Bari Murtuza

Dynamics and mediators of acute graft attrition after myoblast transplantation to the heart

Survival and proliferation of skeletal myoblasts within the cardiac environment are crucial to the therapeutic efficacy of myoblast transplantation to the heart. We have analyzed the early dynamics of myoblasts implanted into the myocardium and investigated the mechanisms underlying graft attrition. At 10 min after implantation of [14C]thymidine‐labeled male myoblasts into female mice hearts, 14C measurement showed that 39.2 ± 3.0% of the grafted cells survived, and this steadily decreased to 16.0 ± 1.7% by 24 h and to 7.4 ± 0.9% by 72 h. PCR of male‐ specific Smcy gene calculated that the total (surviving plus proliferated) number of donor‐derived cells was 18.3 ± 1.6 and 23.3 ± 1.3% at 24 and 72 h, respectively, indicating that proliferation of the surviving cells began after 24 h. Acute inflammation became prominent by 24 h and was reduced by 72 h as indicated by myeloperoxidase activity and histological findings. Multiplex RT‐PCR revealed corresponding changes in IL‐1β, TGF‐β, IL‐6, and TNF‐α expression. Treatment with CuZn‐superoxide dismutase attenuated the initial rapid death and resulted in enhanced cell numbers afterward, giving a twofold increased total number at 72 h compared with the nontreatment. This effect was associated with reduced inflammatory response, suggesting a causative role for superoxide in the initial rapid graft death and subsequent inflammation. These data describe the early dynamics of myoblasts implanted into the myocardium and suggest that initial oxidative stress and following inflammatory response may be important mechanisms contributing to acute graft attrition, both of which could be potential therapeutic targets to improve the efficiency of cell transplantation to the heart.

Minimal access aortic valve replacement: is it worth it?

Controversy surrounds the use of minimal access aortic valve replacement (AVR). This meta-analytical study quantified the effects of minimal access AVR on morbidity and mortality compared with conventional AVR and evaluated study heterogeneity and robustness of the findings using sensitivity analysis. Overall, meta-analysis suggested marginal benefits in perioperative mortality (4,667 patients; odds ratio, 0.72; 95% confidence interval, 0.51-1.00; p = 0.05), intensive care unit stay, total hospital stay, and ventilation time in the minimal access AVR group, although cross-clamp, cardiopulmonary bypass, and total operation times were longer. Study heterogeneity and apparent benefits in perioperative mortality were related to study quality, although results for intensive care unit and hospital stay were maintained according to the sensitivity analysis. This suggests that minimal access AVR can be offered on the basis of patient choice and cosmesis rather than evident clinical benefit.

Transplantation of skeletal myoblasts secreting an IL-1 inhibitor modulates adverse remodeling in infarcted murine myocardium

After myocardial infarction (MI), adverse remodeling with left ventricular (LV) dilatation is a major determinant of poor outcome. Skeletal myoblast (SkM) implantation improves cardiac function post-MI, although the mechanism is unclear. IL-1 influences post-MI hypertrophy and collagen turnover and is implicated in SkM death after grafting. We hypothesized that SkM expressing secretory IL-1 receptor antagonist (sIL-1ra) at MI border zones would specifically attenuate adverse remodeling and exhibit improved graft cell number. Stable murine male SkM lines (5 × 105 cells), expressing or nonexpressing (cont) for sIL-1ra, were implanted into infarct border zones of female nude mice immediately after left coronary artery occlusion. LV ejection fraction (LVEF), end-diastolic diameter, and transmitral peak early/late (E/A) flow velocity ratio were determined by echocardiography. Cardiac myocyte hypertrophy and fibrosis were assessed by morphometry, picrosirius red staining, and hydroxyproline assay. At 3 weeks, cont-SkM-engrafted hearts showed reduced hypertrophy, improved LVEF (55.7 ± 1.2% vs. MI-only: 40.3 ± 2.9%), and preserved E/A ratios. sIL-1ra-SkM implantation enhanced these effects (LVEF, 67.0 ± 2.3%) and significantly attenuated LV dilatation (LV end-diastolic diameter, 4.0 ± 1.1 mm vs. cont-SkM, 4.5 ± 1.2 mm vs. MI-only, 4.8 ± 1.8 mm); this was associated with greater graft numbers, as shown by PCR for male-specific smcy gene. Enzyme zymography showed attenuated matrix metalloproteinase-2 and -9 up-regulation post-MI by either donor SkM type, although infarct-remote zone collagen was reduced only with sIL-1ra-SkM. These results suggest that SkM implantation improves cardiac function post-MI by modulation of adverse remodeling, and that this effect can be significantly enhanced by targeting IL-1 as a key upstream regulator of both adverse remodeling and graft cell death.

