Andrew Kastenmeier

Polymeric gene delivery of ischemia-inducible VEGF significantly attenuates infarct size and apoptosis following myocardial infarct

The development of clinically beneficial myocardial gene therapy has been slowed by reliance on the use of viral carriers and non-physiologic, constitutive gene expression. To specifically address these issues, we have developed a non-viral gene carrier, water-soluble lipopolymer (WSLP), and an ischemia-inducible plasmid construct expressing vascular endothelial growth factor (VEGF), pRTP801-VEGF, to treat myocardial ischemia and infarction. Rabbits underwent ligation of the circumflex artery followed by injection of (a) an ischemia-inducible VEGF gene construct in a WSLP carrier; (b) a constitutively expressed, or unregulated, SV-VEGF gene construct in a WSLP carrier; (c) WSLP carrier alone; or (d) no injection therapy. Following 4 weeks treatment, ligation alone resulted in infarction of 48±7% of the left ventricle. With injection of WSLP carrier alone, 49±6% of the left ventricle was infarcted (P=NS). The constitutively expressed gene construct, SV-VEGF, reduced the infarct size to 32±7% of the left ventricle (P=0.007). The ischemia-inducible gene construct, RTP801-VEGF, further reduced the infarct size to 13±4% of the left ventricle (P<0.001). The use of a non-viral carrier to deliver an ischemia-inducible VEGF construct is effective in the treatment of acutely ischemic myocardium.

Novel polymer carriers and gene constructs for treatment of myocardial ischemia and infarction

The number one cause of mortality in the US is cardiovascular related disease. Future predictions do not see a reduction in this rate especially with the continued rise in obesity [P. Poirier, et al., Obesity and cardiovascular disease: pathophysiology, evaluation, and effect of weight loss, Arterioscler Thromb Vasc Biol. 26(5), (2006) 968-976.; K. Obunai, S. Jani, G.D. Dangas, Cardiovascular morbidity and mortality of the metabolic syndrome, Med.Clin. North Am., 91(6), (2007) 1169-1184]. Even so, potential molecular therapeutic targets for cardiac gene delivery are in no short supply thanks to continuing advances in molecular cardiology. However, efficient and safe delivery remains a bottleneck in clinical gene therapy [O.J. Muller, H.A. Katus, R. Bekeredjian, Targeting the heart with gene therapy-optimized gene delivery methods, Cardiovasc Res, 73(3), (2007) 453-462]. Viral vectors are looked upon favorably for their high transduction efficiency, although their ability to elicit toxic immune responses remains [C.F. McTiernan, et al., Myocarditis following adeno-associated viral gene expression of human soluble TNF receptor (TNFRII-Fc) in baboon hearts, Gene Ther, 14(23), (2007) 1613-1622]. However, this high transduction does not necessarily translate into improved efficacy [X. Hao, et al., Myocardial angiogenesis after plasmid or adenoviral VEGF-A(165) gene transfer in rat myocardial infarction model, Cardiovasc Res., 73(3), (2007) 481-487]. Naked DNA remains the preferred method of DNA delivery to cardiac myocardium and has been explored extensively in clinical trials. The results from these trials have demonstrated efficacy in regard to secondary end-points of reduced symptomatology and perfusion, but have failed to establish significant angiogenesis or an increase in myocardial function [P.B. Shah, D.W. Losordo, Non-viral vectors for gene therapy: clinical trials in cardiovascular disease, Adv Genet, 54, (2005) 339-361]. This may be due in part to reduced transfection efficiency but can also be attributed to use of suboptimal candidate genes. Currently, polymeric non-viral gene delivery to cardiac myocardium remains underrepresented. In the past decade several advances in non-viral vector development has demonstrated increased transfection efficiency [O.J. Muller, H.A. Katus, R. Bekeredjian, Targeting the heart with gene therapy-optimized gene delivery methods, Cardiovasc Res, 73(3), (2007) 453-462]. Of these polymers, those that employ lipid modifications to improve transfection or target cardiovascular tissues have proven themselves to be extremely beneficial. Water-soluble lipopolymer (WSLP) consists of a low molecular weight branched PEI (1800) and cholesterol. The cholesterol moiety adds extra condensation by forming stable micellular complexes and was later employed for myocardial gene therapy to exploit the high expression of lipoprotein lipase found within cardiac tissue. Use of WSLP to deliver hypoxia-responsive driven expression of hVEGF to ischemic rabbit myocardium has proven to provide for even better expression in cardiovascular cells than Terplex and has demonstrated a significant reduction in infarct size (13+/-4%, p<0.001) over constitutive VEGF expression (32+/-7%, p=0.007) and sham-injected controls (48+/-7%). A significant reduction in apoptotic values and an increase in capillary growth were also seen in surrounding tissue. Recently, investigations have begun using bioreducible polymers made of poly(amido polyethylenimines) (SS-PAEI). SS-PAEIs breakdown within the cytoplasm through inherent redox mechanisms and provide for high transfection efficiencies (upwards to 60% in cardiovascular cell types) with little to no demonstrable toxicity. In vivo transfections in normoxic and hypoxic rabbit myocardium have proven to exceed those results of WSLP transfections by 2-5 fold [L.V. Christensen, et al., Reducible poly(amido ethylenediamine) for hypoxia-inducible VEGF delivery, J Control Release, 118(2), (2007) 254-261]. This new breed of polymer(s) may allow for decreased doses and use of new molecular mechanisms not previously available due to low transfection efficiencies. Little development has been seen in the use of new gene agents for treatment of myocardial ischemia and infarction. Current treatment consists of using mitogenic factors, described decades earlier, alone or in combination to spur angiogenesis or modulating intracellular Ca2+ homeostasis through SERCA2a but to date, failed to demonstrate clinical efficacy. Recent data suggests that axonal guidance cues also act on vasculature neo-genesis and provide a new means of investigation for treatment.

