Role of TGFβ1 and WNT6 in FGF2 and BMP4-driven endothelial differentiation of murine embryonic stem cells

Roles of TLR4 in macrophage immunity and macrophage-pulmonary vascular/lymphatic endothelial cell interactions in sepsis

In sepsis, acute lung injury (ALI) is a severe complication and a leading cause of death, involving complex mechanisms that include cellular and molecular interactions between immune and lung parenchymal cells. In recent decades, the role of Toll-like receptor 4 (TLR4) in mediating infection-induced inflammation has been extensively studied. However, how TLR4 facilitates interactions between innate immune cells and lung parenchymal cells in sepsis remains to be fully understood. This study aims to explore the role of TLR4 in regulating macrophage immunity and metabolism in greater depth. It also seeks to reveal how changes in these processes affect the interaction between macrophages and both pulmonary endothelial cells (ECs) and lymphatic endothelial cells (LECs). Using TLR4 knockout mice and the combined approaches of single-cell RNA sequencing and experimental validation, we demonstrate that in sepsis, TLR4-deficient macrophages upregulate Abca1, enhance cholesterol efflux, and reduce glycolysis, promoting M2 polarization and attenuating inflammation. These metabolic and phenotypic shifts significantly affect their interactions with pulmonary ECs and LECs. Mechanistically, we uncovered that TLR4 operates through multiple pathways in endothelial dysfunction: macrophage TLR4 mediates inflammatory damage to ECs/LECs, while endothelial TLR4 both directly sensitizes cells to lipopolysaccharide-induced injury and determines their susceptibility to macrophage-derived inflammatory signals. These findings reveal the complex role of TLR4 in orchestrating both immune-mediated and direct endothelial responses during sepsis-induced ALI, supporting that targeting TLR4 on multiple cell populations may present an effective therapeutic strategy.

Fibroblast growth factor 2 enhances BMSC stemness through ITGA2-dependent PI3K/AKT pathway activation

Bone marrow-derived mesenchymal stem cells (BMSC) are promising cellular reservoirs for treating degenerative diseases, tissue injuries, and immune system disorders. However, the stemness of BMSCs tends to decrease during in vitro cultivation, thereby restricting their efficacy in clinical applications. Consequently, investigating strategies that bolster the preservation of BMSC stemness and maximize therapeutic potential is necessary. Transcriptomic and single-cell sequencing methodologies were used to perform a comprehensive examination of BMSCs with the objective of substantiating the pivotal involvement of fibroblast growth factor 2 (FGF2) and integrin alpha 2 (ITGA2) in stemness regulation. To investigate the impact of these genes on the BMSC stemness in vitro, experimental approaches involving loss and gain of function were implemented. These approaches encompassed the modulation of FGF2 and ITGA2 expression levels via small interfering RNA and overexpression plasmids. Furthermore, we examined their influence on the proliferation and differentiation capacities of BMSCs, along with the expression of stemness markers, including octamer-binding transcription factor 4, Nanog homeobox, and sex determining region Y-box 2. Transcriptomic analyzes successfully identified FGF2 and ITGA2 as pivotal genes responsible for regulating the stemness of BMSCs. Subsequent single-cell sequencing revealed that elevated FGF2 and ITGA2 expression levels within specific stem cell subpopulations are closely associated with stemness maintenance. Moreover, additional in vitro experiments have convincingly demonstrated that FGF2 effectively enhances the BMSC stemness by upregulating ITGA2 expression, a process mediated by the phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT) signaling pathway. This conclusion was supported by the observed upregulation of stemness markers following the induction of FGF2 and ITGA2. Moreover, administration of the BEZ235 pathway inhibitor resulted in the repression of stemness transcription factors, suggesting the substantial involvement of the PI3K/AKT pathway in stemness preservation facilitated by FGF2 and ITGA2. This study elucidates the involvement of FGF2 in augmenting BMSC stemness by modulating ITGA2 and activating the PI3K/AKT pathway. These findings offer valuable contributions to stem cell biology and emphasize the potential of manipulating FGF2 and ITGA2 to optimize BMSCs for therapeutic purposes.

Towards optimized tissue regeneration: a new 3D printable bioink of alginate/cellulose hydrogel loaded with thrombocyte concentrate

Introduction

Autologous platelet concentrate (APC) are pro-angiogenic and can promote wound healing and tissue repair, also in combination with other biomaterials. However, challenging defect situations remain demanding. 3D bioprinting of an APC based bioink encapsulated in a hydrogel could overcome this limitation with enhanced physio-mechanical interface, growth factor retention/secretion and defect-personalized shape to ultimately enhance regeneration.

