Muscle Cell Nuclei Research Articles

Stress fiber strain is zero in normal aortic smooth muscle, elevated in hypertensive stretch, and minimal in wall thickening rats

Hypertension causes aortic wall thickening until the original wall stress is restored. We hypothesized that this regulation involves stress fiber (SF) tension transmission to the nucleus in smooth muscle cells (SMCs) and investigated the strain in the SF direction as a condition required for this transmission. Thoracic aortas from Wistar Kyoto (WKY) and spontaneously hypertensive rats (SHRs) were examined. SFs in aortic SMCs were fluorescently labeled and observed under a confocal microscope while stretched along the circumferential (θ) axis. Three conditions were studied: WKY physiological (WKYphys; blood pressure changes from diastolic to systolic for WKY), high-strain state (WKYhigh; diastolic to hypertensive level for WKY simulating initial hypertension), and SHR physiological (SHRphys; diastolic to systolic for SHR simulating after wall-thickening). SF strain and direction were measured. The SF inclination angle from the θ axis was 18° ± 3° in WKYphys, 13° ± 2° in WKYhigh, and 20° ± 1° in SHRphys. SF strain was 0.01 ± 0.02 in WKYphys, 0.20 ± 0.04 in WKYhigh, and 0.02 ± 0.02 SHRphys. SF strain was minimal in WKYphys, significantly increased in WKYhigh, and reduced to approximately zero in SHRphys. These findings support SFs function as mechanosensors in response to hypertension.

Investigation of PLGF, sFlt-1 expression in Plasenta Previa, Plasenta Accreta and Normotensive Plasentas in the 3rd Trimester of Pregnancy

Background: We aimed to immunohistochemically examine the expression level of Placental growth factor (PLGF) and Soluble FMS-like tyrosine kinase-1 (sFlt-1) proteins in normotensive, Placenta accreta (PA) and Placenta previa (PP). Materials and Methods: Three groups were created for the study: 20 Nomotensive placentas, 20 PP and 20 PA from women diagnosed with placenta samples. 4-6 μm thick sections were taken from the placentas, PLGF and sFlt-1 immunostaining were applied to the obtained sections, and their expression intensities and localizations in the tissues were determined. Results: As a result of our observations, normotensive placenta group; sFlt-1 expression was observed in hofbauer cells and syncytial nodes and PLGF positive expression was observed in nuclei of muscle cells in some tunica media region. PP and PA group; sFlt-1 expression was positive in decidua cells, hofbauer cells and dilated vascular endothelium. PP and PA group; negative PLGF expression was observed in syncytial nodes and positive PLGF expression was observed in hofbauer cells and endothelial cells. There was a significant difference between normotensive, PP and PA groups (p<0.05). Conclusions: It can be thought that sFlt-1 and PLGF may be important signal stimulators and markers in the trophoblastic degeneration, apoptotic cells, increase in angiogenesis and imbalance in implanta-tion seen in cases of PP and PA.

Interplay of atherosclerosis and medial degeneration in human ascending aorta

The previous understanding has been that atherosclerosis tends to increase distally from the ascending aorta, but recent studies and practical experience have indicated that atherosclerosis occurs in the ascending aorta more than previously thought. Medial degeneration is linked to aortic aneurysms, dissection and dilatation and has been related to increased mortality. There is a lack of data on the coexistence of atherosclerosis and medial degeneration in the ascending aorta and its outcome to clinical morbidity and mortality. Earlier studies have shown coexisting atherosclerosis and medial degeneration as significant risk indicators for coronary and cerebrovascular events. We aimed to analyze aortic specimens classified according to the consensus documents of the Society for Cardiovascular Pathology and the Association for European Cardiovascular Pathology particularly the comparison of variable morphological features with the atherosclerotic grade to gain more data about the coexistence of atherosclerosis and medial degeneration. We evaluated 217 specimens of human ascending aorta resected at Tampere University Heart Hospital because of aortic aneurysm, dissection or dilatation. None of the samples contained normal aortic morphology; atherosclerosis was found in a total of 75.8% of the samples and medial degeneration in all the samples. The present study is mostly in agreement with earlier research regarding the prevalence of different histological findings, even though a higher prevalence of atherosclerosis was found compared with most studies. There was no statistically significant association between atherosclerosis and medial degeneration, but a higher atherosclerotic grade was significantly associated with the presence of smooth muscle cell nuclei loss, smooth muscle cell disorganisation, elastic fibre thinning and medial fibrosis. Our study reinforces the perception that atherosclerotic lesions significantly occur in the ascending aorta and coexist with individual components of the medial degeneration.

