Microscale geometrical modulation of PIEZO1 mediated mechanosensing through cytoskeletal redistribution.

The microgeometry of the cellular microenvironment profoundly impacts cellular behaviors, yet the link between it and the ubiquitously expressed mechanosensitive ion channel PIEZO1 remains unclear. Herein, we describe a fluorescent micropipette aspiration assay that allows for simultaneous visualization of intracellular calcium dynamics and cytoskeletal architecture in real-time, under varied micropipette geometries. By integrating elastic shell finite element analysis with fluorescent lifetime imaging microscopy and employing PIEZO1-specific transgenic red blood cells and HEK cell lines, we demonstrate a direct correlation between the microscale geometry of aspiration and PIEZO1-mediated calcium signaling. We reveal that increased micropipette tip angles and physical constrictions lead to a significant reorganization of F-actin, accumulation at the aspirated cell neck, and subsequently amplify the tension stress at the dome of the cell to induce more PIEZO1's activity. Disruption of the F-actin network or inhibition of its mobility leads to a notable decline in PIEZO1 mediated calcium influx, underscoring its critical role in cellular mechanosensing amidst geometrical constraints.

Biomembrane force probe (BFP): Design, advancements, and recent applications to live-cell mechanobiology.

Mechanical forces play a vital role in biological processes at molecular and cellular levels, significantly impacting various diseases such as cancer, cardiovascular disease, and COVID-19. Recent advancements in dynamic force spectroscopy (DFS) techniques have enabled the application and measurement of forces and displacements with high resolutions, providing crucial insights into the mechanical pathways underlying these diseases. Among DFS techniques, the biomembrane force probe (BFP) stands out for its ability to measure bond kinetics and cellular mechanosensing with pico-newton and nano-meter resolutions. Here, a comprehensive overview of the classical BFP-DFS setup is presented and key advancements are emphasized, including the development of dual biomembrane force probe (dBFP) and fluorescence biomembrane force probe (fBFP). BFP-DFS allows us to investigate dynamic bond behaviors on living cells and significantly enhances the understanding of specific ligand-receptor axes mediated cell mechanosensing. The contributions of BFP-DFS to the fields of cancer biology, thrombosis, and inflammation are delved into, exploring its potential to elucidate novel therapeutic discoveries. Furthermore, future BFP upgrades aimed at improving output and feasibility are anticipated, emphasizing its growing importance in the field of cell mechanobiology. Although BFP-DFS remains a niche research modality, its impact on the expanding field of cell mechanobiology is immense.

Microfluidic post method for 3-dimensional modeling of platelet-leukocyte interactions.

Microvascular thrombosis and inflammation (thromboinflammation) are major causes of morbidity and mortality in critically ill patients with limited therapeutic options. Platelets are central to thromboinflammation, and microvascular platelet thrombi are highly effective at recruiting and activating leukocytes at sites of endothelial injury. Whilst parallel-plate flow chambers, microslides and straight microchannel assays have been widely used to recapitulate leukocyte adhesive behavior on 2-dimensional (2D) surfaces, none of these methods achieve high fidelity 3-dimensional (3D) geometries emulating microvascular platelet thrombi. As a result, the role of hydrodynamic factors in regulating leukocyte interactions with platelet thrombi remains ill-defined. Here, we report a microfluidic post model that allows visualization and analysis of neutrophil-platelet interactions in a 3D flow field. We have utilized the unique mechanosensitive features of platelets to enable selective micropatterning of the 3D posts with human or mouse platelets. By modulating the activation status of platelets, our method enables precise control of platelet surface reactivity and neutrophil recruitment. In addition, our microfluidic post assay accurately recapitulated the rolling versus stationary adhesion behavior of single neutrophils and demonstrated the efficacy of the P-selectin and Mac-1 blocking antibodies to reduce neutrophil recruitment and stationary adhesion, respectively. Moreover, the geometry of posts had a major influence on the efficiency of neutrophil recruitment and adhesion stability. This new post method highlights the importance of platelet 3D geometries in facilitating efficient, localized neutrophil recruitment. These findings have potentially important implications for the potent proinflammatory function of microvascular platelet thrombi.

