The kinase inhibitor PKC412 suppresses epiretinal membrane formation and retinal detachment in mice with proliferative retinopathies

PURPOSE: Platelet-derived growth factor (PDGF) is an important stimulatory factor for proliferative retinopathies. Expression of PDGF-B in the retinas of transgenic mice (hemizygous rho/PDGF-B mice) results in rapid-onset retinal detachment caused by proliferation of glial cells, endothelial cells, and pericytes, whereas expression of PDGF-AA (homozygous rho/PDGF-A or PDGF-AA mice) causes slowly progressive retinal detachment from proliferation of glial cells. In this study, we investigated the effect in rho/PDGF-B and rho/PDGF-AA mice of several different receptor kinase inhibitors. METHODS: Hemizygous rhoPDGF-B or homozygous rho/PDGF-A mice were treated orally with PKC412 (an inhibitor of PDGF, VEGF, and c-kit receptor kinases and several isoforms of PKC), PTK787 (an inhibitor of PDGF, VEGF, and c-kit receptor kinases), SU1498 (an inhibitor of VEGF receptor kinases), imatinib mesylate (an inhibitor of PDGF, c-kit, and v-abl receptor kinases), or vehicle, and at appropriate time points epiretinal membrane (ERM) formation and retinal detachment were quantified. RESULTS: In either rho/PDGF-B or rho/PDGF-A mice, oral administration of PKC412 or PTK787, but not SU1498 or imatinib mesylate, significantly reduced ERM formation. PKC412 reduced the incidence of severe retinal detachments in both models and PTK787 did so in homozygous rho/PDGF-A mice. CONCLUSIONS: These data indicate that PKC412 (and possibly PTK787) has appropriate activity and sufficient intraocular bioavailability after oral administration to prevent retinal detachment in models of proliferative retinopathy. PKC412 should be considered for treatment of vascular and nonvascular proliferative retinopathies in humans.     

Immunocytochemical study of an eye with proliferative vitreoretinopathy and retinal tacks

After an eye-wall resection for a choroidal melanoma, a 32-year-old woman had subsequent retinal detachment with proliferative vitreoretinopathy (PVR), and an unsuccessful attempt at repair with retinal tacks. Gross and light-microscopic examination of the globe revealed a total retinal detachment with extensive preretinal and subretinal membranes. The membranes surrounded the tack heads and extended in taut bands to form a tractional detachment of the pars plana. The membranes contained glial and nonglial cells. The glial cells immunolabeled for glial fibrillary acidic protein (GFAP), carbonic anhydrase-C (CA-C), vimentin, and glutamine synthetase (GS), thus suggesting that they were Müller's cells. While the tacks did not seem to cause PVR, in this case they may have provided an anchoring point from which membranes were able to exert traction on the retina and pars plana.     

血小板源性生长因子对增生性玻璃体视网膜病变增生膜形成的影响

目的 探讨血小板源性生长因子（platelet-derived growth factor,PDGF)在增生性玻璃体视网膜病变（proliferative vitreoretinopathy,PVR)增生膜形成中的作用及PVR增生膜中是否存在PDGF的分泌细胞与靶细胞。方法 选择PVR患者的手术标本,其中视网膜前膜（epiretinal membrane,ERM)和视网膜下膜（subretinal membrane,SRM)标本各7例。采用免疫电镜方法检测PDGF及其受体在ERM、SRM中的表达及其与ERM、SRM中两种主要细胞成分即视网膜色素上皮细胞和神经胶质细胞的关系。结果 PDGF－A基7例ERM中均表达阳性,在7例SRM中5例表达阳性,标记物主要位于ERM、SRM部分细胞的胞质中。PDGF－B在7例ERM中均表达阳性,在6例SRM中5例表达阳性,标记物主要位于SRM、SRM的部分细胞胞质中,尤其集中于细胞质内一些电子密度高的椭圆形或不规则形的分泌颗粒中。提示PDGF可由ERM、SRM局部细胞产生,其在ERM、SRM的发病中起重要作用。本实验中PDGF－A和PDGF－B分别与细胞角蛋白和神经胶质纤维酸性蛋白双标记,结果显示细胞角蛋白标记阳性的细胞即视网膜色素上皮细胞和神经胶质纤维酸性蛋白标记阳性细胞－神经胶质细胞中的PDGF－A、PDGF－B蛋白表达阳性,表明视网膜色素上皮细胞和神经胶质细胞是PDGF的分泌细胞。结论 PDGF可由PVR增生膜中的细胞产生,在PVR的发病中起重要作用。视网膜色素上皮细胞和神经胶质细胞是PDGF的分泌细胞,从而为自分泌物、旁分泌机制提供依据。     

