Neuronal nuclear calcium signaling suppression of microglial reactivity is mediated by osteoprotegerin after traumatic brain injury

Background

Traumatic brain injury (TBI) is characterized by massive changes in neuronal excitation, from acute excitotoxicity to chronic hyper- or hypoexcitability. Nuclear calcium signaling pathways are involved in translating changes in synaptic inputs and neuronal activity into discrete transcriptional programs which not only affect neuronal survival and synaptic integrity, but also the crosstalk between neurons and glial cells. Here, we report the effects of blunting neuronal nuclear calcium signals in the context of TBI.

Methods

We used AAV vectors to express the genetically encoded and nuclear-targeted calcium buffer parvalbumin (PV.NLS.mCherry) or the calcium/calmodulin buffer CaMBP4.mCherry in neurons only. Upon TBI, the extent of neuroinflammation, neuronal death and synaptic loss were assessed by immunohistochemistry and targeted transcriptome analysis. Modulation of the overall level of neuronal activity was achieved by PSAM/PSEM chemogenetics targeted to parvalbumin interneurons. The functional impact of neuronal nuclear calcium buffering in TBI was assessed by quantification of spontaneous whisking.

Results

Buffering neuronal nuclear calcium unexpectedly resulted in a massive and long-lasting increase in the recruitment of reactive microglia to the injury site, which was characterized by a disease-associated and phagocytic phenotype. This effect was accompanied by a substantial surge in synaptic loss and significantly reduced whisking activity. Transcriptome analysis revealed a complex effect of TBI in the context of neuronal nuclear calcium buffering, with upregulation of complement factors, chemokines and interferon-response genes, as well as the downregulation of synaptic genes and epigenetic regulators compared to control conditions. Notably, nuclear calcium buffering led to a substantial loss in neuronal osteoprotegerin (OPG), whereas stimulation of neuronal firing induced OPG expression. Viral re-expression of OPG resulted in decreased microglial recruitment and synaptic loss. OPG upregulation was also observed in the CSF of human TBI patients, underscoring its translational value.

Conclusion

Neuronal nuclear calcium signals regulate the degree of microglial recruitment and reactivity upon TBI via, among others, osteoprotegerin signals. Our findings support a model whereby neuronal activity altered after TBI exerts a powerful impact on the neuroinflammatory cascade, which in turn contributes to the overall loss of synapses and functional impairment.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-022-02634-4.

EPO treatment does not alter acute serum profiles of GFAP and S100B after TBI: A brief report on the Australian EPO-TBI clinical trial

PURPOSE

To determine the diagnostic and prognostic value of glial fibrillary acidic protein (GFAP) and S100B after traumatic brain injury (TBI) in an Erythropoietin (EPO) clinical trial and examine whether EPO therapy reduces biomarker concentrations.

MATERIALS AND METHODS

Forty-four patients with moderate-to-severe TBI were enrolled to a sub-study of the EPO-TBI trial. Patients were randomized to either Epoetin alfa 40,000 IU or 1 ml sodium chloride 0.9 as subcutaneous injection within 24 h of TBI.

RESULTS

GFAP and S100B were measured in serum by ELISA from D0 (within 24 h of injury, prior to EPO/vehicle administration) to D5. Biomarker concentrations were compared between injury severities, diffuse vs. focal TBI, 6-month outcome scores (GOS-E) and EPO or placebo treatments. At D0 GFAP was significantly higher than S100B (951 pg/mL vs. 476 pg/mL, p = 0.018). ROC analysis of S100B at 1D post-injury distinguished favorable vs. unfavorable outcomes (area under the curve = 0.73; p = 0.01). EPO did not reduce concentration of either biomarker.

CONCLUSIONS

Elevated serum concentrations of GFAP and S100B after TBI reflect a robust, acute glial response to injury. Consistent with lack of improved outcome in TBI patients treated with EPO and prior findings on neuronal and axonal markers, glial biomarker concentrations and acute profiles were not affected by EPO.