Leptin treatment prevents impaired hypoglycemic counterregulation induced by exposure to severe caloric restriction or exposure to recurrent hypoglycemia.

Hypoglycemia-associated autonomic failure (HAAF) is a maladaptive failure in glucose counterregulation in persons with diabetes (PWD) that is caused by recurrent exposure to hypoglycemia. The adipokine leptin is known to regulate glucose homeostasis, and leptin levels fall following exposure to recurrent hypoglycemia. Yet, little is known regarding how reduced leptin levels influence glucose counterregulation, or if low leptin levels are involved in the development of HAAF. The purpose of this study was to determine the effect of hypoleptinemia on the neuroendocrine responses to hypoglycemia. We utilized two separate experimental paradigms known to induce a hypoleptinemic state: 60% caloric restriction (CR) in mice and three days of recurrent hypoglycemia (3dRH) in rats. A sub-set of animals were also treated with leptin (0.5-1.0 µg/g) during the CR or 3dRH periods. Neuroendocrine responses to hypoglycemia were assessed 60 min following an IP insulin injection on the terminal day of the paradigms. CR mice displayed defects in hypoglycemic counterregulation, indicated by significantly lower glucagon levels relative to controls, 13.5 pmol/L (SD 10.7) versus 64.7 pmol/L (SD 45) (p = 0.002). 3dRH rats displayed reduced epinephrine levels relative to controls, 1900 pg/mL (SD 1052) versus 3670 pg/mL (SD 780) (p = 0.030). Remarkably, leptin treatment during either paradigm completely reversed this effect by normalizing glucagon levels in CR mice, 78.0 pmol/L (SD 47.3) (p = 0.764), and epinephrine levels in 3dRH rats, 2910 pg/mL (SD 1680) (p = 0.522). These findings suggest that hypoleptinemia may be a key signaling event driving the development of HAAF and that leptin treatment may prevent the development of HAAF in PWD.

Hunter disease eClinic: interactive, computer-assisted, problem-based approach to independent learning about a rare genetic disease.

BACKGROUND: Computer-based teaching (CBT) is a well-known educational device, but it has never been applied systematically to the teaching of a complex, rare, genetic disease, such as Hunter disease (MPS II). AIM: To develop interactive teaching software functioning as a virtual clinic for the management of MPS II. IMPLEMENTATION AND RESULTS: The Hunter disease eClinic, a self-training, user-friendly educational software program, available at the Lysosomal Storage Research Group (http://www.lysosomalstorageresearch.ca), was developed using the Adobe Flash multimedia platform. It was designed to function both to provide a realistic, interactive virtual clinic and instantaneous access to supporting literature on Hunter disease. The Hunter disease eClinic consists of an eBook and an eClinic. The eClinic is the interactive virtual clinic component of the software. Within an environment resembling a real clinic, the trainee is instructed to perform a medical history, to examine the patient, and to order appropriate investigation. The program provides clinical data derived from the management of actual patients with Hunter disease. The eBook provides instantaneous, electronic access to a vast collection of reference information to provide detailed background clinical and basic science, including relevant biochemistry, physiology, and genetics. In the eClinic, the trainee is presented with quizzes designed to provide immediate feedback on both trainee effectiveness and efficiency. User feedback on the merits of the program was collected at several seminars and formal clinical rounds at several medical centres, primarily in Canada. In addition, online usage statistics were documented for a 2-year period. Feedback was consistently positive and confirmed the practical benefit of the program. The online English-language version is accessed daily by users from all over the world; a Japanese translation of the program is also available. CONCLUSIONS: The Hunter disease eClinic employs a CBT model providing the trainee with realistic clinical problems, coupled with comprehensive basic and clinical reference information by instantaneous access to an electronic textbook, the eBook. The program was rated highly by attendees at national and international presentations. It provides a potential model for use as an educational approach to other rare genetic diseases.

Lactobacillus helveticus and Bifidobacterium longum taken in combination reduce the apoptosis propensity in the limbic system after myocardial infarction in a rat model.

