Brent R. DeGeorge

G Protein–Coupled Receptor Kinase 2 Ablation in Cardiac Myocytes Before or After Myocardial Infarction Prevents Heart Failure

Myocardial G protein-coupled receptor kinase (GRK)2 is a critical regulator of cardiac &bgr;-adrenergic receptor (&bgr;AR) signaling and cardiac function. Its upregulation in heart failure may further depress cardiac function and contribute to mortality in this syndrome. Preventing GRK2 translocation to activated &bgr;AR with a GRK2-derived peptide that binds G&bgr;&ggr; (&bgr;ARKct) has benefited some models of heart failure, but the precise mechanism is uncertain, because GRK2 is still present and &bgr;ARKct has other potential effects. We generated mice in which cardiac myocyte GRK2 expression was normal during embryonic development but was ablated after birth (&agr;MHC-Cre×GRK2 fl/fl) or only after administration of tamoxifen (&agr;MHC-MerCreMer×GRK2 fl/fl) and examined the consequences of GRK2 ablation before and after surgical coronary artery ligation on cardiac adaptation after myocardial infarction. Absence of GRK2 before coronary artery ligation prevented maladaptive postinfarction remodeling and preserved &bgr;AR responsiveness. Strikingly, GRK2 ablation initiated 10 days after infarction increased survival, enhanced cardiac contractile performance, and halted ventricular remodeling. These results demonstrate a specific causal role for GRK2 in postinfarction cardiac remodeling and heart failure and support therapeutic approaches of targeting GRK2 or restoring &bgr;AR signaling by other means to improve outcomes in heart failure.

Uncovering G protein-coupled receptor kinase-5 as a histone deacetylase kinase in the nucleus of cardiomyocytes

G protein-coupled receptor (GPCR) kinases (GRKs) are critical regulators of cellular signaling and function. In cardiomyocytes, GRK2 and GRK5 are two GRKs important for myocardial regulation, and both have been shown to be up-regulated in the dysfunctional heart. We report that increased levels and activity of GRK5 in failing myocardium may have unique significance due to its nuclear localization, a property not shared by GRK2. We find that transgenic mice with elevated cardiac GRK5 levels have exaggerated hypertrophy and early heart failure compared with control mice after pressure overload. This pathology is not present in cardiac GRK2-overexpressing mice or in mice with overexpression of a mutant GRK5 that is excluded from the nucleus. Nuclear accumulation of GRK5 is enhanced in myocytes after aortic banding in vivo and in vitro in myocytes after increased Gαq activity, the trigger for pressure-overload hypertrophy. GRK5 enhances activation of MEF2 in concert with Gq signals, demonstrating that nuclear localized GRK5 regulates gene transcription via a pathway critically linked to myocardial hypertrophy. Mechanistically, we show that this is due to GRK5 acting, in a non-GPCR manner, as a class II histone deacetylase (HDAC) kinase because it can associate with and phosphorylate the myocyte enhancer factor-2 repressor, HDAC5. Moreover, significant HDAC activity can be found with GRK5 in the heart. Our data show that GRK5 is a nuclear HDAC kinase that plays a key role in maladaptive cardiac hypertrophy apparently independent of any action directly on GPCRs.

Cardiac S100A1 Protein Levels Determine Contractile Performance and Propensity Toward Heart Failure After Myocardial Infarction

Background— Diminished cardiac S100A1 protein levels are characteristic of ischemic and dilated human cardiomyopathy. Because S100A1 has recently been identified as a Ca2+-dependent inotropic factor in the heart, this study sought to explore the pathophysiological relevance of S100A1 levels in development and progression of postischemic heart failure (HF). Methods and Results— S100A1-transgenic (STG) and S100A1-knockout (SKO) mice were subjected to myocardial infarction (MI) by surgical left anterior descending coronary artery ligation, and survival, cardiac function, and remodeling were compared with nontransgenic littermate control (NLC) and wild-type (WT) animals up to 4 weeks. Although MI size was similar in all groups, infarcted S100A1-deficient hearts (SKO-MI) responded with acute contractile decompensation and accelerated transition to HF, rapid onset of cardiac remodeling with augmented apoptosis, and excessive mortality. NLC/WT-MI mice, displaying a progressive decrease in cardiac S100A1 expression, showed a later onset of cardiac remodeling and progression to HF. Infarcted S100A1-overexpressing hearts (STG-MI), however, showed preserved global contractile performance, abrogated apoptosis, and prevention from cardiac hypertrophy and HF with superior survival compared with NLC/WT-MI and SKO-MI. Both Gq-protein–dependent signaling and protein kinase C activation resulted in decreased cardiac S100A1 mRNA and protein levels, whereas Gs-protein–related signaling exerted opposite effects on cardiac S100A1 abundance. Mechanistically, sarcoplasmic reticulum Ca2+ cycling and &bgr;-adrenergic signaling were severely impaired in SKO-MI myocardium but preserved in STG-MI. Conclusions— Our novel proof-of-concept study provides evidence that downregulation of S100A1 protein critically contributes to contractile dysfunction of the diseased heart, which is potentially responsible for driving the progressive downhill clinical course of patients with HF.