Role of Interleukin-1β in Acute Inflammation and Graft Death After Cell Transplantation to the Heart

Background—Poor survival of grafted cells is a major factor hindering the therapeutic effect of cell transplantation; however, the causes of cell death remain unclear. We hypothesized that interleukin-1&bgr; (IL-1&bgr;) might play a role in the acute inflammatory response and graft death after cell transplantation and that inhibition of IL-1&bgr; might improve graft survival. Methods and Results—14C-labeled male skeletal muscle precursor cells were implanted into female mouse hearts by direct intramuscular injection. The amount of 14C-label provides an estimate of the surviving cell number, whereas the amount of male-specific Smcy gene measured by polymerase chain reaction indicates the total (surviving+proliferated) number of donor-derived cells. At 10 minutes after implantation, 44.8±2.4% of the grafted cells survived and this steadily decreased to 14.6±1.1% by 24 hours, and to 7.9±0.6% by 72 hours (n=6 in each point). Proliferation of the surviving cells, which began after 24 hours, resulted in an increase in the total cell number from 15.5±0.8% at 24 hours to 24.4±1.6% at 72 hours. Acute inflammation was prominent at 24 hours and was reduced by 72 hours, in parallel with IL-1&bgr; expression. Administration of anti–IL-1&bgr; antibody improved graft survival at both 24 (25.6±1.6%) and 72 hours (14.8±1.1%) and resulted in a 2-fold increase in the total cell number at 72 hours (45.8±2.4%). The effects of IL-1&bgr; inhibition corresponded with a reduced inflammatory response. Conclusion—IL-1&bgr; is involved in acute inflammation and graft death after direct intramyocardial cell transplantation. Targeted inhibition of IL-1&bgr; may be a useful strategy to improve graft survival.

Targeted cell delivery into infarcted rat hearts by retrograde intracoronary infusion: distribution, dynamics, and influence on cardiac function.

Background—Intracoronary infusion for cell transplantation has potential advantages in disseminating cells globally into the myocardium with less injury over direct intramuscular injection. Arterial route, however, has a risk of coronary embolism and a limitation in cell delivery into ischemic or infarcted areas. We assessed the efficiency of retrograde intracoronary cell implantation into infarcted hearts using a novel rat model. Methods and Results—After left coronary artery ligation in rat, a catheter was inserted into the left cardiac vein, which drains the left ventricular free wall. Through this, 1×106 skeletal muscle precursor cells expressing nuclear &bgr;-galactosidase were infused retrogradely into the vein. In situ staining demonstrated that &bgr;-galactosidase–expressing donor cells had disseminated throughout the left ventricular free wall, including both infarcted and surrounding border areas, at 10 minutes after infusion. At 28 days, in contrast, positively stained multinuclear myotubes were found in border zones, whereas no positive cells were seen in infarcted areas. Measurement of &bgr;-galactosidase enzyme activity estimated that 29.8±6.9% of total infused cells were retained within the myocardium at 10 minutes and that this number decreased to 23.7±8.1% at 3 days but rapidly increased thereafter, reaching a plateau at 90.2±17.1% by 14 days. Echocardiography and Langendorff perfusion demonstrated that cell implantation improved cardiac function and dimensions by 28 days, compared with both sham-treated and phosphate-buffered saline-infused infarcted hearts, and this was associated with decreased collagen deposition. Conclusion—Retrograde intracoronary cell transplantation could provide an effective cell delivery into infarcted hearts and could be a useful strategy for treating myocardial infarction.

Does stentless aortic valve implantation increase perioperative risk? A critical appraisal of the literature and risk of bias analysis

Stentless aortic valve replacement has potential benefits in terms of valve hemodynamics and clinical outcomes, although these may be offset by greater technical complexity of implantation with longer cardiopulmonary bypass and cross-clamp times compared with stented valves. Meta-analyses of the small number of published randomized trials have been limited by their lack of critical synthesis of the literature, including evaluation of the Risk of Bias. Our objective was to determine whether stentless aortic valves increase perioperative risk of mortality. We also examined secondary clinical outcomes of neurological, renal and respiratory complications as well as hemodynamic changes reported by studies following implantation of the two types of aortic prosthesis. The methodology used to answer this question was a rigorous meta-analysis of randomized controlled trials, using bias-assessment techniques designed to address limitations of conventional meta-analysis. Our findings show that many of the existing randomized trials have a high or uncertain risk of bias. Analysis of studies with low risk of bias reveals that stentless valves do not increase perioperative risk in terms of 30-day mortality and morbidity though neither do they exhibit benefits in hemodynamics or clinical outcomes compared with stented valves. Larger, more stringent randomized studies would be required to identify any robust clinical difference.