Myocardial infarction (MI) stimulates the release of pro-inflammatory substances that induce apoptosis in the limbic system. Pro-inflammatory cytokines are considered as the root cause of apoptosis, although the mechanism is not fully explained and/or understood at this time. In addition, depression may induce gastrointestinal perturbations that maintain the elevated levels of pro-inflammatory cytokines. It has been shown that some specific probiotic formulations may reduce gastrointestinal problems induced by stress and the pro/anti-inflammatory cytokine ratio. Therefore, we hypothesised that probiotics, when given prophylactically, may diminish the apoptosis propensity in the limbic system following a MI. Male adult Sprague-Dawley rats were given probiotics (Lactobacillus helveticus and Bifidobacterium longum in combination) or placebo in their drinking-water for four consecutive weeks. A MI was then induced in the rats by occluding the left anterior coronary artery for 40 min. Rats were killed following a 72 h reperfusion period. Infarct size was not different in the two groups. Bax/Bcl-2 (pro-apoptotic/anti-apoptotic) ratio and caspase-3 (pro-apoptotic) activity were reduced in the amygdala (lateral and medial), as well as in the dentate gyrus in the probiotics group when compared with the placebo. Akt activity (anti-apoptotic) was increased in these same three regions. No significant difference was observed in Ca1 and Ca3 for the different markers measured. In conclusion, the probiotics L. helveticus and B. longum, given in combination as preventive therapy, reduced the predisposition of apoptosis found in different cerebral regions following a MI.

Chronic pretreatment with celecoxib reduces infarct size.

This study was designed to evaluate the effect of long-term pretreatment with celecoxib, a cyclooxygenase-2 inhibitor, on myocardial infarct size. Celecoxib (3 mg/kg/day i.p; n = 16) or vehicle (DMSO 50%; EtOH 15%; distilled water, n = 16) was administered chronically to male Sprague-Dawley rats through ALZET osmotic pumps for 28 days. Under anaesthesia, the animals were then subjected to left anterior descending coronary artery occlusion for 40 minutes, followed by 24-hour reperfusion. The results show that myocardial infarct size in celecoxib-treated rats was significantly reduced compared to the control group (37.5 +/- 2.5% versus 48.0 +/- 2.6% of the area at risk, P < 0.05, n = 10 per group). Accumulation of neutrophils, estimated by myeloperoxidase levels, indicated an increase in the ischemic area without any significant difference between groups. No significant difference was observed between the treated and vehicle groups in terms of plasma prostaglandin E2 and tumour necrosis factor-alpha. Apoptosis, evaluated by Bax/Bcl-2 and terminal dUTP nick-end labelled-positive cells, was significantly decreased in the subendocardial layer of the ischemic area in celecoxib-treated rats. This study indicates that pretreatment with celecoxib can reduce infarct size by a mechanism, which may involve apoptosis inhibition.

Molecular characterization of deletion breakpoints in adults with 22q11 deletion syndrome.

22q11 Deletion syndrome (22q11DS) is a common microdeletion syndrome with variable expression, including congenital and later onset conditions such as schizophrenia. Most studies indicate that expression does not appear to be related to length of the deletion but there is limited information on the endpoints of even the common deletion breakpoint regions in adults. We used a real-time quantitative PCR (qPCR) approach to fine map 22q11.2 deletions in 44 adults with 22q11DS, 22 with schizophrenia (SZ; 12 M, 10 F; mean age 35.7 SD 8.0 years) and 22 with no history of psychosis (NP; 8 M, 14 F; mean age 27.1 SD 8.6 years). QPCR data were consistent with clinical FISH results using the TUPLE1 or N25 probes. Two subjects (one SZ, one NP) negative for clinical FISH had atypical 22q11.2 deletions confirmed by FISH using the RP11-138C22 probe. Most (n = 34; 18 SZ, 16 NP) subjects shared a common 3 Mb hemizygous 22q11.2 deletion. However, eight subjects showed breakpoint variability: a more telomeric proximal breakpoint (n = 2), or more centromeric (n = 3) or more telomeric distal breakpoint (n = 3). One NP subject had a proximal nested 1.4 Mb deletion. COMT and TBX1 were deleted in all 44 subjects, and PRODH in 40 subjects (19 SZ, 21 NP). The results delineate proximal and distal breakpoint variants in 22q11DS. Neither deletion extent nor PRODH haploinsufficiency appeared to explain the clinical expression of schizophrenia in the present study. Further studies are needed to elucidate the molecular basis of schizophrenia and clinical heterogeneity in 22q11DS.

