The regulation of β-adrenergic receptor-mediated PKA activation by substrate stiffness via microtubule dynamics in human MSCs

ECM stiffness regulates calcium influx into mitochondria via tubulin and VDAC1 activity

Calcium ions (Ca2+) play pivotal roles in regulating numerous cellular functions, including metabolism and growth, in normal and cancerous cells. Consequently, Ca2+ signaling is a vital determinant of cell fate and influences both cell survival and death. These intracellular signals are susceptible to modulation by various factors, including changes in the extracellular environment, which leads to mechanical alterations. However, the effect of extracellular matrix (ECM) stiffness variations on intracellular Ca2+ signaling remains underexplored. In this study, we aimed to elucidate the mechanisms of Ca2+ regulation through the mitochondria, which are crucial to Ca2+ homeostasis. We investigated how Ca2+ regulatory mechanisms adapt to different levels of ECM stiffness by simultaneously imaging the mitochondria and endoplasmic reticulum (ER) in live cells using genetically encoded biosensors. Our findings revealed that the uptake of mitochondrial Ca2+ through Voltage-Dependent Anion Channel 1 (VDAC1), facilitated by intracellular tubulin, is influenced by ECM stiffness. Unraveling these Ca2+ regulatory mechanisms under various conditions offers a novel perspective for advancing biomedical studies involving Ca2+ signaling.

Geometric constraint-triggered collagen expression mediates bacterial-host adhesion

Cells living in geometrically confined microenvironments are ubiquitous in various physiological processes, e.g., wound closure. However, it remains unclear whether and how spatially geometric constraints on host cells regulate bacteria-host interactions. Here, we reveal that interactions between bacteria and spatially constrained cell monolayers exhibit strong spatial heterogeneity, and that bacteria tend to adhere to these cells near the outer edges of confined monolayers. The bacterial adhesion force near the edges of the micropatterned monolayers is up to 75 nN, which is ~3 times higher than that at the centers, depending on the underlying substrate rigidities. Single-cell RNA sequencing experiments indicate that spatially heterogeneous expression of collagen IV with significant edge effects is responsible for the location-dependent bacterial adhesion. Finally, we show that collagen IV inhibitors can potentially be utilized as adjuvants to reduce bacterial adhesion and thus markedly enhance the efficacy of antibiotics, as demonstrated in animal experiments.

Dental-derived stem cells in tissue engineering: the role of biomaterials and host response

Dental-derived stem cells (DSCs) are attractive cell sources due to their easy access, superior growth capacity and low immunogenicity. They can respond to multiple extracellular matrix signals, which provide biophysical and biochemical cues to regulate the fate of residing cells. However, the direct transplantation of DSCs suffers from poor proliferation and differentiation toward functional cells and low survival rates due to local inflammation. Recently, elegant advances in the design of novel biomaterials have been made to give promise to the use of biomimetic biomaterials to regulate various cell behaviors, including proliferation, differentiation and migration. Biomaterials could be tailored with multiple functionalities, e.g., stimuli-responsiveness. There is an emerging need to summarize recent advances in engineered biomaterials-mediated delivery and therapy of DSCs and their potential applications. Herein, we outlined the design of biomaterials for supporting DSCs and the host response to the transplantation.

Tumour immune rejection triggered by activation of α2-adrenergic receptors

Immunotherapy based on immunecheckpoint blockade (ICB) using antibodies induces rejection of tumours and brings clinical benefit in patients with various cancer types¹. However, tumours often resist immune rejection. Ongoing efforts trying to increase tumour response rates are based on combinations of ICB with compounds that aim to reduce immunosuppression in the tumour microenvironment but usually have little effect when used as monotherapies^2,3. Here we show that agonists of α2-adrenergic receptors (α2-AR) have very strong anti-tumour activity when used as monotherapies in multiple immunocompetent tumour models, including ICB-resistant models, but not in immunodeficient models. We also observed marked effects in human tumour xenografts implanted in mice reconstituted with human lymphocytes. The anti-tumour effects of α2-AR agonists were reverted by α2-AR antagonists, and were absent in Adra2a-knockout (encoding α2a-AR) mice, demonstrating on-target action exerted on host cells, not tumour cells. Tumours from treated mice contained increased infiltrating T lymphocytes and reduced myeloid suppressor cells, which were more apoptotic. Single-cell RNA-sequencing analysis revealed upregulation of innate and adaptive immune response pathways in macrophages and T cells. To exert their anti-tumour effects, α2-AR agonists required CD4⁺ T lymphocytes, CD8⁺ T lymphocytes and macrophages. Reconstitution studies in Adra2a-knockout mice indicated that the agonists acted directly on macrophages, increasing their ability to stimulate T lymphocytes. Our results indicate that α2-AR agonists, some of which are available clinically, could substantially improve the clinical efficacy of cancer immunotherapy.

