Retinal inflammation in murine models of type 1 and type 2 diabetes with diabetic retinopathy

AIMS/HYPOTHESIS

The loss of pericytes surrounding the retinal vasculature in early diabetic retinopathy underlies changes to the neurovascular unit that lead to more destructive forms of the disease. However, it is unclear which changes lead to loss of retinal pericytes. This study investigated the hypothesis that chronic increases in one or more inflammatory factors mitigate the signalling pathways needed for pericyte survival.

METHODS

Loss of pericytes and levels of inflammatory markers at the mRNA and protein levels were investigated in two genetic models of diabetes, Ins2Akita/+ (a model of type 1 diabetes) and Leprdb/db (a model of type 2 diabetes), at early stages of diabetic retinopathy. In addition, changes that accompany gliosis and the retinal vasculature were determined. Finally, changes in retinal pericytes chronically incubated with vehicle or increasing amounts of IFNγ were investigated to determine the effects on pericyte survival. The numbers of pericytes, microglia, astrocytes and endothelial cells in retinal flatmounts were determined by immunofluorescence. Protein and mRNA levels of inflammatory factors were determined using multiplex ELISAs and quantitative reverse transcription PCR (qRT-PCR). The effects of IFNγ on the murine retinal pericyte survival-related platelet-derived growth factor receptor β (PDGFRβ) signalling pathway were investigated by western blot analysis. Finally, the levels of cell death-associated protein kinase C isoform delta (PKCδ) and cleaved caspase 3 (CC3) in pericytes were determined by western blot analysis and immunocytochemistry.

RESULTS

The essential findings of this study were that both type 1 and 2 diabetes were accompanied by a similar progression of retinal pericyte loss, as well as gliosis. However, inflammatory factor expression was dissimilar in the two models of diabetes, with peak expression occurring at different ages for each model. Retinal vascular changes were more severe in the type 2 diabetes model. Chronic incubation of murine retinal pericytes with IFNγ decreased PDGFRβ signalling and increased the levels of active PKCδ and CC3.

CONCLUSIONS/INTERPRETATION

We conclude that retinal inflammation is involved in and sustains pericyte loss as diabetic retinopathy progresses. Moreover, IFNγ plays a critical role in reducing pericyte survival in the retina by reducing activation of the PDGFRβ signalling pathway and increasing PKCδ levels and pericyte apoptosis.

Role of Runx2 in Calcific Aortic Valve Disease in Mouse Models

Background: Calcific aortic valve disease is common in the aging population and is characterized by the histological changes of the aortic valves including extracellular matrix remodeling, osteochondrogenic differentiation, and calcification. Combined, these changes lead to aortic sclerosis, aortic stenosis (AS), and eventually to heart failure. Runt-related transcription factor 2 (Runx2) is a transcription factor highly expressed in the calcified aortic valves. However, its definitive role in the progression of calcific aortic valve disease (CAVD) has not been determined. In this study, we utilized constitutive and transient conditional knockout mouse models to assess the molecular, histological, and functional changes in the aortic valve due to Runx2 depletion. Methods: Lineage tracing studies were performed to determine the provenance of the cells giving rise to Runx2+ osteochondrogenic cells in the aortic valves of LDLr^-/- mice. Hyperlipidemic mice with a constitutive or temporal depletion of Runx2 in the activated valvular interstitial cells (aVICs) and sinus wall cells were further investigated. Following feeding with a diabetogenic diet, the mice were examined for changes in gene expression, blood flow dynamics, calcification, and histology. Results: The aVICs and sinus wall cells gave rise to Runx2+ osteochondrogenic cells in diseased mouse aortic valves. The conditional depletion of Runx2 in the SM22α+ aVICs and sinus wall cells led to the decreased osteochondrogenic gene expression in diabetic LDLr^-/- mice. The transient conditional depletion of Runx2 in the aVICs and sinus wall cells of LDLr^-/-ApoB¹⁰⁰ CAVD mice early in disease led to a significant reduction in the aortic peak velocity, mean velocity, and mean gradient, suggesting the causal role of Runx2 on the progression of AS. Finally, the leaflet hinge and sinus wall calcification were significantly decreased in the aortic valve following the conditional and temporal Runx2 depletion, but no significant effect on the valve cusp calcification or thickness was observed. Conclusions: In the aortic valve disease, Runx2 was expressed early and was required for the osteochondrogenic differentiation of the aVICs and sinus wall cells. The transient depletion of Runx2 in the aVICs and sinus wall cells in a mouse model of CAVD with a high prevalence of hemodynamic valve dysfunction led to an improved aortic valve function. Our studies also suggest that leaflet hinge and sinus wall calcification, even in the absence of significant leaflet cusp calcification, may be sufficient to cause significant valve dysfunctions in mice.

