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. 2006 May 16;8(2):45.

Reversal of myocyte hypertrophy by ventricular unloading: cardiac improvement without adrenergic receptor up-regulation and relocalization

Pippa M Schnee  1 , Naeema Shah, Marianne Bergheim, Brian J Poindexter, L Max Buja, Timothy J Myers, Branislav Radovancevic, O Howard Frazier, Roger J Bick
Affiliations

Reversal of myocyte hypertrophy by ventricular unloading: cardiac improvement without adrenergic receptor up-regulation and relocalization

Pippa M Schnee et al. MedGenMed. .

Abstract

In previous studies, we found that the improved contractile ability of cardiac myocytes from patients who have had left ventricular assist device (LVAD) support was due to a number of beneficial changes, most notably in calcium handling (increased sarcoplasmic reticulum calcium binding and uptake), improved integrity of cell membranes due to phospholipid reconstruction (reduced lysophospholipid content), and an upregulation of adrenoreceptors (increased adrenoreceptor numbers). However, in the case presented here, there was no increase in adrenoreceptor number, which is something that we usually find in core tissue at the time of LVAD removal or organ transplantation; also, there was no homogeneous postassist device receptor distribution. However, the patient was well maintained for 10 months following LVAD implantation, until a donor organ was available, regardless of the lack of adrenoreceptor improvement. We conclude from these studies that cardiac recovery is the result of the initiation of multiple repair mechanisms, and that the lack of expected changes, in this case increased adrenoreceptors, is not always an accurate indicator of anticipated outcome. We suggest that interventions and strategies have to consider multiple, beneficial changes due to unloading and target a number of biochemical and structural areas to produce improvement, even if not all of these improvements occur.

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Figures

Figure 1
Figure 1
Four images from the reported patient demonstrate cross sections (A and B) and longitudinal sections (C and D) for post-left ventricular assist device (LVAD) (A and C) and pre-LVAD (B and D) samples. Note the width of the myofibrils (green fluorescent tag, indicated by the yellow brackets) and the clumped appearance of these receptors (Texas Red tag, Panel C), even after unloading. Image acquisition is as described under the “Methods” section, and each panel is 90 × 90 microns.
Figure 2
Figure 2
Two images of explant vs implant tissue, demonstrating the copious number and distribution of adrenoreceptors after ventricular unloading (first panel), from a second patient in this study, compared with the sparse number of adrenoreceptors before unloading and the disjointed myofibers before unloading. Images are stained for actin and beta adrenoreceptors in this example. Image size is 96 × 96 microns, and acquisitions were made as described under “Methods.”
See this image and copyright information in PMC

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References

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