OSTEOPONTIN PROMOTES PATHOLOGICAL CHANGES IN THE MYOCARDIUM DURING HIV INFECTION.

Abstract

With the introduction of antiretroviral therapy (ART), human immunodeficiency virus (HIV) has progressed to a chronic inflammatory disease with accelerated, subclinical end-organ damage, specifically cardiovascular disease (CVD). People with HIV (PWH) have higher incidence, risk, and mortality from CVD, such as atherosclerosis, diastolic dysfunction, and heart failure. Several recent clinical reports have shown that PWH have a predisposition to developing heart failure with preserved ejection fraction (HFpEF), presenting with pathological concentric hypertrophy, diffuse fibrosis, and diastolic dysfunction. As such, an investigation into immunological and molecular mechanisms promoting pathological changes in the heart is necessary. Recent clinical reports show that people living with HFpEF have elevated plasma osteopontin (Opn), and plasma Opn is a powerful predictor of HFpEF severity, HFpEF-related hospitalizations, and mortality. Second, several animal models of HFpEF phenotypes have suggested Opn is involved in driving or perpetuating diastolic dysfunction and cardiac fibrosis. Therefore, we investigated changes in Opn in a cohort of PWH and two translationally relevant models of HIV infection (non-human primates and humanized mice) to identify the pathological role of Opn in cardiac fibrosis and detail the adjunctive potential of Opn for PWH presenting with HFpEF. In Chapter 2, twenty asymptomatic, antiretroviral-treated women with HIV (WHIV) and fourteen women without HIV (HIV-women) matched on age and body mass index underwent cardiac magnetic resonance imaging (MRI) and immune phenotyping. First, we compared a number of immunological parameters to the extensive cardiac MRI parameters in WHIV. Secondly, we analyzed relationships between plasma Opn with cardiac structure and function and markers of immune activation among WHIV, HIV- women, and the whole cohort. Multivariable modeling among the whole group was performed using myocardial fibrosis and myocardial steatosis, respectively, as the dependent variable and HIV status, atherosclerotic cardiovascular disease (ASCVD) risk score, and plasma Opn as independent variables. Among WHIV, multi-variable modeling was performed using plasma Opn as the dependent variable and CD4+ T cell count, HIV viral load, and the respective immune parameter, relating to plasma OPN in bivariate analyses, as an independent variable. In Chapter 3, we investigated bulk transcriptomic changes in the left ventricle of the heart in a model of HIV infection. We utilize the highly translatable simian immunodeficiency virus (SIV)-infected rhesus macaque model to identify changes in the myocardium with and without ART. Animals were selected by viral load, with SIV-infected animals having a high titer of plasma viral load and the SIV-infected animals with ART having a reduction in viral load by several logs. We performed total RNA-Seq on left ventricle tissue from uninfected animals, SIV-infected animals, and SIV-infected animals receiving a clinically relevant ART regimen. SIV infection led to high plasma viral load, but little to no SIV RNA was detectable in the left ventricle, shown by minimal of SIV RNA+ cells in the heart and no SIV sequences identified from RNA-Seq. SIV infection produced a highly inflammatory reaction in the heart, predominated by interferon and pathogen response. Additionally, interferon gamma (IFNg) and lipopolysaccharide (LPS) were both identified as potential upstream drivers of transcriptomic changes in the heart from SIV infection. Reduction of viral load by ART reduced the interferon and cytokine response in the heart; however, SIV-infected animals receiving ART exhibited decreased expression of integral genes directly involved in fatty acid (FA) metabolism, carnitine shuttling, and beta-oxidation. In Chapter 4, we use both in vitro and in vivo modeling to identify molecular mechanisms involved in the development of cardiac fibrosis. We utilized mouse embryonic fibroblasts (MEFs) modeled cardiac fibroblasts and were stimulated with IFNg, LPS, and TGF-b for phenotypic changes in contraction and cytokine production. The interplay of Opn and cardiac fibrosis was investigated in SIV-infected macaques with/without ART and HIVinfected humanized mice with/without an Opn-inhibiting RNA aptamer. LPS-stimulated MEFs retained myofibroblast-like contractility from TGF-b stimulation, secreted inflammatory cytokines/chemokines, and produced Opn (Spp1 transcripts). SIV-infected animals had elevated plasma Opn at necropsy, accumulation of full-length Opn in the ventricle, and ventricular interstitial fibrosis. Multivariate regression identified growth differentiation factor (GDF)-15, inflammatory CD14+CD16+ monocytes, and CD163 expression on CD14+ CD16+ monocytes as independent predictors of plasma Opn during SIV infection. HIV-infected humanized mice showed increased interstitial fibrosis compared to uninfected/untreated animals, and systemic inhibition of Opn by RNA aptamer reduced left ventricle fibrosis in HIV-infected humanized mice. These studies combined a clinical cohort of WHIV, SIV-infected rhesus macaques, and HIV-infected humanized mice to determine the role of Opn in the pathophysiology of cardiac deficits from HIV infection. Our primary goals were to begin to unravel the role of Opn in the development of HFpEF phenotypes seen in PWH, detail Opn as a converging biomarker of cardiac stress and remodeling and immune dysfunction in HIV infection, and investigate the therapeutic potential of Opn to reduce cardiac fibrosis from HIV infection. While Opn has a broad spectrum of physiological and pathological functions, we aimed to frame Opn as an important protein of interest in future studies into HFpEF in PWH.