Increased erythropoietin production after myocardial infarction in mice

Cardiomyocyte crosstalk with endothelium modulates cardiac structure, function, and ischemia-reperfusion injury susceptibility through erythropoietin

Erythropoietin (EPO) exerts non-canonical roles beyond erythropoiesis that are developmentally, structurally, and physiologically relevant for the heart as a paracrine factor. The role for paracrine EPO signalling and cellular crosstalk in the adult is uncertain. Here, we provided novel evidence showing cardiomyocyte restricted loss of function in Epo in adult mice induced hyper-compensatory increases in Epo expression by adjacent cardiac endothelial cells via HIF-2α independent mechanisms. These hearts showed concentric cellular hypertrophy, elevated contractility and relaxation, and greater resistance to ischemia-reperfusion injury. Voluntary exercise capacity compared to control hearts was improved independent of any changes to whole-body metabolism or blood O2 content or delivery (i.e., hematocrit). Our findings suggest cardiac EPO had a localized effect within the normoxic heart, which was regulated by cell-specific EPO-reciprocity between cardiomyocytes and endothelium. Within the heart, hyper-compensated endothelial Epo expression was accompanied by elevated Vegfr1 and Vegfb RNA, that upon pharmacological pan-inhibition of VEGF-VEGFR signaling, resulted in a paradoxical upregulation in whole-heart Epo. Thus, we provide the first evidence that a novel EPO-EPOR/VEGF-VEGFR axis exists to carefully mediate cardiac homeostasis via cardiomyocyte-endothelial EPO crosstalk.

Application of cell encapsulation for controlled delivery of biological therapeutics

Cell microencapsulation technology is likely to have an increasingly important role in new approaches rather than the classical and pioneering organ replacement. Apart from becoming a tool for protein and morphogen release and long-term drug delivery, it is becoming a new three-dimensional platform for stem cell research. Recent progress in the field has resulted in biodegradable scaffolds that are able to retain and release the cell content in different anatomical locations. Additional advances include the use biomimetic scaffolds that provide greater control over material-cell interactions and the development of more precise encapsulated cell-tracking systems. This review summarises the state of the art of cell microencapsulation and discusses the main directions and challenges of this field towards the controlled delivery of biological therapeutics.

Emerging technologies in the delivery of erythropoietin for therapeutics

Deciphering the function of proteins and their roles in signaling pathways is one of the main goals of biomedical research, especially from the perspective of uncovering pathways that may ultimately be exploited for therapeutic benefit. Over the last half century, a greatly expanded understanding of the biology of the glycoprotein hormone erythropoietin (Epo) has emerged from regulator of the circulating erythrocyte mass to a widely used therapeutic agent. Originally viewed as the renal hormone responsible for erythropoiesis, recent in vivo studies in animal models and clinical trials demonstrate that many other tissues locally produce Epo independent of its effects on red blood cell mass. Thus, not only its hematopoietic activity but also the recently discovered nonerythropoietic actions in addition to new drug delivery systems are being thoroughly investigated in order to fulfill the specific Epo release requirements for each therapeutic approach. The present review focuses on updating the information previously provided by similar reviews and recent experimental approaches are presented to describe the advances in Epo drug delivery achieved in the last few years and future perspectives.

Acute Vhl gene inactivation induces cardiac HIF-dependent erythropoietin gene expression

