Müller cells express the neuronal progenitor cell marker nestin in both differentiated and undifferentiated human foetal retina

Identification and characterization of early human photoreceptor states and cell-state-specific retinoblastoma-related features

Human cone photoreceptors differ from rods and serve as the retinoblastoma cell-of-origin, yet the developmental basis for their distinct behaviors is poorly understood. Here, we used deep full-length single-cell RNA-sequencing to distinguish post-mitotic cone and rod developmental states and identify cone-specific features that contribute to retinoblastomagenesis. The analyses revealed early post-mitotic cone- and rod-directed populations characterized by higher THRB or NRL regulon activities, an immature photoreceptor precursor population with concurrent cone and rod gene and regulon expression, and distinct early and late cone and rod maturation states distinguished by maturation-associated declines in RAX regulon activity. Unexpectedly, both L/M cone and rod precursors co-expressed NRL and THRB RNAs, yet they differentially expressed functionally antagonistic NRL and THRB isoforms and prematurely terminated THRB transcripts. Early L/M cone precursors exhibited successive expression of several lncRNAs along with MYCN, which composed the seventh most L/M-cone-specific regulon, and SYK, which contributed to the early cone precursors' proliferative response to RB1 loss. These findings reveal previously unrecognized photoreceptor precursor states and a role for early cone-precursor-intrinsic SYK expression in retinoblastoma initiation.

Blastocyst-like Structures in the Peripheral Retina of Young Adult Beagles

In this immunohistological study on the peripheral retina of 3-year-old beagle dogs, excised retina specimens were immunostained with antibodies against nestin, Oct4, Nanog, Sox2, CDX2, cytokeratin 18 (CK 18), RPE65, and YAP1, as well as hematoxylin and DAPI, two nuclear stains. Our findings revealed solitary cysts of various sizes in the inner retina. Intriguingly, a mass of small round cells with scant cytoplasms was observed in the cavity of small cysts, while many disorganized cells partially occupied the cavity of the large cysts. The small cysts were strongly positive for nestin, Oct4, Nanog, Sox2, CDX2, CK18, and YAP1. RPE65-positive cells were exclusively observed in the tissue surrounding the cysts. Since RPE65 is a specific marker of retinal pigment epithelial (RPE) cells, the surrounding cells of the peripheral cysts were presumably derived from RPE cells that migrated intraretinally. In the small cysts, intense positive staining for nestin, a marker of retinal stem cells, seemed to indicate that they were derived from retinal stem cells. The morphology and positive staining for markers of blastocyst and RPE cells indicated that the small cysts may have formed structures resembling the blastocyst, possibly caused by the interaction between retinal stem cells and migrated RPE cells.

Statins Inhibit the Gliosis of MIO-M1, a Müller Glial Cell Line Induced by TRPV4 Activation

We characterized Müller cell gliosis induced by the activation of transient receptor potential vanilloid-type 4 (TRPV4) and assessed whether statins could modulate the gliosis. The human Müller cell line, MIO-M1, was used to analyze the gliosis caused by glaucomatous stimulation. To induce Müller gliosis in MIO-M1 cells, GSK101 was used to activate TRPV4, and Müller gliosis was evaluated by analyzing vimentin, nestin, and glial fibrillary acidic protein (GFAP) expression. The expression level of TNF-α was determined by ELISA. To evaluate the GSK101 activation of the NF-κB pathway, p65 phosphorylation was measured by Western blotting, and the nuclear translocation of p65 and IκBα phosphorylation were assessed by immunostaining. To assess the effect of statins on MIO-M1 gliosis, cells were pretreated for 24 h with statins before GSK101 treatment. Vimentin, nestin, and GFAP expression were upregulated by GSK101, while statins effectively inhibited them. The expression of TNF-α was increased by GSK101. The phosphorylation and nuclear translocation of p65 and IκBα phosphorylation, which occurs prior to p65 activation, were induced. Statins suppressed the GSK101-mediated phosphorylation of IκBα and p65 translocation. Statins can mitigate gliosis in the human Müller cell line. Because TRPV4 activation in Müller cells reflects glaucoma pathophysiology, statins may have the potential to prevent RGC death.

Characterization and heme oxygenase-1 content of extracellular vesicles in human biofluids

Heme oxygenase-1 (HO-1), a highly inducible stress protein that degrades heme to biliverdin, carbon monoxide, and free ferrous iron, is increased in blood and other biofluids of subjects with various systemic and neurological disorders. HO-1 does not contain an N-terminal signal peptide and the mechanism responsible for its secretion remains unknown. Extracellular vesicles (EVs) are membrane-bound inclusions that transport microRNAs, messenger RNAs, lipids, and proteins among diverse cellular and extracellular compartments. The objective of the current study was to determine whether EVs in human biofluids contain HO-1, and whether the latter may be transported in EVs from brain to periphery. Total, L1 cell adhesion molecule protein (L1CAM)-enriched (neuron-derived), and glutamate aspartate transporter 1 (GLAST)-enriched (astrocyte-derived) EVs were purified from five different human biofluids (saliva [n = 40], plasma [n = 14], serum [n = 10], urine [n = 10], and cerebrospinal fluid [n = 11]) using polymer precipitation and immuno-affinity-based capture methods. L1CAM-enriched, GLAST-enriched, and L1CAM/GLAST-depleted (LGD) EV, along with EV-depleted (EVD), fractions were validated by nanoparticle tracking analysis, enzyme-linked immunosorbent assay (ELISA), and western blot. HO-1 was assayed in all fractions using ELISA and western blot. The majority of HO-1 protein was localized to LGD, L1CAM-enriched, and GLAST-enriched EVs of all human biofluids surveyed after adjusting for age and sex, with little HO-1 protein detected in EVD fractions. HO-1 protein in human biofluids is predominantly localized to EV compartments. A substantial proportion of EV HO-1 in peripheral human biofluids is derived from the central nervous system and may contribute to the systemic manifestations of various neurological conditions.

Expressions of nestin and glial fibrillary acidic protein in rat retina after optic nerve transection

AIM

To assess the expression of nestin and glial fibrillary acidic protein (GFAP) in rat retina after optic nerve transection.

METHODS

Rats were randomly divided into normal control group, sham group and operation group, and used for establishing an animal model of optic nerve transection. Retinal specimen of each group was collected at 3, 48h, 7 and 14d postoperative. Nestin and GFAP expressions on sagittal sections were analyzed by immunohistochemical staining, and protein extraction was analyzed by Western blot.