Inverse levels of pigment epithelium-derived factor and vascular endothelial growth factor in the vitreous of eyes with rhegmatogenous retinal detachment and proliferative vitreoretinopathy

PURPOSE: To determine the vitreous levels of pigment epithelium-derived factor and vascular endothelial growth factor in eyes with rhegmatogenous retinal detachment and proliferative vitreoretinopathy. DESIGN: Prospective, noncomparative case series. METHODS: Pigment epithelium-derived factor and vascular endothelial growth factor concentrations were measured by enzyme-linked immunosorbent assay in 26 eyes with retinal detachment, 6 with proliferative vitreoretinopathy, and 14 with an idiopathic macular hole. RESULTS: Pigment epithelium-derived factor concentration in proliferative vitreoretinopathy (0.57 +/- 0.05 microg/ml) was lower (P =.0069), and retinal detachment (2.37 +/- 0.34 microg/ml) was higher (P =.16) than that in macular hole (1.71 +/- 0.22 microg/ml). Vascular endothelial growth factor concentration (168 +/- 139 microg/ml) in proliferative vitreoretinopathy was significantly higher than that in retinal detachment (11 +/- 11 microg/ml, P =.0084) and macular hole (not detectable, P =.0095). CONCLUSION: Lower levels of pigment epithelium-derived factor and higher levels of vascular endothelial growth factor may be related to ocular cell proliferation.     

Laser photocoagulation in preproliferative retinopathy of incontinentia pigmenti.

Incontinentia Pigmenti is a rare, X-linked, dominant disorder in which affected female infants develop characteristic abnormalities of the skin, central nervous system, hair, teeth, and eyes. Ocular abnormalities occur in about 35% of patients and consist of proliferative vitreoretinopathy, retinal detachment, strabismus, cataract, microphthalmia, optic nerve atrophy, and iris hypoplasia. Retinal vascular abnormalities, ranging from peripheral retinal avascularity to neovascular and fibrous proliferation with traction retinal detachment, are the primary cause of severe visual dysfunction in patients. Therapeutic intervention with laser photocoagulation and cryotherapy for the proliferative vitreoretinopathy of incontinentia pigmenti has met with variable success. We report a case in which laser photocoagulation was used at the onset of retinopathy with subsequent resolution of the vasculopathy.     

Late traction detachment in retinopathy of prematurity or ROP-like cases

Five cases of traction retinal detachment occurring later in life as a sequel of cicatricial retinopathy of prematurity or showing the clinical picture of retinopathy of prematurity are reported. They presented with taut membranes in vitreous cavity, causing traction retinal detachment, and often showed preretinal membranes. These membranes were collagen-rich and contained cells with glial characteristics. They seemed to be continuously produced on the surface of the retina from which they detached sometimes in multiple generations. It is likely that chronic exudation from vascular abnormalities is a stimulus for this proliferation. These cases are very similar to other vitreoretinal proliferations in association with vascular abnormalities (Coats' and von Hippel disease, exudative vitreoretinopathy). Supported by: Helena Rubinstein Foundation, N.Y., and Research to Prevent Blindness, N.Y.Presented at the Club Jules Gonin, Vienna, Austria, September 9, 1992     

实验性增殖性玻璃体视网膜病变的膜形成及超微结构观察

将培养的异体兔皮成纤维细胞注入兔眼玻璃体中成功地形成了增殖性玻璃体视网膜病变(PVR)。术后28天牵引性视网膜脱离发生率为73%。结果显示增殖膜主要由成纤维细胞、神经胶质细胞、肌成纤维细胞及巨噬细胞构成。玻璃体内可见大量的淋巴细胞、单核细胞及浆细胞。文中详细观察了增殖膜形成过程,以及增殖膜的超微结构,并对实验性PVR的发生机理进行了初步的探讨。     

Antiproliferative drugs in the treatment of experimental proliferative vitreoretinopathy

We used an experimental model of proliferative vitreoretinopathy (PVR) and cell-induced traction retinal detachment to study the therapeutic value of six cytotoxic drugs (actinomycin C, colchicine, cytosine arabinoside hydrochloride, 5-fluorodeoxyuridine, vinblastine sulfate, and daunomycin). Pigmented rabbits were injected with 2.5 X 10(5) cultured homologous dermal fibroblasts. At the same time, cytotoxic drugs were injected into the vitreous in an attempt to inhibit cellular proliferation. The sensitivity of the cells to the drug was also tested in vitro before injection. Daunomycin at a dose of 10 nmol per eye stopped cellular proliferation and subsequent traction retinal detachment in vivo. The electroretinogram (ERG) showed no evidence of drug-induced retinal toxicity with this dose of daunomycin. No alteration in frequency or severity of vitreal membranes and retinal detachment was observed after injection of equivalent doses of the other drugs.     