Von Hippel Lindau (Vhl) gene inactivation results in embryonic lethality. The consequences of its inactivation in adult mice, and of the ensuing activation of the hypoxia-inducible factors (HIFs), have been explored mainly in a tissue-specific manner. This mid-gestation lethality can be also circumvented by using a floxed Vhl allele in combination with an ubiquous tamoxifen-inducible recombinase Cre-ER^T2. Here, we characterize a widespread reduction in Vhl gene expression in Vhl^floxed-UBC-Cre-ER^T2 adult mice after dietary tamoxifen administration, a convenient route of administration that has yet to be fully characterized for global gene inactivation. Vhl gene inactivation rapidly resulted in a marked splenomegaly and skin erythema, accompanied by renal and hepatic induction of the erythropoietin (Epo) gene, indicative of the in vivo activation of the oxygen sensing HIF pathway. We show that acute Vhl gene inactivation also induced Epo gene expression in the heart, revealing cardiac tissue to be an extra-renal source of EPO. Indeed, primary cardiomyocytes and HL-1 cardiac cells both induce Epo gene expression when exposed to low O₂ tension in a HIF-dependent manner. Thus, as well as demonstrating the potential of dietary tamoxifen administration for gene inactivation studies in UBC-Cre-ER^T2 mouse lines, this data provides evidence of a cardiac oxygen-sensing VHL/HIF/EPO pathway in adult mice.

Erythropoietin levels in heart failure after an acute myocardial infarction: determinants, prognostic value, and the effects of captopril versus losartan

BACKGROUND

In patients with chronic heart failure, erythropoietin (Epo) levels are increased and related to a poor prognosis. Furthermore, Epo levels in these patients show a weak correlation with hemoglobin levels.

METHODS

This is a retrospective analysis of a subgroup of the OPTIMAAL (Optimal Trial in Myocardial Infarction with the Angiotensin II Antagonist Losartan) trial in which serum Epo levels were measured at baseline, at 1 month, and at 1 and 2 years in 224 patients with an acute myocardial infarction complicated by signs or symptoms of heart failure. We investigated the determinants and the prognostic role of elevated Epo levels in these patients, and we studied the change in Epo levels by either captopril or losartan.

RESULTS

The correlation between Epo and hemoglobin at baseline (r = 0.348, P < .001) and after 1 month (r = 0.272, P < .001) disappeared after 1 year of follow up (r = 0.129, P = .102). At 1 year, C-reactive protein was the only factor associated with Epo levels. Higher Epo levels at baseline were independently related to a higher mortality during 2 years of follow-up (hazard ratio 2.84, P = .014). In the captopril group, logEpo levels decreased from 1.19 (+/-0.26) to 0.95 (+/-0.20) mIU/mL, and in the losartan group from 1.19 (+/-0.27) to 1.01 (+/-0.17) mIU/mL (P = .036 between groups).

CONCLUSION

In this substudy of the OPTIMAAL trial, the correlation between Epo and hemoglobin disappeared in early post-acute myocardial infarction heart failure patients. Furthermore, elevated Epo levels at baseline predicted increased mortality.

Endogenous erythropoietin and a single bolus of 40,000 IU of epoetin alpha do not protect the heart from ischaemia-reperfusion injury during extracorporeal circulation for cardiac surgery

Erythropoietin (EPO) exerts a tissue-protective activity in several non-haematopoietic tissues such as heart, brain, spinal cord and muscle. We evaluated the relationship between pre-operative endogenous EPO blood levels and myocardial damage in patients undergoing cardiopulmonary bypass (CPB). Furthermore, we investigated whether pre-operative administration of a single bolus of 40,000 IU epoetin alpha (EPOα) would reduce troponin I or creatine kinase isoenzyme (CK-MB) after on-pump coronary artery bypass graft (CABG) surgery. Sixty-seven patients (45 CABG, 22 valvular surgery) were enrolled. EPO was measured in the pre-surgical period and correlated to post-surgical troponin I and CK-MB peaks. Subsequently, forty patients scheduled for CABG were randomized into two groups, receiving, respectively, a) standard medical and surgical treatment (20 patients) and b) the same treatment plus 40,000 IU of EPOα in a single bolus injection in the immediate pre-surgical period (20 patients). In our population, we did not find any correlation between pre-surgical EPO and post-surgical troponin I or CK-MB peaks (p Pearson > 0.05). Furthermore, patients treated with EPOα did not show differences compared to the control group in either troponin I (1.7±1.8 vs 2.6±3.4, p>0.05) or CK-MB (19.6 ±13.2 vs 17.1±12.6, p>0.05) peaks measured in the post-surgical period.