Translation to Practice: Accelerating the Cycle of Innovation to Impact.

The Office of Translation to Practice (OTP) is housed in the Center for Clinical and Translational Sciences at Mayo Clinic. Established in 2015, the office was tasked with developing and managing novel tools, mechanisms, and processes to facilitate and accelerate the translation of products, such as drugs, biological agents, and medical devices, into practice. Since its inception, the OTP is credited with creating valuable services through several strategic alliances and active scientific and project management involvement. The OTP continues to move forward to assist Mayo Clinic physicians and scientists to interact effectively with internal and external collaborators to advance translational projects that will benefit patients. Best practices, innovations, and nascent successes of the OTP are presented and discussed herein.

Novel Techniques in Epilepsy Management: Venous Pacing and Capture of Electrical Activity in the Primate Cortex.

OBJECTIVE: Pharmacotherapy for epilepsy is limited with 30% of patients refractory to this approach of suppressing seizures. Current surgical options are invasive and carry significant morbidities including infection, bleeding, and the potential for deleterious neurocognitive effects. As a result, there is a burgeoning need for innovation to develop safer and efficacious interventions. METHODS: Four distinct catheters (2 existing: Cardima catheter, Standard EPT Blazer catheter; 2 new prototypes: balloon catheter, basket catheters) were tested in 12 baboons (21-30 kg, 100% male). For each, we assessed whether or not the catheter was able to be maneuvered safely in various locations of the cerebral venous system, provide adequate cortical tissue contact to record signals, detect these signals as normal or abnormal, successfully stimulate the cortex, and capture the cortical tissue. Locations trialed included the petrosal sinus, straight sinus, vein of Galen, and occipital vein. Pacing cycle length and pacing thresholds varied among experiments. RESULTS: Successful mapping was conducted in all 12 baboons. The pacing cycle length varied from 75 ms to 650 ms depending on location of the cortex. Pacing threshold was recorded in 4/12 (33%) of the experiments; data is not available for the remaining 8/12 experiments. The threshold values ranged from 0.3 - 20 mAmps. Capture of cortical electrical activity was observed in 11/12 (91.7 %) experiments though the number of successful capture and stimulation attempts varied among experiments. The most reliable and consistent capture occurred with the use of our novel prototyped over-the-wire balloon catheter (9/12; 75%) and basket catheter (3/3; 100%). Necropsy and histology were performed post-experimentation, and only minimal complications were noted (Table 1). CONCLUSION: New electrode design can be maneuvered safely in the venous system, provide adequate cortical tissue contact to record signals, detect these signals as normal or abnormal, successfully stimulate the cortex, and capture cortical tissue. These novel devices merit further study in chronic baboons to establish long-term efficacy of continuous seizure recording.

Novel Percutaneous Epicardial Autonomic Modulation in the Canine for Atrial Fibrillation: Results of an Efficacy and Safety Study.

BACKGROUND: Endocardial ablation of atrial ganglionated plexi (GP) has been described for treatment of atrial fibrillation (AF). Our objective in this study was to develop percutaneous epicardial GP ablation in a canine model using novel energy sources and catheters. METHODS: Phase 1: The efficacy of several modalities to ablate the GP was tested in an open chest canine model (n = 10). Phase 2: Percutaneous epicardial ablation of GP was done in six dogs using the most efficacious modality identified in phase 1 using two novel catheters. RESULTS: Phase 1: Direct current (DC) in varying doses (blocking [7-12 µA], electroporation [300-500 µA], ablation [3,000-7,500 µA]), radiofrequency ablation (25-50 W), ultrasound (1.5 MHz), and alcohol (2-5 mL) injection were successful at 0/8, 4/12, 5/7, 3/8, 1/5, and 5/7 GP sites. DC (500-5,000 µA) along with alcohol irrigation was tested in phase 2. Phase 2: Percutaneous epicardial ablation of the right atrium, oblique sinus, vein of Marshall, and transverse sinus GP was successful in 5/6 dogs. One dog died of ventricular fibrillation during DC ablation at 5,000 µA. Programmed stimulation induced AF in six dogs, preablation and no atrial arrhythmia in three, flutter in one, and AF in one postablation. Heart rate, blood pressure, effective atrial refractory period, and local atrial electrogram amplitude did not change significantly postablation. Microscopic examination showed elimination of GP, and minimal injury to atrial myocardium. CONCLUSION: Percutaneous epicardial ablation of GP using DC and novel catheters is safe and feasible and may be used as an adjunct to pulmonary vein isolation in the treatment of AF in order to minimize additional atrial myocardial ablation.