Class I histone deacetylases in retinal progenitors and differentiating ganglion cells

BACKGROUND

The acetylation state of histones has been used as an indicator of the developmental state of progenitor and differentiating cells. The goal of this study was to determine the nuclear localization patterns of Class I histone deacetylases (HDACs) in retinal progenitor cells (RPCs) and retinal ganglion cells (RGCs), as the first step in understanding their potential importance in cell fate determination within the murine retina.

RESULTS

The only HDAC to label RPC nuclei at E16 and P5 was HDAC1. In contrast, there was generally increased nuclear localization of all Class I HDACs in differentiating RGCs. Between P5 and P30, SOX2 expression becomes restricted to Müller glial, cholinergic amacrine cells, and retinal astrocytes. Cholinergic amacrine showed a combination of changes in nuclear localization of Class I HDACs. Strikingly, although Müller glia and retinal astrocytes express many of the same genes, P30 Müller glial cells showed nuclear localization only of HDAC1, while retinal astrocytes were positive for HDACs 1, 2, and 3.

CONCLUSION

These results indicate there may be a role for one or more of the Class I HDACs in retinal cell type-specific differentiation.

Microglia activation is essential for BMP7-mediated retinal reactive gliosis

Background

Our previous studies have shown that BMP7 is able to trigger activation of retinal macroglia. However, these studies showed the responsiveness of Müller glial cells and retinal astrocytes in vitro was attenuated in comparison to those in vivo, indicating other retinal cell types may be mediating the response of the macroglial cells to BMP7. In this study, we test the hypothesis that BMP7-mediated gliosis is the result of inflammatory signaling from retinal microglia.

Methods

Adult mice were injected intravitreally with BMP7 and eyes harvested 1, 3, or 7 days postinjection. Some mice were treated with PLX5622 (PLX) to ablate microglia and were subsequently injected with control or BMP7. Processed tissue was analyzed via immunofluorescence, RT-qPCR, or ELISA. In addition, cultures of retinal microglia were treated with vehicle, lipopolysaccharide, or BMP7 to determine the effects of BMP7-isolated cells.

Results

Mice injected with BMP7 showed regulation of various inflammatory markers at the RNA level, as well as changes in microglial morphology. Isolated retinal microglia also showed an upregulation of BMP-signaling components following treatment. In vitro treatment of retinal astrocytes with conditioned media from activated microglia upregulated RNA levels of gliosis markers. In the absence of microglia, the mouse retina showed a subdued gliosis and inflammatory response when exposed to BMP7.

Conclusions

Gliosis resulting from BMP7 is mediated through an inflammatory response from retinal microglia.

Electronic supplementary material

The online version of this article (doi:10.1186/s12974-017-0855-0) contains supplementary material, which is available to authorized users.

Bone morphogenetic protein 7 regulates reactive gliosis in retinal astrocytes and Müller glia

PURPOSE

The focus of this study was to determine whether bone morphogenetic proteins (BMPs) trigger reactive gliosis in retinal astrocytes and/or Müller glial cells.

METHODS

Retinal astrocytes and the Müller glial cell line MIO-M1 were treated with vehicle, BMP7, or BMP4. Samples from the treated cells were analyzed for changes in gliosis markers using reverse transcriptase - quantitative PCR (RT-qPCR) and western blotting. To determine potential similarities and differences in gliosis states, control and BMP-treated cells were compared to cells treated with sodium peroxynitrite (a strong oxidizing agent that will bring about some aspects of gliosis). Last, mature mice were microinjected intravitreally with BMP7 and analyzed for changes in gliosis markers using RT-qPCR, western blotting, and immunohistochemistry.