RESULTS

Immunohistochemical analysis showed that nestin positive staining was rarely detected in normal control group and sham group, while sham group showed weak positive staining at 3h postoperative, the reaction gradually increased at 48h postoperative, and reached its maximum at 7d postoperative, and then decreased at 14d postoperative. Compared to the expression of GFAP, there was not statistically significant obvious difference among three groups (P>0.05). Result of Western blot method was consistent with that of immunohistochemical method.

CONCLUSION

The expression of nestin increased in a time dependent fashion in Müller cells of retina following optic nerve transection, which was statistically significant, but there was no obvious difference in GFAP expression. The results indicate that an increase in colloid synthesis in retina following optic nerve transection can improve the retinal neurons' environment.

Neuronal differentiation in the early human retinogenesis

AIM

Our study investigates the differentiation of retinal stem cells towards different neuronal subtypes during the critical period of human eye development.

METHODS

Expression of the neuronal marker neurofilament 200 (NF200), tyrosine hydroxilase (TH) and choline acetyltransferase (ChAT) was seen by immunofluorescence in the 5th-12th - week stage of development in the human eye. Data was analysed by Mann-Whitney, Kruskal-Wallis and Dunn's post hoc tests.

RESULTS

NF200, TH and ChAT cells appeared in the 5th/6th week and gradually increased during further development. The proportion of TH positive areas were distributed similarly to NF200, with a higher proportion in the outer neuroblastic layer. The proportion of a ChAT positive surface was highest in the 5th/6th - week whilst from the 7th week onwards, its proportion became higher in the optic nerve and inner neuroblastic layers than in the outer layer, where a decrease of ChAT positive areas were seen.

CONCLUSIONS

Our study indicates a high differentiation potential of early retinal cells, which decreased with the advancement of development. The observed great variety of retinal phenotypic expressions results from a large scale of influences, taking place at different developmental stages.

SMAD7 deficiency stimulates Müller progenitor cell proliferation during the development of the mammalian retina

The transforming growth factor-β (TGF-β) pathway contributes to maintain the quiescence of adult neural stem and progenitor cells in the brain. In the retina, Müller cells are discussed to represent a glial cell population with progenitor-like characteristics. Here, we aimed to investigate if elevated TGF-β signaling modulates the proliferation of Müller cells during retinal development. We generated mutant mice with a systemic, heterozygous up-regulation of TGF-β signaling by deleting its inhibitor SMAD7. We investigated apoptosis, proliferation, and differentiation of Müller cells in the developing retina. We show that a heterozygous deletion of SMAD7 results in an increased proliferation of Müller cell progenitors in the central retina at postnatal day 4, the time window when Müller cells differentiate in the mouse retina. This in turn results in a thickened retina and inner nuclear layer and a higher number of differentiated Müller cells in the more developed retina. Müller cells in mutant mice contain higher amounts of nestin than those of control animals which indicates that the increase in TGF-β signaling activity during retinal development contribute to maintain some progenitor-like characteristics in Müller cells even after their differentiation period. We conclude that TGF-β signaling influences Müller cell proliferation and differentiation during retinal development.

Nestin Expression in the Adult Mouse Retina with Pharmaceutically Induced Retinal Degeneration

The present study investigated the temporal pattern and cellular localization of nestin in the adult mouse retina with pharmaceutically induced retinal degeneration using N-methyl-N-nitrosourea (MNU). After a single intraperitoneal injection of MNU in 8-week-old C57BL/6 mice, the animals were sacrificed at 1, 3, 5, 7, and 21 days (n = 6, in each stage). The eyes were examined by means of immunohistochemical tests using nestin, ionized calcium-binding adaptor molecule (Iba-1), CD11b, F4/80, and glial fibrillary acidic protein (GFAP). Western blot analysis and manual cell counting were performed for quantification. Nestin expression was increased after MNU administration. Nestin+/Iba-1+ cells were migrated into outer nuclear layer (ONL) and peaked at day 3 post injection (PI). Nestin+/CD11b+ cells were also mainly identified in ONL at day 3 PI and peaked at day 5. Nestin+/F4/80+ cells were shown in the subretinal space and peaked at day 3 PI. Nestin+/GFAP+ cells were distinctly increased at day 1 PI and peaked at day 5 PI. The up-regulation of nestin expression after MNU administration in adult mouse retinal microglia, and monocyte/macrophage suggests that when retinal degeneration progresses, these cells may revert to a more developmentally immature state. Müller cells also showed reactive gliosis and differentiational changes.

Efficacy and Safety of Human Retinal Progenitor Cells

PURPOSE

We assessed the long-term efficacy and safety of human retinal progenitor cells (hRPC) using established rodent models.

METHODS

Efficacy of hRPC was tested initially in Royal College of Surgeons (RCS) dystrophic rats immunosuppressed with cyclosporine/dexamethasone. Due to adverse effects of dexamethasone, this drug was omitted from a subsequent dose-ranging study, where different hRPC doses were tested for their ability to preserve visual function (measured by optokinetic head tracking) and retinal structure in RCS rats at 3 to 6 months after grafting. Safety of hRPC was assessed by subretinal transplantation into wild type (WT) rats and NIH-III nude mice, with analysis at 3 to 6 and 9 months after grafting, respectively.

RESULTS

The optimal dose of hRPC for preserving visual function/retinal structure in dystrophic rats was 50,000 to 100,000 cells. Human retinal progenitor cells integrated/survived in dystrophic and WT rat retina up to 6 months after grafting and expressed nestin, vimentin, GFAP, and βIII tubulin. Vision and retinal structure remained normal in WT rats injected with hRPC and there was no evidence of tumors. A comparison between dexamethasone-treated and untreated dystrophic rats at 3 months after grafting revealed an unexpected reduction in the baseline visual acuity of dexamethasone-treated animals.

CONCLUSIONS

Human retinal progenitor cells appear safe and efficacious in the preclinical models used here.

TRANSLATIONAL RELEVANCE

Human retinal progenitor cells could be deployed during early stages of retinal degeneration or in regions of intact retina, without adverse effects on visual function. The ability of dexamethasone to reduce baseline visual acuity in RCS dystrophic rats has important implications for the interpretation of preclinical and clinical cell transplant studies.

Nestin, A New Marker, Expressed in Müller Cells Following Retinal Injury

Purpose:

To investigate whether nestin would be a useful marker for retinal injury and also to ascertain a better understanding of the roles of Müller cells in the injured retina by the use of damaged rat retina.

Methods:

A total of 33 adult female Wistar rats were used in this study. Three were used as controls and the remaining as retinal injury modes (6 for hypoxia; 15 for experimental glaucoma and 9 for optic nerve transection). Double immunofluorescence labeling was carried out between nestin and glutamine synthetase (GS), and between glial fibrillary acidic protein (GFAP) and GS antisera in normal and pathological retinae.

