Jamie R. Karcher

Bone marrow mononuclear cells induce beneficial remodeling and reduce diastolic dysfunction in the left ventricle of hypertensive SS/MCWi rats.

Bone marrow mononuclear cells (BMMNCs) increase capillary density and reduce fibrosis in rodents after myocardial infarction, resulting in an overall improvement in left ventricular function. Little is known about the effectiveness of BMMNC therapy in hypertensive heart disease. In the current study, we show that delivery of BMMNCs from hypertension protected SS-13(BN)/MCWi donor rats, but not BMMNC from hypertension susceptible SS/MCWi donor rats, resulted in 57.2 and 83.4% reductions in perivascular and interstitial fibrosis, respectively, as well as a 60% increase in capillary-to-myocyte count in the left ventricles (LV) of hypertensive SS/MCWi recipients. These histological changes were associated with improvements in LV compliance and relaxation (103 and 46.4% improvements, respectively). Furthermore, improved diastolic function in hypertensive SS/MCWi rats receiving SS-13(BN)/MCWi derived BMMNCs was associated with lower clinical indicators of heart failure, including reductions in end diastolic pressure (65%) and serum brain natriuretic peptide levels (49.9%) with no improvements observed in rats receiving SS/MCWi BMMNCs. SS/MCWi rats had a lower percentage of endothelial progenitor cells in their bone marrow relative to SS-13(BN)/MCWi rats. These results suggest that administration of BMMNCs can prevent or reverse pathological remodeling in hypertensive heart disease, which contributes to ameliorating diastolic dysfunction and associated symptomology. Furthermore, the health and hypertension susceptibility of the BMMNC donor are important factors influencing therapeutic efficacy, possibly via differences in the cellular composition of bone marrow.

Bone marrow mononuclear cell angiogenic competency is suppressed by a high-salt diet

Autologous bone marrow-derived mononuclear cell (BM-MNC) transplantation is a potential therapy for inducing revascularization in ischemic tissues providing the underlying disease process had not negatively affected BM-MNC function. Previously, we have shown that skeletal muscle angiogenesis induced by electrical stimulation is impaired by a high-salt diet (HSD; 4% NaCl) in Sprague-Dawley (SD) rats. In this study we tested the hypothesis that BM-MNC angiogenic function is impaired by an elevated dietary sodium intake. Following 1 wk on HSD, either vehicle or BM-MNCs derived from SD donor rats on HSD or normal salt diet (NSD; 0.4% NaCl) were injected into male SD rats undergoing hindlimb stimulation. Administration of BM-MNCs (intramuscular or intravenous) from NSD donors, but not HSD donors, restored the angiogenic response in HSD recipients. Angiotensin II (3 ng · kg(-1) · min(-1)) infusion of HSD donor rats restored angiogenic capacity of BM-MNCs, and treatment of NSD donor rats with losartan, an angiotensin II receptor-1 antagonist, inhibited BM-MNC angiogenic competency. HSD BM-MNCs and NSD losartan BM-MNCs exhibited increased apoptosis in vitro following an acute 6-h hypoxic stimulus. HSD BM-MNCs also had increased apoptosis following injection into skeletal muscle. This study suggests that BM-MNC transplantation can restore skeletal muscle angiogenesis and that HSD impairs the angiogenic competency of BM-MNCs due to suppression of the renin-angiotensin system causing increased apoptosis.

Genome‐wide epigenetic and proteomic analysis reveals altered Notch signaling in EPC dysfunction

Endothelial progenitor cells (EPCs) are bone‐marrow‐derived mononuclear cells that participate in tube formation in vitro and vessel formation in vivo. EPC transplantation, as a therapeutic approach in cardiovascular diseases, has produced mixed results likely due to underlying disease states and environmental factors affecting EPC function. In this study, we investigated the mechanisms by which a high‐salt diet impairs EPC function. The number of endothelial progenitor cells (CD34+, VEGFR2+, CD133+, and c‐Kit+) was decreased in the bone marrow of Sprague–Dawley (SD) rats fed a high‐salt diet (HSD; 4% NaCl) as compared to SD rats on a normal‐salt diet (NSD; 0.4% NaCl). NSD EPCs augmented endothelial cell tube formation in vitro, whereas HSD EPCs did not. NSD EPCs were a potent therapeutic restoring electrical stimulation‐induced angiogenesis in vivo. HSD EPCs were not able to restore angiogenesis in vivo. EPC DNA methylation was analyzed by reduced representative bisulfite sequencing and membrane proteins were analyzed using high accuracy liquid chromatography mass spectrometry. Differentially methylated genes and differentially abundant membrane proteins measured between the NSD and HSD EPCs, revealed a total of 886 gene‐protein sets where reciprocal methylation and expression occurred. Based on stringent criteria, Notch4 was found to be hypermethylated in HSD EPCs and had corresponding decrease in protein expression. Suppression of Notch4 protein expression in EPCs using siRNA confirmed a role for Notch4 in EPC‐mediated angiogenesis, suggesting Notch4 suppression as a mechanism by which high‐salt diet inhibits EPC‐mediated angiogenesis.