Computational molecular phenotyping of retinal sheet transplants to rats with retinal degeneration

• Published in: The European journal of neuroscience Vol. 35; no. 11; pp. 1692 - 1704
• Main Authors: Seiler, M. J., Jones, B. W., Aramant, R. B., Yang, P. B., Keirstead, H. S., Marc, R. E.
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 01.06.2012
• Subjects: Animals; Computational Biology - methods; CRALBP; electron microscopy; Female; GABA; Graft Survival - physiology; Humans; Male; molecular phenotyping; Neural Stem Cells - cytology; Neural Stem Cells - physiology; Neural Stem Cells - transplantation; Phenotype; Rats; Rats, Transgenic; Retina - cytology; Retina - embryology; Retina - transplantation; Retinal Degeneration - pathology; Retinal Degeneration - physiopathology; Retinal Degeneration - surgery; retinal transplantation; synaptic circuitry
• ISSN: 0953-816X; 1460-9568
• DOI: 10.1111/j.1460-9568.2012.08078.x

Retinal progenitor sheet transplants have been shown to extend neuronal processes into a degenerating host retina and to restore visual responses in the brain. The aim of this study was to identify cells involved in transplant signals to retinal degenerate hosts using computational molecular phenotyping (CMP). S334ter line 3 rats received fetal retinal sheet transplants at the age of 24–40 days. Donor tissues were incubated with slow‐releasing microspheres containing brain‐derived neurotrophic factor or glial cell‐derived neurotrophic factor. Up to 265 days after surgery, eyes of selected rats were vibratome‐sectioned through the transplant area (some slices stained for donor marker human placental alkaline phosphatase), dehydrated and embedded in Eponate, sectioned into serial ultrathin datasets and probed for rhodopsin, cone opsin, CRALBP (cellular retinaldehyde binding protein), l‐glutamate, l‐glutamine, glutathione, glycine, taurine, γ‐aminobutyric acid (GABA) and DAPI (4′,6‐diamidino‐2‐phenylindole). In large transplant areas, photoreceptor outer segments in contact with host retinal pigment epithelium revealed rod and cone opsin immunoreactivity whereas no such staining was found in the degenerate host retina. Transplant photoreceptor layers contained high taurine levels. Glutamate levels in the transplants were higher than in the host retina whereas GABA levels were similar. The transplant inner nuclear layer showed some loss of neurons, but amacrine cells and horizontal cells were not reduced. In many areas, glial hypertrophy between the host and transplant was absent and host and transplant neuropil appeared to intermingle. CMP data indicate that horizontal cells and both glycinergic and GABAergic amacrine cells are involved in a novel circuit between transplant and host, generating alternative signal pathways between transplant and degenerating host retina. Computational molecular phenotyping (CMP) was used to identify cells involved in the functional connections between retinal sheet transplants and degenerate rat retinas. Outer segments of transplant rods and cones were immunoreactive for opsin but nothing was seen in the host retina. Neuropil mingling occurred with absent glial barriers. CMP data indicate that horizontal cells and amacrine cells are involved in a novel circuit between transplant and host.