Karin Warfvinge

Progenitor cells from the porcine neural retina express photoreceptor markers after transplantation to the subretinal space of allorecipients.

Work in rodents has shown that cultured retinal progenitor cells (RPCs) integrate into the degenerating retina, thus suggesting a potential strategy for treatment of similar degenerative conditions in humans. To demonstrate the relevance of the rodent work to large animals, we derived progenitor cells from the neural retina of the domestic pig and transplanted them to the laser‐injured retina of allorecipients. Prior to grafting, immunocytochemical analysis showed that cultured porcine RPCs widely expressed neural cell adhesion molecule, as well as markers consistent with immature neural cells, including nestin, Sox2, and vimentin. Subpopulations expressed the neurodevelopmental markers CD‐15, doublecortin, β‐III tubulin, and glial fibrillary acidic protein. Retina‐specific markers expressed included the bipolar marker protein kinase Cα and the photoreceptor‐associated markers recoverin and rhodopsin. In addition, reverse transcription‐polymerase chain reaction showed expression of the transcription factors Dach1, Hes1, Lhx2, Pax6, Six3, and Six6. Progenitor cells prelabeled with vital dyes survived as allografts in the subretinal space for up to 5 weeks (11 of 12 recipients) without exogenous immune suppression. Grafted cells expressed transducin, recoverin, and rhodopsin in the pig subretinal space, suggestive of differentiation into photoreceptors or, in a few cases, migrated into the neural retina and extended processes, the latter typically showing radial orientation. These results demonstrate that many of the findings seen with rodent RPCs can be duplicated in a large mammal. The pig offers a number of advantages over mice and rats, particularly in terms of functional testing and evaluation of the potential for clinical translation to human subjects.

Differentiation of Nerve Fibers Storing CGRP and CGRP Receptors in the Peripheral Trigeminovascular System.

Background The dura mater with the meningeal artery has since long been hypothesized to play an important role in migraine. It has been suggested that neuropeptides such as calcitonin gene-related peptide (CGRP) and substance P can activate dura mast cells leading to secretion of vasoactive, pro-inflammatory and neurosensitzing mediators, thereby contributing to migraine pathogenesis. Method: Immunofluorescence was used to study the detailed distribution of and its receptor componentscalcitonin receptor-like receptor (CLR) and receptor activity modifying protein 1 (RAMP1)in whole-mount rat dura mater, using a set of newly characterized antibodies. Their relation to each other, to mast cells, myelin, substance P, neuronal nitric oxide synthase (nNOS), pituitary adenylate cyclase-activating polypeptide (PACAP) and vasoactive intestinal peptide (VIP) were studied. In addition, we examined expression of CGRP and its receptor components in fresly isolated human dura vessels.

Cerebellar distribution of calcitonin gene-related peptide (CGRP) and its receptor components calcitonin receptor-like receptor (CLR) and receptor activity modifying protein 1 (RAMP1) in rat

Clinical and experimental results have revealed a fundamental role of calcitonin gene-related peptide (CGRP) in primary headaches. CGRP is widely expressed in neurons both in the central nervous system (CNS) and in peripheral sensory nerves. In the CNS there is a wide distribution of CGRP-containing neurons with the highest levels seen in striatum, amygdale and cerebellum. Moreover, in acute attacks of migraine there is evidence of cerebellar activation. To understand the role of CGRP, antibodies towards the CGRP receptor components calcitonin receptor-like receptor (CLR) and receptor activity modifying protein type 1 (RAMP1) have been developed. In the present study we therefore examined immunohistochemically the distribution of CGRP and its receptor components in the cerebellum. CGRP immunoreactivity was only found intracellularly in the cerebellar Purkinje cell bodies, whereas CLR and RAMP1 were detected on the surface of the Purkinje cell bodies and in their processes. The elaborate dendritic tree of Purkinje cell fibers was distinctly visualized with the RAMP1 antibody. In addition, profoundly stained fibers spanning from the molecular layer into the medulla was observed with the RAMP1 antibody. Judged from the high density of immunoreactive cells expressing CGRP, RAMP1 or CLR, and from the double staining of CGRP and RAMP1 it is likely that most, if not all, Purkinje cells express both the peptide and the receptor components. Double staining with RAMP1 and the glial cell markers glial fibrillary acidic protein (GFAP) and S-100 revealed an almost identical staining pattern of the antibodies in the area of the cell body surfaces. However, as judged by confocal microscopy, no double staining was present. Instead, it was discovered that the glial cells tightly surrounded the Purkinje cells which easily could be interpreted as co-localization in the epifluorescence microscope. Our observations demonstrate that there is a rich expression of CGRP and CGRP receptor elements in the cerebellum which points towards a functional role of CGRP in cerebellar Purkinje cells. Recent advances in the biology of the cerebellum indicate that there may be a role in nociception; hence a target of the recently discovered CGRP receptor antagonists that have demonstrated improvement in migraine pain and associated symptoms could be cerebellar CGRP receptors.

