Ehsan Benrashid

Dose-dependent restoration of dystrophin expression in cardiac muscle of dystrophic mice by systemically delivered morpholino.

We have earlier shown that antisense morpholino oligomers are able to restore dystrophin expression by systemic delivery in body-wide skeletal muscles of dystrophic mdx mice. However, the levels of dystrophin expression vary considerably and, more importantly, no dystrophin expression has been achieved in cardiac muscle. In this study, we investigate the efficiency of morpholino-induced exon skipping in cardiomyoblasts and myocytes in vitro, and in cardiac muscle in vivo by dose escalation. We showed that morpholino induces targeted exon skipping equally effectively in both skeletal muscle myoblasts and cardiomyoblasts. Effective exon skipping was achieved in cardiomyocytes in culture. In the mdx mice, morpholino rescues dystrophin expression dose dependently in both skeletal and cardiac muscles. Therapeutic levels of dystrophin were achieved in cardiac muscle albeit at higher doses than in skeletal muscles. Up to 50 and 30% normal levels of dystrophin were induced by single systemic delivery of 3 g kg–1 of morpholino in skeletal and cardiac muscles, respectively. High doses of morpholino treatment reduced the serum levels of creatine kinase without clear toxicity. These findings suggest that effective rescue of dystrophin in cardiac muscles can be achieved by morpholino for the treatment of Duchenne muscular dystrophy.

Targeted skipping of human dystrophin exons in transgenic mouse model systemically for antisense drug development.

Antisense therapy has recently been demonstrated with great potential for targeted exon skipping and restoration of dystrophin production in cultured muscle cells and in muscles of Duchenne Muscular Dystrophy (DMD) patients. Therapeutic values of exon skipping critically depend on efficacy of the drugs, antisense oligomers (AOs). However, no animal model has been established to test AO targeting human dystrophin exon in vivo systemically. In this study, we applied Vivo-Morpholino to the hDMD/mdx mouse, a transgenic model carrying the full-length human dystrophin gene with mdx background, and achieved for the first time more than 70% efficiency of targeted human dystrophin exon skipping in vivo systemically. We also established a GFP-reporter myoblast culture to screen AOs targeting human dystrophin exon 50. Antisense efficiency for most AOs is consistent between the reporter cells, human myoblasts and in the hDMD/mdx mice in vivo. However, variation in efficiency was also clearly observed. A combination of in vitro cell culture and a Vivo-Morpholino based evaluation in vivo systemically in the hDMD/mdx mice therefore may represent a prudent approach for selecting AO drug and to meet the regulatory requirement.

Guanine Analogues Enhance Antisense Oligonucleotide-induced Exon Skipping in Dystrophin Gene In Vitro and In Vivo

Exon skipping has demonstrated great potential for treating Duchenne muscular dystrophy (DMD) and other diseases. We have developed a drug-screening system using C2C12 myoblasts expressing a reporter green fluorescent phosphate (GFP), with its reading frame disrupted by the insertion of a targeted dystrophin exon. A library of 2,000 compounds (Spectrum collection; Microsource Discovery System) was screened to identify drugs capable of skipping targeted dystrophin exons or enhancing the exon-skipping effect by specific antisense oligomers. The 6-thioguanine (6TG) was effective for inducing skipping of both human dystrophin exon 50 (hDysE50) and mouse dystrophin exon 23 (mDysE23) in the cell culture systems and increased exon skipping efficiency (more than threefolds) when used in combination with phosphorodiamidate morpholino oligomers (PMO) in both myoblasts and myotubes. Guanine and its analogues were unable to induce detectable skipping of exon 23 when used alone but enhanced PMO-induced exon skipping significantly (approximately two times) in the muscles of dystrophic mdx mouse in vivo. Our results demonstrate that small-molecule compounds could enhance specific exon skipping synergistically with antisense oligomers for experimental therapy to human diseases.Exon skipping has demonstrated great potential for treating Duchenne muscular dystrophy (DMD) and other diseases. We have developed a drug-screening system using C2C12 myoblasts expressing a reporter green fluorescent phosphate (GFP), with its reading frame disrupted by the insertion of a targeted dystrophin exon. A library of 2,000 compounds (Spectrum collection; Microsource Discovery System) was screened to identify drugs capable of skipping targeted dystrophin exons or enhancing the exon-skipping effect by specific antisense oligomers. The 6-thioguanine (6TG) was effective for inducing skipping of both human dystrophin exon 50 (hDysE50) and mouse dystrophin exon 23 (mDysE23) in the cell culture systems and increased exon skipping efficiency (more than threefolds) when used in combination with phosphorodiamidate morpholino oligomers (PMO) in both myoblasts and myotubes. Guanine and its analogues were unable to induce detectable skipping of exon 23 when used alone but enhanced PMO-induced exon skipping significantly (approximately two times) in the muscles of dystrophic mdx mouse in vivo. Our results demonstrate that small-molecule compounds could enhance specific exon skipping synergistically with antisense oligomers for experimental therapy to human diseases.

