Nestin is induced by hypoxia and is attenuated by hyperoxia in Müller glial cells in the adult rat retina

Nestin identifies a subpopulation of rat ventricular fibroblasts and participates in cell migration

Fibroblast progenitor cells migrate to the endocardial region during cardiogenesis, and the migration of ventricular fibroblasts to the ischemically damaged region of the infarcted adult heart is a seminal event of reparative fibrosis. The intermediate filament protein nestin is implicated in cell migration and expression identified in a subpopulation of scar-derived myofibroblasts. The present study tested the hypothesis that fibroblast progenitor cells express nestin, and the intermediate filament protein drives the migratory phenotype of ventricular fibroblasts. Transcription factor 21 (Tcf21)- and Wilms tumor 1 (WT1)-fibroblast progenitor cells identified in the epicardial/endocardial regions of the E12.5- to E13.5-day embryonic mouse heart predominantly expressed nestin. Nuclear Tcf21/WT1 staining was identified in neonatal rat ventricular fibroblasts (NNVFbs), and a subpopulation coexpressed nestin. Nuclear Tcf21/WT1 expression persisted in adult rat ventricular fibroblasts, whereas nestin protein levels were downregulated. Nestin-expressing NNVFbs exhibited a unique phenotype as the subpopulation was refractory to cell cycle reentry in response to selective stimuli. Nestin(-)- and nestin(+)-scar-derived rat myofibroblasts plated in Matrigel unmasked a migratory phenotype characterized by the de novo formation of lumen-like structures. The elongated membrane projections emanating from scar myofibroblasts delineating the boundary of lumen-like structures expressed nestin. Lentiviral short-hairpin RNA (shRNA)-mediated nestin depletion inhibited the in vitro migratory response of NNVFbs as the wound radius was significantly larger compared with NNVFbs infected with the empty lentivirus. Thus, nestin represents a marker of embryonic Tcf21/WT1(+)-fibroblast progenitor cells. The neonatal rat heart contains a distinct subpopulation of nestin-immunoreactive Tcf21/WT1(+) fibroblasts refractory to cell cycle reentry, and the intermediate filament protein may preferentially facilitate ventricular fibroblast migration during physiological/pathological remodeling.NEW & NOTEWORTHY Tcf21/WT1(+)-fibroblast progenitor cells of the embryonic mouse heart predominantly express the intermediate filament protein nestin. A subpopulation of Tcf21/WT1(+)-neonatal rat ventricular fibroblasts express nestin and are refractory to selective stimuli influencing cell cycle reentry. Scar-derived myofibroblasts plated in Matrigel elicit the formation of lumen-like structures characterized by the appearance of nestin(+)-membrane projections. Lentiviral shRNA-mediated nestin depletion in a subpopulation of neonatal rat ventricular fibroblasts suppressed the migratory response following the in vitro scratch assay.

Alteration of Mesenchymal Stem Cells Isolated from Glioblastoma Multiforme under the Influence of Photodynamic Treatment

The central hypothesis for the development of glioblastoma multiforme (GBM) postulates that the tumor begins its development by transforming neural stem cells into cancer stem cells (CSC). Recently, it has become clear that another kind of stem cell, the mesenchymal stem cell (MSC), plays a role in the tumor stroma. Mesenchymal stem cells, along with their typical markers, can express neural markers and are capable of neural transdifferentiation. From this perspective, it is hypothesized that MSCs can give rise to CSC. In addition, MSCs suppress the immune cells through direct contact and secretory factors. Photodynamic therapy aims to selectively accumulate a photosensitizer in neoplastic cells, forming reactive oxygen species (ROS) upon irradiation, initiating death pathways. In our experiments, MSCs from 15 glioblastomas (GB-MSC) were isolated and cultured. The cells were treated with 5-ALA and irradiated. Flow cytometry and ELISA were used to detect the marker expression and soluble-factor secretion. The MSCs' neural markers, Nestin, Sox2, and glial fibrillary acid protein (GFAP), were down-regulated, but the expression levels of the mesenchymal markers CD73, CD90, and CD105 were retained. The GB-MSCs also reduced their expression of PD-L1 and increased their secretion of PGE2. Our results give us grounds to speculate that the photodynamic impact on GB-MSCs reduces their capacity for neural transdifferentiation.

