density

A range of concentrations of several peptide mitogens was tested for growth activity on bovine and human RPE cells under serum free conditions by analysis of 3H-thymidine incorporation within the first 24 hrs of exposure to the agents. For cultures which were subconfluent or in early confluence, TNF-alpha, a product of activated macrophages, was the most effective mitogen; little or no growth stimulation was observed for PDGF, EGF, NGF, IGF-1, IL-1B, bFGF or TGF-beta 1. For TNF-alpha and EGF the growth response was analyzed in cultures of varying density. TNF-alpha was more active in sparse RPE cultures whereas EGF stimulation was greater in dense cultures. The response to growth factors was similar in RPE cells from the two species sources, but the apparent magnitude of the response was greater for bovine cells because the growth rate in serum free medium, which was used as the basal reference, was lower for bovine RPE. It is concluded that culture conditions, especially the timing of the assay and the level of confluence of the cells, affect the detection of a growth response to peptide mitogens. Although several of the agents which were tested did not stimulate DNA synthesis in RPE in this study, they may nonetheless promote growth when assayed in combination with other agents or they may affect other biological functions of RPE cells.     

生长因子诱导视网膜色素上皮细胞增殖的协同作用研究

目的从细胞水平探讨生长因子:肿瘤坏死因子-α(tumor necrosis factor,TNF-α)、白细胞介素-1β(interleukin-1β,IL-1β)和碱性成纤维细胞生长因子(basic fibroblast growth factor,bFGF)对视网膜色素上皮(retinal pigment epithelium,RPE)细胞增殖的协同调控作用。方法通过PPE细胞培养，采用氚标胸腺嘧啶核苷(3 H-thymidine,3 H-TdR)掺入测定三种生长因子单用和分别联用诱导RPE细胞DNA合成改变，细胞计数观察RPE细胞生长变化。结果三种生长因子单用均可明显促进RPE细胞DNA合成及细胞数目增加,TNF-α、IL-β和bFGF的3 H-TdR掺入每分钟计数值(counts per minute,cpm)分别是对照组的2.74、2.66和1.69倍(P<0.05)。两种生长因子联用较单用cpm明显提高,其中TNF-α+IL-βcpm是对照组的3.14倍(P<0.05)。三种生长因子联用时cpm是对照组的3.74倍(P<0.05)。结论三种生长因子间存在促RPE细胞增殖的协同作用,这可能是生长因子对RPE细胞增殖的重要调控机制之一。(中华眼底病杂志,1998,14:95-97)     

Interferon beta affects retinal pigment epithelial cell proliferation via protein kinase C pathways.

BACKGROUND: The aim of this study is to see the effect of interferon beta (IFN-beta) on cell proliferation and the protein kinase C (PKC) signaling pathway. METHODS: Proliferation of cultured human retinal pigment epithelium (RPE) cells, with various concentrations of IFN-beta, and with or without 3% fetal calf serum (FCS), was assessed by cell counting. Effects of short (3 h) or prolonged (48 h) exposure of RPE cells to natural human IFN-beta were assessed by (3)H-thymidine uptake. Cytosolic and membranous PKC activity over time in cells treated with IFN-beta and calphostin C was also measured. RESULTS: IFN-beta inhibited the increased proliferation by FCS in the prolonged-exposure assay. The PKC inhibitor calphostin C also showed an inhibitory effect on RPE cell growth and (3)H-thymidine uptake in the chronic exposure with FCS. Short treatment with IFN-beta had no inhibitory or stimulatory effect on (3)H-thymidine uptake. Cytosolic and membranous PKC activity was strongly upregulated after short IFN-beta exposure but returned to original levels after 1 h. PKC activity was downregulated both in the cytosol and membrane after 24 or 48 h. CONCLUSION: IFN-beta inhibited RPE proliferation in vitro and the effect is mediated by upregulation of the PKC pathway.     

