Traditionally, the evaluation of cardiac function has focused on systolic function; however, there is a growing appreciation for the contribution of diastolic function to overall cardiac health. Given the emerging interest in evaluating diastolic function in all models of heart failure, there is a need for sensitivity, accuracy, and precision in the hemodynamic assessment of diastolic function. Hemodynamics measure cardiac pressures in vivo, offering a direct assessment of diastolic function. In this review, we summarize the underlying principles of diastolic function, dividing diastole into two phases: 1) relaxation and 2) filling. We identify parameters used to comprehensively evaluate diastolic function by hemodynamics, clarify how each parameter is obtained, and consider the advantages and limitations associated with each measure. We provide a summary of the sensitivity of each diastolic parameter to loading conditions. Furthermore, we discuss differences that can occur in the accuracy of diastolic and systolic indices when generated by automated software compared with custom software analysis and the magnitude each parameter is influenced during inspiration with healthy breathing and a mild breathing load, commonly expected in heart failure. Finally, we identify key variables to control (e.g., body temperature, anesthetic, sampling rate) when collecting hemodynamic data. This review provides fundamental knowledge for users to succeed in troubleshooting and guidelines for evaluating diastolic function by hemodynamics in experimental models of heart failure.

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Cardiovascular and respiratory systems are anatomically and functionally linked; inspiration produces negative intrathoracic pressures that act on the heart and alter cardiac function. Inspiratory pressures increase with heart failure and can exceed the magnitude of ventricular pressure during diastole. Accordingly, respiratory pressures may be a confounding factor to assessing cardiac function. While the interaction between respiration and the heart is well characterized, the extent to which systolic and diastolic indices are affected by inspiration is unknown. Our objective was to understand how inspiratory pressure affects the hemodynamic assessment of cardiac function. To do this, we developed custom software to assess and separate indices of systolic and diastolic function into inspiratory, early expiratory, and late expiratory phases of respiration. We then compared cardiac parameters during normal breathing and with various respiratory loads. Variations in inspiratory pressure had a small impact on systolic pressure and function. Conversely, diastolic pressure strongly correlated with negative inspiratory pressure. Cardiac pressures were less affected by respiration during expiration; late expiration was the most stable respiratory phase. In conclusion, inspiration is a large confounding influence on diastolic pressure, but minimally affects systolic pressure. Performing cardiac hemodynamic analysis by accounting for respiratory phase yields more accuracy and analytic confidence to the assessment of diastolic function.

A hallmark of solid tumors is the need for vascularization to supply oxygen and nutrients. Aggressive pro-angiogenic signals induced by tumors lead to malformation of vessels characterized by reduced pericyte coverage and low perfusion. As a result of this vascular dysfunction, tumors have elevated hypoxia and high interstitial fluid pressure (IFP), yielding an aggressive phenotype, and reducing efficacy and trafficking of intravenous therapies to the tumor core. Anti-angiogenic therapies aim to reduce angiogenic stimuli and normalize tumor vessels. The three type-1-repeat (3TSR) region of thrombospondin-1 contains the majority of its anti-angiogenic properties in a small bioactive peptide. These functions are mediated through the membrane protein, CD36. We have previously shown that administration of native 3TSR leads to improved tumor perfusion, and enhancing delivery of chemotherapy drugs and oncolytic viruses. We have developed a novel compound, Fc3TSR, that has two 3TSR peptides linked with a Fc to increase in vitro and in vivo efficacy. In an orthotopic, mouse model of ovarian cancer, we examined the effect of Fc3TSR treatment on tumor IFP using a 1.2Fr pressure catheter guided into the tumor core of anesthetized mice. Compared to untreated controls, mice treated with Fc3TSR had significantly lower IFP, even after considering differences in heart rate among animals. Immunofluorescence on fixed sentinel lymph nodes revealed enhanced presence of immune cells, a positive predictor of lymphatic patency. To determine impact on chemotherapy delivery, mice were injected with 40mCi paclitaxel and tumor uptake of the isotope was measured. At 12, 24 and 48h post injection, Fc3TSR treated tumors had significantly increased uptake of paclitaxel compared to untreated or 3TSR treated mice. In vitro cell viability assays and western blot analysis of cleaved-caspase-3 revealed that Fc3TSR enhances direct apoptosis in human ovarian cell lines (OVCAR-2 and 36M2) compared to untreated cells or those treated with native 3TSR at equimolar concentrations. In a human subcutaneous xenograft model using 36M2 cells in SCID mice, Fc3TSR significantly reduced tumor volume as a single agent compared to PBS controls.Fc3TSR causes direct ovarian tumor cell apoptosis in vitro and significant anti-tumor effects in vivo. In vivo, Fc3TSR causes potent vascular normalization, decreases tumor hypoxia and IFP in the tumor core. As such, Fc3TSR has the potential to remodel multiple aspects of the tumor microenvironment which would otherwise obstruct treatment delivery and efficacy in solid tumors. The multi-modal aspects of Fc3TSR makes this therapeutic approach attractive for the treatment of advanced ovarian cancer and other malignancies that typically overcome single-agent therapy. Citation Format: Kathy Matuszewska, Madison Pereira, Leslie Ogilvie, Duncan Petrik, Allison Gartung, Dipak Panigrahy, Kin-Ming Lo, Jack Lawler, Jeremy Simpson, Jim Petrik. Fc3TSR improves intratumoral treatment delivery by normalizing tumor vasculature and reducing interstitial fluid pressure in an orthotopic, syngeneic mouse model of epithelial ovarian cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1042.