Endonuclear Circ-calm4 regulates ferroptosis via a circR-Loop of the COMP gene in pulmonary artery smooth muscle cells

Pulmonary hypertension (PH) is a serious pulmonary vascular disease characterized by vascular remodeling. Circular RNAs (CircRNAs) play important roles in pulmonary hypertension, but the mechanism of PH is not fully understood, particularly the roles of circRNAs located in the nucleus. Circ-calmodulin 4 (circ-calm4) is expressed in both the cytoplasm and the nucleus of pulmonary arterial smooth muscle cells (PASMCs). This study aimed to investigate the role of endonuclear circ-calm4 in PH and elucidate its underlying signaling pathway in ferroptosis. Immunoblotting, quantitative real-time polymerase chain reaction (PCR), malondialdehyde (MDA) assay, immunofluorescence, iron assay, dot blot, and chromatin immunoprecipitation (ChIP) were performed to investigate the role of endonuclear circ-calm4 in PASMC ferroptosis. Increased endonuclear circ-calm4 facilitated ferroptosis in PASMCs under hypoxic conditions. We further identified the cartilage oligomeric matrix protein (COMP) as a downstream effector of circ-calm4 that contributed to the occurrence of hypoxia-induced ferroptosis in PASMCs. Importantly, we confirmed that endonuclear circ-calm4 formed circR-loops with the promoter region of the COMP gene and negatively regulated its expression. Inhibition of COMP restored the phenotypes related to ferroptosis under hypoxia stimulation combined with antisense oligonucleotide (ASO)-circ-calm4 treatment. We conclude that the circ-calm4/COMP axis contributed to hypoxia-induced ferroptosis in PASMCs and that circ-calm4 formed circR-loops with the COMP promoter in the nucleus and negatively regulated its expression. The circ-calm4/COMP axis may be useful for the design of therapeutic strategies for protecting cellular functionality against ferroptosis and pulmonary hypertension.

The Regulatory Role of Myomaker in the Muscle Growth of the Chinese Perch (Siniperca chuatsi).

The fusion of myoblasts is a crucial stage in the growth and development of skeletal muscle. Myomaker is an important myoblast fusion factor that plays a crucial role in regulating myoblast fusion. However, the function of Myomaker in economic fish during posthatching has been poorly studied. In this study, we found that the expression of Myomaker in the fast muscle of Chinese perch (Siniperca chuatsi) was higher than that in other tissues. To determine the function of Myomaker in fast muscle, Myomaker-siRNA was used to knockdown Myomaker in Chinese perch and the effect on muscle growth was determined. The results showed that the growth of Chinese perch was significantly decreased in the Myomaker-siRNA group. Furthermore, both the diameter of muscle fibers and the number of nuclei in single muscle fibers were significantly reduced in the Myomaker-siRNA group, whereas there was no significant difference in the number of BrdU-positive cells (proliferating cells) between the control and the Myomaker-siRNA groups. Together, these findings indicate that Myomaker may regulate growth of fast muscle in Chinese perch juveniles by promoting myoblast fusion rather than proliferation.

Non-Canonical Localization of Cardiac Troponins: Expanding Functions or Causing Pathologies?

The troponin complex-consisting of three subunits: troponin C (TnC), cardiac troponin I (cTnI) and cardiac troponin T (cTnT)-plays a key role in the regulation of myocardial contraction. Troponins are preferentially localized in the cytoplasm and bind to myofibrils. However, numerous, albeit scattered, studies have shown the presence of troponins in the nuclei of muscle cells. There is increasing evidence that the nuclear localization of troponins may be functionally important, making troponins an important nuclear player in the pathogenesis of various diseases including cancer and myopathies. Further studies in this area could potentially lead to the development of treatments for certain pathologies. In this review, we collected and discussed recent data on the properties of non-canonically localized cardiac troponins, the molecular mechanisms leading to this non-canonical localization, and the possible functions or pathological effects of these non-canonically localized troponins.