Effect of growth factors on bovine retinal pigment epithelial cell migration and proliferation

BACKGROUND: To examine the effects of platelet-derived growth factor (PDGF), basic fibroblast growth factor (bFGF), acidic fibroblast growth factor (aFGF), insulin-like growth factor-1 (IGF-1), epidermal growth factor (EGF), and transforming growth factor beta 2 (TGF(beta2)) on bovine retinal pigment epithelial (RPE) cell migration and proliferation. MATERIALS AND METHODS: Cultured bovine RPE cells were treated with 10 ng/ml PDGF, bFGF, aFGF, IGF-1, EGF, or TGF(beta2). RPE cell migration studies were performed in multiwell plates confluently covered with RPE cells. After inhibition of proliferation and denudation of half of each well, cells were incubated with various growth factors. Migration was measured as the number of cells that had entered the denuded area after 20 h. RPE cell proliferation was determined by [(3)H]thymidine incorporation after growth factor stimulation for 24 h. RESULTS: RPE cell migration was significantly enhanced after incubation with PDGF (stimulation of 213% compared to the negative control, p = 0.002), bFGF (206%, p = 0.003), aFGF (175%, p = 0.003), IGF-1 (150%, p = 0.003), and EGF (144%, p = 0.003). RPE cell proliferation was stimulated by bFGF (322% compared to the negative control, p < 0.005), PDGF (119%, p < 0.005), aFGF (121%, p < 0.005), and EGF (94%, p < 0.005). IGF-1 showed no significant effect on RPE cell proliferation; TGF(beta2) displayed no effect on RPE cell migration nor on proliferation. CONCLUSIONS: The peptide growth factors PDGF, bFGF, aFGF, IGF-1, and EGF play an important role in initiating RPE cell migration. Basic FGF, PDGF, aFGF, and EGF stimulate RPE cell DNA synthesis.     

Human retinal epithelium produces and responds to placenta growth factor

Background Placenta growth factor (PlGF) is an important co-factor in retinal neovascularization. To examine whether retinal pigment epithelial (RPE) cells may represent a source for PlGF during retinopathy, we determined whether human RPE cells in vitro produce and respond to PlGF. In addition, we determined whether the cells express receptors for PlGF, i.e. flt-1 and neuropilins.Methods Cultured human RPE cells of passages 3–5 were used. The regulation of the PlGF gene and protein expression by growth factors and cytokines was evaluated by quantitative PCR and ELISA. Proliferation rates and chemotaxis were determined by a bromodeoxyuridine and a Boyden chamber assay.Results Human RPE cells express mRNAs for various members of the vascular endothelial growth factor family and for their receptors, including mRNAs for PlGF, flt-1, KDR, and neuropilins-1 and -2. The expression levels of the mRNAs for neuropilins-1 and -2 were significantly higher than those for flt-1 and KDR. Members of the transforming growth factor (TGF)-β superfamily of growth factors (BMP-4, TGF-β1, and β2) were strong inducers of PlGF gene expression, and evoked secretion of PlGF-2 protein by RPE cells. Exogenous PlGF-2 induced chemotaxis in RPE cells and reduced slightly the cell proliferation at high concentrations.Conclusion The findings that RPE cells produce and respond to PlGF indicate that the factor exerts an autocrine/paracrine action on these cells. It is suggested that increased expression of TGF-β-related growth factors during diabetic retinopathy may cause PlGF secretion by RPE cells contributing to the stimulation of cell migration as a critical component of the progression of fibrovascular membranes.     

Inhibition of human scleral fibroblast proliferation with heparin

Proliferation of fibroblasts is a serious problem in ocular trauma and surgical wound healing. Depending on the location of the injury, the growth of fibroblasts can lead to different problems. In glaucoma filtering surgery, fibroblast proliferation may contribute to scar tissue formation and premature wound closure. Fibroblastic growth in proliferative vitreoretinopathy may lead to the formation of preretinal membranes, which can contract, causing retinal detachment. In an effort to find a more effective method of inhibiting ocular fibroblast proliferation, we have investigated the effect of heparin, a sulfated polysaccharide, on the proliferation of fibroblasts obtained from the sclera of donor eyes. Heparin inhibits the incorporation of 3H-thymidine in a dose-dependent manner in the presence of fetal bovine serum (FBS). This inhibition is partially reversed by endothelial cell growth factor (ECGF). The heparin antagonist protamine sulfate causes a reversal of heparin inhibition and, in some instances, a significant increase in 3H-thymidine incorporation compared to serum controls. Heparin was equally effective in inhibiting cell proliferation in control and heparin-protamine sulfate-pretreated medium. These results were apparently unrelated to a direct toxic effect on cells, as a Trypan Blue exclusion assay showed no significant difference in viability when heparin treated cells were compared to control cells. Direct cell counts showed that heparin was effective in inhibiting cell proliferation over a long time period, but only if it was reinstilled every 2 days. Heparin treatment shows promise as a method for controlling fibroblast proliferation in the eye.     