Thrombin stimulates the proliferation of human retinal glial cells

Retinal glial cells may play a role in most of the proliferative retinopathies. Although glial cell proliferation is a frequent event in retinal pathobiology, no specific mitogens for human retinal glial cells are known. Using cultured retinal glial cells obtained from postmortem adult human eyes, we found that thrombin stimulates glial cell proliferation in a dose-dependent manner with a half-maximal concentration of 100 ng/ml (0.4 U/ml). Thus, thrombin may be a plasma-derived mitogen capable of stimulating retinal glial cells to proliferate when there is a breakdown of the blood-retinal barrier. We also observed that this proliferative response of retinal glia requires more than 6 h of continuous exposure to thrombin. This finding suggests that a thorough wash-out of a thrombin-containing infusate and/or the rapid inactivation of this molecule would prevent thrombin from exacerbating a proliferative disorder of the retina.     

Thrombin stimulates the proliferation of human retinal glial cells

Retinal glial cells may play a role in most of the proliferative retinopathies. Although glial cell proliferation is a frequent event in retinal pathobiology, no specific mitogens for human retinal glial cells are known. Using cultured retinal glial cells obtained from postmortem adult human eyes, we found that thrombin stimulates glial cell proliferation in a dose-dependent manner with a half-maximal concentration of 100 ng/ml (0.4 U/ml). Thus, thrombin may be a plasma-derived mitogen capable of stimulating retinal glial cells to proliferate when there is a breakdown of the blood-retinal barrier. We also observed that this proliferative response of retinal glia requires more than 6 h of continuous exposure to thrombin. This finding suggests that a thorough wash-out of a thrombin-containing infusate and/or the rapid inactivation of this molecule would prevent thrombin from exacerbating a proliferative disorder of the retina.     

Dissection of epiciliary tissue to treat chronic hypotony after surgery for retinal detachment with proliferative vitreoretinopathy

Surgery was performed on nine eyes of nine consecutive patients with chronic postoperative hypotony after prior vitreous surgery for retinal detachment and proliferative vitreoretinopathy. The operation included lysis of adhesions between the iris and the ciliary processes and removal of lens remnants and other fibrocellular tissue covering and/or causing traction on the pars plicata. The preoperative intraocular pressure was less than or equal to 5 mm Hg in all eyes, and the final postoperative intraocular pressure was 8 to 20 mm Hg in five eyes, 6 mm Hg in one eye, 4 mm Hg in one eye, and 0 mm Hg in two eyes. Minimum postoperative follow-up was 7 months and average follow-up was 10 months. This form of surgery to uncover and minimize traction on the ciliary body substantially increased the intraocular pressure in most of the treated cases and suggests that iridociliary adhesions and tissue proliferation covering and/or causing traction on the ciliary processes account for chronic postoperative hypotony in some cases after extensive surgery for proliferative vitreoretinopathy.     

Stage specificity of novel growth factor expression during development of proliferative vitreoretinopathy

OBJECTIVE: To compare the relative levels of connective tissue growth factor (CTGF), platelet-derived growth factor alpha (PDGF-AA), and hepatocyte growth factor (HGF) in glial and retinal pigment epithelial (RPE) cells of epiretinal membranes from proliferative vitreoretinopathy (PVR). METHODS: A total of 37 PVR membranes, of various stages, underwent fluorescent immunohistochemisty and confocal laser scanning microscopy to localize CTGF, HGF, and PDGF-AA in RPE and glial cells. RESULTS: Numerous RPE, and relatively fewer glial cells, were found in all stages of PVR. CTGF immunoreactivity increased from early to late stage PVR and was principally expressed by RPE cells in early stage, and by glial cells in late stage PVR. HGF, expressed by both RPE and glial cells, was principally expressed in mid-stage PVR. PDGF-AA, expressed by both cell types, demonstrated a uniform level of staining throughout all stages of PVR. CONCLUSIONS: RPE and glial cells contribute to the expression of CTGF, HGF, and PDGF-AA during PVR, but with specific developmental patterns. PDGF-AA is expressed uniformly throughout all stages of PVR, while HGF expression peaks during mid stage, and CTGF expression is highest during late stage PVR. These results allow for the development of stage-specific therapeutics for PVR that may allow targeting of the early proliferative and/or the late tractional stages of PVR.     