Determination of Fat,Moisture, and Protein in Meat and Meat Products by Using the FOSS FoodScan Near-Infrared Spectrophotometer with FOSS Artificial Neural Network Calibration Model and Associated Database: Collaborative Study

A collaborative study was conducted to evaluate the repeatability and reproducibility of the FOSS FoodScan near-infrared spectrophotometer with artificial neural network calibration model and database for the determination of fat, moisture, and protein in meat and meat products. Representative samples were homogenized by grinding according to AOAC Official Method 983.18. Approximately 180 g ground sample was placed in a 140 mm round sample dish, and the dish was placed in the FoodScan. The operator ID was entered, the meat product profile within the software was selected, and the scanning process was initiated by pressing the start button. Results were displayed for percent (g/100 g) fat, moisture, and protein. Ten blind duplicate samples were sent to 15 collaborators in the United States. The within-laboratory (repeatability) relative standard deviation (RSDr) ranged from 0.22 to 2.67% for fat, 0.23 to 0.92% for moisture, and 0.35 to 2.13% for protein. The between-laboratories (reproducibility) relative standard deviation (RSDR) ranged from 0.52 to 6.89% for fat, 0.39 to 1.55% for moisture, and 0.54 to 5.23% for protein. The method is recommended for Official First Action.

Single-Cell Profiling Identifies Key Pathways Expressed by iPSCs Cultured in Different Commercial Media

We assessed the pluripotency of human induced pluripotent stem cells (iPSCs) maintained on an automated platform using StemFlex and TeSR-E8 media. Analysis of transcriptome of single cells revealed similar expression of core pluripotency genes, as well as genes associated with naive and primed states of pluripotency. Analysis of individual cells from four samples consisting of two different iPSC lines each grown in the two culture media revealed a shared subpopulation structure with three main subpopulations different in pluripotency states. By implementing a machine learning approach, we estimated that most cells within each subpopulation are very similar between all four samples. The single-cell RNA sequencing analysis of iPSC lines grown in both media reports the molecular signature in StemFlex medium and how it compares to that observed in the TeSR-E8 medium.

Defined Medium Conditions for the Induction and Expansion of Human Pluripotent Stem Cell-Derived Retinal Pigment Epithelium

We demonstrate that a combination of Noggin, Dickkopf-1, Insulin Growth Factor 1 and basic Fibroblast Growth Factor, promotes the differentiation of human pluripotent stem cells into retinal pigment epithelium (RPE) cells. We describe an efficient one-step approach that allows the generation of RPE cells from both human embryonic stem cells and human induced pluripotent stem cells within 40-60 days without the need for manual excision, floating aggregates or imbedded cysts. Compared to methods that rely on spontaneous differentiation, our protocol results in faster differentiation into RPE cells. This pro-retinal culture medium promotes the growth of functional RPE cells that exhibit key characteristics of the RPE including pigmentation, polygonal morphology, expression of mature RPE markers, electrophysiological membrane potential and the ability to phagocytose photoreceptor outer segments. This protocol can be adapted for feeder, feeder-free and serum-free conditions. This method thereby provides a rapid and simplified production of RPE cells for downstream applications such as disease modelling and drug screening.

Generation of a human induced pluripotent stem cell line CERAi001-A-6 using episomal vectors

We report the generation of the hiPSC line CERAi001-A-6 from primary human dermal fibroblasts. Reprogramming was performed using episomal vector delivery of OCT4, SOX2, KLF4, L-MYC, LIN28 and shRNA for p53.

Development of a Modular Automated System for Maintenance and Differentiation of Adherent Human Pluripotent Stem Cells

Patient-specific induced pluripotent stem cells (iPSCs) have tremendous potential for development of regenerative medicine, disease modeling, and drug discovery. However, the processes of reprogramming, maintenance, and differentiation are labor intensive and subject to intertechnician variability. To address these issues, we established and optimized protocols to allow for the automated maintenance of reprogrammed somatic cells into iPSCs to enable the large-scale culture and passaging of human pluripotent stem cells (PSCs) using a customized TECAN Freedom EVO. Generation of iPSCs was performed offline by nucleofection followed by selection of TRA-1-60-positive cells using a Miltenyi MultiMACS24 Separator. Pluripotency markers were assessed to confirm pluripotency of the generated iPSCs. Passaging was performed using an enzyme-free dissociation method. Proof of concept of differentiation was obtained by differentiating human PSCs into cells of the retinal lineage. Key advantages of this automated approach are the ability to increase sample size, reduce variability during reprogramming or differentiation, and enable medium- to high-throughput analysis of human PSCs and derivatives. These techniques will become increasingly important with the emergence of clinical trials using stem cells.