Validation of a virtual reality-based robotic surgical skills curriculum

BackgroundThe clinical application of robotic-assisted surgery (RAS) is rapidly increasing. The da Vinci Surgical System™ is currently the only commercially available RAS system. The skills necessary to perform robotic surgery are unique from those required for open and laparoscopic surgery. A validated laparoscopic surgical skills curriculum (fundamentals of laparoscopic surgery or FLS™) has transformed the way surgeons acquire laparoscopic skills. There is a need for a similar skills training and assessment tool specific for robotic surgery. Based on previously published data and expert opinion, we developed a robotic skills curriculum. We sought to evaluate this curriculum for evidence of construct validity (ability to discriminate between users of different skill levels).MethodsFour experienced surgeons (>20 RAS) and 20 novice surgeons (first-year medical students with no surgical or RAS experience) were evaluated. The curriculum comprised five tasks utilizing the da Vinci™ Skills Simulator (Pick and Place, Camera Targeting 2, Peg Board 2, Matchboard 2, and Suture Sponge 3). After an orientation to the robot and a period of acclimation in the simulator, all subjects completed three consecutive repetitions of each task. Computer-derived performance metrics included time, economy of motion, master work space, instrument collisions, excessive force, distance of instruments out of view, drops, missed targets, and overall scores (a composite of all metrics).ResultsExperienced surgeons significantly outperformed novice surgeons in most metrics. Statistically significant differences were detected for each task in regards to mean overall scores and mean time (seconds) to completion.ConclusionsThe curriculum we propose is a valid method of assessing and distinguishing robotic surgical skill levels on the da Vinci Si™ Surgical System. Further study is needed to establish proficiency levels and to demonstrate that training on the simulator with the proposed curriculum leads to improved robotic surgical performance in the operating room.

