These data show rapid microglial cell recruitment and activation following the axotomy-induced cell death of differentiated ganglion cells. The processes of microglial cell activation and cell death are slower in the outer retina.

In this study we wanted to examine how an adult neuroretina from an animal with an eye similar to the human one survives in vitro. We also wanted to investigate how the culture process affects the adult retina when used in a transplantation paradigm. Full-thickness neuroretinal sheets from adult porcine eyes were dissected into pieces measuring 3 mm in diameter. These were kept in culture for 1-3 days. After this time, the explants were fixed or transplanted subretinally to adult pigs, which were killed after 72-74 days. Transplanted eyes, as well as tissue kept in culture only, were processed for hematoxylin and eosin staining and immunohistochemistry. Explants kept 1 day in vitro (DIV) displayed the normal morphology. In these specimens, single pyknotic cells were evident in the outer nuclear layer (ONL) and ganglion cell layer, but were more frequent in the inner nuclear layer (INL). After longer times in vitro, severe degenerative changes appeared. Transplanted explants kept 1 DIV prior to transplantation exhibited normal retinal lamination in two out of four specimens. Transducin and recoverin labeling revealed photoreceptors with inner segments in these grafts. Rod bipolar cells displayed a normal morphology. Vertically arranged Müller cells were also seen in the laminated grafts. Two of the three transplants kept 2 DIV displayed minimal lamination. Eyes with transplants kept 3 DIV prior to transplantation displayed degenerated grafts in all eyes. This study shows that adult porcine neuroretinal explants kept in culture for 1 day display a normal morphology in their major part. Additionally, 1-day explants can survive transplantation with retained morphology even after several months. This indicates the possibility of storing adult donor tissue between harvest and transplantation. The culture system may also be used in the future as a tool for manipulating retinal donor tissue prior to transplantation. INTRODUCTIONtice. Transplantation of adult neuronal tissue has previously been associated with poor graft survival (1,27). In contrast, we have previously shown that adult donor For a number of years experiments involving retinal transplantation have been performed in the laboratory tissue can be used for retinal transplantation in the rabbit eye if the neuroretina is kept as a full-thickness sheet, and the clinic, in an attempt to restore the degenerated retina in retinitis pigmentosa and age-related maculohandled with great care, and transplanted within 8 h. Such grafts survive and retain their laminated morpholpathy (2,4,10,18). Different models of retinal grafts have been used in the transplantation paradigm ogy for an extended period of time (28).In the present study, we wanted to extend our earlier (e.g., transplants of cell suspensions, fragmented transplants, and full thickness neuroretinal transplants) (10, results from the rabbit eye to include an eye more similar to the human one. The porcine eye is of a size com-14,17).In almost all retinal transplantation experiments, imparable to the human eye...

The procedure of culturing retina involves several steps causing severe traumatic effects on the tissue, such as ganglion cell axotomy, interruption of the blood flow as well as separation from the retinal pigment epithelium (RPE). In this paper, we have shown that addition of GDNF in the culture medium attenuates the effect of these steps, resulting in enhanced preservation of several retinal neuronal subtypes. The results may be of importance for research in retinal transplantation where storage time of the donor tissue prior to transplantation is a critical issue.

Purpose: To explore neuroretinal transplantation in a large-animal model of severe retinitis pigmentosa, and to establish graft development, long-term survival, graft-host integration and effects on the host retina.Methods: Rhodopsin transgenic pigs, aged 6 months, in 1 eye received a fetal full-thickness neuroretinal sheet in the subretinal space by means of vitrectomy and retinotomy. Six months postoperatively, eyes were studied in the light microscope, and with immunohistochemical markers. Full-field ERG was performed at 4 and 6 months.Results: Laminated grafts with well organized photoreceptors, rod bipolar cells and Müller cells were found in 5 out of 6 eyes. Neuronal connections between graft and host retina were not seen. In the 5 eyes containing a graft, the number of surviving rods in the host retina was significantly higher compared with unoperated eyes. The ERG did not reveal any significant difference in b-wave amplitude between operated and control eyes, but the cone derived response in operated eyes increased significantly from 4 to 6 months while the rod response in control eyes decreased significantly. Conclusions:Fetal full-thickness neuroretina can be transplanted safely to an eye with a severe retinal degeneration. In their major part, the transplants develop a normal laminated morphology and survive for at least 6 months. Graft and host retinal neurons do not form connections. Retinal function in the host is reduced initially by the surgical trauma but the presence of a well laminated graft counteracts this effect and rescues rods from degeneration.

Purpose: It has recently been shown that the flap pedicle does not supply blood to a tarsoconjunctival graft in the modified Hughes procedure in patients. This raises questions concerning the rate of revascularization of the free skin graft commonly used to reconstruct the anterior lamella. The aim of this study was, thus, to monitor the course of revascularization in free skin grafts overlying modified Hughes tarsoconjunctival flaps, using laser-based techniques. Methods: Free skin grafts from the upper eyelid or upper arm in 9 patients were used to cover a tarsoconjunctival flap according to the modified Hughes procedure. Blood perfusion was monitored using laser speckle contrast imaging, and vascular reactivity was studied with laser Doppler velocimetry after heating the tissue to 44°C. Measurements were made at the time of surgery (baseline) and at 1, 3, 8, and 16 weeks postoperatively. Results: The gradual increase in perfusion of the free skin grafts during the healing process indicates revascularization. A slight increase in perfusion was seen already after 1 week. Perfusion reached 50% of the baseline after 3 weeks, and complete restoration of perfusion was seen after 8 weeks. The vascular function monitored with heat-induced hyperemia increased in a similar fashion. Conclusions: Full-thickness skin grafts revascularize within 3 to 8 weeks, despite overlying a tarsoconjunctival flap, which has recently been reported to be avascular. This provides further evidence that it should be possible to repair large eyelid defects using free full-thickness eyelid grafts.