Results:

The results showed that there were no nestin nor GFAP staining in mature Müller cells of the normal retina. A major finding was that nestin expression was induced in Müller cells subjected to hypoxia, glaucoma and optic nerve transection.

Conclusions:

These results suggest that nestin as well as GFAP (even more sensitive than GFAP) are useful and reliable biomarkers for retinal damage. The more intense expression of nestin, GFAP and GS in the end-feet of Müller cells suggest that they may help to maintain the retinal structural integrity and to enhance functional recovery in various retinal diseases.

Pulmonary surfactant protein a is expressed in mouse retina by Müller cells and impacts neovascularization in oxygen-induced retinopathy

PURPOSE

Surfactant protein A (SP-A) up-regulates cytokine expression in lung disease of prematurity. Here we present data that for the first time characterizes SP-A expression and localization in the mouse retina and its impact on neovascularization (NV) in the mouse.

METHODS

Retinal SP-A was localized in wild-type (WT) mice with the cell markers glutamine synthetase (Müller cells), neurofilament-M (ganglion cells), glial acid fibrillary acid protein (astrocytes), and cluster of differentiation 31 (endothelial cells). Toll-like receptor 2 and 4 (TLR-2 and TLR-4) ligands were used to up-regulate SP-A expression in WT and myeloid differentiation primary response 88 (MyD88) protein (necessary for NFκB signaling) null mouse retinas and Müller cells, which were quantified using ELISA. Retinal SP-A was then measured in the oxygen-induced retinopathy (OIR) mouse model. The effect of SP-A on retinal NV was then studied in SP-A null (SP-A(-/-)) mice.

RESULTS

SP-A is present at birth in the WT mouse retina and colocalizes with glutamine synthetase. TLR-2 and TLR-4 ligands increase SP-A both in the retina and in Müller cells. SP-A is increased at postnatal day 17 (P17) in WT mouse pups with OIR compared to that in controls (P = 0.02), and SP-A(-/-) mice have reduced NV compared to WT mice (P = 0.001) in the OIR model.

CONCLUSIONS

Retinal and Müller cell SP-A is up-regulated via the NFκB pathway and up-regulated during the hypoxia phase of OIR. Absence of SP-A attenuates NV in the OIR model. Thus SP-A may be a marker of retinal inflammation during NV.

Type-1 pericytes accumulate after tissue injury and produce collagen in an organ-dependent manner

Introduction

Fibrosis, or scar formation, is a pathological condition characterized by excessive production and accumulation of collagen, loss of tissue architecture, and organ failure in response to uncontrolled wound healing. Several cellular populations have been implicated, including bone marrow-derived circulating fibrocytes, endothelial cells, resident fibroblasts, epithelial cells, and recently, perivascular cells called pericytes. We previously demonstrated pericyte functional heterogeneity in skeletal muscle. Whether pericyte subtypes are present in other tissues and whether a specific pericyte subset contributes to organ fibrosis are unknown.

Methods

Here, we report the presence of two pericyte subtypes, type-1 (Nestin-GFP-/NG2-DsRed+) and type-2 (Nestin-GFP+/NG2-DsRed+), surrounding blood vessels in lungs, kidneys, heart, spinal cord, and brain. Using Nestin-GFP/NG2-DsRed transgenic mice, we induced pulmonary, renal, cardiac, spinal cord, and cortical injuries to investigate the contributions of pericyte subtypes to fibrous tissue formation in vivo.

Results

A fraction of the lung’s collagen-producing cells corresponds to type-1 pericytes and kidney and heart pericytes do not produce collagen in pathological fibrosis. Note that type-1, but not type-2, pericytes increase and accumulate near the fibrotic tissue in all organs analyzed. Surprisingly, after CNS injury, type-1 pericytes differ from scar-forming PDGFRβ + cells.

Conclusions

Pericyte subpopulations respond differentially to tissue injury, and the production of collagen by type-1 pericytes is organ-dependent. Characterization of the mechanisms underlying scar formation generates cellular targets for future anti-fibrotic therapeutics.

Electronic supplementary material

The online version of this article (doi:10.1186/scrt512) contains supplementary material, which is available to authorized users.

Comparison of nestin-expressing multipotent stem cells in the tongue fungiform papilla and vibrissa hair follicle

We have previously reported that hair follicles contain multipotent stem cells, which express nestin and participate in follicle growth at anagen as well as in the extension of the follicle sensory nerve. The nestin-driven green fluorescent protein (ND-GFP) transgenic mouse labels all nestin-expressing cells with GFP. The hair follicle nestin-GFP cells can differentiate into neurons, Schwann cells, and other cell types. In this study, we describe nestin-expressing multipotent stem cells in the fungiform papilla in the tongue. The nestin-expressing multipotent stem cells in the fungiform papilla are located around a peripheral sensory nerve immediately below the taste bud and co-express the neural crest cell marker p75(NTR) . The fungiform papilla cells formed spheres in suspension culture in DMEM-F12 medium supplemented with basic fibroblast growth factor (bFGF). The spheres consisted of nestin-expressing cells that co-expressed the neural crest marker p75(NTR) and which developed expression of the stem cell marker CD34. P75(NTR), CD34 and nestin co-expression suggested that nestin-expressing cells comprising the fungiform papilla spheres were in a relatively undifferentiated state. The nestin-expressing cells of these spheres acquired the following markers: β III tubulin typical of nerve cells; GFAP typical of glial cells; K15 typical of keratinocytes; and smooth-muscle antigen (SMA), after transfer to RPMI 1640 medium with 10% fetal bovine serum (FBS), suggesting they differentiated into multiple cell types. The results of the current study indicate nestin-expressing fungiform papilla cells and the nestin-expressing hair follicle stem cells have common features of cell morphology and ability to differentiate into multiple cell types, suggesting their remarkable similarity.

