Victoria K. Pepper

Clinical Translation of Tissue Engineered Trachea Grafts

Objective: To provide a state-of-the-art review discussing recent achievements in tissue engineered tracheal reconstruction. Data Sources and Review Methods: A structured PubMed search of the current literature up to and including October 2015. Representative articles that discuss the translation of tissue engineered tracheal grafts (TETG) were reviewed. Conclusions: The integration of a biologically compatible support with autologous cells has resulted in successful regeneration of respiratory epithelium, cartilage, and vascularization with graft patency, although the optimal construct composition has yet to be defined. Segmental TETG constructs are more commonly complicated by stenosis and delayed epithelialization when compared to patch tracheoplasty. Implications for Practice: The recent history of human TETG recipients represents revolutionary proof of principle studies in regenerative medicine. Application of TETG remains limited to a compassionate use basis; however, defining the mechanisms of cartilage formation, epithelialization, and refinement of in vivo regeneration will advance the translation of TETG from the bench to the bedside.

Cardiovascular Tissue Engineering: Preclinical Validation to Bedside Application

Advancements in biomaterial science and available cell sources have spurred the translation of tissue-engineering technology to the bedside, addressing the pressing clinical demands for replacement cardiovascular tissues. Here, the in vivo status of tissue-engineered blood vessels, heart valves, and myocardium is briefly reviewed, illustrating progress toward a tissue-engineered heart for clinical use.

Deconstructing the Tissue Engineered Vascular Graft: Evaluating Scaffold Pre-Wetting, Conditioned Media Incubation, and Determining the Optimal Mononuclear Cell Source

Stenosis limits widespread use of tissue-engineered vascular grafts (TEVGs), and bone marrow mononuclear cell (BM-MNC) seeding attenuates this complication. Yet seeding is a multistep process, and the singular effects of each component are unknown. We investigated which components of the clinical seeding protocol confer graft patency and sought to identify the optimal MNC source. Scaffolds composed of polyglycolic acid and ε-caprolactone/ι-lactic acid underwent conditioned media (CM) incubation (n = 25) and syngeneic BM-MNC (n = 9) or peripheral blood (PB)-MNC (n = 20) seeding. TEVGs were implanted for 2 weeks in the mouse IVC. CM incubation and PB-MNC seeding did not increase graft patency compared to control scaffolds prewet with PBS (n = 10), while BM-MNC seeding reduced stenosis by suppressing inflammation and smooth muscle cell, myofibroblast, and pericyte proliferation. IL-1β, IL-6, and TNFα were elevated in the seeded BM-MNC supernatant. Further, BM-MNC seeding reduced platelet activation in a dose-dependent manner, possibly contributing to TEVG patency.

Comparison of 30-day outcomes between thoracoscopic and open lobectomy for congenital pulmonary lesions.

OBJECTIVE To compare postoperative length of stay and 30-day outcomes between thoracoscopic and open lobectomy performed on a nonemergency basis for congenital pulmonary lesions using a validated national database. MATERIALS AND METHODS We identified all nonemergency lobectomies performed on patients with congenital pulmonary lesions in the 2012 National Surgical Quality Improvement Program (NSQIP) Pediatric database and compared demographic, clinical, and 30-day outcome characteristics between patients who underwent an open or thoracoscopic lobectomy. Logistic regression with Firths penalized likelihood bias-reduction method was used to determine predictive risk factors for a postoperative length of stay (LOS) of >3 days. RESULTS Of 101 patients included, 40 (39%) underwent thoracoscopic lobectomy. In comparison with patients undergoing thoracoscopic lobectomy, patients undergoing open lobectomy were significantly more likely to be admitted prior to surgery, be American Society of Anesthesiologists Class ≥ 3, receive oxygen support prior to surgery, and have other congenital anomalies or cardiac risk factors. Both groups had similar total operative times (open versus thoracoscopic, 150 versus 173 minutes; P=.216). Patients undergoing open lobectomy had longer postoperative LOS (4 versus 3 days; P=.001) and more often received an intraoperative or postoperative transfusion (12% versus 0%; P=.003). The procedure type was not an independent risk factor for postoperative LOS >3 days in the multivariable analysis. CONCLUSIONS Patients undergoing thoracoscopic lobectomy have fewer comorbidities at baseline, receive fewer perioperative transfusions, and have a shorter postoperative LOS. Accrual of additional patients within the NSQIP Pediatric database will allow for further risk-adjusted analyses to control for differences in baseline characteristics between patients undergoing open and thoracoscopic resections.