RESULTS

Treatment of retinal astrocyte cells and Müller glial cells with BMP7 regulated various reactive gliosis markers. When compared to the response of cells treated with sodium peroxynitrite, the profiles of gliosis markers regulated due to exposure to BMP7 were similar. However, as expected, the profiles including the oxidative agent and growth factor were not identical. Treatment of cells with BMP4, however, showed an attenuated response in comparison to peroxynitrite and BMP7 treatment. Injection of BMP7 into the mouse retina also triggered a reactive gliosis response 7 days after injection.

CONCLUSIONS

BMP7 induced changes in levels of mRNA and protein markers typically associated with reactive gliosis in retinal astrocytes and Müller glial cells, including glial fibrillary acidic protein (GFAP), glutamine synthetase (GS), a subset of chondroitin sulfate proteoglycans (CSPGs), matrix metalloproteinases (MMPs), and other molecules.

Histone deacetylase expression patterns in developing murine optic nerve

Background

Histone deacetylases (HDACs) play important roles in glial cell development and in disease states within multiple regions of the central nervous system. However, little is known about HDAC expression or function within the optic nerve. As a first step in understanding the role of HDACs in optic nerve, this study examines the spatio-temporal expression patterns of methylated histone 3 (K9), acetylated histone 3 (K18), and HDACs 1–6 and 8–11 in the developing murine optic nerve head.

Results

Using RT-qPCR, western blot and immunofluorescence, three stages were analyzed: embryonic day 16 (E16), when astrocyte precursors are found in the optic stalk, postnatal day 5 (P5), when immature astrocytes and oligodendrocytes are found throughout the optic nerve, and P30, when optic nerve astrocytes and oligodendrocytes are mature. Acetylated and methylated histone H3 immunoreactivity was co-localized in the nuclei of most SOX2 positive glia within the optic nerve head and adjacent optic nerve at all developmental stages. HDACs 1–11 were expressed in the optic nerve glial cells at all three stages of optic nerve development in the mouse, but showed temporal differences in overall levels and subcellular localization. HDACs 1 and 2 were predominantly nuclear throughout optic nerve development and glial cell maturation. HDACs 3, 5, 6, 8, and 11 were predominantly cytoplasmic, but showed nuclear localization in at least one stage of optic nerve development. HDACs 4, 9 and10 were predominantly cytoplasmic, with little to no nuclear expression at any time during the developmental stages examined.

Conclusions

Our results showing that HDACs 1, 2, 3, 5, 6, 8, and 11 were each localized to the nuclei of SOX2 positive glia at some stages of optic nerve development and maturation and extend previous reports of HDAC expression in the aging optic nerve. These HDACs are candidates for further research to understand how chromatin remodeling through acetylation, deacetylation and methylation contributes to glial development as well as their injury response.

Combined inhibition of PDE4 and PI3Kδ modulates the inflammatory component involved in the progression of chronic obstructive pulmonary disease

Chronic Obstructive Pulmonary Disease (COPD) represents a group of disorders with several underlying causes that hamper airflow into the lungs. Despite current intervention therapies, COPD remains a disease with a significant unmet medical need. Treatment with Phosphodiesterase (PDE) 4 inhibitors results in modest efficacy at clinically relevant doses. The objective of the current study is to evaluate the combination of a PDE4 (Roflumilast) and a Phosphoinositide-3-kinase (PI3K) δ (IC87114) inhibitor for their therapeutic potential in diminishing the inflammatory response associated with COPD. Due to their divergent and independent pathways, we hypothesize that the combination would be efficacious at low concentrations in an in vitro setting. Inhibition of TNFα, pAkt, MMP-9 in differentiated U937 macrophages upon stimulation with LPS/CSE was determined. Neutrophil functionality manifested by a modulation of elastase activity was estimated. Protective effect of drug combination on CSE induced apoptosis of lung epithelial cells was also determined. Data demonstrated that the combination of Roflumilast and IC87114 reduced TNFα, pAkt and MMP-9 at nanomolar concentrations and was several fold potent than either of the compounds alone. Inhibition of neutrophil elastase was also increased significantly with the combination along with a better protection against CSE induced apoptosis in alveolar epithelial cells, thereby providing a rationale for their evaluation in COPD patients.