Propranolol suppresses gastric cancer cell growth by regulating proliferation and apoptosis

BACKGROUND

Despite improvements in gastric cancer treatment, the mortality associated with advanced gastric cancer is still high. The activation of β-adrenergic receptors by stress has been shown to accelerate the progression of several cancers. Accordingly, increasing evidence suggests that the blockade of β-adrenergic signaling can inhibit tumor growth. However, the effect of β-blockers, which target several signaling pathways, on gastric cancer remains to be elucidated. This study aimed to investigate the anti-tumor effects of propranolol, a non-selective β-blocker, on gastric cancer.

METHODS

We explored the effect of propranolol on the MKN45 and NUGC3 gastric cancer cell lines. Its efficacy and the mechanism by which it exerts anti-tumor effects were examined using several assays (e.g., cell proliferation, cell cycle, apoptosis, and wound healing) and a xenograft mouse model.

RESULTS

We found that propranolol inhibited tumor growth and induced G1-phase cell cycle arrest and apoptosis in both cell lines. Propranolol also decreased the expression of phosphorylated CREB-ATF and MEK-ERK pathways; suppressed the expression of matrix metalloproteinase-2, 9 and vascular endothelial growth factor; and inhibited gastric cancer cell migration. In the xenograft mouse model, propranolol treatment significantly inhibited tumor growth, and immunohistochemistry revealed that propranolol led to the suppression of proliferation and induction of apoptosis.

CONCLUSIONS

Propranolol inhibits the proliferation of gastric cancer cells by inducing G1-phase cell cycle arrest and apoptosis. These findings indicate that propranolol might have an opportunity as a new drug for gastric cancer.

Activated Cardiac Fibroblasts Control Contraction of Human Fibrotic Cardiac Microtissues by a β-Adrenoreceptor-Dependent Mechanism

Cardiac fibrosis represents a serious clinical problem. Development of novel treatment strategies is currently restricted by the lack of the relevant experimental models in a human genetic context. In this study, we fabricated self-aggregating, scaffold-free, 3D cardiac microtissues using human inducible pluripotent stem cell (iPSC)-derived cardiomyocytes and human cardiac fibroblasts. Fibrotic condition was obtained by treatment of cardiac microtissues with profibrotic cytokine transforming growth factor β1 (TGF-β1), preactivation of foetal cardiac fibroblasts with TGF-β1, or by the use of cardiac fibroblasts obtained from heart failure patients. In our model, TGF-β1 effectively induced profibrotic changes in cardiac fibroblasts and in cardiac microtissues. Fibrotic phenotype of cardiac microtissues was inhibited by treatment with TGF-β-receptor type 1 inhibitor SD208 in a dose-dependent manner. We observed that fibrotic cardiac microtissues substantially increased the spontaneous beating rate by shortening the relaxation phase and showed a lower contraction amplitude. Instead, no changes in action potential profile were detected. Furthermore, we demonstrated that contraction of human cardiac microtissues could be modulated by direct electrical stimulation or treatment with the β-adrenergic receptor agonist isoproterenol. However, in the absence of exogenous agonists, the β-adrenoreceptor blocker nadolol decreased beating rate of fibrotic cardiac microtissues by prolonging relaxation time. Thus, our data suggest that in fibrosis, activated cardiac fibroblasts could promote cardiac contraction rate by a direct stimulation of β-adrenoreceptor signalling. In conclusion, a model of fibrotic cardiac microtissues can be used as a high-throughput model for drug testing and to study cellular and molecular mechanisms of cardiac fibrosis.