Transforming growth factor-beta modulates effects of epidermal growth factor on corneal epithelial cells.

In order to understand the mechanisms that bring about maintenance and restoration of the integrity of corneal epithelium, we investigated independent and combined effects of transforming growth factor-beta (TGF-beta) and epidermal growth factor (EGF) on rabbit corneal epithelial cells in cell and organ culture. Specifically, we determined whether incubation with these factors influenced 1) cellular proliferation, 2) ability of cells to attach to a fibronectin matrix, and 3) the rate of epithelial migration over corneal stroma. Incubation with TGF-beta caused a dose-related decrease in the incorporation of 3H-thymidine by the epithelial cells. EGF increased 3H-thymidine incorporation, but this effect was antagonized by the addition of TGF-beta into the incubation medium. Incubation with EGF increased the numbers of cells that attached to a fibronectin matrix. TGF-beta itself did not affect the number of attached cells but, again, it antagonized the stimulatory effect of EGF. Similarly, when corneal blocks were cultured with EGF, epithelial migration increased in a dose-related manner. TGF-beta itself did not affect epithelial migration at any of the concentrations tested (0.1-10 ng/ml), but it antagonized EGF-stimulated epithelial migration. These findings suggest that the proliferation and the migration of corneal epithelial cells are regulated by different mechanisms, and that TGF-beta serves as a modulator of the effects of EGF.     

Expression of HB-EGF by retinal pigment epithelial cells in vitreoretinal proliferative disease

The heparin-binding epidermal growth factor-like growth factor (HB-EGF) has been implicated in wound-healing processes of various tissues. However, it is not known whether HB-EGF may represent a factor implicated in overstimulated wound-healing processes of the retina during proliferative retinopathies. Therefore, we investigated whether human retinal pigment epithelial (RPE) cells, which are crucially involved in proliferative retinopathies, express and respond to HB-EGF. RPE cells express mRNAs for various members of the EGF-related growth factor family, among them for HB-EGF, as well as for the EGF receptors ErbB1, -2, -3, and -4. The gene expression of HB-EGF is stimulated in the presence of transforming and basic fibroblast growth factors and by oxidative stress and is suppressed during chemical hypoxia. Exogenous HB-EGF stimulates proliferation and migration of RPE cells and the gene and protein expression of the vascular endothelial growth factor (VEGF). HB-EGF activates at least three signal transduction pathways in RPE cells including the extracellular signal-regulated kinases (involved in the proliferation-stimulating action of HB-EGF), p38 (mediates the effects on chemotaxis and secretion of VEGF), and the phosphatidylinositol-3 kinase (necessary for the stimulation of chemotaxis). In epiretinal membranes of patients with proliferative retinopathies, HB-EGF immunoreactivity was partially colocalized with the RPE cell marker, cytokeratins; this observation suggests that RPE cell-derived HB-EGF may represent one factor that drives the uncontrolled wound-healing process of the retina. The stimulating effect on the secretion of VEGF may suggest that HB-EGF is also implicated in the pathological angiogenesis of the retina.     

Hepatocyte growth factor stimulates proliferation and migration during wound healing of retinal pigment epithelial cells in vitro

PURPOSE: A defect in retinal pigment epithelial (RPE) cells may cause dysfunction of the neural retina, so rapid recovery of differentiated RPE cells is required after RPE injury. We investigated the effect of hepatocyte growth factor (HGF) on wound healing in RPE cells. METHODS: Confluent monolayers of bovine RPE cells were denuded, and the cells were allowed to recover in the presence or absence of HGF. The effect of HGF on RPE cell proliferation was evaluated by a 3-(4;5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulphophenyl)-2H-tetraz olium assay. In a migration assay, mitomycin C was used to inhibit proliferation, and the number of migrated cells was counted. The signaling pathways involved were examined using inhibitors of mitogen-activated protein kinase (MAPK), phosphatidylinositol-3 (PI3) kinase and protein kinase C pathways. RESULTS: At 80 ng/mL, HGF stimulated the wound closure of RPE monolayers and rendered the restituted cells more epithelioid in shape. HGF at 10 ng/mL stimulated RPE cell migration the most, whereas 80 ng/mL of HGF inhibited migration, but stimulated proliferation the most. In particular, PI3 kinase and MAPK inhibitor inhibited PRE cell migration and proliferation, respectively. CONCLUSIONS: HGF stimulated wound closure in cultured RPE cells, and rendered restituted cells epithelioid in shape. HGF may become a therapeutic candidate for RPE wound healing.     