Endoscopic management of tissue-engineered tracheal graft stenosis in an ovine model

To evaluate the safety and efficacy of bronchoscopic interventions in the management of tissue‐engineered tracheal graft (TETG) stenosis.

Intravascular Ultrasound Characterization of a Tissue-Engineered Vascular Graft in an Ovine Model.

Patients who undergo implantation of a tissue-engineered vascular graft (TEVG) for congenital cardiac anomalies are monitored with echocardiography, followed by magnetic resonance imaging or angiography when indicated. While these methods provide data regarding the lumen, minimal information regarding neotissue formation is obtained. Intravascular ultrasound (IVUS) has previously been used in a variety of conditions to evaluate the vessel wall. The purpose of this study was to evaluate the utility of IVUS for evaluation of TEVGs in our ovine model. Eight sheep underwent implantation of TEVGs either unseeded or seeded with bone marrow-derived mononuclear cells. Angiography, IVUS, and histology were directly compared. Endothelium, tunica media, and graft were identifiable on IVUS and histology at multiple time points. There was strong agreement between IVUS and angiography for evaluation of luminal diameter. IVUS offers a valuable tool to evaluate the changes within TEVGs, and clinical translation of this application is warranted.

Toward a patient-specific tissue engineered vascular graft

Integrating three-dimensional printing with the creation of tissue-engineered vascular grafts could provide a readily available, patient-specific, autologous tissue source that could significantly improve outcomes in newborns with congenital heart disease. Here, we present the recent case of a candidate for our tissue-engineered vascular graft clinical trial deemed ineligible due to complex anatomical requirements and consider the application of three-dimensional printing technologies for a patient-specific graft. We 3D-printed a closed-disposable seeding device and validated that it performed equivalently to the traditional open seeding technique using ovine bone marrow–derived mononuclear cells. Next, our candidate’s preoperative imaging was reviewed to propose a patient-specific graft. A seeding apparatus was then designed to accommodate the custom graft and 3D-printed on a commodity fused deposition modeler. This exploratory feasibility study represents an important proof of concept advancing progress toward a rationally designed patient-specific tissue-engineered vascular graft for clinical application.

Minimally Invasive Ileal Pouch-Anal Anastomosis with Rectal Eversion Allows for Equivalent Outcomes in Continence in Pediatric Patients

BACKGROUND Different techniques for ileal pouch-anal anastomosis (IPAA) following total proctocolectomy (TPC) have been described in patients with ulcerative colitis (UC), including rectal eversion (RE). RE allows for precise identification of the dentate line, but concerns have been raised regarding continence rates. No studies have specifically evaluated RE in the pediatric population. The purpose of this study was to evaluate the outcomes and continence rates for pediatric patients undergoing minimally invasive surgery (MIS) TPC and IPAA with RE for UC. MATERIALS AND METHODS All patients who underwent TPC and IPAA were reviewed at our institution. Data collected included demographics, proctocolectomy technique (open without RE versus MIS with RE), operative time, postoperative data, and continence outcomes following ileostomy closure. RESULTS Thirty-three patients were identified who underwent TPC and IPAA between July 2006 and October 2014. Thirty of these patients underwent ileostomy takedown and were evaluated for continence. Of these, 17 (56.7%) patients had a laparoscopic procedure, 5 (16.7%) had a robotic-assisted procedure, and 8 (26.7%) had an open procedure. There were no statistically significant differences in regard to demographics, operative time, or length of stay when comparing the two groups. There were no differences in the two groups as measured at 1, 6, and 12 months in terms of number of daily stools (P = .93, .09, and .87, respectively), nighttime stooling (P = .29, .10, and .25, respectively), soiling (P = .43, .36, and .52, respectively), or stool-altering medication usage (P = .26, 1.00, and .37, respectively). CONCLUSIONS The RE technique can be used safely and effectively during MIS TPC and IPAA in children without altering continence rates.

