A Myocardial Slice Culture Model Reveals Alpha-1A-Adrenergic Receptor Signaling in the Human Heart.

BACKGROUND: Translation of preclinical findings could benefit from a simple, reproducible, high throughput human model to study myocardial signaling. Alpha-1A-adrenergic receptors (ARs) are expressed at very low levels in the human heart, and it is unknown if they function. OBJECTIVES: To develop a high throughput human myocardial slice culture model, and to test the hypothesis that alpha-1A- ARs are functional in the human heart. METHODS: Cores of LV free wall 8 mm diameter were taken from 52 hearts (18 failing and 34 nonfailing). Slices 250 µm thick were cut with a Krumdieck apparatus and cultured using a rotating incubation unit. RESULTS: About 60 slices were cut from each LV core, and a typical study could use 96 slices. Myocyte morphology was maintained, and diffusion into the slice center was rapid. Slice viability was stable for at least 3 days in culture by ATP and MTT assays. The beta-AR agonist isoproterenol stimulated phospholamban phosphorylation, and the alpha-1A-AR agonist A61603 stimulated ERK phosphorylation, with nanomolar EC50 values in slices from both failing and nonfailing hearts. Strips cut from the slices were used to quantify activation of contraction by isoproterenol, A61603, and phenylephrine. The slices supported transduction by adenovirus. CONCLUSIONS: We have developed a simple, high throughput LV myocardial slice culture model to study signaling in the human heart. This model can be useful for translational studies, and we show for the first time that the alpha-1A-AR is functional in signaling and contraction in the human heart.

The Alpha-1A Adrenergic Receptor in the Rabbit Heart.

The alpha-1A-adrenergic receptor (AR) subtype is associated with cardioprotective signaling in the mouse and human heart. The rabbit is useful for cardiac disease modeling, but data on the alpha-1A in the rabbit heart are limited. Our objective was to test for expression and function of the alpha-1A in rabbit heart. By quantitative real-time reverse transcription PCR (qPCR) on mRNA from ventricular myocardium of adult male New Zealand White rabbits, the alpha-1B was 99% of total alpha-1-AR mRNA, with <1% alpha-1A and alpha-1D, whereas alpha-1A mRNA was over 50% of total in brain and liver. Saturation radioligand binding identified ~4 fmol total alpha-1-ARs per mg myocardial protein, with 17% alpha-1A by competition with the selective antagonist 5-methylurapidil. The alpha-1D was not detected by competition with BMY-7378, indicating that 83% of alpha-1-ARs were alpha-1B. In isolated left ventricle and right ventricle, the selective alpha-1A agonist A61603 stimulated a negative inotropic effect, versus a positive inotropic effect with the nonselective alpha-1-agonist phenylephrine and the beta-agonist isoproterenol. Blood pressure assay in conscious rabbits using an indwelling aortic telemeter showed that A61603 by bolus intravenous dosing increased mean arterial pressure by 20 mm Hg at 0.14 µg/kg, 10-fold lower than norepinephrine, and chronic A61603 infusion by iPRECIO programmable micro Infusion pump did not increase BP at 22 µg/kg/d. A myocardial slice model useful in human myocardium and an anthracycline cardiotoxicity model useful in mouse were both problematic in rabbit. We conclude that alpha-1A mRNA is very low in rabbit heart, but the receptor is present by binding and mediates a negative inotropic response. Expression and function of the alpha-1A in rabbit heart differ from mouse and human, but the vasopressor response is similar to mouse.

Reduction of lymphedema using complete decongestive therapy: roles of prior radiation therapy and extent of axillary dissection.

Although radiation therapy (RT) contributes to lymphedema (LE), it is unknown whether RT contributes to more difficulty (more treatments) or less success (decreased LE reduction) with therapy for established LE. We reviewed the results of complete decongestive therapy (CDT) for LE with respect to a history of RT and the number of lymph nodes dissected. Breast cancer survivors with LE were referred to CDT-certified therapists. CDT consists of treatment (phase 1) and maintenance (phase 2) phases. During phase 1, the patient meets with a therapist daily until the LE reduction plateaus; then phase 2 (self-care) begins. During phase 1, LE is quantified weekly at a minimum. Fifty-three patients underwent CDT and completed phase 1. The median number of treatments to plateau was 12 (range 6-25); the median limb volume reduction was 36% (-4-119%). Thirty-six patients with an RT history had an insignificant difference in LE reduction (p = .49) and the number of sessions to plateau (p = .54) compared with 17 patients without RT. The median examined number of nodes was 12 (range 3-28). No significant correlation was observed between the number of nodes examined and percent reduction (r = -.390); no significant correlation (r = .291; critical r = .396 for p = .05 for both cases) was observed between the number of nodes sampled and the number of sessions to plateau. Patients with LE obtained relief regardless of whether they received surgery or surgery plus RT. The insignificant correlation between the number of lymph nodes and percent reduction could become significant with a larger sample size.