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Cardiac reserve is a widely used health indicator and prognostic tool. While it is well established how to assess cardiac reserve clinically, in preclinical models it is more challenging lacking standardization. Further, although cardiac reserve incorporates both systolic (i.e., contractile reserve) and diastolic (i.e., relaxation reserve) components of the cardiac cycle, less focus has been placed on diastolic reserve. The aim of our study was to determine which technique (i.e., echocardiography, invasive hemodynamic, Langendorff) and corresponding parameters can be used to assess the systolic and diastolic reserves in preclinical models. Healthy adult male and female CD-1 mice were administered dobutamine and evaluated by echocardiography and invasive hemodynamic, or Langendorff to establish systolic and diastolic reserves. Here we show that systolic reserve can be assessed using all techniques in vivo and in vitro. Yet, the current indices available are ineffective at capturing diastolic reserve of healthy mice in vivo. When assessing systolic reserve, sex affects the dose-response of several commonly used echocardiography parameters (i.e., FS, EF). Taken together, this study improves our understanding of how sex impacts the interpretation assessment of cardiac reserve and establishes for the first time that in healthy adult mice the diastolic reserve cannot be assessed by currently established methods in vivo.

Impaired heart function can develop in diabetic individuals in the absence of coronary artery disease or hypertension, suggesting mechanisms beyond hypertension/increased afterload contribute to diabetic cardiomyopathy. Identifying therapeutic approaches that improve glycemia and prevent cardiovascular disease are clearly required for clinical management of diabetes-related comorbidities. Since intestinal bacteria are important for metabolism of nitrate, we examined if dietary nitrate and fecal microbial transplantation (FMT) from nitrate-fed mice could prevent high-fat diet (HFD)-induced cardiac abnormalities. Male C57Bl/6N mice were fed an 8-week low-fat diet (LFD), HFD, or HFD+Nitrate (4mM sodium nitrate). HFD-fed mice presented with pathological left ventricular (LV) hypertrophy, reduced stroke volume and increased end diastolic pressure, in association with increased myocardial fibrosis, glucose intolerance, adipose inflammation, serum lipids, LV mitochondrial reactive oxygen species (ROS), and gut dysbiosis. In contrast, dietary nitrate attenuated these detriments. In HFD-fed mice, FMT from HFD+Nitrate donors did not influence serum nitrate, blood pressure, adipose inflammation, or myocardial fibrosis. However, microbiota from HFD+Nitrate mice decreased serum lipids, LV ROS, and similar to FMT from LFD donors, prevented glucose intolerance and cardiac morphology changes. Therefore, the cardioprotective effects of nitrate are not dependent on reducing blood pressure, but rather mitigating gut dysbiosis, highlighting a nitrate-gut-heart axis.

Background Heart failure (HF) is a global health concern that affects nearly 26 million people each year. The Spontaneously Hypertensive Rat (SHR) was established in 1963 and is the most commonly used rodent model for studying human HF. Unlike humans, the SHRs develop hypertension around their reproductive age (i.e., when animals are selected for breeding), providing the opportunity for natural selection towards adaptive traits for hypertension‐induced heart failure. Therefore, the primary objective of this review was to evaluate whether SHRs have evolved over time to the cardiac sequelae of hypertension. We hypothesized that, while the severity of hypertension will remain stable within the SHR colony, the HF phenotype will become less pronounced with time as a result of compensatory changes to manage high blood pressure. Methods We performed a retrospective review evaluating several indices of cardiovascular health in the SHR over the past 60 years. For statistical analyses, studies that met the inclusion criteria were separated into 2 cohorts: Initial (mid‐late 1900’s) and Current (early 2000’s ‐present) Colony SHRs. Wistar‐Kyoto rats (i.e., normotensive rats used to establish the SHR line via selective breeding) were used as controls to normalize changes in technique and methods that have occurred over these decades. Results Systolic blood pressure did not differ between Initial and Current Colony SHRs, indicating that the severity of hypertension had remained stable within the SHR Colony over time. Current Colony SHRs presented with increased cardiac concentric hypertrophy (i.e., elevated heart weight and posterior wall thickness). Since these changes were not observed in the Wistar‐Kyoto control rats, cardiac‐derived changes in Current Colony SHRs were unlikely due to differences in techniques, equipment, anesthesia or environmental conditions. Conclusion These findings establish that the SHR colony has evolved over time, with greater concentric hypertrophy. Using natural selection to find positive adaptive traits may be advantageous in identifying new therapeutic treatment strategies.