Perfusion of the subfoveal choriocapillaris affects visual recovery after submacular surgery in presumed ocular histoplasmosis syndrome

Effects of extracellular matrix and neighboring cells on induction of human embryonic stem cells into retinal or retinal pigment epithelial progenitors

To determine the effects of extracellular matrix and neighboring cells on the differentiation of human embryonic stem cells (hESC) into progenitors of retinal cells and/or retinal pigment epithelium (RPE). HESC were cultured on mouse PA6 stromal cells for approximately 2weeks to obtain neural progenitors. To induce photoreceptor marker expression, the neural progenitors were cultured on a confluent monolayer of ARPE19 or on laminin-coated dishes. To induce RPE markers, the neural progenitors were seeded onto human Bruch's membrane or Matrigel. Cells were examined morphologically and stained with different RPE or neural progenitor markers. Microarray techniques were used to compare the gene expression profiles of hESC cultured on mouse fibroblasts or neural progenitors on PA6 cells to the transcriptome of the adult neural retina and RPE. HESC cultured on PA6 cells expressed neural progenitor markers beta-tubulin III, PAX6, neural filament, GFAP and vimentin. Culturing these neural progenitors on confluent ARPE19 monolayer induced expression of the photoreceptor progenitor cell marker CRX; culturing neural progenitors on laminin substrates induced a neuronal phenotype with neurite formation. Neural progenitors expressed the RPE marker ZO-1 after culturing on Matrigel-coated dishes and the RPE marker Bestrophin after culturing on human Bruch's membrane explants. Hierarchical clustering analysis of samples suggested that when cultured on PA6 stromal cells hESC exhibited genetic characteristics towards differentiating into neural retina. Microarray analysis showed that after culturing on PA6 cells, stem cells expressed 117 new genes; among these there were 22 genes present in neural retina or RPE cells. The functions of these genes were highly related to cell proliferation, nervous system development and cell adhesion. HESC can be induced to differentiate into neural progenitors after culturing on PA6 cells. These neural progenitors can express RPE markers when cultured on Bruch's membrane or Matrigel, or photoreceptor markers when cultured on confluent ARPE19 or laminin. Additional studies are required to assess the function of hESC induced to express retinal or RPE markers prior to successful intraocular transplantation into animal models of retinal degeneration.

Adult retinal pigment epithelial transplantation in exudative age-related macular degeneration

PURPOSE

To improve visual function by retinal pigment epithelial (RPE) cell transplantation and systemic immunosuppression at the time of surgical removal of subfoveal choroidal neovascularization in exudative age-related macular degeneration (AMD).

DESIGN

An interventional case series of RPE transplantation in exudative AMD.

METHODS

Twelve patients (one eye only) underwent subfoveal membranectomy with transplantation of a sheet of adult human allogeneic RPE cells at a single institution and were followed for one year. Eligibility criteria included age >60, best-corrected acuity < or =20/63 and subfoveal neovascularization < or =9 disk areas on preoperative fluorescein angiography. All patients were started on triple immunosuppression postoperatively. The primary outcome measure was best-corrected vision, with contrast sensitivity and reading speed as secondary outcome measures.

RESULTS

The best-corrected visual acuity (P = .085), contrast sensitivity (P = .204), and the reading speed (P = .077) did not change significantly at one year compared with preoperative values. Transplants showed no signs of rejection in patients who were able to continue the immunosuppressants for six months. Postoperative surgical complications included cataract progression requiring surgery (three of eight phakic eyes), retinal detachment (three eyes), intraoperative retinal breaks (two eyes), and macular pucker (two eyes). None of the patients developed cystoid macular edema on postoperative fluorescein angiography or postoperative inflammation.

CONCLUSIONS

A sheet of adult human allogeneic RPE can be transplanted into the subretinal space in AMD patients at the time of subfoveal membranectomy. Systemic immune suppression appeared to prevent rejection of the transplanted tissue, but did not lead to an improvement in visual function.

Basic fibroblast growth factor inhibits choriocapillaris atrophy in rabbit

PURPOSE

To examine the effect of basic fibroblast growth factor on induced choriocapillaris atrophy in vivo.

