Expression and proliferation profiles of PKC, JNK and p38MAPK in physiologically stretched human bladder smooth muscle cells

Stable hydrogel adhesion to polydimethylsiloxane enables cyclic mechanical stimulation of 3D-bioprinted smooth muscle constructs

During normal urination, smooth muscle cells (SMCs) in the lower urinary tract (LUT) are exposed to mechanical signals that have a critical impact on tissue structure and function. Nevertheless, the mechanisms underlying the maintenance of the contractile phenotype of SMCs remain poorly understood. This is due, in part, to a lack of studies that have examined the effects of mechanical loading using three-dimensional (3D) models. In this study, surface modifications of polydimethylsiloxane (PDMS) membrane were evaluated to investigate the effects of cyclic mechanical stimulation on SMC maturation in 3D constructs. Commercially available cell stretching plates were modified with amino or methacrylate groups to promote adhesion of 3D constructs fabricated by bioprinting. After 6 days of stimulation, the effects of mechanical stimulation on the expression of contractile markers at the mRNA and protein levels were analyzed. Methacrylate-modified surfaces supported stable adhesion of the 3D constructs to the membrane and facilitated cyclic mechanical stimulation, which significantly increased the expression of contractile markers at the mRNA and protein levels. These effects were found to be mediated by activation of the p38 MAPK pathway, as inhibition of this pathway abolished the effects of stimulation in a dose-dependent manner. These results provide valuable insights into the role of mechanical signaling in maintaining the contractile phenotype of bladder SMCs, which has important implications for the development of future treatments for LUT diseases.

3D Bioprinting of an In Vitro Model of a Biomimetic Urinary Bladder with a Contract-Release System

The development of curative therapy for bladder dysfunction is usually hampered owing to the lack of reliable ex vivo human models that can mimic the complexity of the human bladder. To overcome this issue, 3D in vitro model systems offering unique opportunities to engineer realistic human tissues/organs have been developed. However, existing in vitro models still cannot entirely reflect the key structural and physiological characteristics of the native human bladder. In this study, we propose an in vitro model of the urinary bladder that can create 3D biomimetic tissue structures and dynamic microenvironments to replicate the smooth muscle functions of an actual human urinary bladder. In other words, the proposed biomimetic model system, developed using a 3D bioprinting approach, can recreate the physiological motion of the urinary bladder by incorporating decellularized extracellular matrix from the bladder tissue and introducing cyclic mechanical stimuli. The results showed that the developed bladder tissue models exhibited high cell viability and proliferation rate and promoted myogenic differentiation potential given dynamic mechanical cues. We envision the developed in vitro bladder mimicry model can serve as a research platform for fundamental studies on human disease modeling and pharmaceutical testing.

Osthole down-regulates miR-30a and promotes autophagy to protect rats against myocardial ischemia/reperfusion injury

Background

This study aims to investigate the changes in miR-30a expression and myocardial autophagy following osthole treatment in a myocardial ischemia/reperfusion injury model.

Methods

Thirty male Wistar rats (weighing 170 to 220 g, aged 8 weeks) were randomly divided into three groups as control (sham) group, ischemia/reperfusion (model) group, and ischemia/ reperfusion + osthole post-treatment (osthole) group. Masson"s trichrome staining was used to detect myocardial collagen changes. Apoptotic cardiomyocytes in the ischemic area were labeled in situ by terminal deoxynucleotidyl transferase-mediated dUTP (2'-deoxyuridine 5'-triphosphate) nick end labeling assay. Levels of autophagy markers light chain 3 beta (LC3b) and Beclin-1 in myocardial tissue were detected by western blotting. Expression of miR-30a was detected by quantitative reverse transcriptionpolymerase chain reaction.

Results

Compared with the sham group, ischemia/reperfusion significantly increased collagen contents. Osthole significantly inhibited the ischemia/reperfusion-increased collagen contents. Osthole inhibited the ischemia/reperfusion-increased myocardial fibrosis, myocardial swelling, necrosis, and myocardial atrophy. Osthole also significantly inhibited the ischemia/reperfusionincreased apoptosis of myocardial cells. Moreover, the conversion of LC3b-I to LC3b-II and the Beclin-1 expression were significantly inhibited by ischemia/reperfusion. Osthole treatment significantly increased the conversion of LC3b-I to LC3b-II and Beclin-1 expression in ischemia/reperfusion rats. Finally, the expression of miR-30a was significantly increased in ischemia/reperfusion rats, while Osthole suppressed the expression of miR-30a.