Insulin-like growth factor I stimulates proliferation, migration, and plasminogen activator release by human retinal pigment epithelial cells

The migration of retinal pigment epithelial (RPE) cells from their normal anatomic position to a new position in the vitreous cavity is a critical feature of proliferative vitreous retinopathy. To determine if insulin-like growth factor I (IGF I), which is present in the vitreous fluid of diabetics, stimulates RPE cells, we examined the effects of IGF I on the proliferation, chemotaxis, and release of plasminogen activator by these cells. At the concentrations of IGF I tested, significant proliferation of RPE cells is seen. Significant chemotaxis of the RPE cells also is seen at all the concentrations of IGF I tested. The mean number of migrating cells per high-powered field in control studies was 43 +/- 13 (x +/- SEM), and for IGF I at 2.5 ng and 50 ng/ml the mean numbers of migrating cells were 96 +/- 17 and 483 +/- 62, respectively (P less than 0.001 for each comparison). The IGF I response was noted to be dose-dependent. The chemotactic response noted at 50 ng/ml of IGF I was greater than the positive chemotactic control of 10% fetal calf serum. Addition of alpha IR-3, an IGF I receptor antibody, eliminated the IGF I chemotactic response. The effect of IGF I on the secretion of plasminogen activators was assessed using an immunological assay for tissue-type plasminogen activator (t-PA) and plasminogen activator inhibitor (PAI). Media conditioned by RPE cells have measureable levels of PAI and t-PA antigen. IGF I supplementation resulted in an increase of t-PA secretion and PAI secretion over basal levels. These studies support a role for IGF I in modulating RPE cell function.     

Effect of insulin-like growth factors 1 and 2, and glucose on the migration and proliferation of bovine retinal pigment epithelial cellsin vitro

BACKGROUND: The retinal pigment epithelium (RPE) has been implicated in the development of diabetic retinopathy and it has been suggested that insulin-like growth factors (IGF) and glucose may be among those factors which are responsible for the RPE changes in diabetics. The purpose of this study was to investigate the effect of IGF-1, IGF-2, and glucose on the migration and proliferation of bovine RPE cells in vitro. METHODS: Primary cultures of bovine RPE cells were established from freshly enucleated eyes and passages 5-8 were used for these experiments. RPE cell migration was studied in confluent RPE cultures grown in multiwell plates. After inhibition of proliferation with mitomycin C (10 microg/ml) and partial denudation of the RPE in each well, the cells were incubated with IGF-1 (10 ng/ml), IGF-2 (10 ng/ml) or glucose (10 mM). Migration was measured as the number of cells that had entered the denuded area after 20 h. RPE cell proliferation was determined by [(3)H]-thymidine incorporation after incubation with IGF-1, IGF-2, and glucose for 24 h. Statistical analysis was performed with the paired Student's t test. RESULTS: Exposure of RPE cells to IGF-1, IGF-2, and glucose resulted in a significantly higher RPE cell migration as compared to the control medium (p < 0.008) with 21, 20, 17, and 9 cells/raster field, respectively. Additionally, IGF-1 (p = 0.004) and IGF-2 (p = 0.008) but not glucose caused a statistically significant stimulation of DNA synthesis with 761, 747, and 593 ccpm, respectively, as compared to the negative control (352 ccpm). CONCLUSION: This study indicates that IGF-1 and IGF-2 influence RPE cell migration and proliferation. This is further evidence that these factors are among those which have to be kept in mind when trying to modulate the development of diabetic eye diseases.     

