Sensational astrocytes: Mechanotransduction in adult brain function

Research progress on the immunological functions of Piezo1 a receptor molecule that responds to mechanical force

The human immune system is capable of defending against, monitoring, and self-stabilizing various immune cells. Differentiation, proliferation, and development of these cells are regulated by biochemical signals. Moreover, biophysical signals, such as mechanical forces, have been found to affect immune cell function, thus introducing a new area of immunological research. Piezo1, a mechanically sensitive ion channel, was awarded the Nobel Prize for Physiology and Medicine in 2021. This channel is present on the surface of many cells, and when stimulated by mechanical force, it controls calcium (Ca2+) inside the cells, leading to changes in downstream signals and thus regulating cell functions. Piezo1 is also expressed in various innate and adaptive immune cells and plays a major role in the immune function. In this review, we will explore the physiological functions and regulatory mechanisms of Piezo1 and its impact on innate and adaptive immunity. This may offer new insights into diagnostics and therapeutics for the prevention and treatment of diseases and surgical infections.

Astrocyte regulation of extracellular space parameters across the sleep-wake cycle

Multiple subfields of neuroscience research are beginning to incorporate astrocytes into current frameworks of understanding overall brain physiology, neuronal circuitry, and disease etiology that underlie sleep and sleep-related disorders. Astrocytes have emerged as a dynamic regulator of neuronal activity through control of extracellular space (ECS) volume and composition, both of which can vary dramatically during different levels of sleep and arousal. Astrocytes are also an attractive target of sleep research due to their prominent role in the glymphatic system, a method by which toxic metabolites generated during wakefulness are cleared away. In this review we assess the literature surrounding glial influences on fluctuations in ECS volume and composition across the sleep-wake cycle. We also examine mechanisms of astrocyte volume regulation in glymphatic solute clearance and their role in sleep and wake states. Overall, findings highlight the importance of astrocytes in sleep and sleep research.

Investigating the efficacy of vacuum sealing drainage versus traditional negative pressure drainage in treating deep incision infections following posterior cervical internal fixation-a retrospective cohort study

BACKGROUND

Assessing the efficacy and safety of Vacuum Sealing Drainage (VSD) in treating deep incision infections (DII) following posterior cervical internal fixation.

METHODS

We retrospectively studied the clinical effects of VSD and Traditional Negative Pressure Drainage (TND) on 12 patients with deep incision infection after posterior cervical fixation surgery who were treated in our department from 2012 to 2020. A comparison of patient-related factors (age, gender, BMI, comorbidities, initial internal fixation surgery segment, preoperative laboratory inflammation indicators) and surgical-related factors (postoperative duration of fever, positive rate of drainage fluid bacterial culture, Visual Analogue Scale (VAS) score at 3 days after surgery, laboratory indicators at 3 days after surgery, debridement frequency and drainage time, hospital stay, internal fixation retention rate, and infection recurrence rate) between the VSD group and the TND group was conducted using independent sample t tests to draw experimental conclusions.

RESULTS

This study included 12 patients, with six cases of VSD (5 males and 1 female) and six cases of TND (4 males and 2 females). The VSD group had significantly lower postoperative fever time (1.50 ± 0.46 days vs. 4.28 ± 0.97 days, P < 0.05), a higher positive rate of bacterial cultures in drainage fluid (5/6 vs. 2/6, P < 0.05), lower 3 day VAS scores (3.13 ± 0.83 vs. 3.44 ± 0.88, P < 0.05), lower 3 day CRP levels (66.89 ± 23.65 mg/L vs. 57.11 ± 18.18 mg/L, P < 0.05), a shorter total drainage time (14.50 ± 2.98 days vs. 22.56 ± 3.01 days, P < 0.05), and a higher total drainage flow rate (395.63 ± 60.97 ml vs. 155.56 ± 32.54 ml, P < 0.05) than the TND group (the total drainage volume throughout the entire treatment process). In addition, the frequency of debridement (2.67 ± 0.52 times vs. 3.17 ± 0.41 times, P < 0.05) and average hospital stay (23.13 ± 3.27 days vs. 34.33 ± 6.86 days, P < 0.05) were significantly lower in the VSD group, although both groups retained internal fixation.

CONCLUSIONS

VSD is a secure and effective treatment for deep incision infections that results from cervical posterior internal fixation surgery.

Exploring Piezo1, Piezo2, and TMEM150C in human brain tissues and their correlation with brain biomechanical characteristics

Unraveling the intricate relationship between mechanical factors and brain activity is a pivotal endeavor, yet the underlying mechanistic model of signaling pathways in brain mechanotransduction remains enigmatic. To bridge this gap, we introduced an in situ multi-scale platform, through which we delineate comprehensive brain biomechanical traits in white matter (WM), grey-white matter junctions (GW junction), and the pons across human brain tissue from four distinct donors. We investigate the three-dimensional expression patterns of Piezo1, Piezo2, and TMEM150C, while also examining their associated histological features and mechanotransduction signaling networks, particularly focusing on the YAP/β-catenin axis. Our results showed that the biomechanical characteristics (including stiffness, spring term, and equilibrium stress) associated with Piezo1 vary depending on the specific region. Moving beyond Piezo1, our result demonstrated the significant positive correlations between Piezo2 expression and stiffness in the WM. Meanwhile, the expression of Piezo2 and TMEM150C was shown to be correlated to viscoelastic properties in the pons and WM. Given the heterogeneity of brain tissue, we investigated the three-dimensional expression of Piezo1, Piezo2, and TMEM150C. Our results suggested that three mechanosensitive proteins remained consistent across different vertical planes within the tissue sections. Our findings not only establish Piezo1, Piezo2, and TMEM150C as pivotal mechanosensors that regulate the region-specific mechanotransduction activities but also unveil the paradigm connecting brain mechanical properties and mechanotransduction activities and the variations between individuals.

Mechanical properties of the brain: Focus on the essential role of Piezo1-mediated mechanotransduction in the CNS

BACKGROUND

The brain is a highly mechanosensitive organ, and changes in the mechanical properties of brain tissue influence many physiological and pathological processes. Piezo type mechanosensitive ion channel component 1 (Piezo1), a protein found in metazoans, is highly expressed in the brain and involved in sensing changes of the mechanical microenvironment. Numerous studies have shown that Piezo1-mediated mechanotransduction is closely related to glial cell activation and neuronal function. However, the precise role of Piezo1 in the brain requires further elucidation.

OBJECTIVE

This review first discusses the roles of Piezo1-mediated mechanotransduction in regulating the functions of a variety of brain cells, and then briefly assesses the impact of Piezo1-mediated mechanotransduction on the progression of brain dysfunctional disorders.

CONCLUSIONS

Mechanical signaling contributes significantly to brain function. Piezo1-mediated mechanotransduction regulates processes such as neuronal differentiation, cell migration, axon guidance, neural regeneration, and oligodendrocyte axon myelination. Additionally, Piezo1-mediated mechanotransduction plays significant roles in normal aging and brain injury, as well as the development of various brain diseases, including demyelinating diseases, Alzheimer's disease, and brain tumors. Investigating the pathophysiological mechanisms through which Piezo1-mediated mechanotransduction affects brain function will give us a novel entry point for the diagnosis and treatment of numerous brain diseases.