Sex Differences in the Histopathology of Acute Type A Aortic Dissections.

Although sex-related differences in cardiovascular surgery outcomes have increasingly garnered attention in the past decades, knowledge about sex disparities in the pathophysiology of acute type A aortic dissections (ATAADs) remains sparse. In this study, we evaluate the histopathologic and atherosclerotic lesions in female and male ATAAD patients. A total of 68 patients were studied: 51 ATAAD patients (mean age: 62.5 ± 10.8 years; 49% women) and 17 control patients (mean age: 63 ± 5.5 years; 53% women). Cardiovascular risk factors were assessed clinically. Intimal and medial histopathological features were systematically evaluated in all. Compared to the control group, all ATAAD patients showed significantly more elastic fiber pathology, mucoid extracellular matrix accumulation, smooth muscle cell nuclei loss, and overall medial degeneration (p < 0.0001). The tunica intima was significantly thinner in the ATAAD patients than in the control group (p < 0.023), with the latter exhibiting significantly more progressive atherosclerotic lesions than the former. No difference in medial vessel wall pathology was seen between female and male patients. As compared to male ATAAD patients, atherosclerotic lesions were more severe in female ATAAD patients, independent of age and the cardiovascular risk factor hypertension. All ATAAD patients had a significantly thinner tunica intima and significantly diseased tunica media compared to the control patients. Our results suggest that the severity of medial aortic pathology is not sex specific in ATAAD patients. Intimal differences between females and males could, however, be considered a potential risk factor for the development of an aortic dissection.

Regenerative role of mast cells and mesenchymal stem cells in histopathology of the sciatic nerve and tibialis cranialis muscle, following denervation in rats.

Atrophy of the muscles following denervation can lead to the death of myofibers. This study evaluated the sciatic nerve and tibialis cranialis muscle (TCM) regeneration using scaffold and cells. Ninety adult male Wistar rats were divided into six main groups (n=15) and three subgroups (2, 4, and 8 weeks). Groups: control; without surgery, Tr; sciatic nerve transected in silicone tube, S; collagen gel put inside the silicone tube, MC; placed 3×104 mast cells mixed with scaffold, MSC; placed 3×104 mesenchymal stem cells mixed with scaffold, and MC+MSC; 3×104 of each of the mast cell and mesenchymal stem cells along with scaffold. Animals were euthanized and sampled for muscle and nerve histological and nerve immunohistochemical evaluations. Diameter of muscle fibers, ratio of the muscle fiber's nuclei to the fibrocyte nuclei (mn/fn), ratio of the muscle fibers nuclei number to the muscle fiber's number (mn/mf), and ratio of the blood vessels number to the number of muscle fibers (v/mf) in all treatment groups, especially the MC + MSC group, increased compared to the Tr group but the number of mast cells, the percentage of sarcoplasmolysis, and necrosis fibers decreased. Histomorphometric results of the nerve in its various parts and immunohistochemistry results also showed improved nerve conduction, especially in the MC + MSC group. In this study, nerve improvement happened mainly for two reasons: cells and time. So, the most obvious improvement occurred in the group with mast and mesenchymal cells in the 8th week.

Decline of DNA damage response along with myogenic differentiation.

DNA integrity is incessantly confronted to agents inducing DNA lesions. All organisms are equipped with a network of DNA damage response mechanisms that will repair DNA lesions and restore proper cellular activities. Despite DNA repair mechanisms have been revealed in replicating cells, still little is known about how DNA lesions are repaired in postmitotic cells. Muscle fibers are highly specialized postmitotic cells organized in syncytia and they are vulnerable to age-related degeneration and atrophy after radiotherapy treatment. We have studied the DNA repair capacity of muscle fiber nuclei and compared it with the one measured in proliferative myoblasts here. We focused on the DNA repair mechanisms that correct ionizing radiation (IR)-induced lesions, namely the base excision repair, the nonhomologous end joining, and the homologous recombination (HR). We found that in the most differentiated myogenic cells, myotubes, these DNA repair mechanisms present weakened kinetics of recruitment of DNA repair proteins to IR-damaged DNA. For base excision repair and HR, this decline can be linked to reduced steady-state levels of key proteins involved in these processes.

