The Journal of Thoracic and Cardiovascular Surgery, 2015
We pursued a multimodality approach to the treatment of patients with pulmonary vein stenosis, in... more We pursued a multimodality approach to the treatment of patients with pulmonary vein stenosis, incorporating sutureless surgical repair, catheter interventions, and adjunctive chemotherapy. We report our outcomes after surgery. Between January 2007 and August 2013, 49 patients with multivessel pulmonary vein stenosis underwent operations at our institution. We retrospectively reviewed data from a pulmonary vein stenosis registry and the medical records. At the time of the index operation, the median patient age was 6 months (range, 32 days-48 months) and weight was 4.9 kg (range, 2.1-13.4 kg). Fourteen patients (28%) died during the follow-up period (median follow-up was 0.5 years [range, 0.04-4.9 years]). There were 2 deaths (4%) within 30 days. Age at repair <6 months, weight at repair <3 kg, and a preoperative right ventricular systolic pressure < ¾ systemic were found to be associated with mortality. One patient required repeat operation for recurrent stenosis. Thirty-nine patients (80%) underwent postoperative catheterizations. The median number of catheterizations per patient was 2 (range, 0-14). Twenty-nine patients (59%) underwent catheterizations with pulmonary vein intervention. The median number of catheterizations with intervention per patient was 1 (range, 0-14). There were no identifiable associations with need for or number of catheterizations with intervention. Ten patients were listed for lung transplantation: 4 patients were de-listed, 3 patients died waiting, and 3 patients underwent transplant. Using a multimodality approach, we observed acceptable early survival after operation in patients with pulmonary vein stenosis, despite the need for catheter reinterventions. Lung transplantation remains a viable option.
Other uses, including reproduction and distribution, or selling or licensing copies, or posting t... more Other uses, including reproduction and distribution, or selling or licensing copies, or posting to personal, institutional or third party websites are prohibited.
Page 1. IMAGINATION, COGNITION AND PERSONALITY, Vol. 26(1-2) 3-41, 2006-2007 THE LIFE SPACE: A FR... more Page 1. IMAGINATION, COGNITION AND PERSONALITY, Vol. 26(1-2) 3-41, 2006-2007 THE LIFE SPACE: A FRAMEWORK AND METHOD TO DESCRIBE THE INDIVIDUAL'S EXTERNAL TRAITS MARC A. BRACKETT Yale University ...
The Journal of thoracic and cardiovascular surgery, 2005
This study was undertaken to evaluate the effect of triiodothyronine replacement on the early pos... more This study was undertaken to evaluate the effect of triiodothyronine replacement on the early postoperative course of neonates undergoing aortic arch reconstruction. We performed a randomized, double-blind, placebo-controlled trial of triiodothyronine supplementation in neonates undergoing either a Norwood procedure or two-ventricle repair of interrupted aortic arch and ventricular septal defect. Patients were assigned to receive a continuous infusion of triiodothyronine (0.05 micro/kg/h) or placebo for 72 hours after cardiopulmonary bypass. Primary end points were a composite clinical outcome score and cardiac index at 48 postoperative hours. We enrolled 42 patients (triiodothyronine n = 22, placebo n = 20). Baseline characteristics were similar in the treatment groups. Study drug was discontinued prematurely because of hypertension (n = 1) and ectopic atrial tachycardia (n = 1), both cases in the triiodothyronine group. Free and total triiodothyronine levels were higher in the tri...
The Journal of thoracic and cardiovascular surgery, 2014
In a previous study of infants less than 6 month old, we found that delayed revision of residual ... more In a previous study of infants less than 6 month old, we found that delayed revision of residual lesions resulted in worse patient outcomes compared with intraoperative revision. We explored a larger cohort to determine if this finding persisted. A prospective cohort followed from index surgery to discharge from January 2011 to September 2013 were divided into 4 groups: (1) intraoperative revisions (IO) of residual lesions, (2) delayed postoperative revision (PO) of residual lesions during the same hospital stay, (3) both intraoperative and delayed (BOTH) revision of residual lesions, (4) no intraoperative or postoperative revision (NO). Linear and logistic regression analyses were used to compare outcomes of postoperative hospital length of stay, postoperative adverse events (AE), hospital costs, and mortality, after adjusting for age, prematurity, presence of extracardiac anomalies, and RACHS-1 (Risk Adjustment for Congenital Heart Surgery-1) risk category known to affect outcomes...
Arterial conduits are increasingly preferred for surgical bypass because of inherent functional p... more Arterial conduits are increasingly preferred for surgical bypass because of inherent functional properties conferred by arterial endothelial cells, especially nitric oxide production in response to physiologic stimuli. We tested whether endothelial progenitor cells can replace arterial endothelial cells and promote patency of tissue-engineered small diameter blood vessels (4 mm). To address this, endothelial progenitor cells were isolated non-invasively from peripheral blood of sheep, expanded ex vivo, and subsequently seeded onto decellularized porcine iliac vessels. Endothelial progenitor cell-seeded grafts remained patent for 130 days as a carotid interposition graft in sheep, while non-seeded grafts occluded within 15 days. Importantly, the endothelial progenitor cellexplanted grafts exhibited contractile activity and nitric oxide-mediated vascular relaxation that was similar to native carotid arteries but which has not been reported previously for tissue-engineered small diameter grafts. These results suggest that endothelial progenitor cells can function similarly to arterial endothelial cells and thereby confer longer vascular graft survival. Due to their unique properties, endothelial progenitor cells may have more general applications for other tissueengineered structures and also in treating vascular diseases.
