Assessing Rodent Cardiac Function in vivo Using Hemodynamic Pressure-Volume Loops

Effect of experimental periodontitis on cardiac functions: a comprehensive study using echocardiography, hemodynamic analysis, and histopathological evaluation in a rat model

Introduction

Periodontitis is a prevalent and severe dental condition characterized by the gradual degradation of the bone surrounding the teeth. Over the past two decades, numerous epidemiological investigations have suggested a potential link between periodontitis and cardiovascular disease. However, the complex mechanistic relationship between oral health issues and cardiovascular disorders remains unclear.

Aim

This study aimed to explore comprehensively the cardiac function through various methods, including conventional echocardiography, intraventricular pressure gradient (IVPG) analysis, speckle tracking echocardiography (STE), and hemodynamics analysis.

Methods

Ligature-induced periodontitis was established in a group of rats while the second group served as sham. The successful establishment of the periodontitis model was confirmed through staining and radiographic examination of the affected mandibles.

Results

X-ray films and methylene blue staining revealed alveolar bone resorption in the affected first molar in the model rats, confirming the successful induction of periodontitis. The rats with periodontitis displayed a decrease in ejection fraction compared to the sham group, accompanied by a decrease in mid-to-apical IVPG and mid IVPG. Lower values of strain rate were recorded in the apical segment of the septum, the middle segment of the septum, and the basal segment of the lateral free wall in the periodontitis group, which was associated with histopathological examination showing some degree of myocardial tissue damage. Conversely, rats with periodontitis showed an increase in heart rate, end-systolic volume, and arterial elastance when compared to the sham rats. However, they also exhibited a decrease in stroke work, stroke volume, cardiac output, and end-systolic pressure.

Conclusion

This study suggests that experimental periodontitis may lead to cardiac dysfunction especially compromised systolic function and myocardial relaxation, potentially indicating an increased risk of cardiovascular events in clinical periodontitis cases. The comprehensive assessment of cardiac function, hemodynamics, and histopathological evaluation underscores the profound impact of periodontitis on heart functions within this specific experimental model.

A Platform for Assessing Cellular Contractile Function Based on Magnetic Manipulation of Magnetoresponsive Hydrogel Films

Despite significant advancements in in vitro cardiac modeling approaches, researchers still lack the capacity to obtain in vitro measurements of a key indicator of cardiac function: contractility, or stroke volume under specific loading conditions-defined as the pressures to which the heart is subjected prior to and during contraction. This work puts forward a platform that creates this capability, by providing a means of dynamically controlling loading conditions in vitro. This dynamic tissue loading platform consists of a thin magnetoresponsive hydrogel cantilever on which 2D engineered myocardial tissue is cultured. Exposing the cantilever to an external magnetic field-generated by positioning magnets at a controlled distance from the cantilever-causes the hydrogel film to stretch, creating tissue load. Next, cell contraction is induced through electrical stimulation, and the force of the contraction is recorded, by measuring the cantilever's deflection. Force-length-based measurements of contractility are then derived, comparable to clinical measurements. In an illustrative application, the platform is used to measure contractility both in untreated myocardial tissue and in tissue exposed to an inotropic agent. Clear differences are observed between conditions, suggesting that the proposed platform has significant potential to provide clinically relevant measurements of contractility.

Combined effects of sepsis and extracorporeal membrane oxygenation on left ventricular performance in a murine model

Extracorporeal membrane oxygenation (ECMO) may be a viable salvage therapy in selected patients with septic shock. As ECMO use increases, we studied left ventricular (LV) performance during sepsis with and without ECMO using a pressure-volume (PV) loop in a murine model and aimed to understand LV hemodynamics in septic shock with ECMO. The rats were divided into Group 1 (ECMO applied to healthy rats), Group 2 (ECMO for septic rats), Group 3 (Controls, n = 20) and Group 4 (Sepsis induction only, n = 20). The cardiac parameters include end-diastolic volume (EDV), end-systolic volume (ESV), end-diastolic pressure (EDP), and end-systolic pressure (ESP), ejection fraction (EF), end-systolic elastance (Ees), diastolic time constant (Tau) index, arterial elastance (Ea), pressure-volume area (PVA), stroke work (SW), and potential energy (PE). We compared the changes of parameters in all groups. A total of 74 rats were included in the analyses. After 2 h on ECMO, Group 2 was associated with significant increases in ESP, EDV, ESV, PVA, PE, and SW. The difference ratio of PE and PVA was significantly higher in Group 2 compared to Group 1 (P < 0.01). In conclusion, myocardial oxygen consumption was higher in septic shock with ECMO than in controls.