Retinal integration of grafts of brain-derived precursor cell lines implanted subretinally into adult, normal rats.

The ability of in vitro-expanded neural precursor cells or cell lines to differentiate following transplantation has significant implications for current research on central nervous system repair. Recently, interest has been focussed on grafts of such neural precursors implanted also into the eye or retina. Here, we demonstrate with a non-traumatizing subretinal transplantation method, that grafts of the two immortalized brain-derived cell lines C 17-2 (from postnatal mouse cerebellum) and RN33B (from the embryonic rat medullary raphe) survive for at least up to four weeks, after implantation into the adult normal rat retina. For both cell lines, implanted cells gradually integrate into all major retinal cell layers, including the retinal pigment epithelium, and judged by the morphology differentiate into both glial- and neuron-like cells, as shown by thymidine autoradiography, mouse-specific in situ hybridization, and using immunohistochemistry to detect the reporter gene LacZ. Our results suggest that these and other similar neural cell lines could be very useful in the continuous experiments in models of retinal disorders to further assess both the cell replacement and ex vivo gene therapy approaches.

Isolation of progenitor cells from GFP-Transgenic pigs and transplantation to the retina of allorecipients

Work in rodents has demonstrated that progenitor transplantation can achieve limited photoreceptor replacement in the mammalian retina; however, replication of these findings on a clinically relevant scale requires a large animal model. To evaluate the ability of porcine retinal progenitor cells to survival as allografts and integrate into the host retinal architecture, we isolated donor cells from fetal green fluorescent protein (GFP)-transgenic pigs. Cultures were propagated from the brain, retina, and corneo-scleral limbus. GFP expression rapidly increased with time in culture, although lower in conjunction with photoreceptor markers and glial fibrillary acid protein (GFAP), thus suggesting downregulation of GFP during differentiation. Following transplantation, GFP expression allowed histological visualization of integrated cells and extension of fine processes to adjacent plexiform layers. GFP expression in subretinal grafts was high in cells expressing vimentin and lower in cells expressing photoreceptor markers, again consistent with possible downregulation during differentiation. Cells survived transplantation to the injured retina of allorecipients at all time points examined (up to 10 weeks) in the absence of exogenous immune suppression without indications of rejection. These findings demonstrate the feasibility of allogeneic progenitor transplantation in a large mammal and the utility of the pig in ocular regeneration studies.

Distribution of vasoactive intestinal peptide, pituitary adenylate cyclase-activating peptide, nitric oxide synthase, and their receptors in human and rat sphenopalatine ganglion.

Cranial parasympathetic outflow is mediated through the sphenopalatine ganglion (SPG). The present study was performed to examine the expression of the parasympathetic signaling transmitters and their receptors in human and rat SPG. Indirect immunofluorescence technique was used for the demonstration of vasoactive intestinal peptide (VIP), pituitary adenylate cyclase-activating peptide (PACAP), nitric oxide synthase (NOS), glutamine synthetase (GS), glial fibrillary acidic protein (GFAP), VIP and PACAP common receptors (VPAC1, VPAC2), and PACAP receptor (PAC1). In addition, double labeling was carried out to reveal the co-localization of neurotransmitters. VIP-immunoreactive (-ir) neurons as well as fibers were frequently found in human SPG. Many, homogenously stained NOS-ir cells were found, but no positive fibers. In addition, PACAP-ir was observed in some of the neurons and in fibers. Co-localization was found between VIP and NOS. In rat VIP-, NOS-, and PACAP-ir were found in many neurons and fibers. Co-localization of PACAP and NOS was observed in neurons. PACAP and GS double staining revealed that the PACAP-ir was localized in/close to the cell membrane, but not in the satellite glial cells. PAC1 and VPAC1 immunoreactivity was found in the satellite glial cells of both human and rat. Western blot revealed protein expression of PAC1, VPAC1, and VPAC2 in rat SPG. The trigeminal-autonomic reflex may be active in migraine attacks. We hypothesized that VIP, PACAP, NOS, PAC1, VPAC1, and VPAC2 play a role in the activation of parasympathetic cranial outflow during migraine attacks.

Retinal progenitor cell xenografts to the pig retina: immunological reactions.

We evaluated the host response to murine retinal progenitor cells (RPCs) following transplantation to the subretinal space (SRS) of the pig. RPCs from GFP mice were transplanted subretinally in 18 nonimmunosuppressed normal or laser-treated pigs. Evaluation of the SRS was performed on hematoxylin-eosin (H&E)-stained sections. Serum samples were taken from naive and RPC-grafted pigs and mouse-reactive antibody responses were assessed. At 1 week, histology showed a few perivascular lymphocytes consistent with a mild retinal vasculitis, and depigmentation of the RPE with large numbers of mononuclear inflammatory cells in the choroid near the transplantation site. Large choroidal infiltrates were evident at 2–5 weeks. Serum from naive and RPC-xenografted pigs contained significant levels of preformed IgG and IgM antibodies against murine antigens. Xenogeneic RPCs transplanted to the porcine SRS induced mononuclear infiltration in the choroid with graft rejection occurring over 2–5 weeks. Serum analysis confirmed that mice and pigs are discordant species; however, a cell-mediated acute mechanism appears to be responsible, rather than an antibody-mediated rejection.