Expression profiling of human donor lungs to understand primary graft dysfunction after lung transplantation

Lung transplantation is the treatment of choice for end-stage pulmonary diseases. A limited donor supply has resulted in 4,000 patients on the waiting list. Currently, 10-20% of donor organs offered for transplantation are deemed suitable under the selection criteria, of which 15-25% fail due to primary graft dysfunction (PGD). This has spawned efforts to re-examine the current selection criteria as well as search for alternative donor lungs selection criteria. In this study, we attempt to further our understanding of PGD by observing the changes in gene expression across donor lungs that developed PGD versus those that did not. From our analysis, we have obtained differentially expressed transcripts that were involved in signaling, apoptosis and stress-activated pathways. Results also indicate that metallothionein 3 was over expressed in lungs that didn't develop PGD. This is the first such attempt to perform expression profiling of actual human lungs used for transplantation, for the identification of a molecular signature for PGD.

Acceptance of HIV-1 education & voluntary counselling/testing by & seroprevalence of HIV-1 among, pregnant women in rural south India

BACKGROUND & OBJECTIVE

Since the first report of HIV-1 infection in Tamil Nadu, India, HIV-1 seroprevalence in India has increased steadily. Though interventions to prevent mother-to-child transmission (MTCT) are available, their implementation is a significant challenge. Therefore, among pregnant women in rural Tamil Nadu, the acceptance of education regarding HIV-1 infection and transmission and, among a systematic sample, knowledge, attitudes, and beliefs; the acceptance of HIV-1 voluntary counselling and testing (VCT); and the seroprevalence of HIV-1 infection as well as risk factors for seropositivity were assessed.

METHODS

Pregnant women registered in the antenatal clinics at Namakkal District Hospital and Rasipuram Government Hospital, Tamil Nadu, India, were offered an educational session regarding HIV-1 infection and transmission. HIV-1 VCT, with informed consent, was offered. Positive results with HIV-1 rapid testing were confirmed with HIV-1 ELISA and Western blot assays. With informed consent, a systematic sample of the study population was asked to participate in pre- and posteducation assessments. Chi-square tests were used to evaluate HIV-1 risk factors.

RESULTS

The educational session as well as VCT were well accepted by rural, pregnant, HIV-1- infected women. Of 3722 women registered for antenatal care at the two hospitals over a one year period, 3691 (99.2%) agreed to participate in the educational session and 3715 (99.8%) had VCT [74 had confirmed HIV-1 infection [seroprevalence: 2.0% (95% confidence interval (95%CI): 1.6%, 2.5%)]]. Of 759 eligible women, a systematic sample of 757 (99.7%) women participated in the pre- and post-education assessments. Although baseline knowledge regarding HIV-1 was limited, a highly significant improvement in such knowledge was observed (P<0.0001 for all comparisons of changes in knowledge, attitudes, and beliefs measured before and immediately after the educational session). The median per cent of correct responses increased from 26.4 per cent before the educational session to 93.8 per cent afterwards. Women whose husbands were long distance truck drivers were at increased risk of HIV-1 infection. Other factors associated with HIV-1 infection were clinical site (Namakkal District Hospital), a smaller number of persons in the household, being unmarried, and a history of previous surgeries.

INTERPRETATION & CONCLUSION

The acceptability of education and of VCT among antenatal clinic attendees in this study was encouraging. However, the relatively high seroprevalence highlights the spread of HIV-1 from high risk groups to the general population and emphasizes the need for primary prevention of HIV-1 infection among adolescent girls and women of reproductive age in India.

Oral facial digital syndrome

We report a female infant with features suggestive of Oral Facial Digital Syndrome (OFDS) Type I and associated cerebellar anomalies with Dandy-Walker malformation which suggest OFDS Type VI. The phenotypic overlap in this child OFDS type I and TypeVI raises the question as to whether they represent separate genetic entities. This pattern of abnormalities appears to be unique.