Conclusion

Osthole promoted autophagy, thereby alleviating myocardial ischemia/reperfusion injury. Osthole protects the myocardium during autophagy by down-regulating miR-30a expression.

Mechanism of Stiff Substrates up-Regulate Cultured Neuronal Network Activity

Our previous work provided compelling evidence showing that substrate stiffness is crucial for regulating synaptic connectivity and excitatory synaptic transmission among neurons in the neuronal network. However, the underlying mechanisms remain elusive. In our study, polydimethylsiloxane (PDMS) substrates with different stiffness have been fabricated to investigate the mechanisms by which the substrate stiffness upregulates the formation and activity of the cultured neuronal network. Here we report that stiff substrate increased both the number of synapses and the efficacy of excitatory synaptic transmission. More colocalization of synaptotagmin and PSD-95 was observed in the neuronal network on stiff substrate, which indicated the synapse number has increased. We also found that the increased synapse number was mediated by Hevin and SPARC that are secreted from astrocyte. The increased efficacy of excitatory synaptic transmission induced by stiff substrate was explored in three aspects. First, stiff substrate enhanced the presynaptic activity through increasing the vesicular release probability (Pr) of neurotransmitters as well as the calcium influx. Second, stiff substrate reduced voltage-dependent Mg²⁺ blockade to N-methyl-d-aspartate receptor (NMDAR) channels, which led to higher postsynaptic activity. Third, our work suggested that the increased excitatory synaptic transmission in the neural network on stiff substrate involved the upregulated synaptic glutamate concentration. Taken together, these findings may provide a molecular mechanism underlying substrate stiffness regulation of excitatory synaptic transmission in the cultured neural network.

β-Adrenoceptor signaling regulates proliferation and contraction of human bladder smooth muscle cells under pathological hydrostatic pressure

BACKGROUND

Partial bladder outlet obstruction (PBOO) promotes bladder detrusor hyperplasia, increases bladder pressure, and decreases bladder compliance. To extensively explore its underlying mechanism, our study aimed to investigate the effect of pathological hydrostatic pressure on human bladder smooth muscle cell (hBSMC) proliferation and contraction through β-adrenoceptor (ADRB) signaling in vitro.

METHODS

hBSMCs were subjected to pathological hydrostatic pressure (100 cm H₂ O) to investigate the effect of ADRBs on the proliferation and contraction of hBSMCs treated with its agonists and/or antagonists.

RESULTS

Firstly, exposure to 100 cm H₂ O hydrostatic pressure significantly upregulated the expression of α-smooth muscle actin (α-SMA) in hBSMCs at 6 hours, and promoted cell proliferation at 24 hours. When subjected to hydrostatic pressure alone, hBSMCs treated with ADRB2 and ADRB3 agonists for 6 hours inhibited α-SMA expression compared with untreated cells. By contrast, hBSMCs treated with ADRB2 agonists for 24 hours suppressed cell proliferation compared with untreated cells. The two classical pathways of ADRB, protein kinase A (PKA), and exchange factor directly activated by cAMP (EPAC) inhibited the contraction of hBSMCs under hydrostatic pressure via regulating mothers against decapentaplegic homolog 2 (SMAD2) activity. The proliferation of hBSMCs was mainly regulated by the EPAC pathway through extracellular signal-regulated kinase 1/2 (ERK1/2) activity.

CONCLUSION

The contraction of hBSMCs under hydrostatic pressure was regulated by ADRB2 and ADRB3 via the PKA/EPAC-SMAD2 pathway, and the proliferation of hBSMCs was regulated by ADRB2 via the EPAC-ERK1/2 pathway. Compared with ADRB3, ADRB2 played a predominant role under pathological hydrostatic pressure. These findings markedly uncovered the underlying mechanism of ADRBs in PBOO and provided new insights into the efficient treatment of patients with PBOO.