Abstract 17276: NOTCH3-BMPR Interactions Drive Smooth Muscle Cell Proliferation and Medial Hyperplasia in Pulmonary Arterial Hypertension

Background: One of the characteristics of pulmonary arterial hypertension (PAH) is the proliferation of smooth muscle cells. In heritable PAH, aberrant BMPR2 signaling results in low levels of intracellular ID1. An important pathway involved in vascular smooth muscle cell proliferation and the development of non-heritable PAH is the NOTCH3-HES5 signaling pathway. Previous studies have demonstrated that HES-5 and ID-1 are peptides belonging to the basic helix-loop-helix family, and they act as transcriptional enhancers of cell cycle genes. Transcriptional enhancement or repression requires the heterodimerization of different HES and ID proteins. Hypothesis: We hypothesize that HES-5 binds to and degrades IDs in non-heritable cases of PAH. Methods: The half-life of ID proteins was assessed in human small pulmonary artery smooth muscle cells that either constitutively expressed or minimally expressed HES-5. In order to understand whether this effect was due to direct binding between HES-5 and ID1, co-immunoprecipitation experiments were performed. Immunofluorescent staining was used to detect the expression level of ID1 and HES-5. Proximity ligation assay (PLA) was utilized to examine of endogenous in-situ interaction of ID1-HES5. Results: We found that overexpression of HES-5 significantly diminished the half-life of ID1 and ID3, and had little effect on ID2. All three proteins localized to the nucleus of small pulmonary artery smooth muscle cells. Immunofluorescent staining confirmed elevated levels of HES and reduced levels of ID1 and ID3 in the medial layer of PAH vessels. By PLA assay, we show that HES-5 and ID1 as well as HES-5 and ID-3 physically associate with each other to the level of 40 nanometers. Conclusions: Constitutive NOTCH3 signaling and high intracellular HES-5 levels drive vascular smooth muscle cell proliferation in non-familial PAH by binding to and degrading ID intracellular proteins. Our study demonstrates cross-talk between the NOTCH3-pathway and the BMPR2 pathway in this disease, at the level of their downstream effectors: ID1 and HES-5. Further studies should shed light on how these two pathways control the PAH disease process.

FRI014 Exploring The Epigenetic Fingerprint Of Sedentary Behavior

Abstract Disclosure: A. Brener: None. D. Lorber: None. A. Reuveny: None. Y. Lebenthal: None. T. Volk: None. Eating habits and physical activity play a central role among the environmental factors that modulate biological aging. Sedentary lifestyle, characterized by increased waking time spent in minimal energy expenditure activity, is closely associated with increased cardiometabolic risk, a principal hallmark of aging. The biological mechanisms linking a sedentary lifestyle with metabolic derangements are incompletely understood. Exercise was reported as a stimulator of epigenetic modifications of the DNA in human muscle cell nuclei (myonuclei). Exploring the specific impact of sedentary behavior on epigenetics, especially among younger individuals, requires the exclusion of the effects of inflammatory and nutritional contributors to medical conditions. We developed an experimental animal model that imitates sedentary behavior in which a chromatin epigenetic landscape could be explored. We used third-instar Drosophila larvae carrying a temperature-sensitive mutation in the shibire gene coding for GTPase involved in neuronal synaptic vesicle transport. Shibire homozygous mutant larvae are paralyzed at restrictive temperature (&amp;gt;∼29°C) due to inhibition of neuromuscular junction vesicular transport, while muscle contraction is abolished without affecting other systems. Shibire and control (y,w) larvae were kept at 18°C or 30°C without food for six hours. They were then dissected, fixed and double-labeled with antibodies specific for epigenetic marks of active (H3K9ac) and repressive (H3K27me3) histone modifications. An anti-lamin fluorescent antibody served for nuclear membrane demarcation. Immunofluorescence images of epigenetic marks were acquired on a confocal microscope Zeiss LSM 800, after which a quantitative analysis of epigenetics marks was performed. At the restrictive temperature (30°C), the crawling motion of shibire mutant larvae ceased in contrast to control (shibire at 18°C). The crawling motion of the y,w larvae was similar at 18°C and 30°C. The mean repressive mark H3K27me3 decreased (p&amp;lt;0.001), while the mean active H3KPac increased (p&amp;lt;0.001) in the myonuclei of sedentary shibire larvae (30°C). The mean myonuclear active/repressed ratio of epigenetic marks (H3K9ac/H3K27me) was similar in both active shibire (18°C) and y,w at 18°C, while it increased significantly in sedentary shibire (30°C) (p&amp;lt;0.001). In contrast, this ratio decreased in the control larvae (y,w at 30°C) (p&amp;lt;0.001). The findings of this model, which was aimed at reflecting sedentary behavior in youth, revealed that muscle inactivity changed the epigenetic fingerprint in myonuclei, with a balance shift towards decreased chromatin methylation relative to acetylation. Our finding suggests a decline in the epigenetic control of gene transcription, reminiscent of decreased epigenetic repression described with aging. Presentation: Friday, June 16, 2023