A2AR Antagonists Upregulate Expression of GS and GLAST in Rat Hypoxia Model

Background

The aim of this study was to research the effects of glutamine synthetase (GS) and glutamate aspartate transporter (GLAST) in rat Müller cells and the effects of an adenosine A_2AR antagonist (SCH 442416) on GS and GLAST in hypoxia both in vivo and in vitro.

Methods

This study used RT-PCR and Western blotting to quantify the expressions of GS and GLAST under different hypoxic conditions as well as the expressions of GS and GLAST at different drug concentrations. A cell viability assay was used to assess drug toxicity.

Results

mRNA and protein expression of GS and GLAST in hypoxia Group 24 h was significantly increased. mRNA and protein expressions of GS and GLAST both increased in Group 1 μM SCH 442416 compared with other groups. One micromolar SCH 442416 could upregulate GS and GLAST's activity in hypoxia both in vivo and in vitro.

Conclusions

Hypoxia activates GS and GLAST in rat retinal Müller cells in a short time in vitro. (2) A_2AR antagonists upregulate the activity of GS and GLAST in hypoxia both in vivo and in vitro.

Brn3a and Brn3b knockout mice display unvaried retinal fine structure despite major morphological and numerical alterations of ganglion cells

Ganglion cells (GCs), the retinal output neurons, receive synaptic inputs from bipolar and amacrine cells in the inner plexiform layer (IPL) and send information to the brain nuclei via the optic nerve. Although GCs constitute less than 1% of the total retinal cells, they occur in numerous types and are the first neurons formed during retinal development. Using Brn3a and Brn3b mutant mice in which the alkaline phosphatase gene was knocked-in (Badea et al. [Neuron] 2009;61:852-864; Badea and Nathans [Vision Res] 2011;51:269-279), we studied the general effects after gene removal on the retinal neuropil together with the consequences of lack of development of large numbers of GCs onto the remaining retinal neurons of the same class. We analyzed the morphology, number, and general architecture of various neuronal types presynaptic to GCs, searching for changes secondary to the decrement in the number of their postsynaptic partners, as well as the morphology and distribution of retinal astrocytes, for their strong topographical relation to GCs. We found that, despite GC losses, retinal organization in Brn3 null mice is remarkably similar to that of wild-type controls. J. Comp. Neurol. 527:187-211, 2019. © 2016 Wiley Periodicals, Inc.

Comparison of histopathological findings between idiopathic and secondary epiretinal membranes

To evaluate the histopathological findings of idiopathic and secondary epithelial membranes (ERMs). This study involved 19 ERM cases that underwent pars plana vitrectomy (PPV). ERM specimens were obtained from each patient during PPV and immediately fixed in 10 % formalin. Paraffin sections were stained with hematoxylin eosin (HE) and immunohistochemical analysis was performed with glial fibrillary acidic protein (GFAP), Ki-67, CD34, and nestin antibodies. The 19 ERM cases included 11 idiopathic ERM cases and 8 secondary ERM cases i.e., 2 eyes that underwent PPV for retinal detachment and 6 eyes that underwent PPV for proliferative diabetic retinopathy. HE staining showed that some of the idiopathic ERM specimens consisted of internal limiting membrane. In contrast, numerous invasive cells were observed in the secondary ERM specimens compared to the idiopathic ERM specimens. Immunohistochemical analysis revealed GFAP-positive cells in 4 of the 11 idiopathic ERMs cases, yet no nestin-, Ki-67-, or CD34-positive cells in those cases. In contrast, there were 4 GFAP-positive cases, 2 Ki67-positive cases, 3 CD34-positive cases, and 7 cases including nestin-positive cells. The findings of this study indicate that there are different histological characteristics between idiopathic and secondary ERM and that mature nestin-positive cells in the retina might be related to secondary ERM formation.

Modeling transient retinal ischemia in mouse by ligation of pterygopalatine artery

Background

Retinal ischemia is a major cause of visual impairment and blindness worldwide. The available therapeutic strategies have limited potential.

Purpose

In order to understand the pathophysiology and validating therapies for retinal ischemia, establishment of reproducible animal models is necessary.

Methods

In the model discussed in this article, the pterygopalatine artery (PPA) is ligated along with the external carotid artery for 3.5 hours and thereafter allowed to reperfuse. Because PPA supplies the blood to the ophthalmic artery, the ligation of this artery causes retinal ischemia.