A mouse model of endocardial fibroelastosis

BACKGROUND Endocardial fibroelastosis (EFE) is a pathologic condition of abnormal deposition of collagen and elastin within the endocardium of the heart. It is seen in conjunction with a variety of diseases including hypoplastic left heart syndrome and viral endocarditis. While an experimental model using heterotopic heart transplant in rats has been described, we sought to fully describe a mouse model that can be used to further elucidate the potential mechanisms of and treatments for EFE. MATERIALS AND METHODS The hearts of 2-day-old C57BL/6 mice were transplanted into the abdomen of 7-week-old C57BL/6 mice. At 2 weeks, the hearts were harvested and histologic analysis was performed using hematoxylin and eosin, Massons trichrome, Russell-Movats pentachrome, Picrosirius red, Harts, Verhoeff-Van Gieson, and Weigerts Resorcin-Fuchsin stains. Additionally, one heart was analyzed using transmission electron microscopy (TEM). RESULTS Specimens demonstrated abnormal accumulation of both collagen and elastin within the endocardium with occasional expansion into the myocardium. Heterogeneity in extracellular matrix deposition was noted in the histologic specimens. In addition, TEM demonstrated the presence of excess collagen within the endocardium. CONCLUSIONS The heterotopic transplantation of an immature heart into a mouse results in changes consistent with EFE. This model is appropriate to investigate the etiology and treatment of EFE.

Clinical validation and reproducibility of endoscopic airway measurement in pediatric aerodigestive evaluation

BACKGROUND Endoscopic airway measurement (EAM) combines optical endoscopic instruments with open source image processing to accurately obtain airway dimensions. Preclinical models have demonstrated EAM as an accurate technique of airway measurement with the added advantage of characterizing multilevel stenosis, non-circular lesions, and distal obstruction. The aim of this prospective clinical study was to compare EAM to airway measurements obtained from endotracheal tube approximation (ETTA) during pediatric aerodigestive evaluation and to evaluate reproducibility of EAM across practitioners. METHODS Thirty-seven pediatric patients undergoing routine microlaryngoscopy and bronchoscopy at a single tertiary care childrens hospital were prospectively recruited. Patients undergoing emergent procedures were excluded. Two blinded reviewers performed airway measurements using ImageJ (NIH) as previously described and average values were compared to ETTA measurements. Additional EAMs were obtained from an ex vivo airway model by 28 separate clinicians and were analyzed by the same reviewers to evaluate reproducibility. RESULTS EAM and ETTA measurements were themselves significantly different (p = 0.0003); however, the average absolute difference between the two methods was small (Mean: 0.5 mm, 95%CI: -2.6-1.6 mm). There were notable differences between raters such that estimates of raters with more experience were more similar to ETTA. Despite observed differences between EAM and ETTA, endoscopic airway measurement was highly correlated with ETTA (p = 0.0002, Spearman r = 0.4185), and strong agreement was observed (Bias: -0.4974 ± 1.083 mm, 95% LOA: -2.62-1.625 mm). CONCLUSION Clinical use of EAM is a valid and precise approach for quantification of airway luminal dimensions. This method may provide advantages over traditional ETTAs for evaluation of asymmetric airway morphology in the pediatric population.