Tissue engineered vascular grafts: Origins, development, and current strategies for clinical application

Since the development of a dependable and durable synthetic non-autogenous vascular conduit in the mid-twentieth century, the field of vascular surgery has experienced tremendous growth. Concomitant with this growth, development in the field of bioengineering and the development of different tissue engineering techniques have expanded the armamentarium of the surgeon for treating a variety of complex cardiovascular diseases. The recent development of completely tissue engineered vascular conduits that can be implanted for clinical application is a particularly exciting development in this field. With the rapid advances in the field of tissue engineering, the great hope of the surgeon remains that this conduit will function like a true blood vessel with an intact endothelial layer, with the ability to respond to endogenous vasoactive compounds. Eventually, these engineered tissues may have the potential to supplant older organic but not truly biologic technologies, which are used currently.

Evolving practice pattern changes and outcomes in the era of hybrid aortic arch repair

OBJECTIVE The role of hybrid repair in the management of aortic arch pathology, and long-term outcomes with these techniques, remains uncertain. We report a decade of experience with hybrid arch repair (HAR) and assess institutional practice patterns with regard to the use of hybrid and open techniques. METHODS Hybrid and open total and distal arch procedures performed between July 2005 and January 2015 were identified from a prospectively maintained, institutional aortic surgery database. Perioperative morbidity and mortality, freedom from reintervention, and long-term survival were calculated. Hybrid and open procedural volumes over the study period were assessed to evaluate for potential practice pattern changes. RESULTS During the study period 148 consecutive procedures were performed for repair of transverse and distal aortic arch pathology, including 101 hybrid repairs and 47 open total or distal arch repairs. Patients in the hybrid repair group were significantly older with a greater incidence of chronic kidney disease, peripheral vascular disease, and chronic lung disease. Perioperative mortality and outcomes were not significantly different between the hybrid and open groups, aside from decreased median length of stay after hybrid repair. Need for subsequent reintervention was significantly greater after hybrid repair. Unadjusted long-term survival was superior after open repair (70% 5-year survival open vs 47% hybrid; P = .03), although aorta-specific survival was similar (98% 5-year aorta-specific survival open vs 93% hybrid; P = .59). Institutional use of HAR decreased over the final 3 years of the study, with an associated increased use of open total or distal arch repairs. This was primarily the result of decreased use of native zone 0 hybrid procedures. Concurrent with this apparent increased stringency around patient selection for HAR, perioperative morbidity and mortality was reduced, including avoidance of retrograde type A dissection. CONCLUSIONS HAR remains a viable option for higher-risk patients with transverse arch pathology with perioperative outcomes and long-term aorta-specific survival similar to open repair, albeit at a cost of increased reintervention. This observational single-institution study would suggest decreased use in more recent years in favor of open repair due to avoidance of native zone 0 hybrid procedures. This decline in the institutional use of native zone 0 hybrid repairs was associated with improved perioperative outcomes.

Determining the Optimal Timing for Initiation of Adjuvant Chemotherapy After Resection for Stage II and III Colon Cancer.

BACKGROUND: Several reports suggest that the efficacy of adjuvant chemotherapy on survival diminishes over time for colon cancer; however, precise timing of its loss of benefit has not been established. OBJECTIVE: This study aimed to determine the relationship between time to adjuvant chemotherapy and survival and to identify a threshold for increased risk of mortality. DESIGN: This was a retrospective study. Multivariable Cox proportional hazard modeling with restricted cubic splines was used to evaluate the adjusted association between time to adjuvant chemotherapy and overall survival and to establish an optimal threshold for the initiation of therapy. SETTINGS: Data were collected from the National Cancer Data Base. PATIENTS: Adults who received adjuvant chemotherapy following resection of stage II to III colon cancers were selected. MAIN OUTCOME MEASURES: The primary outcome measured was overall survival. RESULTS: A total of 7794 patients were included. After adjusting for clinical, tumor, and treatment characteristics, our model determined a critical threshold of chemotherapy initiation at 44 days from surgery, after which there was an increase in the overall mortality. At a median follow-up of 61 months, the risk of mortality was increased in those who received adjuvant chemotherapy after 44 days from surgery (adjusted HR, 1.14; 95% CI, 1.05–1.24; p = 0.002), but not in those who received chemotherapy before 44 days from surgery (p = 0.11). Each additional week of delay was associated with a 7% decrease in survival (HR, 1.07; 95% CI, 1.04–1.10; p < 0.001). LIMITATIONS: This study was limited by selection bias and the inability to compare specific chemotherapy regimens. CONCLUSIONS: This study objectively determines the optimal timing of adjuvant chemotherapy for patients with resected colon cancer. Delay beyond 6 weeks is associated with compromised survival. These findings emphasize the importance of the timely initiation of therapy, and suggest that efforts to enhance recovery following surgery have the potential to improve survival by decreasing delay to adjuvant chemotherapy.