Neuroprotective and Cardiometabolic Role of Vitamin E: Alleviating Neuroinflammation and Metabolic Disturbance Induced by AlCl3 in Rat Models.

Cardiovascular diseases (CVDs) and neurodegenerative disorders, such as diabetes mellitus and Alzheimer's disease, share a common pathophysiological link involving insulin resistance (IR), inflammation, and hypertension. Aluminium chloride (AlCl3), a known neurotoxicant, has been associated with neurodegeneration, cognitive impairment, and various organ dysfunctions due to the production of reactive oxygen species (ROS) and oxidative stress. In this study, we aimed to investigate the potential protective effects of metformin and vitamin E against AlCl3-induced neuroinflammation and cardiometabolic disturbances in rat models. Rats were divided into five groups: a normal control group, an AlCl3-treated diseased group without any treatment, and three groups exposed to AlCl3 and subsequently administered with metformin (100 mg/kg/day) alone, vitamin E (150 mg/kg/day) orally alone, or a combination of metformin (100 mg/kg/day) and vitamin E (150 mg/kg/day) for 45 days. We analyzed serum biomarkers and histopathological changes in brain, heart, and pancreatic tissues using H&E and Masson's trichrome staining and immunohistochemistry (IHC). Electrocardiogram (ECG) patterns were observed for all groups. The AlCl3-treated group showed elevated levels of inflammatory biomarkers, MDA, and disturbances in glycemic and lipid profiles, along with reduced insulin levels. However, treatment with the combination of metformin and vitamin E resulted in significantly reduced glucose, cholesterol, LDL, and TG levels, accompanied by increased insulin and HDL levels compared to the individual treatment groups. Histopathological analyses revealed that combination therapy preserved neuronal structures, muscle cell nuclei, and normal morphology in the brain, heart, and pancreatic tissues. IHC demonstrated reduced amyloid plaques and neurofibrillary tangles in the combination-treated group compared to the AlCl3-treated group. Moreover, the combination group showed a normal ECG pattern, contrasting the altered pattern observed in the AlCl3-treated group. Overall, our findings suggest that metformin and vitamin E, in combination, possess neuroprotective and cardiometabolic effects, alleviating AlCl3-induced neuroinflammation and metabolic disturbances.

Regulation of DNA damage and transcriptional output in the vasculature through a cytoglobin-HMGB2 axis

Identifying novel regulators of vascular smooth muscle cell function is necessary to further understand cardiovascular diseases. We previously identified cytoglobin, a hemoglobin homolog, with myogenic and cytoprotective roles in the vasculature. The specific mechanism of action of cytoglobin is unclear but does not seem to be related to oxygen transport or storage like hemoglobin. Herein, transcriptomic profiling of injured carotid arteries in cytoglobin global knockout mice revealed that cytoglobin deletion accelerated the loss of contractile genes and increased DNA damage. Overall, we show that cytoglobin is actively translocated into the nucleus of vascular smooth muscle cells through a redox signal driven by NOX4. We demonstrate that nuclear cytoglobin heterodimerizes with the non-histone chromatin structural protein HMGB2. Our results are consistent with a previously unknown function by which a non-erythrocytic hemoglobin inhibits DNA damage and regulates gene programs in the vasculature by modulating the genome-wide binding of HMGB2.