反义寡核苷酸对人视网膜色素上皮细胞迁移的影响

目的探讨脂质体介导表皮生长因子(epidermal growthfactor receptor,EGFR)反义寡核苷酸对人视网膜色素上皮(retinal pigment epithelium,RPE)细胞迁移的影响。方法采用Murphy细胞计数方法评价反义寡核苷酸对人RPE细胞体外迁移的影响;分别应用ELISA法和半定量PCR检测反义寡核苷酸对RPE细胞EGFR蛋白和mRNA的抑制作用。结果脂质体介导EGFR反义寡核苷酸组与对照组比较,细胞迁移活性受到明显抑制(P<0.05),24h后抑制率75.27%.转染24h后EGFR蛋白和mRNA表达的抑制率分别为67.60%和35.20%.结论脂质体介导EGFR反义寡核苷酸可抑制EGFR蛋白表达和mRNA的表达,并可抑制人RPE细胞体外迁移,脂质体介导的反义寡核苷酸可能是针对RPE的一种有希望的基因治疗方法。     

Retinal pigment epithelial cells secrete substances that are chemotactic for monocytes

Monocyte/macrophages play a prominent role in several forms of retinal pathology including proliferative vitreoretinopathy, senile macular degeneration, and retinal wound healing. In each of these entities, the retinal pigment epithelium (RPE) is characteristically involved as well. Since RPE cells are known to secrete chemoattractants for astrocytes, we considered the possibility that they might secrete chemotactic factors for monocytes in addition. We have found in in vitro assays that a 5% concentration of medium from 6 different well-established RPE culture lines each consistently induced monocyte migration greater than that elicited by either buffer or unconditioned medium. "Checkerboard" analysis indicated that RPE culture supernatants induced optimal migration with a stimulus gradient (chemotaxis as opposed to chemokinesis alone). Chemotactic activity could be detected in eluates from ion exchange high performance liquid chromatography or gel filtration columns. Several peaks of activity suggested that more than one factor may be responsible for the ability to induce cell migration. The chemotactic activity was largely heat stable. The chemotactic factor induced only minimal migration of polymorphonuclear leukocytes. The secretion of chemotactic factors for monocytes could contribute significantly to the pathogenesis of several retinal diseases.     

EGF促进RPE细胞β2肾上腺能受体诱导的cAMP形成：受体间交互作用分析

研究证实表皮生长因子(EGF)不影响培养人眼视网膜色常上皮(RPE)细胞cAMP的基础水平，但促进异丙肾上腺索激活β₂受体后诱导cAMP水平升高的效应，井呈量效信赖关系。EGF对腺嘌呤核苷A₂受体激动剂NECA诱导cAMP水子升高的效应没有明显影响．细胞增殖分析表明，EGF刺激人眼RPE细胞增殖，而DibutyrylcAMP和异丙肾上腺素抑制RGF刺激增殖的效应。结果提示，在人眼RPE细胞EGF和β₂受体之间存在受体间交互作用． （中华眼底病杂志，1995，11：25-27）     

Effect of thalidomide, octreotide, and prednisolone on the migration and proliferation of RPE cells in vitro.

PURPOSE. The retinal pigment epithelium (RPE) is involved in the pathogenesis of age-related macular degeneration. The purpose of this study was to assess the effect of thalidomide, octreotide, and prednisolone on the proliferation and migration of bovine RPE cells in vitro. METHODS. The migration assay was performed in double-chamber-wells separated by a membrane filter with 8 microm pores. Cells were allowed to migrate vertically for 7 hr, afterwards the cells on both filtersides were fixed, stained, and the migrated cells were counted. To examine RPE proliferation, bovine RPE cells were seeded subconfluently followed by an incubation with octreotide, thalidomide or prednisolone in a concentration gradient for 24 hr. Stimulation or inhibition of DNA synthesis was measured by [(3)H]-thymidine incorporation. Statistical analysis was performed with the paired student's t-test. RESULTS. Statistically significant (p < 0.05) inhibition of RPE cell proliferation was measured for thalidomide at a concentration of 10-50 microg/ml, for octreotide at a concentration of 5 x 10(-4) and 5 x 10(-5) M, and for prednisolone at a concentration of 250 and 500 microg/ml as compared to the negative control. RPE cell migration was significantly (p < 0.05) inhibited by thalidomide at a concentration of 10 microg/ml, by octreotide at a concentration of 5 x 10(-5) M, and also by prednisolone at a concentration of 500 microg/ml as compared to the negative control. CONCLUSIONS. Although the main effect of thalidomide, octreotide, and prednisolone when treating patients with choroidal neovascular membranes is probably related to the inhibition of angiogenesis it should be kept in mind that these substances may additionally inhibit RPE proliferation and migration.