Direct Pulmonary Vein Ablation With Stenosis Prevention Therapy.

INTRODUCTION: The dominant location of electrical triggers for initiating atrial fibrillation (AF) originates from the muscle sleeves inside pulmonary veins (PVs). Currently, radiofrequency ablation (RFA) is performed outside of the PVs to isolate, rather than directly ablate these tissues, due to the risk of intraluminal PV stenosis. METHODS: In 4 chronic canine experiments, we performed direct PV muscle sleeve RFA ± postablation drug-coated balloon (DCB) treatment with paclitaxel/everolimus. Of the 4 PVs, 2 PVs were ablated and treated with DCB, 1 PV was ablated without DCB treatment (positive control), and 1 PV was left as a negative control. Local electrograms were assessed in PVs for near-field signals and were targeted for ablation. After 12-14 weeks survival, PVs were interrogated for absence of near-field PV potentials, and each PV was assessed for stenosis. RESULTS: All canines survived the study period without cardiorespiratory complications, and remained ambulatory. In all canines, PVs that were ablated and treated with DCB remained without any significant intraluminal stenosis. In contrast, PVs that were ablated and not treated with DCB showed near or complete intraluminal stenosis. At terminal study, PV potentials remained undetectable. A blinded, histologic analysis demonstrated that ablated PVs without DCB treatment had extensive thrombus, fibrin, mineralization, and elastin disruption. CONCLUSION: Our chronic canine data suggest that direct PV tissue ablation without subsequent stenosis is feasible with the use of postablation DCBs.

Percutaneous Epicardial Pacing using a Novel Insulated Multi-electrode Lead.

INTRODUCTION: Epicardial cardiac resynchronization therapy (CRT) permits unrestricted electrode positioning. However, this requires surgical placement of device leads and the risk of unwanted phrenic nerve stimulation. We hypothesized that shielded electrodes can capture myocardium without extracardiac stimulation. METHODS: In 6 dog and 5 swine experiments, we used a percutaneous approach to access the epicardial surface of the heart, and deploy novel leads housing multiple electrodes with selective insulation. Bipolar pacing thresholds at prespecified sites were tested compare electrode threshold data both facing towards and away from the epicardial surface. RESULTS: In 151 paired electrode recordings (70 in 6 dogs; 81 in 5 swine), thresholds facing myocardium were lower than facing away (median [IQR] mA: dogs 0.9 [0.4-1.6] vs 4.6 [2.1 to >10], p<0.0001; swine 0.5 [0.2-1] vs 2.5 [0.5-6.8], p<0.0001). Myocardial capture was feasible without extracardiac stimulation at all tested sites, with mean ± SE threshold margin 3.6±0.7 mA at sites of high output extracardiac stimulation (p=0.004). CONCLUSION: Selective electrode insulation confers directional pacing to a multielectrode epicardial pacing lead. This device has the potential for a novel percutaneous epicardial resynchronization therapy that permits placement at an optimal pacing site, irrespective of the anatomy of the coronary veins or phrenic nerves.

Novel balloon catheter device with pacing, ablating, electroporation, and drug-eluting capabilities for atrial fibrillation treatment--preliminary efficacy and safety studies in a canine model.

Pulmonary vein isolation is an established therapeutic procedure for symptomatic atrial fibrillation (AF). This approach involves ablation of atrial tissue just outside the pulmonary veins. However, patient outcomes are limited because of a high rate of arrhythmia recurrence. Ablation of electrically active tissue inside the pulmonary vein may improve procedural success, but is currently avoided because of the complication of postablation stenosis. An innovative device that can ablate inside pulmonary veins and prevent stenosis is a viable strategy to increase long-term efficacy. We have developed a prototypical balloon catheter device capable of nonthermal pulmonary vein ablation along with elution of an antifibrotic agent intended to eliminate arrhythmogenic substrate without the risk of stenosis and have demonstrated its functionality in 4 acute canine experiments. Further optimization of this device may provide an innovative means to simultaneously ablate and prevent pulmonary vein stenosis for improved AF treatment in humans.

Transvenous stimulation of the renal sympathetic nerves increases systemic blood pressure: a potential new treatment option for neurocardiogenic syncope.