Results

This article describes the validation of retinal ischemia-reperfusion model in mouse through PPA ligation and its validation through fluorescein fundus angiography (FFA) and immunofluorescence staining for glial fibrillary acidic protein (GFAP), a glial injury marker.

Conclusions

In conclusion this article describes the creation of mouse model of retinal ischemia-reperfusion injury which can be reproduced in a shorter time duration resulting in reduced mortality.

Nestin expression in mesenchymal stromal cells: regulation by hypoxia and osteogenesis

Background

The intermediate filament protein nestin is used as a marker for neural stem cells, and its expression is inversely correlated with cellular differentiation. More recently, nestin expression has also been described in other cell types including multipotential mesenchymal stromal cells (MSCs). In this study, we examined the expression of nestin in equine, canine and human bone marrow-derived MSCs undergoing osteogenic differentiation, to determine whether nestin levels were attenuated as the cells acquired a more mature phenotype. In addition, the expression of nestin may be under the influence of cellular hypoxia, as nestin expression is known to increase in areas of ischemic tissue damage. Therefore, we also examined the effects of hypoxia on expression of nestin in human MSCs and examined a role for hypoxia inducible factor 1-alpha (HIF-1α) and vascular endothelial growth factor (VEGF) in the response. Additionally, we quantified the temporal expression of nestin in the fracture callus during bone regeneration, a site that has been characterized as hypoxic.

Results

There were no significant changes in nestin expression in MSCs during osteogenic differentiation. There was a significant increase in expression of nestin mRNA and protein in human MSCs in response to hypoxia (1% O₂) or the chemical hypoxia mimetic desferroxamine. This may be due to upregulation of VEGF under hypoxia, as treatment of cells with the VEGF receptor antagonist CPO-P11 attenuated hypoxia-induced nestin expression. A significant increase in nestin mRNA expression was observed in the fracture callus of mice three and seven days post fracture.

Conclusions

Nestin was not a selective marker for MSCs, as its expression was maintained during osteogenic differentiation, in all species examined. Furthermore our data suggest that nestin expression can be induced by hypoxia, and that this increase in nestin is partially regulated by HIF-1α and VEGF. Interestingly, nestin levels were significantly upregulated at the fracture site. Further studies are required to understand the role of nestin in bone cell biology and ultimately bone regeneration.

Müller cell reactivity in response to photoreceptor degeneration in rats with defective polycystin-2

Background

Retinal degeneration in transgenic rats that express a mutant cilia gene polycystin-2 (CMV-PKD2(1/703)HA) is characterized by initial photoreceptor degeneration and glial activation, followed by vasoregression and neuronal degeneration (Feng et al., 2009, PLoS One 4: e7328). It is unknown whether glial activation contributes to neurovascular degeneration after photoreceptor degeneration. We characterized the reactivity of Müller glial cells in retinas of rats that express defective polycystin-2.

Methods

Age-matched Sprague-Dawley rats served as control. Retinal slices were immunostained for intermediate filaments, the potassium channel Kir4.1, and aquaporins 1 and 4. The potassium conductance of isolated Müller cells was recorded by whole-cell patch clamping. The osmotic swelling characteristics of Müller cells were determined by superfusion of retinal slices with a hypoosmotic solution.

Findings

Müller cells in retinas of transgenic rats displayed upregulation of GFAP and nestin which was not observed in control cells. Whereas aquaporin-1 labeling of photoreceptor cells disappeared along with the degeneration of the cells, aquaporin-1 emerged in glial cells in the inner retina of transgenic rats. Aquaporin-4 was upregulated around degenerating photoreceptor cells. There was an age-dependent redistribution of Kir4.1 in retinas of transgenic rats, with a more even distribution along glial membranes and a downregulation of perivascular Kir4.1. Müller cells of transgenic rats displayed a slight decrease in their Kir conductance as compared to control. Müller cells in retinal tissues from transgenic rats swelled immediately under hypoosmotic stress; this was not observed in control cells. Osmotic swelling was induced by oxidative-nitrosative stress, mitochondrial dysfunction, and inflammatory lipid mediators.

Interpretation

Cellular swelling suggests that the rapid water transport through Müller cells in response to osmotic stress is altered as compared to control. The dislocation of Kir4.1 will disturb the retinal potassium and water homeostasis, and osmotic generation of free radicals and inflammatory lipids may contribute to neurovascular injury.