Matrix metalloproteinase-9 regulates afferent arteriolar remodeling and function in hypertension-induced kidney disease

This study tested if matrix metalloproteinase (MMP)-9 promoted microvascular pathology that initiates hypertensive (HT) kidney disease in salt-sensitive (SS) Dahl rats. SS rats lacking Mmp9 (Mmp9-/-) and littermate control SS rats were studied after one week on a normotensive 0.3% sodium chloride (Pre-HT SS and Pre-HT Mmp9-/-) or a hypertension-inducing diet containing 4.0% sodium chloride (HT SS and HT Mmp9-/-). Telemetry-monitored blood pressure of both the HT SS and HT Mmp9-/- rats increased and did not differ. Kidney microvessel transforming growth factor-beta 1 (Tgfb1) mRNA did not differ between Pre-HT SS and Pre-HT Mmp9-/- rats, but with hypertension and expression of Mmp9 and Tgfb1 increased in HT SS rats, along with phospho-Smad2 labeling of nuclei of vascular smooth muscle cells, and with peri-arteriolar fibronectin deposition. Loss of MMP-9 prevented hypertension-induced phenotypic transformation of microvascular smooth muscle cells and the expected increased microvascular expression of pro-inflammatory molecules. Loss of MMP-9 in vascular smooth muscle cells invitro prevented cyclic strain-induced production of active TGF-β1 and phospho-Smad2/3 stimulation. Afferent arteriolar autoregulation was impaired in HT SS rats but not in HT Mmp9-/- rats or the HT SS rats treated with doxycycline, an MMP inhibitor. HT SS but not HT Mmp9-/- rats showed decreased glomerular Wilms Tumor 1 protein-positive cells (a marker of podocytes) along with increased urinary podocin and nephrin mRNA excretion, all indicative of glomerular damage. Thus, our findings support an active role for MMP-9 in a hypertension-induced kidney microvascular remodeling process that promotes glomerular epithelial cell injury in SS rats.

Intrinsic histological and morphological abnormalities of the pediatric thoracic aorta in bicuspid aortic valve patients are predictive for future aortopathy

BackgroundPatients with a bicuspid aortic valve (BAV) have an increased risk to develop aortic complications. Many studies are pointing towards a possible embryonic explanation for the development of both a bicuspid aortic valve as well as a defective ascending aortic wall in these patients. The fetal and newborn ascending aortic wall has however scarcely been studied in bicuspid aortic valve patients. We hypothesize that early histopathological defects might already be visible in the fetal and pediatric ascending aortic wall of bicuspid aortic valve patients, indicating at an early embryonic defect. MethodsNon-dilated BAV ascending aortic wall samples were collected (n = 40), categorized in five age groups: premature (age range 17.5 weeks + days GA till 37.6 weeks + days GA) 2. neonate (age range 1 – 21 days) 3. infant (age range 1 month – 4 years) 4. adolescent (age range 12 years – 15 years) and 5. adult (age range 41 – 72 years). Specimen were studied for intimal and medial histopathological features. ResultsThe premature ascending aortic wall has a significantly thicker intimal and significantly thinner medial layer as compared to all other age categories (p < 0.05). After birth the intimal thickness decreases significantly. The medial layer increases in thickness before adulthood (p < 0.05) with an increasing number of elastic lamellae (p < 0.01) and interlamellar mucoid extracellular matrix accumulation (p < 0.0001). Intimal atherosclerosis was scarce and medial histopathological features such as overall medial degeneration, smooth muscle cell nuclei loss and elastic fiber fragmentation were not appreciated in the BAV ascending aortic wall of any age. ConclusionsThe main characteristics of a bicuspid ascending aortic wall are already present before adulthood, albeit not before birth. Considering the early manifestations of ascending aortic wall pathology in bicuspid aortic valve patients, the pediatric population should be considered while searching for markers predictive for future aortopathy.

Development of a cell line from skeletal trunk muscle of the fish Labeo rohita.