Induced pluripotent stem cells generated from adult bone marrow-derived cells of the nonhuman primate (Callithrix jacchus) using a novel quad-cistronic and excisable lentiviral vector

Regenerative medicine is in need of solid, large animal models as a link between rodents and humans to evaluate the functionality, immunogenicity, and clinical safety of stem cell-derived cell types. The common marmoset (Callithrix jacchus) is an excellent large animal model, genetically close to humans and readily used worldwide in clinical research. Until now, only two groups showed the generation of induced pluripotent stem cells (iPSCs) from the common marmoset using integrating retroviral vectors. Therefore, we reprogrammed bone marrow-derived mesenchymal cells (MSCs) of adult marmosets in the presence of TAV, SB431542, PD0325901, and ascorbic acid via a novel, excisable lentiviral spleen focus-forming virus (SFFV)-driven quad-cistronic vector system (OCT3/4, KLF4, SOX2, C-MYC). Endogenous pluripotency markers like OCT3/4, KLF4, SOX2, C-MYC, LIN28, NANOG, and strong alkaline phosphatase signals were detected. Exogenous genes were silenced and additionally the cassette was removed with a retroviral Gag precursor system. The cell line could be cultured in absence of leukemia inhibitory factor (LIF) and basic fibroblast growth factor (bFGF) and could be successfully differentiated into embryoid bodies and teratomas with presence of all three germ layers. Directed differentiation generated neural progenitors, megakaryocytes, adipocytes, chondrocytes, and osteogenic cells. Thus, all criteria for fully reprogrammed bone marrow-MSCs of a nonhuman primate with a genetically sophisticated construct could be demonstrated. These cells will be a promising tool for future autologous transplantations.

Skeletal muscle neural progenitor cells exhibit properties of NG2-glia

Reversing brain degeneration and trauma lesions will depend on cell therapy. Our previous work identified neural precursor cells derived from the skeletal muscle of Nestin-GFP transgenic mice, but their identity, origin, and potential survival in the brain are only vaguely understood. In this work, we show that Nestin-GFP+ progenitor cells share morphological and molecular markers with NG2-glia, including NG2, PDGFRα, O4, NGF receptor (p75), glutamate receptor-1(AMPA), and A2B5 expression. Although these cells exhibit NG2, they do not express other pericyte markers, such as α-SMA or connexin-43, and do not differentiate into the muscle lineage. Patch-clamp studies displayed outward potassium currents, probably carried through Kir6.1 channels. Given their potential therapeutic application, we compared their abundance in tissues and concluded that skeletal muscle is the richest source of predifferentiated neural precursor cells. We found that these cells migrate toward the neurogenic subventricular zone displaying their typical morphology and nestin-GFP expression two weeks after brain injection. For translational purposes, we sought to identify these neural progenitor cells in wild-type species by developing a DsRed expression vector under Nestin-Intron II control. This approach revealed them in nonhuman primates and aging rodents throughout the lifespan.

Retinal astrocytes pretreated with NOD2 and TLR2 ligands activate uveitogenic T cells

On entering the tissues, infiltrating autoreactive T cells must be reactivated locally to gain pathogenic activity. We have previously reported that, when activated by Toll-like receptor 3 (TLR3) and TLR4 ligands, retinal astrocytes (RACs) are able to function as antigen-presenting cells to re-activate uveitogenic T cells and allow responder T cells to induce uveitis in mice. In the present study, we found that, although the triggering of TLR2 or nucleotide-binding oligomerization domain receptor 2 (NOD2) alone did not activate RACs, their combined triggering induced RACs with the phenotypes required to efficiently re-activate interphotoreceptor retinoid-binding protein (IRBP)-specific T cells. The synergistic effect of TLR2 and NOD2 ligands on RAC activation might be explained by the observations that bacterial lipoprotein (BLP, a TLR2 ligand) was able to upregulate NOD2 expression and the combination of BLP and muramyldipeptide (MDP, a NOD2 ligand) enhanced the expression of RICK (Rip2), the signaling molecule of NOD2. Moreover, the synergistic effect of MDP and BLP on RACs was lost when the RACs were derived from NOD2 knockout mice or were pre-treated with Rip2 antagonist. Thus, our data suggest that exogenous or endogenous molecules acting on both TLR2 and NOD2 on RACs might have an enhancing effect on susceptibility to autoimmune uveitis.

Characterization of Progenitor Cells during Canine Retinal Development

We identify the presence of progenitor cells during retinal development in the dog, as this species represents a natural model for studying several breed-specific degenerative retinal disorders. Antibodies to detected progenitor cells (Pax6, C-kit, and nestin) and ganglion cells (BDNF, Brn3a, and Thy1) were used in combination with H3 for the purpose of identifying proliferating cells. Pax6, nestin, C-kit, and H3 were localized mainly in the neuroblastic layer of the retina during the embryonic stage. During the fetal stage, proteins were expressed in the inner neuroblastic layer (INL) as well as in the outer neuroblastic layer; BDNF, Thy1, and Brn3a were also expressed in the INL. During the neonatal stage only C-kit was not expressed. Proliferating cells were present in both undifferentiated and differentiated retina. These results suggest that, during canine retinogenesis, progenitor cells are distributed along the retina and some of these cells remain as progenitor cells of the ganglion cells during the first postnatal days.

In situ dividing and phagocytosing retinal microglia express nestin, vimentin, and NG2 in vivo

Background

Following injury, microglia become activated with subsets expressing nestin as well as other neural markers. Moreover, cerebral microglia can give rise to neurons in vitro. In a previous study, we analysed the proliferation potential and nestin re-expression of retinal macroglial cells such as astrocytes and Müller cells after optic nerve (ON) lesion. However, we were unable to identify the majority of proliferative nestin⁺ cells. Thus, the present study evaluates expression of nestin and other neural markers in quiescent and proliferating microglia in naïve retina and following ON transection in adult rats in vivo.

Methodology/Principal Findings

For analysis of cell proliferation and cells fates, rats received BrdU injections. Microglia in retinal sections or isolated cells were characterized using immunofluorescence labeling with markers for microglia (e.g., Iba1, CD11b), cell proliferation, and neural cells (e.g., nestin, vimentin, NG2, GFAP, Doublecortin etc.). Cellular analyses were performed using confocal laser scanning microscopy. In the naïve adult rat retina, about 60% of resting ramified microglia expressed nestin. After ON transection, numbers of nestin⁺ microglia peaked to a maximum at 7 days, primarily due to in situ cell proliferation of exclusively nestin⁺ microglia. After 8 weeks, microglia numbers re-attained control levels, but 20% were still BrdU⁺ and nestin⁺, although no further local cell proliferation occurred. In addition, nestin⁺ microglia co-expressed vimentin and NG2, but not GFAP or neuronal markers. Fourteen days after injury and following retrograde labeling of retinal ganglion cells (RGCs) with Fluorogold (FG), nestin⁺NG2⁺ microglia were positive for the dye indicating an active involvement of a proliferating cell population in phagocytosing apoptotic retinal neurons.

Conclusions/Significance

The current study provides evidence that in adult rat retina, a specific resident population of microglia expresses proteins of immature neural cells that are involved in injury-induced cell proliferation and phagocytosis while transdifferentiation was not observed.