Characterization of the retinal pigment epithelium in Friedreich ataxia

We assessed structural elements of the retina in individuals with Friedreich ataxia (FRDA) and in mouse models of FRDA, as well as functions of the retinal pigment epithelium (RPE) in FRDA using induced pluripotent stem cells (iPSCs). We analyzed the retina of the FRDA mouse models YG22R and YG8R containing a human FRATAXIN (FXN) transgene by histology. We complemented this work with post-mortem evaluation of eyes from FRDA patients. Finally, we derived RPE cells from patient FRDA-iPSCs to assess oxidative phosphorylation (OXPHOS) and phagocytosis. We showed that whilst the YG22R and YG8R mouse models display elements of retinal degeneration, they do not recapitulate the loss of retinal ganglion cells (RGCs) found in the human disease. Further, RPE cells differentiated from human FRDA-iPSCs showed normal OXPHOS and we did not observe functional impairment of the RPE in Humans.

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We examined the retinal pigment epithelium in Friedreich ataxia.

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We used mouse models, human postmortem eyes and human induced pluripotent stem cell-derived retinal pigment epithelium cells.

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We did not find evidence of retinal pigment epithelium impairment in humans.

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We described elements of degeneration in YG22R and YG8R mouse retina and human eyes.

Traumatic brain injury induces elevation of Co in the human brain

Following acute brain injury (<3 hours post-event), cobalt levels in the brain are significantly elevated. This elevation may have important implications for positron emission tomography neuroimaging for assessing brain injury severity.

Effects of Fetal Sex on Expression of the (Pro)renin Receptor and Genes Influenced by its Interaction With Prorenin in Human Amnion

Males are more likely to be born preterm than females. The causes are unknown, but it is suggested that intrauterine tissues regulate fetal growth and survival in a sex-specific manner. We postulated that prorenin binding to its prorenin/renin receptor receptor (ATP6AP2) would act in a fetal sex-specific manner in human amnion to regulate the expression of promyelocytic zinc finger, a negative regulator of ATP6AP2 expression as well as 2 pathways that might influence the onset of labor, namely transforming growth factor β1 (TGFB1) and prostaglandin endoperoxide synthase 2 (PTGS2). Our findings demonstrate that there are strong interactions between prorenin, ATP6AP2, and TGFB1 and that this system has a greater capacity in female amnion to stimulate profibrotic pathways, thus maintaining the integrity of the fetal membranes. In contrast, glucocorticoids or other factors independent of the prorenin/prorenin receptor pathway may be important regulators of PTGS2 in human pregnancy.

Anti-lysophosphatidic acid antibodies improve traumatic brain injury outcomes

Background

Lysophosphatidic acid (LPA) is a bioactive phospholipid with a potentially causative role in neurotrauma. Blocking LPA signaling with the LPA-directed monoclonal antibody B3/Lpathomab is neuroprotective in the mouse spinal cord following injury.

Findings

Here we investigated the use of this agent in treatment of secondary brain damage consequent to traumatic brain injury (TBI). LPA was elevated in cerebrospinal fluid (CSF) of patients with TBI compared to controls. LPA levels were also elevated in a mouse controlled cortical impact (CCI) model of TBI and B3 significantly reduced lesion volume by both histological and MRI assessments. Diminished tissue damage coincided with lower brain IL-6 levels and improvement in functional outcomes.

Conclusions

This study presents a novel therapeutic approach for the treatment of TBI by blocking extracellular LPA signaling to minimize secondary brain damage and neurological dysfunction.