BACKGROUND: Neurocardiogenic syncope (NCS) is a common and sometimes debilitating disorder, with no consistently effective treatment. NCS is due to a combination of bradycardia and vasodilation leading to syncope. Although pacemaker devices have been tried in treating the bradycardic aspect of NCS, no device-based therapy exists to treat the coexistent vasodilation that occurs. The renal sympathetic innervation has been the target of denervation to treat hypertension. We hypothesized that stimulation of the renal sympathetic nerves can increase blood pressure and counteract vasodilation in NCS. METHODS AND RESULTS: High-frequency stimulation (800-900 pps, 10 V, 30-200 seconds) was performed using a quadripolar catheter in the renal vein of 7 dogs and 1 baboon. A significant increase in blood pressure (BP; mean [SD] systolic BP 117 [±28] vs. 128 [±33], diastolic BP 75 [±19] vs. 87 [±29] mmHg) was noted during the stimulation, which returned to baseline after cessation of stimulation. The mean increase in systolic and diastolic BP was 13.0 (±3.3) (P = 0.006) and 10.2 (±4.6) (P = 0.08), respectively. CONCLUSION: We report the first ever study of feasibility and safety of high-frequency electrical stimulation of the renal sympathetic innervation to increase BP in animal models. This has potential applications in the treatment of hypotensive states such as NCS.

Advances in radiofrequency ablation of the cerebral cortex in primates using the venous system: Improvements for treating epilepsy with catheter ablation technology.

BACKGROUND: Pharmacology frequently fails for the treatment of epilepsy. Although surgical techniques are effective, these procedures are highly invasive. We describe feasibility and efficacy of minimally invasive mapping and ablation for the treatment of epilepsy. METHODS: Mapping and radiofrequency ablations were performed via the venous system in eleven baboons and three dogs. RESULTS: Mapping in deep cerebral areas was obtained in all animals. High-frequency pacing was able to induce seizure activity of local cerebral tissue in 72% of our attempts. Cerebral activity could be seen during mapping. Ablative lesions were deployed at deep brain sites without steam pops or sudden impedance rise. Histologic analysis showed necrosis at the sites of ablation in all primates. CONCLUSION: Navigation through the cerebral venous system to map seizure activity is feasible. Radiofrequency energy can be delivered transvenously or transcortically to successfully ablate cortical tissue in this animal model using this innovative approach.

Use of the aortoatrial continuity as means of providing left ventricular assist support without entering the ventricle: a feasibility study.

BACKGROUND: Left ventricular assist devices (LVADs) are increasingly used to treat patients with refractory heart failure. Current-generation LVADs have major limitations, including the need for open chest surgery, limiting their widespread use. We hypothesized that the aortoatrial continuity could be used as a unique anatomic vantage point for entirely percutaneous LVAD placement. METHODS AND RESULTS: Forty human autopsied hearts were examined to ascertain the presence and define the dimensions of the continuity between the posterior aortic wall and the left atrium. In all cases, a "septum" between the aorta and left atrium was identified. In 3 animal experiments, a custom mechanical shunt was deployed in the wall between the left atrium and noncoronary cusp. With continuous intracardiac ultrasound imaging, and at necropsy, there was no evidence of device dislodgement, pericardial effusion, or aortic or coronary artery trauma noted. CONCLUSIONS: It is feasible to use the wall between the aorta and left atrium as an access route for a potentially entirely percutaneous LVAD. Such a system obviates the need for accessing the left ventricle, minimizing complications. In the future, such devices may allow widespread treatment of heart failure, malignant cardiac arrhythmia, and severe aortic and mitral valvular disease.

Percutaneous epicardial left atrial appendage closure: intermediate-term results.