Stem cell marker nestin is expressed in plasma cells of multiple myeloma patients

Nestin is considered to be a characteristic marker of multipotent proliferative precursors found in some embryonic and fetal tissues. Its expression might be a suitable diagnostic and prognostic indicator of malignancy and a potential marker of cancer stem cells in solid tumors. Unexpectedly, nestin protein was detected in mature CD138(+)CD38(+) plasma cells of multiple myeloma patients and statistical analysis confirmed significant differences between myeloma patients and control group without hematological malignancy. Our results represent the first evidence of nestin expression in multiple myeloma. Further studies are required to elucidate the role of this protein in multiple myeloma.

Tumor-associated retinal astrocytes promote retinoblastoma cell proliferation through production of IGFBP-5

Retinoblastomas consist of cone-like neoplastic cells and diverse non-neoplastic cells whose roles in tumorigenesis have not been defined. Here, we investigated the glial cells that constitute 2% to 3% of the cells in retinoblastoma tumors, including their origin, their relationship to a potential retinoblastoma stem cell population, and their effects on tumor cell proliferation. Retinoblastoma glia consistently expressed the retinal astrocyte marker Pax2 but inconsistently expressed the Müller cell and occasional astrocyte marker CRALBP. Many of the glia expressed the stem cell-associated Sox2 but nevertheless were non-neoplastic as they coexpressed Rb and/or retained two RB1 alleles. Conversely, the glia were distinct from the non-neoplastic cells that strongly expressed the stem cell-associated ABCG2. Adherent Pax2(+),Sox2(+),Rb(+) glia readily grew from explanted retinoblastomas and produced soluble factors that enhanced the proliferation of cocultured retinoblastoma cells. This effect was emulated by normal retinal glia and appeared to be mediated by insulin-like growth factor binding protein-5 (IGFBP-5), as it was mimicked by recombinant IGFBP-5 and mitigated by neutralizing IGFBP-5 antibody. As glia-derived IGFBP-5 was earlier found to promote photoreceptor survival, our findings indicate that retinal astrocytes enhance the proliferation of cone-like retinoblastoma cells by deploying a factor that also provides trophic support to the tumor cells' non-neoplastic counterparts. These observations suggest that a tissue-specific microenvironmental feature cooperates with oncogenic mutations in a cancer cell of origin to promote retinoblastoma tumorigenesis.

A conditional immortalized mouse muller glial cell line expressing glial and retinal stem cell genes

PURPOSE

Müller glia have multiple functions in the retina, including synthesis of neurotrophic factors, uptake and metabolism of neurotransmitters, spatial buffering of ions, maintenance of the blood-retinal barrier, and response to injury. A population of Müller glia has some stem cell-like characteristics both in vivo and in vitro. The purpose of this study was to generate and characterize novel Müller glial cell lines from the postnatal mouse retina.

METHODS

Cells were cultured from postnatal day (P) 10 double heterozygous transgenic (H-2K(b)-tsA58/+; HRhoGFP/+) or C57BL/6 mice after papain dissociation. Interferon gamma (IFNγ) induction of the SV40 T-antigen (TAg) was assayed by immunohistochemistry and Western blot analysis. Proliferation was assayed by BrdU uptake and cell counts of calcein AM/ethidium bromide-stained cells. Gene expression was analyzed by RT-PCR and immunohistochemistry.

RESULTS

Conditionally immortalized (ImM10 [Immortmouse Müller P10]) and spontaneously immortalized (C57M10 [C57BL/6 Müller P10]) Müller glial cell lines were selected by differential adherence to laminin; both consisted of adherent flat cells with large, diffusely staining nuclei and an epithelial morphology. TAg induction stimulated BrdU uptake by Müller glia in mixed retinal cultures from H-2K(b)-tsA58/+; HRhoGFP/+ mice and increased the proliferation of ImM10 cells. ImM10 and C57M10 cells expressed genes characteristic of Müller glia but not genes characteristic of differentiated retinal neurons. ImM10 cells also expressed retinal stem cell genes.

CONCLUSIONS

The ImM10 cell line is a novel, conditionally immortalized Müller glial cell line isolated from the P10 mouse retina that expresses genes characteristic of Müller glial and retinal stem cells.

Nestin expression in glial and neuronal progenitors of the developing human spinal ganglia

Expression of the neural crest marker nestin was studied in glial and neuronal progenitors of developing human spinal ganglia using immunohistochemistry in 10 conceptuses, 5-10 weeks old. Quantification was performed by counting the ratio of positive cells in the total cell number, expressed as mean + or - SD and by the Mann-Whitney test. Strong expression of nestin in the 5th-6th developmental week (56%) decreased to 49% in the foetal period. During the same period, number of PGP9.5-positive cells increased from 38% to 42%. At earliest stages, the number of cells expressing GFAP was two folds higher (21%) than S100 (11%). During further development, their number nearly levelled (23% and 28%, respectively), and finally reached level of 25% for GFAP and 40% for S100. While expression of nestin was constantly higher in the dorsal parts of spinal ganglia, number of PGP9.5-, GFAP- and S100-positive cells was higher in their ventral parts, thus indicating ventral to dorsal direction of spinal ganglia differentiation. Co-localization of nestin and GFAP or nestin and S100 was observed during the whole investigate period, while PGP9.5 did not co-localize with nestin. Some ganglion cells simultaneously co-expressing GFAP and S100 might be satellite cells and immature Schwann cells. We suggest that some nestin-positive cells might be capable to differentiate into neurons during the earliest stages of development. Gangliogenesis seems to be important process during the whole ganglion development. Continuous presence of neural crest cells during development might be important in regenerative processes following damage of the spinal ganglia.

Cellular signaling and factors involved in Müller cell gliosis: neuroprotective and detrimental effects

Müller cells are active players in normal retinal function and in virtually all forms of retinal injury and disease. Reactive Müller cells protect the tissue from further damage and preserve tissue function by the release of antioxidants and neurotrophic factors, and may contribute to retinal regeneration by the generation of neural progenitor/stem cells. However, Müller cell gliosis can also contribute to neurodegeneration and impedes regenerative processes in the retinal tissue by the formation of glial scars. This article provides an overview of the neuroprotective and detrimental effects of Müller cell gliosis, with accounts on the cellular signal transduction mechanisms and factors which are implicated in Müller cell-mediated neuroprotection, immunomodulation, regulation of Müller cell proliferation, upregulation of intermediate filaments, glial scar formation, and the generation of neural progenitor/stem cells. A proper understanding of the signaling mechanisms implicated in gliotic alterations of Müller cells is essential for the development of efficient therapeutic strategies that increase the supportive/protective and decrease the destructive roles of gliosis.