Targeted Inhibition of Cardiomyocyte Gi Signaling Enhances Susceptibility to Apoptotic Cell Death in Response to Ischemic Stress

Background— A salient characteristic of dysfunctional myocardium progressing to heart failure is an upregulation of the adenylyl cyclase inhibitory guanine nucleotide (G) protein &agr; subunit, G&agr;i2. It has not been determined conclusively whether increased Gi activity in the heart is beneficial or deleterious in vivo. Gi signaling has been implicated in the mechanism of cardioprotective agents; however, no in vivo evidence exists that any of the G&agr; subunits are cardioprotective. We have created a novel molecular tool to specifically address the role of Gi proteins in normal and dysfunctional myocardium. Methods and Results— We have developed a class-specific Gi inhibitor peptide, GiCT, composed of the region of G&agr;i2 that interacts specifically with G protein–coupled receptors. GiCT inhibits Gi signals specifically in vitro and in vivo, whereas Gs and Gq signals are not affected. In vivo expression of GiCT in transgenic mice effectively causes a “functional knockout” of cardiac G&agr;i2 signaling. Inducible, cardiac-specific GiCT transgenic mice display a baseline phenotype consistent with nontransgenic mice. However, when subjected to ischemia/reperfusion injury, GiCT transgenic mice demonstrate a significant increase in infarct size compared with nontransgenic mice (from 36.9±2.5% to 50.9±4.3%). Mechanistically, this post-ischemia/reperfusion phenotype includes increased myocardial apoptosis and resultant decreased contractile performance. Conclusions— Overall, our results demonstrate the in vivo utility of GiCT to dissect specific mechanisms attributed to Gi signaling in stressed myocardium. Our results with GiCT indicate that upregulation of G&agr;i2 is an adaptive protective response after ischemia to shield myocytes from apoptosis.

Comparison study of two types of expander-based breast reconstruction: acellular dermal matrix-assisted versus total submuscular placement.

AbstractRecent reported complications have called some authors to express concern regarding the increased popularity of acellular dermal matrix (ADM)-based breast reconstruction, and its role as an alternative to traditional total submuscular approaches. To address this issue, we compared tissue expansion properties, complication rates, and patient satisfaction for both operative techniques at the same institution. A retrospective review was completed on 75 patients and 100 tissue expander/implant-based breast reconstructions at a single academic institution from 2007 to 2010. Of these cases, 31 patients were reconstructed with ADM and 44 with a submuscular coverage technique. Total complications including seroma, hematoma, infection, skin necrosis, and explantation did not significantly differ between groups (n = 13 for ADM vs. 17 for submuscular, P = 0.814). Consistent with prior reports, ADM-based reconstructions were associated with significantly increased intraoperative fill volumes and lower total number of sessions to achieve final volume. Submuscular reconstructions required a significantly higher tissue expander fill volume. Eight patients in the submuscular group required surgical revision of the breast and inframammary fold, compared with 4 in the ADM group; however, this difference was not significant. Patient satisfaction was equivalent between the 2 groups; however, it was higher in patients with bilateral reconstruction and lower among those who had received adjuvant radiation therapy. Satisfaction with nipple reconstruction was inversely proportional to time elapsed from the procedure to survey conduction. This is the first study to perform a head-to-head comparison on the basis of patient satisfaction, the results of which may be useful in preoperative planning and counseling.