A Battery of Cell- and Structure-specific Markers for the Adult Porcine Retina.

The pig is becoming an increasingly used non-primate model in experimental studies of human retinal diseases and disorders. The anatomy, size, and vasculature of the porcine eye and retina closely resemble their human counterparts, which allows for application of standard instrumentation and diagnostics used in the clinic. Despite many reports that demonstrate immunohistochemistry as a useful method for exploring neuropathologi-cal changes in the mammalian central nervous system, including the pig, the porcine retina has been sparsely described. Hence, to facilitate further immunohistochemical analysis of the porcine retina, we report on the successful use of a battery of antibodies for staining of paraformaldehyde-fixed cryosectioned retina. The following antibodies were evaluated for neuronal cells and structures: recoverin (cones and rods), Rho4D2 (rods), transducin-γ (cones), ROM-1 (photoreceptor outer segments), calbindin (horizontal cells), PKC-α (bipolar cells), parvalbumin (amacrine and displaced amacrine cells), and NeuN (ganglion cells and displaced amacrines). For detecting synaptic connections in fiber layers, we used an antibody against synaptobrevin. For detecting retinal pigment epithelium, we studied antibodies against cytokeratin and RPE65, respectively. The glial cell markers used were bFGF (Müller cells and displaced amacrine cells), GFAP (Müller cells and astrocytes), and vimentin (Müller cells). Each staining effect was evaluated with regard to its specificity, sensitivity, and repro-ducibility in the identification of individual cells, specific cell structures, and fiber layers, respectively. The markers parvalbumin and ROM-1 were tested here for the first time for the porcine retina. All antibodies tested resulted in specific staining of high quality. In conclusion, all immunohistochemical protocols presented here will be applicable in fixed, cryosectioned pig retina.

Mercury distribution in the rat brain after mercury vapor exposure.

Brown Norwegian rats were exposed to mercury vapor at a concentration of approximately 1 mg/m3 for 5 weeks 24 hr/day 7 days a week and 6 hr/day 3 days a week, respectively. The total mercury absorption was calculated to 264 and 35 micrograms per week and 100 g body weight. The mean blood mercury concentration was 0.25 +/- 0.03 and 0.09 +/- 0.01 microgram/g, and the total concentration in the brain was 5.03 +/- 0.73 and 0.71 +/- 0.10 microgram/g tissue, respectively. The mercury distribution in the brains was examined using a method based on chemographic principles. Mercury was found primarily in the neocortex, in the basal nuclei, and in the cerebellar Purkinje cells. This distribution pattern corresponded to the pattern of inorganic mercury described after exposure to methyl mercury. Distribution of mercury after administration of different mercury compounds is discussed.

Delayed administration of glial cell line-derived neurotrophic factor (GDNF) protects retinal ganglion cells in a pig model of acute retinal ischemia

This study investigates whether intravitreal administration of glial cell line-derived neurotrophic factor (GDNF) enhances survival of NeuN positive retinal cells in a porcine model of retinal ischemia. 16 pigs were subjected to an ischemic insult where intraocular pressure was maintained at 5 mmHg below mean arterial blood pressure for 2 h. The mean IOP during the ischemic insult was 79.5 mmHg (s.e.m. 2.1 mmHg, n = 15). Three days after the insult the pigs received an intravitreal injection of GDNF microspheres or blank microspheres. The pigs were evaluated by way of multifocal electroretinography (mfERG), quantification of NeuN positive cells and evaluation of the degree of retinal perivasculitis and inflammation 6 weeks after the insult. In the post-injection eyes (days 14, 28 and 42), the ratios of the iN1 and the iP2 amplitudes were 0.10 (95% CI: 0.05-0.15) and 0.09 (95% CI: 0.04-0.16) in eyes treated with blank microspheres, and 0.24 (95% CI: 0.18-0.32) and 0.23 (95% CI: 0.15-0.33) in eyes treated with GDNF microspheres. These differences were statistically significant (P < 0.05). The number of NeuN positive cells in the area of the visual streak area was significantly higher in eyes injected with GDNF microspheres compared to eyes injected with blank microspheres. In eyes injected with GDNF microspheres the ganglion cell count was 9.5/field (s.e.m.: 2.1, n = 8), in eyes injected with blank microspheres it was 3.5/field (s.e.m.: 1.2, n = 7). This difference was statistically significant (P < 0.05). There was also a significant difference (P < 0.01) in the degree of perivasculiitis between GDNF treated eyes (median perivasculitis score 1.5) and blank treated eyes (median perivasculitis score 3.0). In conclusion, injection of GDNF microspheres 3 days after an ischemic insult results in functional and morphological rescue of NeuN positive cells in a porcine model of acute ocular ischemia.