UNLABELLED: Chronic Percutaneous Epicardial Appendage Closure. OBJECTIVES: To assess the chronic safety and feasibility of percutaneous epicardial closure of the left atrial appendage (LAA) guided by electrical navigation. BACKGROUND: Atrial fibrillation (AF) is associated with stroke, and LAA occlusion may be a useful nonpharmacologic strategy for stroke prevention in AF. METHODS: Percutaneous epicardial access was obtained in 6 dogs under general anesthesia. The ligation system included a grabber that captures the LAA guided by local electrograms (EGMs) and a looped hollow suture preloaded with a central wire enabling control and visualization. After a satisfactory position is confirmed the loop is tightened remotely, and the suture cut. Transesophageal echocardiography (TEE) assessed LAA dimensions and flow. LAA EGMs were recorded pre- and postclosure, and neurohormonal markers measured. Pathologic examination was performed. RESULTS: LAA ligation was successful in all dogs. LAA flow was immediately abolished in 5 of 6 dogs. Disappearance of local LAA EGMs following ligation was observed in all animals. Follow-up TEE at mean 54 days (range 23-75 days) documented residual flow in only the first 2 dogs. Prior to necropsy the LAA was examined at thoracotomy in 3 animals. Following a minor design change, complete closure and fibrosis with a remnant atretic LAA was noted in all animals. No damage to adjacent structures was noted. Neurohormonal markers were unchanged. CONCLUSION: Percutaneous epicardial LAA ligation guided by electrical navigation is feasible with promising intermediate-term results in the canine model. The technique may be useful as an alternative to existing methods of LAA obliteration in humans.

Percutaneous epicardial left atrial appendage closure: preliminary results of an electrogram guided approach.

BACKGROUND: Pharmacologic therapies to prevent stroke in atrial fibrillation (AF) have numerous limitations, prompting the development of device-based therapies. We investigated whether an electrogram-based approach using a novel hollow suture can safely capture and ligate the left atrial appendage (LAA). METHODS AND RESULTS: A novel system for closure of the LAA within the confines of the closed pericardium with a single sheath puncture was tested in 4 dogs. The tool used to grasp the appendage was fitted with electrodes and utilized electrical navigation to identify and confirm LAA capture. A hollow suture preloaded with a mechanical support wire to permit its manipulation and fluoroscopic visualization was advanced over the grasper, and the wire removed after the suture was positioned. The LAA was successfully closed in all dogs. In 2 dogs, after closure, a thoracotomy was performed and the LAA amputated without bleeding, confirming closure integrity. Necropsy confirmed closure in all animals. CONCLUSIONS: Using electrical navigation, percutaneous epicardial LAA ligation with a remotely tightened suture was performed successfully within the confines of the intact pericardial space. This technique may allow decreasing the risk of stroke in AF patients without the need for thoracotomy or an endocardially placed prosthetic device.

Membrane localization of v-ErbB is required but not sufficient for ligand-independent transformation.

The v-ErbB retroviral oncogene is a transduced, mutated copy of the avian EGF receptor gene, and its expression is sufficient to induce tumor formation in vivo. The structural alterations that release the oncogenic potential of the v-ErbB oncogene are similar to EGFR gene mutations described in human tumors. Thus, the study of v-ErbB tumor biology offers a useful model through which we can gain insight into the mechanism of EGFR-induced malignancies. Despite years of study, however, questions remain regarding the domains of v-ErbB required for oncogenicity. We sought to clarify the role of the transmembrane domain of v-ErbB during transformation using S3-v-ErbB, an acutely transforming retroviral oncogene isolated from avian sarcomas. Infection of primary fibroblasts with a retroviral vector containing S3-v-ErbB results in the formation of a transformation-associated phosphoprotein signaling complex, soft agar colony formation, and the rapid induction of highly vascularized sarcomas in vivo. To address contribution of the transmembrane domain of S3-v-ErbB during these processes, we constructed a mutant version of this oncogene with a precise deletion in this domain. Specifically, the S3-v-ErbB-TM- mutant was created through an in-frame deletion of the entire transmembrane domain. Primary fibroblasts expressing this S3-v-ErbB-TM- mutant fail to form a characteristic transformation-associated phosphoprotein complex and do not grow in an anchorage-independent manner. In addition, day-old chicks injected with a helper-independent retrovirus expressing the S3-v-ErbB-TM- mutant exhibit only limited tumor formation in vivo. These results demonstrate that the transmembrane domain and, consequently membrane localization, are essential for S3-v-ErbB-mediated transformation.

Grb2 regulation of the actin-based cytoskeleton is required for ligand-independent EGF receptor-mediated oncogenesis.