The impact of conflict of interest in abdominal wall reconstruction with acellular dermal matrix.

IntroductionConflict of interest (COI) and disclosure of financial relationships have received increased attention recently owing in part to the passage of the Physician Payments Sunshine Act, which requires manufacturers of drugs, medical devices, and biological to record payments to physicians and health care systems. The impact of financial relationships with industry sponsorship and COI reporting on surgical outcomes of abdominal wall reconstruction with acellular dermal matrices (ADMs) has not been previously explored. MethodsA systematic review of the literature for studies that evaluated surgical outcomes in abdominal wall reconstruction using ADM was conducted. The level of evidence of these studies was evaluated; and data concerning the type of industry, government, or national society sponsorship, primary outcome, complications, and statistical results were collected. The overall favorability of the study with respect to ADM use was systematically assessed. Comparisons between type of sponsorship and significant results were analyzed using the Pearson &khgr;2 test. ResultsA total of 204 studies were identified, of which 124 fulfilled our inclusion criteria. Sixty-four (52%) studies had a disclosure statement present. Conflict of interest was reported in 39 (61%) of these studies. Taken collectively, studies that report no COI are more likely to be unfunded (P < 0.001). Studies with a reported COI are more likely to report a favorable outcome with respect to infection (P < 0.01), wound complications (P < 0.01), and overall morbidity (P < 0.07) and mortality (P < 0.05). ConclusionsIndustry sponsorship and COI are common in abdominal wall reconstruction studies with ADM. Studies authored by groups disclosing an industry conflict that report clinical outcomes are significantly associated with reporting lower postoperative complications, and consequently describing positive research findings.

BMP‐2 and FGF‐2 Synergistically Facilitate Adoption of a Cardiac Phenotype in Somatic Bone Marrow c‐kit+/Sca‐1+ Stem Cells

The aim of this study was to explore the effect of bone morphogenetic protein‐2 (BMP‐2) and fibroblast growth factor‐2 (FGF‐2)— paracrine factors implicated in both cardiac embryogenesis and cardiac repair following myocardial infarction (MI)—on murine bone marrow stem cell (mBMSC) differentiation in an ex vivo cardiac microenvironment. For this purpose, green fluorescent protein (GFP) expressing hematopoietic lineage negative (lin‐) c‐kit ligand (c‐kit) and stem cell antigen‐1 (Sca‐1) positive (GFP‐lin‐/c‐kit+/sca+) mBMSC were co‐cultured with neonatal rat ventricular cardiomyocytes (NVCMs). GFP+ mBMSC significantly induced the expression of BMP‐2 and FGF‐2 in NVCMs, and approximately 4% GFP+ mBMSCs could be recovered from the co‐culture at day 10. The addition of BMP‐2 in concert with FGF‐2 significantly enhanced the amount of integrated GFP+ mBMSCs by 5‐fold (∼20%), whereas the addition of anti‐BMP‐2 and/or anti‐FGF‐2 antibodies completely abolished this effect. An analysis of calcium cycling revealed robust calcium transients in GFP+ mBMSCs treated with BMP‐2/FGF‐2 compared to untreated co‐cultures. BMP‐2 and FGF‐2 addition led to a significant induction of early (NK2 transcription factor related, locus 5; Nkx2.5, GATA binding protein 4; GATA‐4) and late (myosin light chain kinase [MLC‐2v], connexin 43 [Cx43]) cardiac marker mRNA expression in mBMSCs following co‐culture. In addition, re‐cultured fluorescence‐activated cell sorting (FACS)‐purified BMP‐2/FGF‐2‐treated mBMSCs revealed robust calcium transients in response to electrical field stimulation which were inhibited by the L‐type calcium channel (LTCC) inhibitor, nifedipine, and displayed caffeine‐sensitive intracellular calcium stores. In summary, our results show that mBMSCs can adopt a functional cardiac phenotype through treatment with factors essential to embryonic cardiogenesis that are induced after cardiac ischemia. This study provides the first evidence that mBMSCs with long‐term self‐renewal potential possess the capability to serve as a functional cardiomyocyte precursor through the appropriate paracrine input and cross‐talk within an appropriate cardiac microenvironment.