The pathophysiology of proliferative vitreoretinopathy in its management

Cellular proliferation following retinal reattachment surgery frequently results in contraction and subsequent recurrent detachment of the retina, negating an initial successful reattachment. This process has been called by a variety of names, such as massive vitreous retraction, massive preretinal retraction, and, more recently, proliferative vitreoretinopathy. Although a good start has been made by the Retina Society to classify the various types of proliferative vitreoretinopathy, some modifications in the classification are required. The fundamental problem in the treatment of proliferative vitreoretinopathy is a lack of knowledge regarding the factors that stimulate the proliferation of cells. The vitreoretinal surgeon should recognize in the life cycle of this process that stage which an eye with retinal detachment has reached. If there is no active cellular proliferation, then a scleral buckle will usually suffice. If there is traction from epiretinal membranes which cannot be relieved by a buckle, then vitrectomy and adjunct procedures are necessary. If there is active cellular proliferation and epiretinal membranes, then the arguments related to proper timing of vitrectomy must be considered. In cases where the retinal holes can be identified and closed, scleral buckling may be performed with subsequent delayed vitrectomy. In most cases, in my experience, a combination of revision of the scleral buckle is required at the time of vitrectomy and membrane segmentation for proliferative vitreoretinopathy. Until such time as drugs are available to inhibit cellular proliferation or until our basic understanding of the cell biology of this process allows other means of pharmacologic intervention, mechanical approaches will remain necessary for the treatment of the most advanced cases.     

Retinal microglia: a new cell in idiopathic proliferative vitreoretinopathy?

Despite numerous studies of the role of mononuclear phagocytes in proliferative vitreoretinopathy, the origin of these cells has remained obscure. Notably, retinal microglial cells have consistently been neglected. Applying double label immunohistology with a set of new cell markers to 37 preretinal traction membranes, we have identified a distinct population of proliferating cells presumably of microglial origin. The identification of microglia relies on positive labels for LN-1, Ricinus communis agglutinin-1, vimentin, HLA-DR, and nucleoside diphosphatase, and negative labels for Leu-M1, Leu-M3, EBM-11, von Willebrand factor, CD22, cytokeratin, and glial fibrillary acidic protein. Microglia are much more prevalent in idiopathic than in traumatic proliferative vitreoretinopathy and insignificant in proliferative diabetic retinopathy. HLA-DR expression was not restricted to pigment epithelium as previously reported but also observed in microglia, macrophages, endothelial and glial cells. The detection of retinal microglial cell proliferation suggests a pathogenetic role of these cells and questions current concepts of the cellular biology of proliferative vitreoretinopathy.     

Suprachoroidal collection of internal tamponading agents through a choroidal hole

We report two cases of significantly large choroidal holes following penetrating trauma that led to suprachoroidal migration of internal tamponading agents during repair of retinal detachments with proliferative vitreoretinopathy secondary to penetrating trauma. In the first case, choroidal hole was a direct result of the injury and was identified immediately after vitreoretinal surgery which was done for traumatic retinal detachment with hemorrhagic choroidal detachment. In the second case, the hole occurred over a period of several months after the repair of traumatic retinal detachment with silicone oil tamponade. This was attributed to progressive fibrosis exerting traction on the bare choroid/retinal pigment epithelium. Choroidal hole significant enough to cause suprachoroidal migration of internal tamponading agents is a very rare complication seen in eyes with posttraumatic retinal detachment with proliferative vitreoretinopathy.     

Mitogenic and chemotactic effects of platelet-derived growth factor on human retinal glial cells.

Glial cell migration and proliferation appear to play a role in many of the proliferative retinopathies. Knowledge concerning the regulation of the migratory and proliferative responses of glial cells to pathophysiologic conditions in the human retina is limited. Here, we report that platelet-derived growth factor (PDGF) has both mitogenic and chemotactic effects on human retinal glial cells in culture. These effects of PDGF support the idea that this growth factor may be one of the molecules influencing glial cell activities in the proliferative retinopathies. Both the mitogenic and chemotactic responses of retinal glial cells to PDGF could be inhibited by the calcium-channel blocker, nifedipine. Although this finding suggests that nifedipine-sensitive calcium channels may help mediate these responses to PDGF, an electrophysiologic effect of PDGF on voltage-gated calcium channels was not detected. Also, the concentration of nifedipine required to inhibit proliferation was higher than the dose needed to block calcium channels. It seems likely that nifedipine inhibits the mitogenic and chemotactic responses of human retinal glial cells to PDGF by affecting cellular processes in addition to calcium channels.     