Development of an in vivo ischemia-reperfusion model in heterotopically transplanted rat hearts.

Background. Heart transplantation has been extensively used in animal models, including studies on gene therapy for myocardial preservation. We investigated the feasibility of in situ left coronary artery (LCA) ligation as a physiological system for the examination of strategies to modulate myocardial tolerance against ischemia-reperfusion injury, such as gene therapy, using heterotopically transplanted rat hearts. Methods. Lewis rat hearts that had been transplanted into syngeneic recipients’ abdomens were subjected to 30-min ischemia, by occluding the LCA, and subsequent blood reperfusion by releasing the suture in situ (I/R group). Transplanted hearts in the sham group underwent laparotomy only. Results. At 24 hr of reperfusion, the size of the ischemic region was 40.1±3.1% of the total left ventricular mass, and the infarct size was 47.5±3.3% of the area at risk in the I/R group. Cardiac function was reduced in the I/R group compared with the sham group, associated with higher myeloperoxidase activity (5.12±1.35 vs. 0.97±0.33 U/g wt) and higher incidence of apoptosis as defined by TUNEL (29.8±3.2 vs. 3.8±0.7%) and DNA ladder. In the I/R group, up-regulation of Bax, Bak, and caspase-3 was observed. Conclusions. These data on myocardial damage of transplanted hearts are consistent and equivalent to those of the usual LCA occlusion model, suggesting that this method is useful to investigate strategies for modulating myocardial tolerance against ischemia-reperfusion injury using heterotopically transplanted rat hearts in a more physiological blood-perfused model.

Does preservation of the sub-valvular apparatus during mitral valve replacement affect long-term survival and quality of life? A Microsimulation Study

BackgroundTechniques to preserve the sub-valvular apparatus in order to reduce morbidity and mortality following mitral valve replacement have been frequently reported. However, it is uncertain what impact sub-valvular apparatus preservation techniques have on long-term outcomes following mitral valve replacement. This study investigated the effect of sub-valvular apparatus preservation on long-term survival and quality of life following mitral valve replacement.MethodsA microsimulation model was used to compare long-term survival and quality-adjusted life years following mitral valve replacement after conventional valve replacement and sub-valvular apparatus preservation. Probabilistic sensitivity analysis and alternative analysis were performed to investigate uncertainty associated with the results.ResultsOur Analysis suggests that patients survive longer if the sub-valvular apparatus are preserved (65.7% SD 1.5%, compared with 58.1% SD 1.6% at 10 years). The quality adjusted life years gained over a 10 year period where also greater after sub-valvular apparatus preservation. (6.54 QALY SD 0.07 QALY, compared with 5.61 QALY, SD 0.07 QALY). The superiority of preservation techniques was insensitive to patient age, parameter or model uncertainty.ConclusionThis study suggests that long-term outcomes may be improved when the sub-valvular apparatus are preserved. Given the lack of empirical data further research is needed to investigate health-related quality of life after mitral valve replacement, and to establish whether outcomes differ between preservation techniques.

Lung volume reduction surgery in a ventilated patient with severe pulmonary emphysema

There are a limited number of reports in the literature cocerning lung volume reduction surgery in patients receiving mechanical ventilation. We present a case in which a ventilator-dependent patient with apparent endstage pulmonary emphysema underwent lung volume reduction with a successful outcome. Although the role of this procedure for selected nonventilated patients has been widely discussed its use in ventilated patients is still not clearly defined. We show that lung volume reduction surgery may facilitate ventilatory weaning in such cases and improve functional status.

How to Structure an Academic Lecture

This chapter is concerned with the overall nature of an academic lecture, its importance and context and its place in surgical education and practice. First we define what an academic lecture is, and then consider the types of academic lecture as well as its overall structure and purpose. We also describe the essential ideas of the lecture format using principles from linguistics and use this as a platform for describing the planning and delivery of a lecture for a variety of forums.