CmyoSize: An ImageJ macro for automated analysis of cardiomyocyte size in images of routine histology staining

Effects of porosity distribution on mechanical properties and osseointegration of porous polyetheretherketone

Porous polyetheretherketone (P-PEEK) is widely used as the material for making implant screws, and yet its mechanical properties and osseointegration for ultilization are still unsatisfied. In this work, the effects of the porosity distribution on the mechanical properties and osseointegration were investigated. Functionally graded P-PEEK (FGP-PEEK) and uniform P-PEEK (UP-PEEK) were developed by infiltration casting technology. The mechanical properties of the P-PEEK were studied by compressive and bending tests, and the osseointegration was evaluated by in vitro and rabbit femur experiments. The prepared FGP-PEEK was composed of the central dense part and its surrounding porous one where the pores were isodiametric and interconnected. Both the compressive strength and bending strength of the FGP-PEEK with graded porosity were higher than those of the UP-PEEK with uniform porosity. The mechanical properties of the FGP-PEEK were comparable to that of the human cancellous bone. The in vitro and in vivo experiments indicated the FGP-PEEK had no cytotoxicity, and its osseointegration was better than the UP-PEEK. The results demonstrated that the graded porosity had a superiority in the mechanical properties and osseointegration of the P-PEEK scaffolds compared to the uniform porosity. The influencing mechanisms of the porosity distribution on the mechanical properties and osseointegration were also clarified. Additionally, the osseointegration of the FGP-PEEK gradually increased as the surface porosity increased from 30 % to 50 %. The 50 %-surface porosity FGP-PEEK was a promising material on the application of the implant screws.

An atypical E3 ligase safeguards the ribosome during nutrient stress

Metabolic stress must be effectively mitigated for the survival of cells and organisms. Ribosomes have emerged as signaling hubs that sense metabolic perturbations and coordinate responses that either restore homeostasis or trigger cell death. As yet, the mechanisms governing these cell fate decisions are not well understood. Here, we report an unexpected role for the atypical E3 ligase HOIL-1 in safeguarding the ribosome. We find HOIL-1 mutations associated with cardiomyopathy broadly sensitize cells to nutrient and translational stress. These signals converge on the ribotoxic stress sentinel ZAKα. Mechanistically, mutant HOIL-1 excludes a ribosome quality control E3 ligase from its functional complex and remodels the ribosome ubiquitin landscape. This quality control failure renders glucose starvation ribotoxic, precipitating a ZAKα-ATF4-xCT-driven noncanonical cell death. We further show HOIL-1 loss exacerbates cardiac dysfunction under pressure overload. These data reveal an unrecognized ribosome signaling axis and a molecular circuit controlling cell fate during nutrient stress.

Cardiac Molecular Analysis Reveals Aging-Associated Metabolic Alterations Promoting Glycosaminoglycans Accumulation via Hexosamine Biosynthetic Pathway

Age is a prominent risk factor for cardiometabolic disease, often leading to heart structural and functional changes. However, precise molecular mechanisms underlying cardiac remodeling and dysfunction exclusively resulting from physiological aging remain elusive. Previous research demonstrated age-related functional alterations in baboons, analogous to humans. The goal of this study is to identify early cardiac molecular alterations preceding functional adaptations, shedding light on the regulation of age-associated changes. Unbiased transcriptomics of left ventricle samples are performed from female baboons aged 7.5-22.1 years (human equivalent ≈30-88 years). Weighted-gene correlation network and pathway enrichment analyses are performed, with histological validation. Modules of transcripts negatively correlated with age implicated declined metabolism-oxidative phosphorylation, tricarboxylic acid cycle, glycolysis, and fatty-acid β-oxidation. Transcripts positively correlated with age suggested a metabolic shift toward glucose-dependent anabolic pathways, including hexosamine biosynthetic pathway (HBP). This shift is associated with increased glycosaminoglycan synthesis, modification, precursor synthesis via HBP, and extracellular matrix accumulation, verified histologically. Upregulated extracellular matrix-induced signaling coincided with glycosaminoglycan accumulation, followed by cardiac hypertrophy-related pathways. Overall, these findings revealed a transcriptional shift in metabolism favoring glycosaminoglycan accumulation through HBP before cardiac hypertrophy. Unveiling this metabolic shift provides potential targets for age-related cardiac diseases, offering novel insights into early age-related mechanisms.

Soft robotic platform for progressive and reversible aortic constriction in a small-animal model

Our understanding of cardiac remodeling processes due to left ventricular pressure overload derives largely from animal models of aortic banding. However, these studies fail to enable control over both disease progression and reversal, hindering their clinical relevance. Here, we describe a method for progressive and reversible aortic banding based on an implantable expandable actuator that can be finely tuned to modulate aortic banding and debanding in a rat model. Through catheterization, imaging, and histologic studies, we demonstrate that our platform can recapitulate the hemodynamic and structural changes associated with pressure overload in a controllable manner. We leveraged soft robotics to enable noninvasive aortic debanding, demonstrating that these changes can be partly reversed because of cessation of the biomechanical stimulus. By recapitulating longitudinal disease progression and reversibility, this animal model could elucidate fundamental mechanisms of cardiac remodeling and optimize timing of intervention for pressure overload.

