Survival, migration and differentiation of retinal progenitor cells transplanted on micro-machined poly(methyl methacrylate) scaffolds to the subretinal space

Stem and progenitor cells can be combined with polymer substrates to generate tissue equivalents in culture. The replacement of retinal tissue lost to disease or trauma using retinal progenitor cells (RPCs) delivered on polymer scaffolds and transplanted into the sub-retinal space of the damaged retina is a promising therapeutic strategy. Micromachining-based, ultra-thin PMMA poly(methyl methacrylate) scaffolds may provide a suitable cytoarchitectural environment for tissue engineering and transplantation to the diseased eye. Here, adhesion of RPCs to polymer, as well as migration and differentiation in the host retina were compared for PMMA scaffolds (6 microm thickness) with either smooth or porous (11 microm diameter) surface topography. RPCs were cultured under identical conditions on smooth or porous laminin-coated polymer scaffolds and transplanted into the subretinal space of C57BL/6 mice. RPCs could be cultured on both scaffolds with similar results, although transplantation with non-porous scaffolds showed limited RPC retention. Porous scaffolds demonstrated enhanced RPC adherence during transplantation and allowed for greater process outgrowth and cell migration into the host retinal layers. Integrated cells expressed the mature neuronal marker neurofilament-200 (nf-200), the glial marker glial fibrillary acidic protein (GFAP) and the retinal-specific marker recoverin. No host foreign body response was seen. In conclusion, ultra-thin film PMMA scaffolds micromachined to contain through pores retain adherent RPCs to a considerably greater extent than unmachined versions during the transplantation process and can serve as a biocompatible substrate for cell delivery in vivo.

[Cancer associated retinopathy (CAR). Two clinical cases and review of the literature]

The cancer associated retinopathy (CAR) is a paraneoplasic retinopathy in which an antigen-antibody reaction, due to retinal antigens, also expressed in tumours, leads to degeneration of retinal photoreceptor cells. We observed in CHL-Luxembourg, 2 clinical cases of non-Hodgkin's lymphoma with severe prognosis in whom we described the presence of anti-recoverin antibodies. The CAR is most frequently associated with small cell lung and ovarian carcinomas. Clinical symptoms (phosphenes, progressive loss of eyesight) sometimes, occur before the diagnostics of primary cancer. Retinal degeneration may be assessed by electroretinogram, visual field, fundus oculi. A crossed reactivity between tumour and retinal antigens may initiate an antigen-antibody reaction, that implicates optic lesions. Different antigenic proteins have been evidenced, the most frequent being the recoverin. This protein plays a role in the adaptation to light and darkness. It is expressed in more than 50% of different types of neoplastic cells and would play a role in tumour proliferation. The antigen-antibody reaction leads to death by apoptosis of photoreceptor and bipolar retinal cells. These antirecoverin antibodies are also observed in other retinal degenerative diseases. The diagnosis is confirmed by titration of antibodies in the serum by Western Blot, Elisa and immunohistochemical methods. However, this diagnosis is by exclusion (vs. brain metastasis, drug toxicity, demyelinating diseases, autoimmune non paraneoplastic retinopathies). Corticosteroids are the only therapy that can bring some benefit. There is no value in starting a therapy if the retinal degeneration has reached an advanced stage. Note that the CAR must be distinguished from the Melanoma Associated Retinopathy (MAR) which is a similar paraneoplastic syndrome, but with rapid evolution of its symptoms and different etio-pathogenesis.

CNTF induces dose-dependent alterations in retinal morphology in normal and rcd-1 canine retina

Ciliary neurotrophic factor (CNTF) provides morphologic preservation of rods in several animal models of retinitis pigmentosa (RP). However, CNTF may alter photoreceptor morphology and rod photoreceptor differentiation in vitro, as well as affecting normal retinal electrophysiology. In addition, the capacity of CNTF to support other cell types affected secondarily in RP (cones and ganglion cells) is unclear. The purposes of this study were to examine the effects of CNTF upon a canine model of RP, the rod-cone degeneration (rcd-1) dog. Archival tissue from a previous study assessing the capacity of CNTF to rescue photoreceptors in rcd-1 dogs was used. One eye was treated for 7 weeks before being explanted. The contralateral eye was untreated. A total of 23 rcd-1 dogs and seven control dogs (four untreated and three CNTF-treated) were used. Morphometric data describing outer and inner nuclear layer thickness, inner retinal thickness, cones and ganglion cells were collected at nine evenly spaced points along each retina and analysed using a mixed effects model. Immunohistochemistry was performed on a subset of 11 dogs for expression of rhodopsin, human cone arrestin (hCAR) and recoverin. CNTF protected the outer nuclear layer and increased inner retinal thickness in a dose-dependent manner (both were maximal at CNTF doses of 1-6 ng day-1). Significant cone loss or reduction of inner nuclear layer width in rcd-1 did not occur in this model, therefore we were unable to assess the protective effect of CNTF upon these parameters. CNTF did not afford significant ganglion cell protection. CNTF induced morphologic changes in rods and ganglion cells, as well as reducing expression of hCAR and rhodopsin, but not recoverin. The dose of CNTF which provided optimal outer nuclear layer protection also resulted in several other effects, including altered ganglion cell morphology, increased thickness of the entire retina, and reduced expression of some phototransduction proteins. These changes were more marked in rcd-1 retinas than in wild-type retinas. This implies that the consequences of CNTF treatment may be substantially influenced by the cellular context into which it is introduced.