Proficiency training on a virtual reality robotic surgical skills curriculum

AbstractIntroduction The clinical application of robotic surgery is increasing. The skills necessary to perform robotic surgery are unique from those required in open and laparoscopic surgery. A validated laparoscopic surgical skills curriculum (Fundamentals of Laparoscopic Surgery or FLS™) has transformed the way surgeons acquire laparoscopic skills. There is a need for a similar skills training and assessment tool for robotic surgery. Our research group previously developed and validated a robotic training curriculum in a virtual reality (VR) simulator. We hypothesized that novice robotic surgeons could achieve proficiency levels defined by more experienced robotic surgeons on the VR robotic curriculum, and that this would result in improved performance on the actual daVinci Surgical System™.Methods25 medical students with no prior robotic surgery experience were recruited. Prior to VR training, subjects performed 2 FLS tasks 3 times each (Peg Transfer, Intracorporeal Knot Tying) using the daVinci Surgical System™ docked to a video trainer box. Task performance for the FLS tasks was scored objectively. Subjects then practiced on the VR simulator (daVinci Skills Simulator) until proficiency levels on all 5 tasks were achieved before completing a post-training assessment of the 2 FLS tasks on the daVinci Surgical System™ in the video trainer box.ResultsAll subjects to complete the study (1 dropped out) reached proficiency levels on all VR tasks in an average of 71 (± 21.7) attempts, accumulating 164.3 (± 55.7) minutes of console training time. There was a significant improvement in performance on the robotic FLS tasks following completion of the VR training curriculum.ConclusionsNovice robotic surgeons are able to attain proficiency levels on a VR simulator. This leads to improved performance in the daVinci surgical platform on simulated tasks. Training to proficiency on a VR robotic surgery simulator is an efficient and viable method for acquiring robotic surgical skills.

Consequences of Gastrointestinal Surgery on Drug Absorption

Gastrointestinal (GI) surgery associated with resection or bypass can affect the absorption and kinetics of certain drugs. The goal of this article is 3-fold: (1) highlight the physiologic changes associated with selected GI surgeries (specifically gastric, small intestine, and colon), (2) review the implications for drug and nutrient absorption, and (3) suggest modifications of the pharmacologic agents, dosing regimens, and routes of delivery. Few large trials are available to use as references, but there is a wealth of individual reports and small series. Understanding the predictable challenges of drug administration in these patients will improve care.

The evolution of resource utilization in regional burn centers.

Regional burn centers provide unique multidisciplinary care that has been associated with dramatically improved outcomes for burn victims. Patients with complex skin and soft tissue injuries are increasingly admitted to these centers for definitive care. This study was designed to assess current trends in burn center resource utilization. Members of the Multicenter Trials Group of American Burn Association were invited to participate in this retrospective review of all patients admitted to their respective regional burn centers during a 10-year period. Collected data included admission diagnosis, demographics, length of stay (LOS), hospital charges, and mortality. Five regional academic burn centers participated. They collectively admitted 18,246 patients during the study period, of whom 15,219 (83.4%) had a primary burn diagnosis and 3027 (16.6%) were patients with nonburn diagnoses. During this period, annual admissions for the five centers increased by 34.7%, ranging from 19 to 83% for individual centers. Simultaneously, mean burn size decreased from 12.3 to 8.8% TBSA. From 1998 to 2006, admissions for nonburn diagnoses increased by 244.9%, whereas burn admissions increased by 31.1%. Although mean LOS was reduced by >25%, total charges for all patients increased by 37.7% after adjustment for inflation. Nonburn patients had significantly higher mean age, longer LOS, greater mortality, and higher daily charges. This review of admissions to five academic burn centers reveals that these centers are treating more patients with smaller burns and an increasing number of complex nonburn conditions. Nonburn patients represent an older and more debilitated population that consumes disproportionately more resources than burn patients. These data show a dramatic shift in burn center resource utilization and the concurrent evolution of regional burn centers into centers for the care of complex wounds.

Robotic applications in the treatment of diseases of the esophagus.

Minimally invasive treatment of esophageal diseases such as gastroesophageal reflux disease, achalasia, and esophageal cancer is associated with many of the benefits observed after the minimally invasive surgery for other diseases (such as symptomatic cholelithiasis) when compared with the open approach. Laparoscopic treatment of these esophageal conditions is technically complex and subject to several inherent limitations. Robotic surgical systems may allow surgeons to overcome many of these obstacles, enabling more widespread adaptation of these techniques.