Quantitative analysis of tumor size in a murine model of retinoblastoma

Murine models can provide valuable insight into mechanisms of tumorigenesis. Tumor size is often used to assess the impact of genetic insult or therapeutic treatment, usually using in vivo imaging of advanced tumors. We now describe a highly sensitive method to quantify tumor volume in a mouse model of retinoblastoma, from the earliest stages of tumor initiation to large, advanced tumors. This methodology combines immunohistochemistry, digital slide scanning and computer image analysis, and can be applied to quantitatively assess and characterize early tumor development in other models.

Immunolocalization of nestin in pancreatic tissue of mice at different ages

AIM: To localize nestin positive cells (NPC) in pancreatic tissue of mice of different ages.

METHODS: Paraffin sections of 6-8 μm of fixed pancreatic samples were mounted on poly-L-lysine coated slides and used for Immunolocalization using appropriate primary antibodies (Nestin, Insulin, Glucagon), followed by addition of a fluorescently labeled secondary antibody. The antigen-antibody localization was captured using a confocal microscope (Leica SP 5 series).

RESULTS: In 3-6 d pups, the NPC were localized towards the periphery of the endocrine portion, as evident from immunolocalization of insulin and glucagon, while NPC were absent in the acinar portion. At 2 wk, NPC were localized in both the exocrine and endocrine portions. Interestingly, in 4-wk-old mice NPC were seen only in the endocrine portion, towards the periphery, and were colocalized with the glucagon positive cells. In the pancreas of 8- wk-old mice, the NPC were predominantly localized in the central region of the islet clusters, where immunostaining for insulin was at a maximum.

CONCLUSION: We report for the first time the immunolocalization of NPC in the pancreas of mice of different ages (3 d to 8 wk) with reference to insulin and glucagon positive cells. The heterogeneous localization of the NPC observed may be of functional and developmental significance and suggest(s) that mice pancreatic tissue can be a potential source of progenitor cells. NPC from the pancreas can be isolated, proliferated and programmed to differentiate into insulin secreting cells under the appropriate microenvironment.

Vimentin isoform expression in the human retina characterized with the monoclonal antibody 3CB2

The antigen recognized by the monoclonal antibody 3CB2 (3CB2-Ag and 3CB2 mAb) is expressed by radial glia and astrocytes in the developing and adult vertebrate central nervous system (CNS) of vertebrates as well as in neural stem cells. Here we identified the 3CB2-Ag as vimentin by proteomic analysis of human glial cell line U-87 extracts (derived from a malignant astrocytoma). Indeed, the 3CB2 mAb recognized three vimentin isoforms in glial cell lines. In the human retina, 3CB2-Ag was expressed in Müller cells, astrocytes, some blood vessels, and cells in the horizontal cell layer, as determined by immunoprecipitation and immunofluorescence. Three populations of astrocytes were distinguishable by double-labeling immunohistochemistry: vimentin+/GFAP+, vimentin-/GFAP+, and vimentin+/GFAP-. Hence, we conclude that 1) the 3CB2-Ag is vimentin; 2) vimentin isoforms are differentially expressed in normal and transformed astrocytes; 3) human retinal astrocytes display molecular heterogeneity; and 4) the 3CB2 mAb is a valuable tool to study vimentin expression and its function in the human retina.

Regulation of prenatal human retinal neurosphere growth and cell fate potential by retinal pigment epithelium and Mash1

During development of the central nervous system, stem and progenitor cell proliferation and differentiation are controlled by complex inter- and intracellular interactions that orchestrate the precise spatiotemporal production of particular cell types. Within the embryonic retina, progenitor cells are located adjacent to the retinal pigment epithelium (RPE), which differentiates prior to the neurosensory retina and has the capacity to secrete a multitude of growth factors. We found that secreted proteinaceous factors in human prenatal RPE conditioned medium (RPE CM) prolonged and enhanced the growth of human prenatal retinal neurospheres. The growth-promoting activity of RPE CM was mitogen-dependent and associated with an acute increase in transcription factor phosphorylation. Expanded populations of RPE CM-treated retinal neurospheres expressed numerous neurodevelopmental and eye specification genes and markers characteristic of neural and retinal progenitor cells, but gradually lost the potential to generate neurons upon differentiation. Misexpression of Mash1 restored the neurogenic potential of long-term cultures, yielding neurons with phenotypic characteristics of multiple inner retinal cell types. Thus, a novel combination of extrinsic and intrinsic factors was required to promote both progenitor cell proliferation and neuronal multipotency in human retinal neurosphere cultures. These results support a pro-proliferative and antiapoptotic role for RPE in human retinal development, reveal potential limitations of human retinal progenitor culture systems, and suggest a means for overcoming cell fate restriction in vitro.

Trophic factors and neuronal interactions regulate the cell cycle and Pax6 expression in Müller stem cells

The finding that Müller cells have stem cell properties in the retina has led to the hypothesis that they might be a source for replacing neurons lost in neurodegenerative diseases. However, utilization of Müller cells for regenerative purposes in the mammalian eye still requires identifying those factors that regulate their multipotentiality and proliferation. In addition, because Pax6 expression is indispensable for eye development, its regulation would be required during regeneration. In the present study we investigated the regulation of cell-cycle progression and Pax6 expression in pure Müller glial cell cultures and neuroglial cocultures from rat retinas. At early times in vitro, glial cells showed high expression of Pax6 and of nestin, a stem cell marker, and of markers of cell-cycle progression; expression of these markers decreased during development in parallel with increased glial differentiation. The addition of glial-derived neurotrophic factor, basic fibroblast growth factor, and insulin restored proliferation and also Pax6 and nestin expression in glial cells. Noteworthy, in neuroglial cocultures Müller cells retained Pax6 expression for longer periods, and, in turn, neuronal progenitors preserved their proliferative potential for several days in vitro. This suggests that neuroglial interactions mutually regulate their mitogenic capacity. In addition, in glial secondary cultures incubated with insulin, many neuroblast-like cells expressed the neuronal marker NeuN. Our results suggest that the proliferative capacity and the features of eye stem cells of Müller glial cells are regulated by molecular and cellular factors, which might then provide potential tools for manipulating retinal regeneration.