The treatment of advanced retinopathy of prematurity by cryotherapy and scleral buckling surgery

Seventeen eyes of nine extremely premature infants with severe acute proliferative retinopathy of prematurity (ROP, Grades III-V) were treated. Cryotherapy alone was used in ten eyes to ablate extensive areas of avascular retina to thereby induce involution of widespread intravitreous neovascularization. No attempt was made to directly treat the arteriovenous shunt or neovascularization itself. Scleral buckling surgery was used in combination with cryotherapy in seven additional eyes to relieve diffuse vitreous traction to intravitreous neovascularization which had caused extensive traction retinal detachment. Cryotherapy was uniformly successful in causing involution of widespread intravitreous neovascularization in all patients treated. Scleral buckling surgery was initially effective in reattaching the retina in all cases but late manifestations of severe ongoing vitreoretinal traction required additional open-sky vitrectomy in two eyes and resulted in inoperable recurrent total traction retinal detachment in one eye and extensive macular scarring in another. A comparison is made between the proliferative retinopathies seen in ROP and diabetes mellitus and a rationale for effective cryotherapy in ROP is presented. In our clinical experience, the single most important prognostic factor determining the potential severity of ROP is the width and extent of the retinal avascular zone. The wider the zone, the greater the probability of rapid progression from early to advanced grades of disease.     

Perisilicone proliferation after vitrectomy for proliferative vitreoretinopathy

From 1983 to 1986, silicone oil injections were used to treat 31 patients with retinal detachment (RD) and advanced proliferative vitreoretinopathy (PVR). In 19 eyes (61%), perisilicone proliferation (PSP) developed causing recurrent RDs in 15 eyes (49%). At an average of 5 weeks after surgery, PSP occurred and was characterized by extensive transparent preretinal membranes with denser focal areas. Microscopic examination of five preretinal membranes showed droplets of silicone oil and necrotic cells on the silicone side and glial or retinal pigment epithelial cells, or both, on the retinal side, often in layers separated by extracellular matrix. Silicone oil was present in periretinal membranes removed several months after the intraocular silicone had been evacuated indicating that silicone within cells may persist despite the removal of silicone. The use of silicone oil to provide tamponade in eyes with recurrent PVR is associated with a high incidence of periretinal proliferation that frequently leads to recurrent RD and visual failure.     

Intraoperative perfluorocarbon liquids in the management of proliferative vitreoretinopathy

Three low-viscosity perfluorocarbon liquids were used intraoperatively for hydrokinetic manipulation of the retina during vitreous surgery for retinal detachment with advanced proliferative vitreoretinopathy. All 23 patients had massive proliferative vitreoretinopathy (Grade D, Retina Society classification), and 16 (69.6%) had Grade D-3 with a closed-funnel configuration. In 21 eyes the retina could be flattened intraoperatively by perfluorocarbon liquids without requiring posterior retinotomy for internal drainage of subretinal fluid. The temporary mechanical fixation of the retina provided by this tool facilitated the removal of epiretinal membranes and release of traction. Fifteen eyes (65.2%) maintained long-term retinal reattachment with follow-up of six months or more. These liquids are useful adjuncts in the management of retinal detachment with severe proliferative vitreoretinopathy.     

血小板源性生长因子受体a在兔增殖性玻璃体视网膜病变中的作用

目的 血小板源性生长因子(platelet-derived growth factor,PDGF)可引起增殖性玻璃体视网膜病变,本研究评价特异性的PDGF-a受体酪氨酸激酶阻断剂AG1295对兔PVR的治疗作用.方法 兔结膜成纤维细胞(rabbit conjunctical fibroblats,RCF)培养,用MTT法检测PDGF-AA和-BB以及AG1295和AG1296对兔RCF增殖状况的影响.眼视网膜电图检查和HE染色分析药物的毒性.建立PVR动物模型,玻璃体腔内分别给予AG1295和AG1296.用牵引性视网膜脱离(tractional ratinal detachment,TRD) 的发生率评价药物的体内疗效.结果 体外10umol/L的AG1295和AG1296和均可显著抑制由PDGF-AA和-BB诱导的成纤维细胞的增生,体内100umol/L AG1295和AG1296均减慢了兔TRD的发生,但AG1295的作用仅持续至14d.相同浓度的AG1296和AG1295相比,作用更持久.在两个治疗组中,均未发现明显的视网膜毒性.结论 特异性的PDGF-a受体酪氨酸激酶抑制剂AG1296可显著抑制兔TRD的发生,其作用明显强于PDGF-a受体酪氨激酶抑制AG1295,提示PDGF对PBR的促进作用主要由a受体介导,这一通路的阻断可能成为治疗PVR的一种方法.