Cardiac Molecular Analysis Reveals Aging-Associated Metabolic Alterations Promoting Glycosaminoglycans Accumulation Via Hexosamine Biosynthetic Pathway

Age is a prominent risk factor for cardiometabolic disease, and often leads to heart structural and functional changes. However, precise molecular mechanisms underlying cardiac remodeling and dysfunction resulting from physiological aging per se remain elusive. Understanding these mechanisms requires biological models with optimal translation to humans. Previous research demonstrated that baboons undergo age-related reduction in ejection fraction and increased heart sphericity, mirroring changes observed in humans. The goal of this study was to identify early cardiac molecular alterations that precede functional adaptations, shedding light on the regulation of age-associated changes. We performed unbiased transcriptomics of left ventricle (LV) samples from female baboons aged 7.5-22.1 years (human equivalent ~30-88 years). Weighted-gene correlation network and pathway enrichment analyses were performed to identify potential age-associated mechanisms in LV, with histological validation. Myocardial modules of transcripts negatively associated with age were primarily enriched for cardiac metabolism, including oxidative phosphorylation, tricarboxylic acid cycle, glycolysis, and fatty-acid β-oxidation. Transcripts positively correlated with age suggest upregulation of glucose uptake, pentose phosphate pathway, and hexosamine biosynthetic pathway (HBP), indicating a metabolic shift towards glucose-dependent anabolic pathways. Upregulation of HBP commonly results in increased glycosaminoglycan precursor synthesis. Transcripts involved in glycosaminoglycan synthesis, modification, and intermediate metabolism were also upregulated in older animals, while glycosaminoglycan degradation transcripts were downregulated with age. These alterations would promote glycosaminoglycan accumulation, which was verified histologically. Upregulation of extracellular matrix (ECM)-induced signaling pathways temporally coincided with glycosaminoglycan accumulation. We found a subsequent upregulation of cardiac hypertrophy-related pathways and an increase in cardiomyocyte width. Overall, our findings revealed a transcriptional shift in metabolism from catabolic to anabolic pathways that leads to ECM glycosaminoglycan accumulation through HBP prior to upregulation of transcripts of cardiac hypertrophy-related pathways. This study illuminates cellular mechanisms that precede development of cardiac hypertrophy, providing novel potential targets to remediate age-related cardiac diseases.

Semiautomated pipeline for quantitative analysis of heart histopathology

BACKGROUND

Heart diseases are among the leading causes of death worldwide, many of which lead to pathological cardiomyocyte hypertrophy and capillary rarefaction in both patients and animal models, the quantification of which is both technically challenging and highly time-consuming. Here we developed a semiautomated pipeline for quantification of the size of cardiomyocytes and capillary density in cardiac histology, termed HeartJ, by generating macros in ImageJ, a broadly used, open-source, Java-based software.

METHODS

We have used modified Gomori silver staining, which is easy to perform and digitize in high throughput, or Fluorescein-labeled lectin staining. The latter can be easily combined with other stainings, allowing additional quantitative analysis on the same section, e.g., the size of cardiomyocyte nuclei, capillary density, or single-cardiomyocyte protein expression. We validated the pipeline in a mouse model of cardiac hypertrophy induced by transverse aortic constriction, and in autopsy samples of patients with and without aortic stenosis.

RESULTS

In both animals and humans, HeartJ-based histology quantification revealed significant hypertrophy of cardiomyocytes reflecting other parameters of hypertrophy and rarefaction of microvasculature and enabling the analysis of protein expression in individual cardiomyocytes. The analysis also revealed that murine and human cardiomyocytes had similar diameters in health and extent of hypertrophy in disease confirming the translatability of our murine cardiac hypertrophy model. HeartJ enables a rapid analysis that would not be feasible by manual methods. The pipeline has little hardware requirements and is freely available.

CONCLUSIONS

In summary, our analysis pipeline can facilitate effective and objective quantitative histological analyses in preclinical and clinical heart samples.

Hyperbaric oxygen therapy mitigates left ventricular remodeling, upregulates MMP-2 and VEGF, and inhibits the induction of MMP-9, TGF-β1, and TNF-α in streptozotocin-induced diabetic rat heart

AIMS

Hyperbaric oxygen (HBO) therapy has been widely used for the adjunctive treatment of diabetic wounds, and is currently known to influence left ventricular (LV) function. However, morphological and molecular repercussions of the HBO in the diabetic myocardium remain to be described. We aimed to investigate whether HBO therapy would mitigate adverse LV remodeling caused by streptozotocin (STZ)-induced diabetes.

MAIN METHODS

Sixty-day-old Male Wistar rats were divided into four groups: Control (n = 8), HBO (n = 7), STZ (n = 10), and STZ + HBO (n = 8). Diabetes was induced by a single STZ injection (60 mg/kg, i.p.). HBO treatment (100% oxygen at 2.5 atmospheres absolute, 60 min/day, 5 days/week) lasted for 5 weeks. LV morphology was evaluated using histomorphometry. Gene expression analyzes were performed for LV collagens I (Col1a1) and III (Col3a1), matrix metalloproteinases 2 (Mmp2) and 9 (Mmp9), and transforming growth factor-β1 (Tgfb1). The Immunoexpression of cardiac tumor necrosis factor-α (TNF-α) and vascular endothelial growth factor (VEGF) were also quantified.

KEY FINDINGS

HBO therapy prevented LV concentric remodeling, heterogeneous myocyte hypertrophy, and fibrosis in diabetic rats associated with attenuation of leukocyte infiltration. HBO therapy also increased Mmp2 gene expression, and inhibited the induction of Tgfb1 and Mmp9 mRNAs caused by diabetes, and normalized TNF-α and VEGF protein expression.

SIGNIFICANCE

HBO therapy had protective effects for the LV structure in STZ-diabetic rats and ameliorated expression levels of genes involved in cardiac collagen turnover, as well as pro-inflammatory and pro-angiogenic signaling.