The utility of the aortic dissection team: outcomes and insights after a decade of experience.

BACKGROUND Mortality rates following acute type A aortic dissection (ATAAD) repair are reduced when operations are performed by a high-volume acute aortic dissection (AAD) team, leading to efforts to centralize ATAAD care. Here, we describe our experience with ATAAD repair by our AAD team over the last 10 years, with a focus on patient selection, transfer protocols, operative approach, and volume trends over time. METHODS An AAD team was implemented at our institution in 2005, with dedicated high-volume AAD surgeons, a multidisciplinary approach to thoracic aortic disease management, and a standardized protocol for ATAAD repair. Further process improvements were made in 2013 to facilitate the rapid transfer of ATAAD patients to our institution using stream-lined triage, diagnostic, and transfer protocols for patients with suspected ATAAD (RACE-AD protocol). Volume trends and outcomes were assessed longitudinally over this period. RESULTS Institutional ATAAD repair volume remained constant at 12±2 cases per year from 2005-2013, but increased nearly two-fold to 22±6 cases per year (P=0.004) from 2013-2015 following implementation of the RACE-AD protocol. To accommodate this increased volume, two additional surgeons were added to the AAD team. Surgeon ATAAD repair volume was unchanged over the 10-year interval (7.9±3.9 cases per year from 2005-2013 versus 5.5±1.5 cases per year from 2013-2015; P=0.36), and all AAD team surgeons consistently met or exceeded the high-volume surgeon threshold of 5 ATAAD repairs per year. Thirty-day/in-hospital mortality rates of less than 10% were maintained over the study period. CONCLUSIONS Centralization of ATAAD care has begun to occur at our center, with maintenance of low mortality rates for ATAAD repair. These data confirm a net positive impact on regional ATAAD outcomes through transfer of patients to a high-volume center with dedicated AAD surgeons.

Operative and perioperative management of infected arteriovenous grafts.

Vascular graft infections are a particularly troublesome complication for dialysis patients, many of whom are in an already immunocompromised state. The objective of this review is to detail the risk factors, etiology, diagnosis, perioperative and operative management of vascular graft infections.

Neurophysiological Intraoperative Monitoring During Aortic Arch Surgery

Circulatory management during replacement of the aortic arch is complex and involves a period of circulatory arrest to provide a bloodless field during arch vessel anastomosis. To guard against ischemic brain injury, tissue metabolic demand is reduced by systemically cooling the patient prior to circulatory arrest. Neurophysiological intraoperative monitoring (NIOM) is often used during the course of these procedures to provide contemporaneous assessment of brain status to help direct circulatory management decisions and detect brain ischemia. In this review, we discuss the characteristics of electrocerebral activity through the process of cooling, circulatory arrest, and rewarming as depicted through commonly used NIOM modalities, including electroencephalography and peripheral nerve somatosensory-evoked potentials. Attention is directed toward the role NIOM has traditionally played during deep hypothermic circulatory arrest, where it is used to define the point of electrocerebral inactivity or maximal cerebral metabolic suppression prior to initiating circulatory arrest while also discussing the evolving utility of NIOM when systemic circulatory arrest is initiated at more moderate degrees of hypothermia in conjunction with regional brain perfusion. The use of cerebral tissue oximetry by near-infrared spectroscopy as an alternative NIOM modality during surgery of the aortic arch is addressed as well. Finally, special considerations for NIOM and the detection of spinal cord ischemia during hybrid aortic arch repair and emerging operative techniques are also discussed.

Mycotic Saccular Abdominal Aortic Aneurysm in an Infant after Cardiac Catheterization: A Case Report

Abdominal aortic aneurysms (AAAs) are a rare entity in the pediatric population. Children with mycotic (infectious) AAA in particular are at risk of life-threatening rupture due to their rapid expansion coupled with aortic wall thinning and deterioration. Here, we present the case of a 10-month-old infant with prior 2-staged repair for hypoplastic left heart syndrome that was incidentally discovered to have a mycotic AAA on abdominal ultrasound (US) for evaluation of renovascular hypertension. Before the time of evaluation with US, the infant had developed methicillin-resistant Staphylococcus aureus bacteremia 3 days after cardiac catheterization with percutaneous thoracic aortic balloon angioplasty. She had normal aortic contours on contrasted computed tomography scan of the abdomen approximately 2 weeks before the aforementioned US evaluation. This infant subsequently underwent open aneurysmorrhaphy with cryopreserved vein patch angioplasty with resolution of her aneurysmal segment.