Cardiac‐Restricted Overexpression of the A2A‐Adenosine Receptor in FVB Mice Transiently Increases Contractile Performance and Rescues the Heart Failure Phenotype in Mice Overexpressing the A1‐Adenosine Receptor

In the heart, adenosine binds to pharmacologically distinct G‐protein‐coupled receptors (A1‐R, A2A‐R, and A3‐R). While the role of A1‐and A3‐Rs in the heart has been clarifed, the effect of genetically manipulating the A2A‐R has not been defned. Thus, we created mice overexpressing a cardiac‐restricted A2A‐R transgene. Mice with both low (Lo) and high (Hi) levels of A2A‐R overexpression demonstrated an increase in cardiac contractility at 12 weeks. These changes were associated with a signifcantly higher systolic but not diastolic [Ca2+]i, higher maximal contraction amplitudes, and a signifcantly enhanced sarcoplasmic reticulum Ca2+ uptake activity. At 20 weeks, the effects of A2A‐R overexpression on cardiac contractility diminished. The positive effects elicited by A2A‐R overexpression differ from the heart failure phenotype we observed with A1‐R overexpresson. Interestingly, coexpression of A2A‐R TGHi, but not A2A‐R TGLo, enhanced survival, prevented the development of left ventricular dysfunction and heart failure, and improved Ca2+ handling in mice overexpressing the A1‐R. These results suggest that adenosine‐mediated signaling in the heart requires a balance between A1‐ and A2A‐Rs—a fnding that may have important implications for the ongoing clinical evaluation of adenosine receptor subtype‐specifc agonists and antagonists for the treatment of cardiovascular diseases.

Acellular Flexor Tendon Allografts: A New Horizon for Tendon Reconstruction

Flexor tendon injuries continue to pose a significant challenge to the hand surgeon. In particular, chronic tendon ruptures with adhesions of the tendons and sheath, damage or loss of the intrasynovial flexor tendons in zone II, and combined soft tissue and bone injuries present especially difficult problems for restoring satisfactory digital function. This challenge in flexor tendon reconstruction has motivated hand surgeons to explore and develop novel solutions for nearly a century. Recent advances and techniques in processing and decellularizing allograft human flexor tendon constructs may prove to be a new horizon for tendon reconstruction.

The single fascial incision modification of the "open-book" component separation repair: A 15-year experience

PurposeComplex abdominal wall hernias can be challenging for the reconstructive surgeon. The use of autologous tissue is preferable when possible. The authors review their 15-year experience regarding the “open-book” technique of ventral hernia repair. This repair entails a single fascial incision releasing the external oblique and concurrently incorporates the anterior rectus sheath as a turnover flap for abdominal wall reconstruction. This modification allows large defects to be closed with autologous tissue alone in a 2-layer fascial repair in a vest-over-pants fashion in a simple, straightforward surgical approach. MethodsA 15-year, single-surgeon retrospective review was conducted of 35 consecutive select patients who underwent component separation using the open-book variation. Hospital and office-based charts were reviewed. Complications were recorded as either major (hernia recurrence or any complication requiring readmission or reoperation) or minor (treated on an outpatient basis). Individual complications included hernia recurrence, infection, seroma, hematoma, and skin necrosis. ResultsSixty-three percent of the patients in the study had, at minimum, 1 recognized comorbidity before reconstructive surgery. Only 2 (6%) of 35 patients experienced hernia recurrence during the course of the 15 years. The minor complication rate was 8/35 (23%), including infection (5; 14%), skin necrosis (5; 14%), and hematoma (1; 3%). The major complication rate was 5/35 (14%), including hernia recurrence (2; 6%), infection (2; 6%), skin necrosis (2; 6%), and hematoma (1; 3%). Factors associated with a statistically significant increased rate of overall complications included chronic obstructive pulmonary disease (80%; P = 0.03) and hypertension (39%; P = 0.04). The average length of follow-up was 16 (3) months. ConclusionsOur series suggests that with appropriate patient selection, this technique is associated with a low hernia recurrence rate when compared to the published literature. Additionally, the major complication rate is acceptable given these patients’ many comorbidities and complicated surgical history. The presence of chronic obstructive pulmonary disease and/or hypertension was found to be statistically associated with an increased complication rate. The single fascial incision modification of the open-book component separation technique is an effective addition to the reconstructive surgeons’ armamentarium in the management of these patients.