A method for accurate detection of genomic microdeletions using real-time quantitative PCR.

BACKGROUND: Quantitative Polymerase Chain Reaction (qPCR) is a well-established method for quantifying levels of gene expression, but has not been routinely applied to the detection of constitutional copy number alterations of human genomic DNA. Microdeletions or microduplications of the human genome are associated with a variety of genetic disorders. Although, clinical laboratories routinely use fluorescence in situ hybridization (FISH) to identify such cryptic genomic alterations, there remains a significant number of individuals in which constitutional genomic imbalance is suspected, based on clinical parameters, but cannot be readily detected using current cytogenetic techniques. RESULTS: In this study, a novel application for real-time qPCR is presented that can be used to reproducibly detect chromosomal microdeletions and microduplications. This approach was applied to DNA from a series of patient samples and controls to validate genomic copy number alteration at cytoband 22q11. The study group comprised 12 patients with clinical symptoms of chromosome 22q11 deletion syndrome (22q11DS), 1 patient trisomic for 22q11 and 4 normal controls. 6 of the patients (group 1) had known hemizygous deletions, as detected by standard diagnostic FISH, whilst the remaining 6 patients (group 2) were classified as 22q11DS negative using the clinical FISH assay. Screening of the patients and controls with a set of 10 real time qPCR primers, spanning the 22q11.2-deleted region and flanking sequence, confirmed the FISH assay results for all patients with 100% concordance. Moreover, this qPCR enabled a refinement of the region of deletion at 22q11. Analysis of DNA from chromosome 22 trisomic sample demonstrated genomic duplication within 22q11. CONCLUSION: In this paper we present a qPCR approach for the detection of chromosomal microdeletions and microduplications. The strategic use of in silico modelling for qPCR primer design to avoid regions of repetitive DNA, whilst providing a level of genomic resolution greater than standard cytogenetic assays. The implementation of qPCR detection in clinical laboratories will address the need to replace complex, expensive and time consuming FISH screening to detect genomic microdeletions or duplications of clinical importance.

High-resolution mapping of amplifications and deletions in pediatric osteosarcoma by use of CGH analysis of cDNA microarrays.

Conventional cytogenetic and comparative genomic hybridization (CGH) studies have shown that osteosarcomas (OSs) are characterized by complex structural and numerical chromosomal alterations and gene amplification. In this study, we used high-resolution CGH to investigate recurrent patterns of genomic imbalance by use of DNA derived from nine OS tumors hybridized to a 19,200-clone cDNA microarray. In six OSs, there was copy number gain or amplification of 6p, with a minimal region of gain centering on segment 6p12.1. In seven OSs, the pattern of amplification affecting chromosome arm 8q showed high-level gains of 8q12-21.3 and 8q22-q23, with amplification of the MYC oncogene at 8q24.2. Seven OSs showed copy number gain or amplification of 17p between the loci bounded by GAS7 and PMI (17p11.2-17p12), and three of these tumors also showed small losses at 17p13, including the region containing TP53. An in silico analysis of the distribution of segmental duplications (duplicons) in this region identified a large number of tracts consisting of paralogous sequences mapping to the 17p region, encompassing the region of deletions and amplifications in OS. Interestingly, within this same region there were clusters of duplicons and several genes that are expressed during bone morphogenesis and in OS. In summary, microarray CGH analysis of the chromosomal imbalances of OS confirm the overall pattern observed by use of metaphase CGH and provides a more precise refinement of the boundaries of genomic gains and losses that characterize this tumor.