Connexins and angiogenesis: Functional aspects, pathogenesis, and emerging therapies (Review)

PDGF-AA guides cell crosstalk between human dental pulp stem cells in vitro via the PDGFR-α/PI3K/Akt axis

AIM

To explore the influence of PDGF-AA on cell communication between human dental pulp stem cells (DPSCs) by characterizing gap junction intercellular communication (GJIC) and its potential biomechanical mechanism.

METHODOLOGY

Quantitative real-time PCR was used to measure connexin family member expression in DPSCs. Cell migration and CCK-8 assays were utilized to examine the influence of PDGF-AA on DPSC migration and proliferation. A scrape loading/dye transfer assay was applied to evaluate GJIC triggered by PDGF-AA, a PI3K/Akt signalling pathway blocker (LY294002) and a PDGFR-α blocker (AG1296). Western blotting and immunofluorescence were used to test the expression and distribution of the Cx43 and p-Akt proteins in DPSCs. Scanning electron microscopy (SEM) and immunofluorescence were used to observe the morphology of GJIC in DPSCs.

RESULTS

PDGF-AA promoted gap junction formation and intercellular communication between human dental pulp stem cells. PDGF-AA upregulates the expression of Cx43 to enhance gap junction formation and intercellular communication. PDGF-AA binds to PDGFR-α and activates PI3K/Akt signalling to regulate cell communication.

CONCLUSIONS

This research demonstrated that PDGF-AA can enhance Cx43-mediated GJIC in DPSCs via the PDGFR-α/PI3K/Akt axis, which provides new cues for dental pulp regeneration from the perspective of intercellular communication.

Identification of angiogenesis-related subtypes, the development of a prognosis model, and features of tumor microenvironment in colon cancer

Angiogenesis is associated with tumor progression, prognosis, and treatment effect. However, the angiogenesis' underlying mechanisms in the tumor microenvironment (TME) still remain unclear. Understanding the dynamic interactions between angiogenesis and TME in colon adenocarcinoma (COAD) is necessary. We downloaded the transcriptome data and corresponding clinical data of colon cancer patients from The Cancer Genome Atlas (TCGA) and the Gene Expression Omnibus (GEO) databases, respectively. We identified two distinct angiogenesis-related molecular subtypes (subtype A and subtype B) and assessed the clinical features, prognosis, and infiltrating immune cells of patients in the two subtypes. According to the prognostic differential genes, we defined two different gene clusters to further explore the correlation between angiogenesis and tumor heterogeneity. Then, we construct the prognostic risk scoring model angiogenesis-related gene (ARG-score) including seven genes (ARMCX2, latent transforming growth factor β binding protein 1, ADAM8, FABP4, CCL11, CXCL11, ITLN1) using Lasso-multivariate cox method. We analyzed the correlation between ARG-score and prognosis, clinicopathological features, TME, molecular feature, cancer stem cells (CSCs), and microsatellite instability (MSI) status. To assess the application value of ARG-score in clinical treatment, immunophenotype score was used to predict patients' immunotherapy response in colon cancer. We found the mutations of ARGs in TCGA-COAD dataset from genetic levels and discussed their expression patterns based on TCGA and GEO datasets. We observed important differences in clinicopathological features, prognosis, immune feature, molecular feature between the two molecular subgroups. Then, we established an ARG-score for predicting OS and validated its predictive capability. A high ARG-score characterized by higher transcription level of ARGs, suggested lower MSI-high (MSI-H), lower immune score, and worse clinical stage and survival outcome. Additionally, the ARG-score was remarkably related to the CSCs index and immunotherapy sensitivity. We found two new molecular subtypes and two gene clusters based on ARGs and established an ARG-score. Multilayered analysis revealed that ARGs were remarkably correlated to the heterogeneity of colon cancer patients and explained the process of tumorigenesis and progression better. The ARG-score can help us better assess patients' survival outcomes and provide guidance for individualized treatment.

Opening of Cx43-formed hemichannels mediates the Ca2+ signaling associated with endothelial cell migration

Endothelial cell migration is a key process in angiogenesis. Progress of endothelial cell migration is orchestrated by coordinated generation of Ca2+ signals through a mechanism organized in caveolar microdomains. Connexins (Cx) play a central role in coordination of endothelial cell function, directly by cell-to-cell communication via gap junction and, indirectly, by the release of autocrine/paracrine signals through Cx-formed hemichannels. However, Cx hemichannels are also permeable to Ca2+ and Cx43 can be associated with caveolin-1, a structural protein of caveolae. We proposed that endothelial cell migration relies on Cx43 hemichannel opening. Here we show a novel mechanism of Ca2+ signaling in endothelial cell migration. The Ca2+ signaling that mediates endothelial cell migration and the subsequent tubular structure formation depended on Cx43 hemichannel opening and is associated with the translocation of Cx43 with caveolae to the rear part of the cells. These findings indicate that Cx43 hemichannels play a central role in endothelial cell migration and provide new therapeutic targets for the control of deregulated angiogenesis in pathological conditions such as cancer.