Cx43 in Neural Progenitors Promotes Glioma Invasion in a 3D Culture System

Scaffold-based spheroid models of glioblastoma multiforme and its use in drug screening

Among several types of brain cancers, glioblastoma multiforme (GBM) is a terminal and aggressive disease with a median survival of 15 months despite the most intensive surgery and chemotherapy. Preclinical models that accurately reproduce the tumor microenvironment are vital for developing new therapeutic alternatives. Understanding the complicated interactions between cells and their surroundings is essential to comprehend the tumor's microenvironment, however the monolayer cell culture approach falls short. Numerous approaches are used to develop GBM cells into tumor spheroids, while scaffold-based spheroids provides the opportunity to investigate the synergies between cells as well as cells and the matrix. This review summarizes the development of various scaffold-based GBM spheroid models and the prospective for their use as drug testing systems.

Connexin 43: An Interface Connecting Neuroinflammation to Depression

Major depressive disorder (MDD) is a leading chronic mental illness worldwide, characterized by anhedonia, pessimism and even suicidal thoughts. Connexin 43 (Cx43), mainly distributed in astrocytes of the brain, is by far the most widely and ubiquitously expressed connexin in almost all vital organs. Cx43 forms gap junction channels in the brain, which mediate energy exchange and effectively maintain physiological homeostasis. Increasing evidence suggests the crucial role of Cx43 in the pathogenesis of MDD. Neuroinflammation is one of the most common pathological features of the central nervous system dysfunctions. Inflammatory factors are abnormally elevated in patients with depression and are closely related to nearly all links of depression. After activating the inflammatory pathway in the brain, the release and uptake of glutamate and adenosine triphosphate, through Cx43 in the synaptic cleft, would be affected. In this review, we have summarized the association between Cx43 and neuroinflammation, the cornerstones linking inflammation and depression, and Cx43 abnormalities in depression. We also discuss the significant association of Cx43 in inflammation and depression, which will help to explore new antidepressant drug targets.

Advances in 3D culture systems for therapeutic discovery and development in brain cancer

This review focuses on recent advances in 3D culture systems that promise more accurate therapeutic models of the glioblastoma multiforme (GBM) tumor microenvironment (TME), such as the unique anatomical, cellular, and molecular features evident in human GBM. The key components of a GBM TME are outlined, including microbiomes, vasculature, extracellular matrix (ECM), infiltrating parenchymal and peripheral immune cells and molecules, and chemical gradients. 3D culture systems are evaluated against 2D culture systems and in vivo animal models. The main 3D culture techniques available are compared, with an emphasis on identifying key gaps in knowledge for the development of suitable platforms to accurately model the intricate components of the GBM TME.

Abnormal Expression of Connexin43 in Cardiac Injury Induced by S-Band and X-Band Microwave Exposure in Rats

Although the effects of microwave exposure on the heart have gradually become the focus of domestic and foreign scholars, the biological effects caused by different doses and different frequency bands of exposure are still unclear. In this study, we will investigate the damaging effect of S-band and X-band microwave composite exposure on cardiac structure and function, as well as the pathophysiological significance of Cx43 in cardiac conduction dysfunction after exposure. We used S- and X-band radiation sources with the average power density of 5 and 10 mW/cm² to expose Wistar rats to single or composite exposure. At the 6^th hour, on the 7^th, 14^th, and 28^th days after exposure, ECG was used to detect the electrical conduction of the heart, and the myocardial enzyme was measured by the automatic biochemical analyzer. We selected the observation time points and groups with severe damage to observe the changes of myocardial structure and ultrastructure with an optical microscope and TEM; and to detect the expression and distribution of Cx43 by western blotting and immunohistochemistry. After exposure, the heart rate increased, the P wave amplitude decreased, and the R wave amplitude increased; the content of the myocardial enzyme in serum increased; the structure and ultrastructure of cardiac tissue were damaged. The damage was dose-dependent and frequency-dependent. The expression of Cx43 in myocardial tissue decreased, and distribution was abnormal. Taken together, these findings suggested that the mechanism of abnormal electrical conduction in the heart of rats by S- and X-band microwave exposure might be related to the decreased expression and disordered distribution of Cx43 after microwave exposure.

The Impact of Astrocytes and Endothelial Cells on Glioblastoma Stemness Marker Expression in Multicellular Spheroids

Introduction

Glioblastoma multiforme (GBM), the most common primary brain tumor in adults, is extremely malignant and lethal. GBM tumors are highly heterogenous, being comprised of cellular and matrix components, which contribute to tumor cell invasion, cancer stem cell maintenance, and drug resistance. Here, we developed a heterotypic 3D spheroid model integrating GBM cells with astrocytes and endothelial cells (ECs) to better simulate the cellular components of the tumor microenvironment and investigate their impact on the stemness marker expression of GBM cells, which has not been previously investigated.