Stathmin expression during newt retina regeneration

Japanese common newts (Cynops pyrrhogaster) have high ability to regenerate their injured organs including neural tissues, for example, the neural retina belonging to central nervous system. We attempted to clarify the molecular mechanism underlying the formation of a neural network during newt retina regeneration, and focused on the microtubule dynamics controlled by stathmin family proteins. Stathmin is a small cytoplasmic phosphoprotein known to be a microtubule regulator. We isolated a clone encoding stathmin from the newt. The expression level of stathmin is higher in lung and spleen than in the adult intact retina where stathmin was localized on plexiform layers, the ganglion layer and in photoreceptor inner segments. However, in a regenerating process of the retina, stathmin was upregulated from an early regenerating stage until the retinal layered structure was formed. Immunohistochemical analyses revealed that stathmin existed all around the regenerating retina consisting of retinal progenitor cells. These results suggest that stathmin plays important roles in the construction and maintenance of retinal structure and its neural network, by controlling the proliferation of retinal progenitor cells and the microtubule dynamics of retinal neurons. Moreover, stathmin may function in the dedifferentiating process of retinal pigment epithelium cells.

Reactive changes of retinal astrocytes and Müller glial cells in kainate-induced neuroexcitotoxicity

The aim of this study was to investigate reactive changes of astrocytes and Müller glial cells in rats subjected to kainate treatment, which leads to neuronal degeneration in the ganglion cell layer and the inner border of the inner nuclear layer as confirmed by labelling with Fluoro-Jade B, a marker for degenerating neurons and fibres. Both the astrocytes and the Müller glial cells reacted vigorously to kainate injection as shown by their up-regulated expression of nestin, glial fibrillary acidic protein and glutamine synthetase. A major finding was the induced expression of nestin together with glial fibrillary acidic protein beginning at 1 day post-injection of kainate. The marked nestin expression appeared to be most intense at 1 day and was sustained till 2 weeks as compared with the untreated/normal retina. Western blotting analysis confirmed a marked increase in expression of nestin, glial fibrillary acidic protein and glutamine synthetase as compared with untreated/normal retina. Double labelling study revealed that astrocytes and Müller glial cells expressed the radial glia marker nestin, and incorporated bromodeoxyuridine to re-enter into their cell cycle. The induced expression of these proteins in astrocytes and Müller glial cells indicated an induction of gliotic responses and de-differentiation that may be associated with regenerative efforts after kainate-induced injury. Indeed, with the acquisition of an immature molecular profile as manifested by the induced expression of brain lipid-binding protein and doublecortin in astrocytes and Müller glial cells, the potential of these cells to de-differentiate in retinal neurodegeneration is greatly amplified.

Neurotrophin-3 administration alters neurotrophin, neurotrophin receptor and nestin mRNA expression in rat dorsal root ganglia following axotomy

In the months following transection of adult rat peripheral nerve some sensory neurons undergo apoptosis. Two weeks after sciatic nerve transection some neurons in the L4 and L5 dorsal root ganglia begin to show immunoreactivity for nestin, a filament protein expressed by neuronal precursors and immature neurons, which is stimulated by neurotrophin-3 (NT-3) administration. The aim of this study was to examine whether NT-3 administration could be compensating for decreased production of neurotrophins or their receptors after axotomy, and to determine the effect on nestin synthesis. The levels of mRNA in the ipsilateral and contralateral L4 and L5 dorsal root ganglia were analyzed using real-time polymerase chain reaction, 1 day, 1, 2 and 4 weeks after unilateral sciatic nerve transection and NT-3 or vehicle administration via s.c. micro-osmotic pumps. In situ hybridization was used to identify which cells and neurons expressed mRNAs of interest, and the expression of full-length trkC and p75NTR protein was investigated using immunohistochemistry. Systemic NT-3 treatment increased the expression of brain-derived neurotrophic factor, nestin, trkA, trkB and trkC mRNA in ipsilateral ganglia compared with vehicle-treated animals. Some satellite cells surrounding neurons expressed trkA and trkC mRNA and trkC immunoreactivity. NT-3 administration did not affect neurotrophin mRNA levels in the contralateral ganglia, but decreased the expression of trkA mRNA and increased the expression of trkB mRNA and p75NTR mRNA and protein. These data suggest that systemically administered NT-3 may counteract the decrease, or even increase, neurotrophin responsiveness in both ipsi- and contralateral ganglia after nerve injury.

EAAT1 and D-serine expression are early features of human retinal development

In the developing central nervous system (CNS), the activation of N-methyl-D-aspartate (NMDA) receptors is probably an important regulator of processes such as synaptogenesis and neurite growth. NMDA receptor activation is dependent upon the homeostasis of glutamate and the presence of co-agonists such as D-serine. We have investigated the expression of the glutamate transporter excitatory amino acid transporter-1 (EAAT1 or GLAST) as the key regulator of retinal extracellular glutamate levels, and the ontogeny of D-serine expression in the developing human retina. The expression of EAAT1 and D-serine was compared to the temporal and spatial distribution of the synaptic vesicle marker synaptophysin and the synaptic vesicle glutamate transporter vGLUT1. We also examined the co-expression of EAAT1 and cellular retinaldehyde-binding protein (CRALBP), and the co-expression of EAAT1 and D-serine. Human retinae aged 10-20 weeks' gestation (WG) were prepared for immunocytochemistry or for Western blotting. Expression of EAAT1 was evident at 10 WG in cell bodies, processes and end-feet of radial glia-like cells at all retinal eccentricities. D-serine immunolabelling was also evident in radial glia-like cells by 12 WG. In contrast, immunoreactivity for synaptophysin only started to appear in the central retina at 12 WG whilst immunoreactivity for vGLUT was slightly later. EAAT1 and d-serine were co-localised to the same cell population. In addition, EAAT1 and CRALBP were also co-localised to the same cell population of radial glia-like cells, suggesting that the EAAT1 and D-serine-positive cells may be Müller cells. This study shows that key potential modifiers of NMDA receptor activity are present before synaptic vesicle proteins are evident and may thus play a role in shaping synaptogenesis in the developing human retina.

Conversion of mammalian Müller glial cells into a neuronal lineage by in vitro aggregate-culture

Mammalian Müller glial cells are major glial cells in the retina. Here we report that these glial cells can be redirected towards a neuronal lineage by an aggregate-culture in vitro. Rat and macaque Müller glial cells did not express neuronal markers except after transfer to adhesive conditions. Furthermore, this expression could only take place in the presence of platelet-derived growth factor and valproic acid. We compared a normal monolayer-culture and an aggregate-culture, and rat Müller glial cells could only differentiate into neurons under non-adhesive conditions. However, Müller glial cells did not express the photoreceptor markers in vitro. After transplantation into the subretinal space, a retina-specific niche, rat Müller glial cells expressed the photoreceptor-specific marker, opsin (RET-P1). We demonstrate the potential of mammalian Müller glial cells as a source of photoreceptors, which may possibly contribute to the treatment of degenerative retinal diseases such as retinitis pigmentosa.