Molecular characterization of renin-angiotensin system components in human intrauterine tissues and fetal membranes from vaginal delivery and cesarean section

A prorenin-angiotensin system (RAS) could, via the (pro)renin receptor (ATP6AP2), have various effects in human intrauterine tissues, either directly by prorenin/ATP6AP2 cell signaling, or indirectly via angiotensin II and/or angiotensin 1-7. Here we describe RAS components in fetal membranes, decidua and placenta collected at elective cesarean section (non-laboring), after spontaneous delivery (after labor, n = 38), and in myometria (n = 16) from elective (non-laboring) or emergency cesarean (laboring) deliveries. Angiotensinogen (AGT), angiotensin-converting enzyme 1 and 2 (ACE; ACE2), angiotensin receptor 1 and 2 (AGTR1; AGTR2) and angiotensin 1-7 receptor (MAS1) mRNAs were measured by qRT-PCR and proteins were localized by immunohistochemistry. In myometrium, prorenin (REN), ATP6AP2, and downstream signaling proteins zinc finger and BTB domain-containing protein 16 (ZBTB16), transforming growth factor-β1 (TGFβ1) and prostaglandin-endoperoxide synthase 2 (PTGS2) mRNAs were also measured. RAS mRNAs, except AGTR1 and AGTR2, were abundant in decidua and lowest in amnion compared to the other tissues. ACE, AGT and PTGS2 mRNAs were higher in laboring than non-laboring myometrium, suggesting that the myometrial RAS is involved in labor. Angiotensinogen and prorenin staining in amnion, chorion and decidua was pervasive despite their mRNAs being low in amnion and chorion. In placenta, prorenin, angiotensinogen and AGTR2 were present in syncytiotrophoblasts, ACE was in fetal endothelium, while ACE2 distribution was diffuse. AGTR1 and AGTR2 mRNAs and proteins were abundant. No differences were evident in the staining patterns with labor. These results are consistent with the hypothesis that fetal vascular ACE might contribute angiotensin II to the fetus, whilst syncytial ACE2 might hypothetically have a role in converting angiotensin II to angiotensin 1-7 in maternal blood.

147. MOLECULAR CHARACTERIZATION OF RENIN - ANGIOTENSIN SYSTEM COMPONENTS IN HUMAN INTRAUTERINE TISSUES AND FETAL MEMBRANES FROM VAGINAL DELIVERY AND CAESAREAN SECTION

The expression of the (pro)renin receptor (ATP6AP2) in late gestational human tissues suggests that the prorenin-angiotensin system (RAS) might influence pregnancy outcome. Here w e characterized the RAS in term fetal membranes (amnion and chorion), decidua and placenta (n = 38) from women undergoing elective cesarean section (non-labouring) or following spontaneous delivery (after labour), and myometrium (n = 16) from elective or emergency cesarean (labouring) deliveries. RT-qPCR was used to quantify prorenin (REN), AGT, ACE, ACE2, AGTR1, AGTR2, ATP6AP2 and MAS1 mRNAs, and immunohistochemistry was used to localize prorenin, AGT, ACE, ACE2 and AGTR1 proteins. In myometrium, mRNAs for downstream signalling proteins (ZBTB16, TGFB1 and PTGS2) were also measured. ACE and AGT mRNA levels were higher in labouring myometrium (P < 0.05), consistent with elevated production of angiotensin II (Ang II), which, by the upregulation of PTGS2 occurring in labour (P = 0.022), could influence labour. In amnion, expression of all RAS component mRNAs, except ATP6AP2, was low. After labour amnion showed lower ACE (P = 0.014) and higher AGTR2 (P = 0.01) mRNA levels. In decidua, RAS components other than AGTR1 and AGTR2 were abundant. Amnion and chorion exhibited higher immunostaining of AGT and prorenin than expected from their low mRNA levels, suggesting that these proteins could have been originated from decidua, where the cognate genes are more active. In placenta, prorenin and AGT were localized to syncytiotrophoblasts and ACE was localized to fetal capillary endothelial cells, while ACE2 distribution was diffuse. AGTR1 mRNA and protein expression was high in the placenta. We propose that ACE in fetal vessels could contribute Ang II to the fetus, while ACE2 in syncytiotrophoblasts might convert placental or maternal circulating Ang II to angiotensin-(1–7), which might then be supplied to the maternal bloodstream. In conclusion, the abundance and distribution of intrauterine RAS components suggest diverse roles for this local RAS in pregnancy.