N-terminal pro-brain natriuretic peptide predicts myocardial ischemia and is related to postischemic left-ventricular dysfunction in patients with stable coronary artery disease.

BACKGROUND: The N-terminal-pro-B natriuretic peptide (Nt-pro-BNP) is of diagnostic and prognostic value in coronary artery disease (CAD). We assessed the relationship between Nt-pro-BNP and (1) the extent of ischemia on stress myocardial perfusion imaging (MPI), and (2) changes between the basal and postexercise ejection fraction (EF), in stable patients with a normal EF. METHODS AND RESULTS: One hundred and two patients with stable, documented CAD (EF, 62% +/- 8%) underwent an exercise-rest thallium-201 gated-MPI and serial Nt-pro-BNP assays. Myocardial perfusion imaging produced abnormal results in 57 patients (56%; group 1), and normal results in 45 patients (44%; group 2). Median baseline, immediate postexercise, and 3-hour postexercise Nt-pro-BNP values were higher in group 1 than in group 2: 182 vs 85, 201 vs 86, and 212 vs 99 pg/mL, respectively (P < .001 for all). Postexercise EF decreased in group 1 (53% +/- 11% vs 62% +/- 10%, P < .001), but not in group 2 (61% +/- 9% vs 62% +/- 7%, NS). The Nt-pro-BNP ruled out significant ischemia with a negative predictive value of 0.90, whereas patients within the higher tertile of Nt-pro-BNP had a fivefold higher risk of ischemia compared with patients within the lower tertile. CONCLUSIONS: The post-stress increase in Nt-pro-BNP is related to myocardial ischemia and to postischemic left-ventricular dysfunction, and accurately predicts the presence or absence of myocardial perfusion defects.     

Relationship of lower extremity skin blood flow to the ankle brachial index in patients with peripheral arterial disease and normal volunteers

Changes in posture of the lower extremities induce changes in skin blood flow, known as veno-arteriolar response (VAR). We investigated the relationship between ankle brachial index (ABI) and VAR in patients (ABI<0.9) with peripheral arterial disease (PAD) and age-matched normal controls (ABI>1). We measured ankle pressure, ABI at rest, and post-exercise ABI. Using laser Doppler flowmetry, skin blood flow was measured with the lower extremity in extended and flexed positions and the fractional change (extended-flexed/extended) in blood flow (VAR) was calculated. With external pressure applied serially to the lower extremity in the extended position using a sphygmomanometer, the pressure (PVAR) at which the VAR was similar to that in the flexed position was recorded. Patients and controls did not differ by age or comorbidity, except higher cigarette smoking in patients (95.8% vs. 4.3%, p=0.001). VAR and PVAR were significantly lower in patients than controls (0.42+/-0.16 vs. 0.65+/-0.11 flux/min, p=0.001 and 29+/-8 vs. 48+/-9 mm Hg, p=0.001, respectively). There was significant correlation between ABI-post and VAR (r=0.6, p=0.01) and between the VAR and PVAR (r=0.8, p=0.001). VAR<0.3 flux/min was 100% sensitive, 80% specific, and area under curve of 0.88, p=0.001 for detecting PAD as defined by ABI<0.9. Similarly, PVAR of 22 mm Hg was 100% sensitive, 85% specific, and area under curve of 0.94, p=0.001 for detecting PAD. Skin blood flow by this method correlates with the presence and severity of an abnormal ABI. This may offer a method of monitoring the effect of therapy and regression of peripheral atherosclerosis.     

<Emphasis Type="Italic">Vegf-A</Emphasis> mRNA transfection as a novel approach to improve mouse and human islet graft revascularisation

Aims/hypothesis

The initial avascular period following islet transplantation seriously compromises graft function and survival. Enhancing graft revascularisation to improve engraftment has been attempted through virus-based delivery of angiogenic triggers, but risks associated with viral vectors have hampered clinical translation. In vitro transcribed mRNA transfection circumvents these risks and may be used for improving islet engraftment.

Methods

Mouse and human pancreatic islet cells were transfected with mRNA encoding the angiogenic growth factor vascular endothelial growth factor A (VEGF-A) before transplantation under the kidney capsule in mice.

Results

At day 7 post transplantation, revascularisation of grafts transfected with Vegf-A (also known as Vegfa) mRNA was significantly higher compared with non-transfected or Gfp mRNA-transfected controls in mouse islet grafts (2.11- and 1.87-fold, respectively) (vessel area/graft area, mean?±?SEM: 0.118?±?0.01 [n?=?3] in Vegf-A mRNA transfected group (VEGF) vs 0.056?±?0.01 [n?=?3] in no RNA [p?<?0.05] vs 0.063?±?0.02 [n?=?4] in Gfp mRNA transfected group (GFP) [p?<?0.05]); EndoC-bH3 grafts (2.85- and 2.48-fold. respectively) (0.085?±?0.02 [n?=?4] in VEGF vs 0.030?±?0.004 [n?=?4] in no RNA [p?<?0.05] vs 0.034?±?0.01 [n?=?5] in GFP [p?<?0.05]); and human islet grafts (3.17- and 3.80-fold, respectively) (0.048?±?0.013 [n?=?3] in VEGF vs 0.015?±?0.0051 [n?=?4] in no RNA [p?<?0.01] vs 0.013?±?0.0046 [n?=?4] in GFP [p?<?0.01]). At day 30 post transplantation, human islet grafts maintained a vascularisation benefit (1.70- and 1.82-fold, respectively) (0.049?±?0.0042 [n?=?8] in VEGF vs 0.029?±?0.0052 [n?=?5] in no RNA [p?<?0.05] vs 0.027?±?0.0056 [n?=?4] in GFP [p?<?0.05]) and a higher beta cell volume (1.64- and 2.26-fold, respectively) (0.0292?±?0.0032 μl [n?=?7] in VEGF vs 0.0178?±?0.0021 μl [n?=?5] in no RNA [p?<?0.01] vs 0.0129?±?0.0012 μl [n?=?4] in GFP [p?<?0.001]).

Conclusions/interpretation

Vegf-A mRNA transfection before transplantation provides a promising and safe strategy to improve engraftment of islets and other cell-based implants.

     

Lymphoid progenitors in normal mouse lymph nodes develop into NK cells and T cells in vitro and in vivo

We have identified a population of normal mouse LN cells, termed LN lymphoid progenitor (LNLP), resembling common lymphoid progenitor (CLP) in the bone marrow. LNLPs lack lineage markers and express CD127, low levels of CD117 (c-Kit), and Sca-1, but lack fms-related tyrosine kinase 3. They efficiently differentiate in vitro into natural killer (NK) cells and T cells, but not mature B cells. LNLPs injected into nonirradiated lymphopenic mice that have no LN develop into mostly splenic T cells with low numbers of NK cells and B cells. When injected into irradiated mice, they generate NK cells and T cells, but not B cells, in the LN. By contrast, bone marrow CLPs develop into mostly B cells with very small numbers of T and NK cells in recipients' spleen and LN. LNLPs have NK and T-cell potentials, but little B-cell potential, and they can develop into NK cells within the LN of normal mice, but their contribution to the T-cell lineage is unknown.