Labeo rohita is a widely cultivated tropical freshwater carp and found in rivers of South Asian region. A new cell line, designated LRM, has been developed from the muscle tissue of L. rohita. Muscle cells were subcultured up to 38 passages in a Leibovitz's-15 (L-15) supplemented with 10% FBS (Fetal Bovine Serum) and 10 ng/ml bFGF. The LRM cells exhibited fibroblastic morphology with a doubling time of 28h, and a plating efficiency of 17%. A maximum growth rate was observed for LRM cells at 28°C, 10% FBS and 10 ng/ml bFGF. A cytochrome C oxidase subunit I (COI) gene sequence was used to authenticate the developed cell line. Chromosome analysis revealed 50 diploid chromosomes. The fibroblastic characteristics of the of the LRM cells was confirmed by immunocytochemistry. The expression of MyoD gene in LRM cells was analyzed by quantitative PCR in comparison with passages 3, 18 and 32. The expression of MyoD was higher at passage 18 compared to the passages 3 and 32. The LRM cells attached properly onto the 2D scaffold and the expression of the F-actin filament protein was confirmed by phalloidin staining followed by counter staining with DAPI to observe the distribution of the muscle cell nuclei and the cytoskeleton protein. A revival rate of 70-80% was achieved when the LRM cells were cryopreserved at - 196°C using liquid nitrogen. This study would further contribute to understanding the in vitro myogenesis and progress toward cultivated fish meat production.

Hallazgos histopatológicos en la disección y rotura de la aorta torácica. Estudio de 54 casos de autopsia

IntroductionThoracic aortic dissection/rupture has a high mortality, constituting 3.9-5.4% of sudden deaths in forensic series. Medial histopathological findings associated with these entities have received multiple terms and definitions. In 2016, the European Association for Cardiovascular Pathology and the Society for Cardiovascular Pathology published a consensus document, applied to surgical specimens, to unify criteria. The aim of this work is to assess its application in forensic autopsies. A secondary objective is to study inflammatory changes useful for dating. Material and methodsAortic histological preparations of the 54 cases of sudden deaths due to aortic rupture/dissection studied between 2019 and 2022 were reviewed. ResultsMedial degeneration was observed in 49 cases (90.8%) (severe in 42.9%). By lesions, the order of frequency was: fragmentation and/or loss of elastic fibers (74.1%); accumulation of extracellular mucoid matrix (61.1%); loss of smooth muscle cell nuclei (48.1%) and collapse of the media (44.4%). Some lesions of the consensus paper could not be assessed. No significant differences were found by age; presence or not of collagenopathies; or bi/tricuspid aortic valves. Granulation tissue or neutrophilic infiltrate was observed in those deceased with pain several days or <24 h before death, respectively. ConclusionWith the application of the document, lesions in the media are found in >90% of cases and fundamental lesions can be studied. The inflammatory response to rupture/dissection appears to correlate with the timing of dissection/rupture.

Ligustrazine alleviates pulmonary arterial hypertension in rats by promoting the formation of myocardin transcription complex in the nucleus of pulmonary artery smooth muscle cells.

Pulmonary arterial hypertension (PAH) is a pathophysiological state of abnormally elevated pulmonary arterial pressure caused by drugs, inflammation, toxins, viruses, hypoxia, and other risk factors. We studied the therapeutic effect and target of tetramethylpyrazine (tetramethylpyrazine [TMP]; ligustrazine) in the treatment of PAH and we speculated that dramatic changes in myocardin levels can significantly affect the progression of PAH. In vivo, the results showed that administration of TMP significantly prolonged the survival of PAH rats by reducing the proliferative lesions, right ventricular systolic pressure (RVSP), mean pulmonary arterial pressure (mPAP), and the Fulton index in the heart and lung of PAH rats. In vitro, TMP can regulate the levels of smooth muscle protein 22-alpha (SM22-α), and myocardin as well as intracellular cytokines such as NO, transforming growth factor beta (TGF-β), and connective tissue growth factor (CTGF) in a dose-dependent manner (25, 50, or 100 μM). Transfection of myocardin small interfering RNA (siRNA) aggravated the proliferation of pulmonary artery smooth muscle cells (PSMCs), and the regulatory effect of TMP on α-smooth muscle actin (α-SMA) and osteopontin (OPN) disappeared. The application of 10 nM estrogen receptor alpha (ERα) inhibitor MPP promoted the proliferation of PSMCs, but it does not affect the inhibition of TMP on PSMCs proliferation. Finally, we found that TMP promoted the nucleation of myocardin-related transcription factor-A (MRTF-A) and combined it with myocardin. In conclusion, TMP can inhibit the transformation of PSMCs from the contractile phenotype to the proliferative phenotype by promoting the formation of the nuclear (MRTF-A/myocardin) transcription complex to treat PAH.