Combination Treatment With Antihypertensive Agents Enhances the Effect of Qiliqiangxin on Chronic Pressure Overload-induced Cardiac Hypertrophy and Remodeling in Male Mice

Supplemental Digital Content is Available in the Text.

We previously showed that Qiliqiangxin (QL) capsules could ameliorate cardiac hypertrophy and remodeling in a mouse model of pressure overload. Here, we compared the effects of QL alone with those of QL combined with the following 3 types of antihypertensive drugs on cardiac remodeling and dysfunction induced by pressure overload for 4 weeks in mice: an angiotensin II type 1 receptor (AT₁-R) blocker (ARB), an angiotensin-converting enzyme inhibitor (ACEI), and a β-adrenergic receptor (β-AR) blocker (BB). Adult male mice (C57B/L6) were subjected to either transverse aortic constriction or sham operation for 4 weeks, and the drugs (or saline) were orally administered through gastric tubes. Cardiac function and remodeling were evaluated through echocardiography, catheterization, histology, and analysis of hypertrophic gene expression. Cardiomyocyte apoptosis and autophagy, AT₁-R and β₁-AR expression, and cell proliferation–related molecules were also examined. Although pressure overload–induced cardiac remodeling and dysfunction, hypertrophic gene reprogramming, AT₁-R and β₁-AR expression, and ERK phosphorylation were significantly attenuated by QL alone, QL + ARB, QL + ACEI, and QL + BB, the attenuation was stronger in the combination treatment groups. Moreover, apoptosis was reduced to a larger extent by each combination treatment than by QL alone, whereas autophagy was more strongly attenuated by either QL + ARB or QL + ACEI. None of the treatments significantly upregulated ErbB2 or ErbB4 phosphorylation, and none significantly downregulated C/EBPβ expression. Therefore, the effects of QL on chronic pressure overload–induced cardiac remodeling may be significantly increased when QL is combined with an ARB, an ACEI, or a BB.

Signal transduction of the physical environment in the neural differentiation of stem cells

Neural differentiation is largely dependent on extracellular signals within the cell microenvironment. These extracellular signals are mainly in the form of soluble factors that activate intracellular signaling cascades that drive changes in the cell nucleus. However, it is becoming increasingly apparent that the physical microenvironment provides signals that can also influence lineage commitment and very low modulus surfaces has been repeatedly demonstrated to promote neurogenesis. The molecular mechanisms governing mechano-induced neural differentiation are still largely uncharacterized; however, a growing body of evidence indicates that physical stimuli can regulate known signaling cascades and transcription factors involved in neural differentiation. Understanding how the physical environment affects neural differentiation at the molecular level will enable research and design of materials that will eventually enhance neural stem cell (NSC) differentiation, homogeneity and specificity.

Cellular modulation by the elasticity of biomaterials

The elasticity of the extracellular matrix has been increasingly recognized as a dominating factor of cell fate and activities. This review provides an overview of the general principles and recent advances in the field of matrix elasticity-dependent regulation of a variety of cellular activities and functions, the underlying biomechanical and molecular mechanisms, as well as the pathophysiological implications.

Spatiotemporal stability of neonatal rat cardiomyocyte monolayers spontaneous activity is dependent on the culture substrate

In native conditions, cardiac cells must continuously comply with diverse stimuli necessitating a perpetual adaptation. Polydimethylsiloxane (PDMS) is commonly used in cell culture to study cellular response to changes in the mechanical environment. The aim of this study was to evaluate the impact of using PDMS substrates on the properties of spontaneous activity of cardiomyocyte monolayer cultures. We compared PDMS to the gold standard normally used in culture: a glass substrate. Although mean frequency of spontaneous activity remained unaltered, incidence of reentrant activity was significantly higher in samples cultured on glass compared to PDMS substrates. Higher spatial and temporal instability of the spontaneous rate activation was found when cardiomyocytes were cultured on PDMS, and correlated with decreased connexin-43 and increased CaV3.1 and HCN2 mRNA levels. Compared to cultures on glass, cultures on PDMS were associated with the strongest response to isoproterenol and acetylcholine. These results reveal the importance of carefully selecting the culture substrate for studies involving mechanical stimulation, especially for tissue engineering or pharmacological high-throughput screening of cardiac tissue analog.