Human pluripotent stem cell-derived cardiomyocytes as a target platform for paracrine protection by cardiac mesenchymal stromal cells.

Ischemic heart disease remains the foremost cause of death globally, with survivors at risk for subsequent heart failure. Paradoxically, cell therapies to offset cardiomyocyte loss after ischemic injury improve long-term cardiac function despite a lack of durable engraftment. An evolving consensus, inferred preponderantly from non-human models, is that transplanted cells benefit the heart via early paracrine signals. Here, we tested the impact of paracrine signals on human cardiomyocytes, using human pluripotent stem cell-derived cardiomyocytes (hPSC-CMs) as the target of mouse and human cardiac mesenchymal stromal cells (cMSC) with progenitor-like features. In co-culture and conditioned medium studies, cMSCs markedly inhibited human cardiomyocyte death. Little or no protection was conferred by mouse tail tip or human skin fibroblasts. Consistent with the results of transcriptomic profiling, functional analyses showed that the cMSC secretome suppressed apoptosis and preserved cardiac mitochondrial transmembrane potential. Protection was independent of exosomes under the conditions tested. In mice, injecting cMSC-conditioned media into the infarct border zone reduced apoptotic cardiomyocytes > 70% locally. Thus, hPSC-CMs provide an auspicious, relevant human platform to investigate extracellular signals for cardiac muscle survival, substantiating human cardioprotection by cMSCs, and suggesting the cMSC secretome or its components as potential cell-free therapeutic products.

Enhanced exercise capacity in mice with severe heart failure treated with an allosteric effector of hemoglobin, myo-inositol trispyrophosphate.

A major determinant of maximal exercise capacity is the delivery of oxygen to exercising muscles. myo-Inositol trispyrophosphate (ITPP) is a recently identified membrane-permeant molecule that causes allosteric regulation of Hb oxygen binding affinity. In normal mice, i.p. administration of ITPP (0.5-3 g/kg) caused a dose-related increase in the oxygen tension at which Hb is 50% saturated (p50), with a maximal increase of 31%. In parallel experiments, ITPP caused a dose-related increase in maximal exercise capacity, with a maximal increase of 57 +/- 13% (P = 0.002). In transgenic mice with severe heart failure caused by cardiac-specific overexpression of G alpha q, i.p. ITPP increased exercise capacity, with a maximal increase of 63 +/- 7% (P = 0.005). Oral administration of ITPP in drinking water increased Hb p50 and maximal exercise capacity (+34 +/- 10%; P < 0.002) in normal and failing mice. Consistent with increased tissue oxygen availability, ITPP decreased hypoxia inducible factor-1alpha mRNA expression in myocardium. It had no effect on myocardial contractility in isolated mouse cardiac myocytes and did not affect arterial blood pressure in vivo in mice. Thus, ITPP decreases the oxygen binding affinity of Hb, increases tissue oxygen delivery, and increases maximal exercise capacity in normal mice and mice with severe heart failure. ITPP is thus an attractive candidate for the therapy of patients with reduced exercise capacity caused by heart failure.

Impact of oxypurinol in patients with symptomatic heart failure. Results of the OPT-CHF study.

OBJECTIVES: This study evaluated whether a xanthine oxidase (XO) inhibitor, oxypurinol, produces clinical benefits in patients with New York Heart Association functional class III to IV heart failure due to systolic dysfunction receiving optimal medical therapy. BACKGROUND: Increased XO activity may contribute to heart failure pathophysiology. METHODS: Patients (n = 405) were randomized to oxypurinol (600 mg/day) or placebo. Efficacy at 24 weeks was assessed using a composite end point comprising heart failure morbidity, mortality, and quality of life. RESULTS: The percentage of patients characterized as improved, unchanged, or worsened did not differ between those receiving oxypurinol or placebo. Oxypurinol reduced serum uric acid (SUA) by approximately 2 mg/dl (p < 0.001). In a subgroup analysis, patients with elevated SUA (>9.5 mg/dl, n = 108) responded favorably to oxypurinol (p = 0.02 for interaction term), whereas oxypurinol patients with SUA <9.5 mg/dl exhibited a trend towards worsening. In addition, SUA reduction to oxypurinol correlated with favorable clinical response. Within the entire oxypurinol patient cohort, those characterized as either improved or unchanged had significantly greater reductions in SUA compared with patients who worsened (-2.3 +/- 2.1 mg/dl vs. -1.0 +/- 1.9 mg/dl, p = 0.0006). In placebo patients, lower baseline SUA, but not change in SUA, correlated with improved clinical outcome. CONCLUSIONS: Oxypurinol did not produce clinical improvements in unselected patients with moderate-to-severe heart failure. However, post-hoc analysis suggests that benefits occur in patients with elevated SUA in a manner correlating with the degree of SUA reduction. Serum uric acid may serve as a valuable biomarker to target XO inhibition in heart failure. (Oxypurinol Compared With Placebo for Class III-IV NYHA Congestive Heart Failure; NCT00063687).

Rationale, design and organisation of an efficacy and safety study of oxypurinol added to standard therapy in patients with NYHA class III - IV congestive heart failure.

Oxypurinol, the active metabolite of allopurinol and a potent xanthine oxidase inhibitor (XOI), is under evaluation as a novel agent for the treatment of congestive heart failure (HF). Several lines of evidence provide the rationale for the hypothesis that XOIs will improve clinical outcomes in patients with HF. First, XOIs have unique positive inotropic effects, improving myocardial contraction and performance while simultaneously improving myocardial energy metabolism. Second, XOIs ameliorate endothelial dysfunction in humans with HF. Finally, XO activity is upregulated in the heart and vasculature of subjects with HF, which may in turn contribute to oxidative stress and/or increased uric acid levels. Together these findings form the rationale for the Controlled Efficacy and Safety Study of Oxypurinol Added to Standard Therapy in Patients with New York Heart Association (NYHA) class III - IV Congestive Heart Failure (OPT-CHF) trial (Food and Drug Administration IND 65,125), a Phase II - III prospective, randomised, double-blind, placebo-controlled trial, which will include patients with stable symptomatic HF in NYHA class III - IV congestive HF who are deemed clinically stable on a standard and appropriately maximised heart failure therapy regimen. The efficacy end point for OPT-CHF is a composite that incorporates measures of patient outcome and well-being.