METHODS

Choriocapillaris atrophy was surgically induced in rabbits by a hydraulic retinal detachment followed by debridement of the retinal pigment epithelium under the detached retina. Three concentrations of basic fibroblast growth factor (0.1 microg/0.1 ml, 1 microg/0.1 ml, or 5 microg/0.1 ml) were injected into the subretinal space and into the vitreous cavity 1, 3, and 5 days after the surgery. For control, only Tris buffer was injected in the same manner. The rabbits were euthanized 7 days after the surgery. Choroidal vascular casts were made and examined by scanning electron microscopy. The choriocapillaris atrophy was quantified by computer-assisted image analysis of photographs of the choriocapillaries. The area of the choriocapillaris and number of intercapillary spaces in the choriocapillaris that corresponded to the density of the capillary network were measured.

RESULTS

The average area of the choriocapillaris in the eyes treated with 1 microg/0.1 ml of basic fibroblast growth factor was significantly larger at 75.1 +/- 3.0% than that in the control eyes at 67.2 +/- 5.6% (P =.021). The average area of the choriocapillaris in the 0.1 microg/0.1 ml of basic fibroblast growth factor group was not statistically different from the control. The number of intercapillary spaces of the choriocapillaris was 132 +/- 12 in the 0.1 microg/0.1 ml of basic fibroblast growth factor group, 124 +/- 46 in the 1 microg/0.1 ml of basic fibroblast growth factor group, and 75 +/- 14 in the control group. The higher number of spaces in the treated group was statistically significant (P =.026).

CONCLUSIONS

Basic fibroblast growth factor decreased the atrophy of the choriocapillaris after removal of the retinal pigment epithelium in rabbit eyes. These results suggest that basic fibroblast growth factor may play a role in the survival of the choriocapillaris in vivo.

Retinal pigment epithelial cell transplantation after subfoveal membranectomy in age-related macular degeneration: clinicopathologic correlation

PURPOSE

To report the histopathology after retinal pigment epithelial cell transplantation and subfoveal membranectomy in age-related macular degeneration.

METHODS

An 85-year-old white woman with bilateral choroidal neovascularization underwent subfoveal membranectomy combined with transplantation of a sheet of human adult retinal pigment epithelium (retinal pigment epithelium) under the foveal center in the right eye. The patient was immunosuppressed postoperatively with prednisone, cyclosporine, and azathioprine. The patient died from congestive heart failure 114 days after surgery.

RESULTS

A patch of hyperpigmentation was visible at the transplant site under the foveola after surgery. Mound-like clusters of individual round, large densely pigmented cells were present in the subretinal space and outer retina in this area. There was loss of the photoreceptor outer segments and native retinal pigment epithelium in the center of the transplant bed, with disruption of the outer nuclear layer predominantly over regions of multilayered pigmented cells. Cystic spaces were present in the inner and outer retina. A residual intra-Bruchs membrane component of the original choroidal neovascular complex was present under the transplant site.

CONCLUSIONS

The transplant site contained clusters of round, pigmented cells that did not form a uniform monolayer in most areas. The morphology at the transplant site is consistent with the lack of visual improvement seen after surgery in this patient.

Update on surgical removal of choroidal neovascularization

Surgical management of choroidal neovascularization may offer patients with subretinal membranes another therapeutic option. Current techniques allow extraction of subretinal membranes, but not all patients have favorable clinical outcomes with such an approach. This article reviews the current state of subretinal surgery and attempts to summarize those characteristics that may predict good surgical results. Vitreoretinal surgical techniques for the management of subretinal membranes are reasonably well established. Certain characteristics of choroidal neovascularization have been identified that may suggest favorable surgical outcomes; however, no randomized prospective data are yet available to show the role of these procedures. The National Institutes of Health-sponsored Submacular Surgery Trials are designed to determine whether surgery or observation is better for eyes with subfoveal choroidal neovascularization in presumed ocular histoplasmosis syndrome or age-related macular degeneration and in eyes with age-related macular degeneration-associated hematomas.

The role of submacular surgery in the treatment of choroidal neovascular membranes

The growth of choroidal neovascular membranes (CNVM) beneath the macula can cause significant disturbances of central vision. Conditions such as age-related macular degeneration (AMD) and presumed ocular histoplasmosis syndrome (POHS) are the most common etiologies. The Macular Photocoagulation Study group presented data that clearly showed laser photocoagulation to be beneficial in the treatment of CNVM. Poor visual results and a high rate of recurrence have prompted clinicians to seek out alternative treatments. Experiences with CNVM removal utilizing submacular surgical techniques have shown that central visual function may be restored or preserved in POHS, multifocal choroiditis and idiopathic causes. The Submacular Surgery Trials were designed to investigate whether submacular surgery is more effective in retaining central acuity in patients with subfoveal CNVM, than observation alone. The goal of this paper is to review the role of submacular surgery in the treatment of subfoveal choroidal neovascular membranes.