Methods

We used U87 GBM cells, C8-D1A mouse astrocytes, and human umbilical vein ECs to construct co- and tri-culture spheroid models in low-attachment U-well plates. We characterized the expression of known stemness markers NESTIN, SOX2, CD133, NANOG, and OCT4 in these models and compared it to respective mixed monoculture spheroids (control) using qRT-PCR and immunostaining.

Results

We incorporated GBM cells and astrocytes/ECs in 1:1, 1:2, 1:4, and 1:9 ratio and observed spontaneous self-assembled spheroids in all coculture conditions. We observed changing spheroid size dynamics over 7 days and an increased expression in stemness markers in GBM-astrocyte and GBM-EC coculture spheroids in 1:4 and 1:9 coculture conditions, respectively. In a triculture model employing GBM cells, astrocytes, and ECs in a 1:4:9 ratio, we found an increased expression of all the stemness markers.

Conclusions

We elucidated the impact of astrocytes and ECs on GBM stemness marker expression. This multicellular spheroid model may provide an important tool for investigating the crosstalk between cell types in GBM.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12195-021-00691-y.

Chronic Stress and Gonadectomy Affect the Expression of Cx37, Cx40 and Cx43 in the Spinal Cord

The study aimed to determine whether the exposure to chronic stress and/or performance of gonadectomy might lead to disturbance in the expression of connexin (Cx) 37, 40 and 43 in the spinal cord (SC), as a potential explanation for sex differences in stress-related chronic pain conditions. After the rats were sham-operated or gonadectomized, three 10-day sessions of sham or chronic stress were applied. Immunohistochemistry and transmission electron microscopy (TEM) were used to examine Cx localization and expression in the SC. The gonadectomy resulted in an increase of Cx37 expression in the dorsal horn (DH) of the female rats, but chronic stress suppressed the effects of castration. In male rats, only the combined effects of castration and chronic stress increased Cx37 expression. The influence of chronic stress on the DH Cx40 expression was inversely evident after the castration: increased in the ovariectomized female rats, while decreased in the orchidectomized male rats. We did not find any effect of chronic stress and castration, alone or together, on Cx43 expression in the DH, but the percentage of Cx43 overlapping the astrocyte marker glial fibrillary acidic protein (gfap) increased in the male stressed group after the castration. In conclusion, the association of the chronic stress with sex hormone depletion results in disturbances of the SC Cx expression and might be a possible mechanism of disturbed pain perception after chronic stress exposure.

Connexin 43 and Sonic Hedgehog Pathway Interplay in Glioblastoma Cell Proliferation and Migration

Simple Summary

Glioblastoma is the product of accumulated genetic and epigenetic alteration where tumor cells support each other through cellular communication mechanisms and deregulated signalling processes. The autocrine and paracrine pathways between the intracellular and extracellular milieu is mediated by connexin 43, the main gap junction-forming protein driving glioblastoma progression. In this scenario, sonic hedgehog pathway, a key deregulated pathway involved in cell network signalling may affect connexin 43 expression, promoting glioblastoma pathobiology. In this study, we sought to explore how the modulation of the sonic hedgehog affects connexin 43 inducing glioblastoma hallmarks. To do this we evaluated biological effects of sonic hedgehog pathway modulation by purmorphamine and cyclopamine, a smoothened agonist and antagonist, respectively. We revealed that cell migration and proliferation are associated with connexin 43 expression upon sonic hedgehog modulation. Our study suggests that sonic hedgehog and connexin 43 axis may represent a potential therapeutic strategy for glioblastoma.

Abstract

Glioblastoma (GBM) represents the most common primary brain tumor within the adult population. Current therapeutic options are still limited by high rate of recurrences and signalling axes that promote GBM aggressiveness. The contribution of gap junctions (GJs) to tumor growth and progression has been proven by experimental evidence. Concomitantly, tumor microenvironment has received increasing interest as a critical process in dysregulation and homeostatic escape, finding a close link between molecular mechanisms involved in connexin 43 (CX43)-based intercellular communication and tumorigenesis. Moreover, evidence has come to suggest a crucial role of sonic hedgehog (SHH) signalling pathway in GBM proliferation, cell fate and differentiation. Herein, we used two human GBM cell lines, modulating SHH signalling and CX43-based intercellular communication in in vitro models using proliferation and migration assays. Our evidence suggests that modulation of the SHH effector smoothened (SMO), by using a known agonist (i.e., purmorphamine) and a known antagonist (i.e., cyclopamine), affects the CX43 expression levels and therefore the related functions. Moreover, SMO activation also increased cell proliferation and migration. Importantly, inhibition of CX43 channels was able to prevent SMO-induced effects. SHH pathway and CX43 interplay acts inducing tumorigenic program and supporting cell migration, likely representing druggable targets to develop new therapeutic strategies for GBM.