Development and technique of per oral endoscopic myotomy (POEM) for achalasia

SummaryBACKGROUND: Achalasia is a primary esophageal motor disorder involving the absence of esophageal body peristalsis and defective relaxation of the lower esophageal sphincter. The optimal treatment is still controversial. Per oral endoscopic myotomy (POEM) has recently evolved from developments in Natural Orifice Translumenal Endoscopic Surgery (NOTES). METHODS: Substantial experimental work in animals and cadavers was performed to establish the technical approach for POEM before clinical implementation. This flexible endoscopic procedure involved incising the mid-esophageal mucosa followed by access into the submucosal space. A tunnel onto the gastric cardia was dissected and selective division of the circular/sling-fibers of the lower esophageal sphincter (LES) was performed by needle knife cautery. The mucosotomy was closed by conventional endoscopic hemoclips. Subsequently, a 61-year-old male patient with achalasia was enrolled in an ongoing study. RESULTS: Based on preclinical work, the steps of endoscopic submucosal myotomy were defined. In the patient described, mucosal balloon-dilatation facilitated access into the submucosal space. Dissection was performed until 3 cm below the gastroesophageal junction and the partial myotomy was 7 cm. The mucosal entry was easily closed. Postoperative esophagogram did not detect esophageal leakage and the patient was discharged on the next morning. He reported immediate symptom relief on the 2-week clinical follow-up without the need of pain medication. CONCLUSIONS: POEM for achalasia is a perfect example of the true surgical revolution resulting from NOTES research. Although the long-term outcome of POEM has still to be evaluated, the promise of this novel procedure seems more than obvious.

Wisconsin's Enterra Therapy Experience: A multi-institutional review of gastric electrical stimulation for medically refractory gastroparesis

Background: Gastric electrical stimulation is a treatment for symptoms of diabetic or idiopathic gastroparesis refractory to medical management. We sought to evaluate the outcomes of gastric electrical stimulation in the state of Wisconsin during a more than 10‐year period. Methods: Data were collected prospectively from patients undergoing implantation of the gastric electrical stimulation to initiate gastric electrical stimulation therapy at two Wisconsin institutions from 2005–2017. The Gastroparesis Cardinal Symptom Index was administered during clinical encounters and over the phone preoperatively and postoperatively. Results: A total of 119 patients received gastric electrical stimulation therapy (64 diabetic and 55 idiopathic). All devices were placed laparoscopically. Mean follow‐up was 34.1 ± 27.2 months in diabetic and 44.7 ± 26.2 months in idiopathic patients. A total of 18 patients died during the study interval (15.1%). No mortalities were device‐related. Diabetics had the greatest rate of mortality (25%; mean interval of 17 ± 3 months post implantation). GCSI scores improved, and prokinetic and narcotic medication use decreased significantly at ≥1 year. Satisfaction scores were high. Conclusion: Gastric electrical stimulation therapy led to the improvement of symptoms of gastroparesis and a better quality of life. Patients were able to decrease the use of prokinetic and narcotic medications and achieve long‐term satisfaction. Diabetic patients who develop symptomatic gastroparesis have a high mortality rate over time.

Individual learning plans foster self-directed learning skills and contribute to improved educational outcomes in the surgery clerkship

BACKGROUND The Individual Learning Plan (ILP) is a newly implemented curricular element designed to foster self-directed learning (SDL) skills among medical students during our surgery clerkship. Our aim was to determine the impact of ILPs on educational outcomes and acquisition of SDL skills. METHODS Students were surveyed regarding the educational value of ILPs, their acquisition of SDL skills, and the impact of the surgery clerkship on fostering these skills. Mean scores for the NBME surgery subject exam (SSE) were compared before and after implementation of the ILP requirement. RESULTS Students perceived the ILP requirement as having strong educational value. Mean scores for the SSE increased significantly in the year following ILP implementation (74.9 vs 76.6; p = .042; d = 0.21). Students reported successful acquisition and frequent utilization of SDL skills. CONCLUSIONS SDL exercises, such as the ILP requirement, lead to improved education outcomes while fostering the acquisition of SDL skills.