Methods

This study used extrusion-based bioprinting to create a novel bioink of alginate/cellulose hydrogel loaded with thrombocyte concentrate. Chemico-physical testing exhibited an amorphous structure characterized by high shape fidelity. Cytotoxicity assay and incubation of human osteogenic sarcoma cells (SaOs2) exposed excellent biocompatibility. enzyme-linked immunosorbent assay analysis confirmed pro-angiogenic growth factor release of the printed constructs, and co-incubation with HUVECS displayed proper cell viability and proliferation. Chorioallantoic membrane (CAM) assay explored the pro-angiogenic potential of the prints in vivo. Detailed proteome and secretome analysis revealed a substantial amount and homologous presence of pro-angiogenic proteins in the 3D construct.

Results

This study demonstrated a 3D bioprinting approach to fabricate a novel bioink of alginate/cellulose hydrogel loaded with thrombocyte concentrate with high shape fidelity, biocompatibility, and substantial pro-angiogenic properties.

Conclusion

This approach may be suitable for challenging physiological and anatomical defect situations when translated into clinical use.

Pathological angiogenesis: mechanisms and therapeutic strategies

In multicellular organisms, angiogenesis, the formation of new blood vessels from pre-existing ones, is an essential process for growth and development. Different mechanisms such as vasculogenesis, sprouting, intussusceptive, and coalescent angiogenesis, as well as vessel co-option, vasculogenic mimicry and lymphangiogenesis, underlie the formation of new vasculature. In many pathological conditions, such as cancer, atherosclerosis, arthritis, psoriasis, endometriosis, obesity and SARS-CoV-2(COVID-19), developmental angiogenic processes are recapitulated, but are often done so without the normal feedback mechanisms that regulate the ordinary spatial and temporal patterns of blood vessel formation. Thus, pathological angiogenesis presents new challenges yet new opportunities for the design of vascular-directed therapies. Here, we provide an overview of recent insights into blood vessel development and highlight novel therapeutic strategies that promote or inhibit the process of angiogenesis to stabilize, reverse, or even halt disease progression. In our review, we will also explore several additional aspects (the angiogenic switch, hypoxia, angiocrine signals, endothelial plasticity, vessel normalization, and endothelial cell anergy) that operate in parallel to canonical angiogenesis mechanisms and speculate how these processes may also be targeted with anti-angiogenic or vascular-directed therapies.

Elevated trophoblastic Siglec6 contributes to the impairment of vascular endothelial cell functions by downregulating Wnt6/β-catenin signaling in preeclampsia

Preeclampsia (PE), a systemic vascular disorder, is the leading cause of maternal and perinatal morbidity and mortality, and its pathogenesis has yet to be fully elucidated. Siglec6, a transmembrane protein, is highly expressed in human placental trophoblasts, and previous studies have shown that Siglec6 overexpression correlates with PE, but the role of Siglec6 during PE progression is unknown. Here, we demonstrated that the mRNA and protein expression levels of Siglec6 were upregulated in early-onset PE placentas compared with uncomplicated pregnancies, and Siglec6 was primarily located in syncytiotrophoblasts (STBs) and extravillous trophoblasts (EVTs). Moreover, our results showed that chemical reagent-induced HIF-1α accumulation promoted the mRNA and protein levels of Siglec6 in HTR8/SVneo and BeWo cells. Although Siglec6 overexpression did not affect HTR8/SVneo cell proliferation, migration, and invasion, the conditional medium derived from the Siglec6 overexpressed HTR8/SVneo cells (Siglec6-OE-CM) significantly impaired the proliferation, migration, invasion, and tube formation of human umbilical vein endothelial cells (HUVECs). Subsequently, the transcriptome sequencing results revealed that Siglec6 overexpression led to the downregulation of Wnt6 in HTR8/SVneo cells, which was further confirmed by qPCR and ELISA. Recombinant human Wnt6 reversed Siglec6-OE-CM-mediated suppression of HUVEC functions by reactivating the Wnt/β-catenin signaling pathway. Altogether, our study found that elevated trophoblastic Siglec6 contributed to the impairment of vascular endothelial cell functions by downregulating Wnt6/β-catenin signaling.