Daine T. Bennett

Spinal Cord Ischemia-Reperfusion Injury Induces Erythropoietin Receptor Expression

BACKGROUND Paraplegia remains a devastating complication of aortic surgery, occurring in up to 20% of complex thoracoabdominal repairs. Erythropoietin (EPO) attenuates this injury in models of spinal cord ischemia. Upregulation of the beta-common receptor (βcR) subunit of the EPO receptor is associated with reduced damage in murine models of neural injury. This receptor activates anti-apoptotic pathways including signaling transducer and activator of transcription 3 (STAT3). We hypothesized that spinal cord ischemia-reperfusion injury upregulates the βcR subunit with a subsequent increase in activated STAT3. METHODS Adult male C57/BL6 mice received an intraperitoneal injection of 0.5 mL of EPO (10 U/kg) or 0.9% saline after induction of anesthesia. Spinal cord ischemia was induced through sternotomy and 4-minute thoracic aortic cross-clamp. Sham mice underwent sternotomy without cross-clamp placement. Four groups were studied: ischemic and sham groups, each with and without EPO treatment. After 4 hours of reperfusion, spinal cords were harvested and homogenized. The βcR subunit expression and STAT3 activation were evaluated by immunoblot. RESULTS Ischemia reperfusion increased βcR subunit expression in spinal cords of ischemia + saline and ischemia + EPO mice compared with shams (3.4 ± 1.39 vs 1.31 ± 0.3, p = 0.01 and 3.80 ± 0.58 vs 1.56 ± 0.32, p = 0.01). Additionally, both ischemic groups demonstrated increased STAT3 activation compared with shams (1.35 ± 0.14 vs 1.09 ± 0.07, p = 0.01 and 1.66 ± 0.35 vs 1.08 ± 0.17, p = 0.02). CONCLUSIONS Ischemia-reperfusion injury induces EPO receptor βcR subunit expression and early downstream anti-apoptotic signaling through STAT3 activation. Further investigation into the role of the βcR subunit is warranted to determine tissue protective functions of EPO. Elucidation of mechanisms involved in spinal cord protection is essential for reducing delayed paraplegia.

Extended Chest Wall Resection and Reconstruction in the Setting of Lung Cancer

Reconstruction of large chest wall defects after resection remains a significant undertaking. Obtaining a negative margin is of paramount importance for long-term survival. While reconstructing the chest wall, recreating a stable chest wall with adequate functional capacity and reasonable cosmesis are always the end goals. Morbidity from these procedures is significant, and mortality continues to hover around 5%. With continued advancement in reconstructive techniques and improved perioperative management, these procedures will continue to result in improved outcomes for patients.

Ex vivo lung perfusion allows successful transplantation of donor lungs from hanging victims.

BACKGROUND Donor lungs acquired from victims of asphyxiation by hanging are not routinely used for lung transplantation because of the associated lung injury. Ex vivo lung perfusion (EVLP) is a technique to evaluate marginal donor lungs before transplantation. We report here our experience with the use of EVLP in donor lungs procured from victims of asphyxia by hanging. METHODS Lungs from 5 donors who became brain dead secondary to hanging were evaluated by EVLP. Donor organs were perfused according to trial protocol. Donor lungs were accepted for transplantation if they maintained a PaO2 greater than or equal to 350 mm Hg, had a clear roentgenogram, and had no significant worsening of physiologic metrics. RESULTS Perfused organs included single and double lung blocs, and all were perfused without technical incident. Three of the 5 donor organs evaluated met criteria for transplantation after 3 hours of EVLP and were transplanted. Donor organs rejected for transplantation showed either signs of worsening PaO2 or deterioration of physiologic metrics. There were no intraoperative complications in the patients who underwent transplantation, and all were alive at 30 days. CONCLUSIONS We report here the successful use of EVLP to assess donor lungs acquired from victims of asphyxiation by hanging. The use of EVLP in this particular group of donors has the potential to expand the available donor pool. We demonstrate that EVLP is a viable option for evaluating the function of lung allografts before transplantation and would recommend that all donor lungs obtained from hanging victims undergo EVLP to assess their suitability for transplantation.