Persistent distention of colon damages interstitial cells of Cajal through Ca2+ -ERK-AP-1-miR-34c-SCF deregulation

Gastrointestinal motility disorders (GMDs) are attributed to loss of interstitial cells of Cajal (ICC), whose survival and function are deeply dependent on the activation of KIT/SCF signalling. Based on the facts that gastrointestinal distention is common in GMD patients and SCF produced by smooth muscle cells (SMCs) is usually decreased before ICC loss, we considered a possible contribution of persistent gastrointestinal distention/stretch to SCF deficiency. In this study, chronic colonic distention mouse model, diabetic gastrointestinal paresis mouse model, cultured mouse colonic SMCs and colon specimens from Hirschsprung's disease patients were used. The results showed that SCF was clearly decreased in distent colon of mice and patients, and microRNA array and real-time PCR indicated a concomitant increase of miR-34c in distent colon. A negative regulation of miR-34c on SCF expression was confirmed by luciferase reporter assays together with knock-down and overexpression of miR-34c in cultured colonic SMCs. Using EMSA and ChIP assays, we further consolidated that in response to persistent stretch, the transcription factor AP-1/c-Jun was highly activated in colonic SMCs and significantly promoted miR-34c transcription by binding to miR-34c promoter. Knock-down or overexpression of AP-1/c-Jun in cultured colonic SMCs leads to down- or up-regulation of miR-34c, respectively. In addition, the activation of AP-1/c-Jun was through ERK1/2 signalling provoked by Ca²⁺ overload in colonic SMCs that were subject to persistent stretch. In conclusion, our data demonstrated that persistent distention/stretch on colonic SMCs could suppress SCF production probably through Ca²⁺ -ERK-AP-1-miR-34c deregulation, resulting in ICC loss or impairment and GMD progress.

Mechanical stretch regulates microRNA expression profile via NF-κB activation in C2C12 myoblasts

MicroRNAs (miRNAs/miRs) and nuclear factor (NF)-κB activation are involved in mechanical stretch-induced skeletal muscle regeneration. However, there are a small number of miRNAs that have been reported to be associated with NF‑κB activation during mechanical stretch-induced myogenesis. In the present study, C2C12 myoblasts underwent cyclic mechanical stretch in vitro, to explore the relationship between miRNA expression and NF‑κB activation during stretch-mediated myoblast proliferation. The results revealed that 10% deformation, 0.125 Hz cyclic mechanical stretch could promote myoblast proliferation. The miRNA expression profile was subsequently altered; miR‑500, ‑1934, ‑31, ‑378, ‑331 and ‑5097 were downregulated, whereas miR‑1941 was upregulated. These miRNAs were all involved in stretch‑mediated myoblast proliferation. Notably, the expression of these miRNAs was reversed following treatment of 0.125 Hz mechanically stretched C2C12 cells with NF‑κB inhibitors, which was accompanied by C2C12 cell growth suppression. Therefore, the present study is the first, to the best of our knowledge, to demonstrate that the NF‑κB‑dependent miRNA profile is associated with mechanical stretch-induced myoblast proliferation.

Persistent mechanical stretch-induced calcium overload and MAPK signal activation contributed to SCF reduction in colonic smooth muscle in vivo and in vitro

Gastrointestinal (GI) distention is a common pathological characteristic in most GI motility disorders (GMDs), however, their detail mechanism remains unknown. In this study, we focused on Ca²⁺ overload of smooth muscle, which is an early intracellular reaction to stretch, and its downstream MAPK signaling and also reduction of SCF in vivo and in vitro. We successfully established colonic dilation mouse model by keeping incomplete colon obstruction for 8 days. The results showed that persistent colonic dilation clearly induced Ca²⁺ overload and activated all the three MAPK family members including JNK, ERK and p38 in smooth muscle tissues. Similar results were obtained from dilated colon of patients with Hirschsprung's disease and stretched primary mouse colonic smooth muscle cells (SMCs). Furthermore, we demonstrated that persistent stretch-induced Ca²⁺ overload was originated from extracellular Ca²⁺ influx and endoplasmic reticulum (ER) Ca²⁺ release identified by treating with different Ca²⁺ channel blockers, and was responsible for the persistent activation of MAPK signaling and SCF reduction in colonic SMCs. Our results suggested that Ca²⁺ overload caused by smooth muscle stretch led to persistent activation of MAPK signaling which might contribute to the decrease of SCF and development of the GMDs.