Mutations within members of the EGF/ErbB receptor family frequently release the oncogenic potential of these receptors, resulting in the activation of downstream signaling events independent of ligand regulatory constraints. We previously have demonstrated that the signal transduction events originating from S3-v-ErbB, a ligand-independent, oncogenic EGF receptor mutant, are qualitatively distinct from the ligand-dependent mitogenic signaling pathways associated with the wild-type EGF receptor. Specifically, expression of S3-v-ErbB in primary fibroblasts results in anchorage-independent growth, increased invasive potential, and the formation of a transformation-specific phosphoprotein signaling complex, all in a Ras-independent manner. Here we demonstrate the transformation-specific interaction between two components of this complex: the adaptor protein Grb2 and the cytoskeletal regulatory protein caldesmon. This interaction is mediated via both the amino-terminal SH3 and central SH2 domains of Grb2, and the amino-terminal (myosin-binding) domain of caldesmon. Expression of a dominant-negative Grb2 deletion mutant, which lacks the carboxy-terminal SH3 domain, in fibroblasts expressing S3-v-ErbB results in a reduction in phosphoprotein complex formation, the loss of anchorage-independent growth, and a reduction in invasive potential. Together, these results demonstrate a Ras-independent role for Grb2 in modulating cytoskeletal function during ligand-independent EGF receptor-mediated transformation, and provide further support for the hypothesis that ligand-independent oncogenic signaling is qualitatively distinct from ligand-dependent mitogenic signaling by the EGF receptor.

The EGF/ErbB receptor family and apoptosis.

The ErbB receptor family can activate a multitude of cell signaling pathways that involve many aspects of cellular function. The four members of the ErbB receptor family interact with diverse ligands and substrates, as well as with each other through cell surface heterodimerization. The sum of these diverse interactions is a signaling network that is complex but also finely regulated. Among the cellular functions influenced by ErbB signaling is cell survival. ErbB receptor signaling has been demonstrated to interact with all of the major mechanisms of cell death signaling in a manner that promotes cell survival. Survival factors such as Ras, PI3-K, Akt, and Bcl-x/-2 all have been shown to be activated by ErbB signaling (Fig. 5). ErbB abrogation of apoptotic signals has been shown to play an important role during embryonic tissue development, in normal adult tissue maintenance (e.g. mammary tissue, wound healing), and also in tumor development and progression. Although the majority of studies suggest that ErbB receptor family members are mediators of cell survival, there have been occasional reports suggesting that ErbB receptors can induce cell death under selected experimental conditions. While this apparent discrepancy remains unresolved, in many of these reports, cell death may be the result of anoikis in response to changes in the cytoskeleton associated with hyperstimulation of ErbB signaling. The notion that ErbB receptor family members function to promote cell survival is not a recent observation. However, how this family functions to prevent apoptosis is an area that only recently has been considered. The understanding of ErbB receptor signaling as it relates to the avoidance of apoptosis had profound implications for the treatment of solid tumors originating in multiple tissues, as well as for the treatment of neurodegenerative disease. Further elucidation of the complex relationships between ErbB receptor signaling networks and the apoptotic machinery is certain to yield biologically important and potentially life-saving information.

Ligand-independent oncogenic transformation by the EGF receptor requires kinase domain catalytic activity.

The retroviral oncogene S3-v-erbB is a transduced, truncated form of the avian EGF (ErbB-1) receptor. Infection of avian fibroblasts with a retroviral vector expressing S3-v-ErbB results in ligand-independent cell transformation, which is accompanied by the assembly of a transformation-specific phosphoprotein signaling complex and anchorage-independent cell growth. It previously had been reported, using lysine-721 mutants (K721), that kinase domain function was required for ErbB-mediated cell transformation. However, since these initial reports, several studies using aspartate-813 mutants (D813) have demonstrated the ability of kinase-impaired ErbB receptors to induce mitogenic signal transduction pathways and cell transformation in a ligand-dependent manner. To determine the necessity of ErbB receptor kinase domain catalytic activity in ligand-independent cell transformation, we created S3-v-ErbB-K(-), a kinase-impaired oncoprotein constructed by replacing aspartate-813 with alanine (D813A). Subcellular routing as well as cell surface membrane and nuclear localization of the S3-v-ErbB-K(-) mutant receptor were unaffected by impairment of kinase activity. In contrast, avian fibroblasts expressing S3-v-ErbB-K(-) do not form the characteristic transformation-specific phosphoprotein complex, or induce soft agar colony growth in vitro. These results suggest that in contrast to ligand-dependent oncogenic signaling, ligand-independent cell transformation by a constitutively activated mutant form of the EGF receptor requires receptor kinase catalytic activity. In addition, these results demonstrate that phosphorylation and assembly of downstream signaling complexes require tyrosine phosphorylation events that are directly mediated by oncogenic forms of the EGF receptor.