Clinical indicators of paraplegia underplay universal spinal cord neuronal injury from transient aortic occlusion.

Paraplegia following complex aortic intervention relies on crude evaluation of lower extremity strength such as whether the patient can lift their legs or flex the ankle. Little attention has been given to the possible long-term neurologic sequelae following these procedures in patients appearing functionally normal. We hypothesize that mice subjected to minimal ischemic time will have functional and histological changes despite the gross appearance of normal function. Male mice underwent 3 min of aortic occlusion (n=14) or sham surgery (n=4) via a median sternotomy. Neurologic function was graded by Basso Motor Score (BMS) preoperatively and at 24h intervals after reperfusion. Mice appearing functionally normal and sham mice were placed on a walking beam and recorded on high-definition, for single-frame motion analysis. After 96 hrs, spinal cords were removed for histological analysis. Following 3 min of ischemia, functional outcomes were split evenly with either mice displaying almost normal function n=7 or near complete paraplegia n=7. Additionally, single-frame motion analysis revealed significant changes in gait. Histologically, there was a significant stepwise reduction of neuronal viability, with even the normal function ischemic group demonstrating significant loss of neurons. Despite the appearance of normal function, temporary ischemia induced marked cyto-architectural changes and neuronal degeneration. Furthermore high-definition gait analysis revealed significant changes in gait and activity following thoracic aortic occlusion. These data suggest that all patients undergoing procedures, even with short ischemic times, may have spinal cord injury that is not evident clinically.

Cancer Stem Cell Phenotype Is Supported by Secretory Phospholipase A2 in Human Lung Cancer Cells

BACKGROUND Lung cancer stem cells (CSCs) are a subpopulation of cells that drive growth, invasiveness, and resistance to therapy. Inflammatory eicosanoids are critical to maintain this malignant subpopulation. Secretory phospholipase A2 group IIa (sPLA2) is an important mediator of the growth and invasive potential of human lung cancer cells and regulates eicosanoid production. We hypothesized that sPLA2 plays a role in the maintenance of lung CSCs. METHODS Cancer stem cells from lung adenocarcinoma cell lines H125 and A549 were isolated using aldehyde dehydrogenase activity and flow cytometry. Protein and mRNA levels for sPLA2 were compared between sorted cells using Western blotting and quantitative reverse transcriptase-polymerase chain reaction techniques. Chemical inhibition of sPLA2 and short-hairpin RNA knockdown of sPLA2 were used to evaluate effects on tumorsphere formation. RESULTS Lung CSCs were isolated in 8.9%±4.1% (mean±SD) and 4.1%±1.6% of H125 and A549 cells respectively. Both sPLA2 protein and mRNA expression were significantly elevated in the CSC subpopulation of H125 (p=0.002) and A549 (p=0.005; n=4). Knockdown of sPLA2 significantly reduced tumorsphere formation in H125 (p=0.026) and A549 (p=0.001; n=3). Chemical inhibition of sPLA2 resulted in dose-dependent reduction in tumorsphere formation in H125 (p=0.003) and A549 (p=0.076; n=3). CONCLUSIONS Lung CSCs express higher levels of sPLA2 than the non-stem cell population. Our findings that viral knockdown and chemical inhibition of sPLA2 reduce tumorsphere formation in lung cancer cells demonstrate for the first time that sPLA2 plays an important role in CSCs. These findings suggest that sPLA2 may be an important therapeutic target for human lung cancer.

The Year in Thoracic Surgery Highlights From 2013

Over the course of 2013, many important studies have been published affecting the care of thoracic surgery patients. Novel chemotherapeutics are being developed to target specific tumor mutations. The utilization of robotic-assisted surgery continues to expand within this exciting field as well. Improved data on endobronchial ultrasound staging and sublobar resections for non–small cell lung cancer as well as postoperative surveillance after esophagectomy have also been reported. This review summarizes important publications of the past year influencing the practice of thoracic surgery today.