Nestin expression in Müller glial cells in postnatal rat retina and its upregulation following optic nerve transection

This study examined the nestin immunoexpression and its specific cellular localization in the developing retina of rats and investigated its putative changes in an altered environment. At postnatal day 0, nestin immunoexpression was detected in radially oriented cells considered to be neural progenitors that were glutamine synthetase (GS) negative. With age, it was localized in differentiating and differentiated GS positive Müller glial cells. Nestin expression was down-regulated as maturation proceeded, so that by 12 weeks, it was almost completely diminished as confirmed also by real time-polymerase chain reaction analysis. Nestin expression along with that of glial fibrillary acidic protein (GFAP) was induced and upregulated in mature Müller glial cells following optic nerve transection. It is suggested that both nestin and GFAP may be useful biomarkers in retinal injuries. In view of their cytoskeletal nature, the marked expression of nestin and GFAP may provide a structural support for the framework of retina which would be disrupted as a result of loss of neurons in optic nerve lesion. It may also be neuronal protective taking into consideration the close spatial and functional links between Müller glial cells and the axotomized ganglion cells.

Neural stem cell properties of Müller glia in the mammalian retina: regulation by Notch and Wnt signaling

The retina in adult mammals, unlike those in lower vertebrates such as fish and amphibians, is not known to support neurogenesis. However, when injured, the adult mammalian retina displays neurogenic changes, raising the possibility that neurogenic potential may be evolutionarily conserved and could be exploited for regenerative therapy. Here, we show that Müller cells, when retrospectively enriched from the normal retina, like their radial glial counterparts in the central nervous system (CNS), display cardinal features of neural stem cells (NSCs), i.e., they self-renew and generate all three basic cell types of the CNS. In addition, they possess the potential to generate retinal neurons, both in vitro and in vivo. We also provide direct evidence, by transplanting prospectively enriched injury-activated Müller cells into normal eye, that Müller cells have neurogenic potential and can generate retinal neurons, confirming a hypothesis, first proposed in lower vertebrates. This potential is likely due to the NSC nature of Müller cells that remains dormant under the constraint of non-neurogenic environment of the adult normal retina. Additionally, we demonstrate that the mechanism of activating the dormant stem cell properties in Müller cells involves Wnt and Notch pathways. Together, these results identify Müller cells as latent NSCs in the mammalian retina and hence, may serve as a potential target for cellular manipulation for treating retinal degeneration.

Presence of endocrine and exocrine markers in EGFP-positive cells from the developing pancreas of a nestin/EGFP mouse

In order to purify and characterize nestin-positive cells in the developing pancreas a transgenic mouse was generated, in which the enhanced green fluorescent protein (EGFP) was driven by the nestin second intronic enhancer and upstream promoter. In keeping with previous studies on the distribution of nestin, EGFP was expressed in the developing embryo in neurones in the brain, eye, spinal cord, tail bud and glial cells in the small intestine. In the pancreas there was no detectable EGFP at embryonic day 11.5 (E11.5). EGFP expression appeared at E12.5 and increased in intensity through E14.5, E18.5 and post-natal day 1. Flow cytometry was used to quantify and purify the EGFP positive population in the E15.5 pancreas. The purified (96%) EGFP-expressing cells, which represent 20% of the total cell population, were shown by RT/PCR to express exocrine cell markers (amylase and P48) and endocrine cell markers (insulin 1, insulin 2, and Ngn3). They also expressed, at a lower level, PDX-1, Isl-1, and the islet hormones pancreatic polypeptide, glucagon and somatostatin as well as GLUT2, the stem cell marker ABCG2 and PECAM, a marker of endothelial cells. It was further shown by immunocytochemistry of the E15.5 pancreas that EGFP colocalised in separate subpopulations of cells that expressed nestin, insulin and amylase. These results support the conclusion that nestin expressing cells can give rise to both endocrine and exocrine cells. The ability to purify these putative progenitor cells may provide further insights into their properties and function.

Induced expression of hematopoietic- and neurologic-expressed sequence 1 in retinal pigment epithelial cells during newt retina regeneration

Newts can regenerate their organs even as adults. For instance, when their neural retinas are completely removed by operation, the remaining retinal pigment epithelial (RPE) cells dedifferentiate to reconstruct neural retinas. To elucidate the molecular mechanisms of newt retina regeneration, we investigated genes upregulated in dedifferentiating RPE cells using differential display methods. We observed that a cDNA fragment of hematopoietic- and neurologic-expressed sequence 1 (Hn1) appeared to be induced within a few days of surgical removal of newt neural retina. Using an anti-HN1 antiserum against the recombinant HN1 protein, we carried out immunohistochemical analyses. The anti-HN1 antiserum recognized the plexiform layers and ganglion cell layer (GCL) but not the RPE cell layer in unoperated (normal) newt retinas. Using a glial fibrillary acidic protein antibody, Hn1 was shown to be possibly expressed in glial cells in normal neural retina. During retina regeneration, immunoreactivity for HN1 appeared in dedifferentiating RPE cells 10 days post-operation, and in retinal progenitor cells 18 days post-operation. Twenty seven days post-operation, HN1 immunoreactivity was localized in the plexiform layers and GCL as in the normal retina. Therefore, HN1 possibly plays an undefined role in dedifferentiating RPE cells and retinal progenitor cells during newt retina regeneration.

Endothelial cell proliferation in the choriocapillaris during human retinal differentiation

BACKGROUND

Differentiation patterns of the neural retina and its retinal vasculature are not well matched. The foveal region differentiates first, however the central retina is not vascularised until late in gestation. The authors explored the hypothesis that higher rates of endothelial cell proliferation in the choriocapillaris of the central retina might compensate for the slow growth of central retinal vessels, providing supplementary nutrients to the region during the early stages of neuronal maturation.

METHODS

Frozen sections of five human fetal eyes (14-18.5 weeks' gestation), were examined for Ki-67 and CD34 immunoreactivity using confocal microscopy. Measurements of choriocapillaris area and the number of proliferating choroidal endothelial cells were used to calculate the rate of choroidal endothelial proliferation at five different chorioretinal locations.

RESULTS

The choriocapillaris area is consistently greater in the foveal region than at other locations and increases progressively with age. A higher rate of endothelial cell proliferation was found in parts of the choriocapillaris associated with the undifferentiated (proliferating) neural retina, compared with the differentiated, central region.

CONCLUSION

The findings suggest that mechanisms regulating proliferation and growth of the choroidal vasculature are independent of differentiation in the neural retina, and are thus profoundly different from mechanisms that regulate formation of the retinal vasculature.