Generation of bicistronic Dmp1-Cre knock-in mice using a self-cleaving 2A peptide.

The conditional manipulation of genes using the Cre recombinase-locus of crossover in P1 (Cre/loxP) system is an important tool for revealing gene functions and cell lineages in vivo. The outcome of this method is dependent on the performance of Cre-driver mouse strains. In most cases, Cre knock-in mice show better specificity than randomly inserted Cre transgenic mice. However, following knock-in, the expression of the original gene replaced by Cre is lost. We generated a new differentiated osteoblast- and osteocyte-specific Cre knock-in mouse line that carries the viral T2A sequence encoding a 2A self-cleaving peptide at the end of the coding region of the dentin matrix protein 1 (Dmp1) gene accompanied by the Cre gene. We confirmed that Dmp1-T2A-Cre mice showed high Cre expression in osteoblasts, osteocytes, odontoblasts, and periodontal ligament cells and that the 2A self-cleaving peptide efficiently produced both Dmp1 and Cre proteins. Furthermore, unlike the Dmp1 knockout mice, homozygous Dmp1-T2A-Cre mice showed no skeletal abnormalities. Analysis using the Cre reporter strain confirmed differentiated osteoblast- and osteocyte-specific Cre-mediated recombination in the skeleton. Furthermore, recombination was also detected in some nuclei of skeletal muscle cells, spermatocytes, and intestinal cells. 2A-Cre functions effectively in vivo, and Dmp1-T2A-Cre knock-in mice are a useful tool for studying the functioning of various genes in hard tissues.

Combined effects of heavy ion exposure and simulated Lunar gravity on skeletal muscle

BackgroundThe limitations to prolonged spaceflight include unloading-induced atrophy of the musculoskeletal system which may be enhanced by exposure to the space radiation environment. Previous results have concluded that partial gravity, comparable to the Lunar surface, may have detrimental effects on skeletal muscle. However, little is known if these outcomes are exacerbated by exposure to low-dose rate, high-energy radiation common to the space environment. Therefore, the present study sought to determine the impact of highly charge, high-energy (HZE) radiation on skeletal muscle when combined with partial weightbearing to simulate Lunar gravity. We hypothesized that partial unloading would compromise skeletal muscle and these effects would be exacerbated by radiation exposure. MethodsFor month old female BALB/cByJ mice were -assigned to one of 2 groups; either full weight bearing (Cage Controls, CC) or partial weight bearing equal to 1/6th bodyweight (G/6). Both groups were then divided to receive either a single whole body absorbed dose of 0.5 Gy of 300 MeV 28Si ions (RAD) or a sham treatment (SHAM). Radiation exposure experiments were performed at the NASA Space Radiation Laboratory (NSRL) located at Brookhaven National Laboratory on Day 0, followed by 21 d of CC or G/6 loading. Muscles of the hind limb were used to measure protein synthesis and other histological measures. ResultsTwenty-one days of Lunar gravity (G/6) resulted in lower soleus, plantaris, and gastrocnemius muscle mass. Radiation exposure did not further impact muscle mass. 28Si exposure in normal ambulatory animals (RAD+CC) did not impact gastrocnemius muscle mass when compared to SHAM+CC (p>0.05), but did affect the soleus, where mass was higher following radiation compared to SHAM (p<0.05). Mixed gastrocnemius muscle protein synthesis was lower in both unloading groups. Fiber type composition transitioned towards a faster isoform with partial unloading and was not further impacted by radiation. The combined effects of partial loading and radiation partially mitigated fiber cross-sectional area when compared to partial loading alone. Radiation and G/6 reduced the total number of myonuclei per fiber while leading to elevated BrdU content of skeletal muscle. Similarly, unloading and radiation resulted in higher collagen content of muscle when compared to controls, but the effects of combined exposure were not additive. ConclusionsThe results of this study confirm that partial weightbearing causes muscle atrophy, in part due to reductions of muscle protein synthesis in the soleus and gastrocnemius as well as reduced peripheral nuclei per fiber. Additionally, we present novel data illustrating 28Si exposure reduced nuclei in muscle fibers despite higher satellite cell fusion, but did not exacerbate muscle atrophy, CSA changes, or collagen content. In conclusion, both partial loading and HZE radiation can negatively impact muscle morphology.