Journal of molecular and cellular cardiology, Jan 26, 2015
Thickening of mitral leaflets, endothelial-to-mesenchymal transition (EndMT), and activated myofi... more Thickening of mitral leaflets, endothelial-to-mesenchymal transition (EndMT), and activated myofibroblast-like interstitial cells have been observed in ischemic mitral valve regurgitation. We set out to determine if interactions between mitral valve endothelial cells (VEC) and interstitial cells (VIC) might affect these alterations. We used in vitro co-culture in Transwell™ inserts to test the hypothesis that VIC secrete factors that inhibit EndMT and conversely, that VEC secrete factors that mitigate the activation of VIC to a myofibroblast-like, activated phenotype. Primary cultures and clonal populations of ovine mitral VIC and VEC were used. Western blot, quantitative reverse transcriptase PCR (qPCR) and functional assays were used to assess changes in cell phenotype and behavior. VIC or conditioned media from VIC inhibited transforming growth factorβ (TGFβ)-induced EndMT in VEC, as indicated by reduced expression of EndMT markers α-smooth muscle actin (α-SMA), Slug, Snai1 and M...
Seminars in Thoracic and Cardiovascular Surgery, 2014
Recognition of late problems following repair of tetralogy of Fallot (TOF) with a transannular pa... more Recognition of late problems following repair of tetralogy of Fallot (TOF) with a transannular patch has stimulated modifications to preserve pulmonary valve (PV) function. This study assesses the ability of technical performance score (TPS) to determine the need for post-discharge reinterventions (RIs) in valve-sparing TOF repair. We retrospectively reviewed 157 patients following valve-sparing repair of TOF from 2007-2012. We assigned TPS as Class 1 (optimal), Class 2 (adequate), or Class 3 (inadequate) based on discharge echo and clinical criteria. Preoperative, discharge, and follow-up PV Z scores and post-discharge RIs were documented. Reasons for Class 2 or 3 designation were right ventricular outflow tract (RVOT) gradient in 52, pulmonary regurgitation in 13, residual ventricular septal defects in 7, both RVOT gradient and ventricular septal defects in 13, and both RVOT gradient and pulmonary regurgitation in 37 patients. Median follow-up was 19.6 (range: 0.1-86.1) months. Class 3 patients had a significantly longer median intensive care unit and hospital stay compared with Class 1 (3 vs 2 days [P = 0.015] and 7 vs 5 days [P < 0.001], respectively). Post-discharge RIs were significantly lower in Class 1 vs Class 2 and Class 3 (P = 0.003). Class 1 patients had significantly larger PV Z scores compared with Class 2 or Class 3 patients (P < 0.001). TPS is associated with post-discharge RI rate after valve-sparing TOF repair. Preoperative PV Z score is highly correlated with Class I TPS. Patient selection based on preoperative PV Z scores may help determine if valve-sparing approach is appropriate, thus minimizing the need for RIs.
The Journal of Thoracic and Cardiovascular Surgery, 2014
Aortic root translocation is a promising surgical option for repair of transposition of the great... more Aortic root translocation is a promising surgical option for repair of transposition of the great arteries, ventricular septal defect, and pulmonary stenosis. There are little data on the outcomes of this procedure, with no long-term follow-up available. We reviewed our experience with aortic root translocation and the impact of the type of right ventricular outflow tract reconstruction. The demographic, procedural, and outcome data were obtained for 32 patients who underwent aortic root translocation from 1997 to 2013 at Boston Children's Hospital. Patients were grouped on the basis of right ventricular outflow tract reconstruction with a valved conduit or a nonvalved anastomosis of the pulmonary artery bifurcation to the right ventricular outflow tract with anterior patch augmentation (transannular patch). The median age was 7.5 months (16 days to 42 years). Twenty-six patients had valved conduits, and 6 patients had transannular patches. There were no significant differences between groups in baseline and operative characteristics. There was 1 early death (transannular patch group). There were no late deaths during a median follow-up of 20.8 months (1 month to 16.5 years). No patients developed late left ventricular outflow tract obstruction. Transcatheter reintervention was required in 14 patients, 9 with valved conduits (34.6%) and 1 with transannular patch (20%, P > .99). Six patients (19.4%) required reoperation, all with a valved conduit (P = .34). Aortic root translocation can be done with low early and late mortality. There was preserved aortic valve function and no left ventricular outflow tract obstruction at late follow-up. The use of a transannular patch had early outcomes comparable to valved conduits, with a trend for fewer late reoperations.
Objectives: Creating functional small-diameter tissue-engineered blood vessels has not been succe... more Objectives: Creating functional small-diameter tissue-engineered blood vessels has not been successful to date. Moreover, the processes underlying the in vivo remodeling of these grafts and the fate of cells seeded onto scaffolds remain unclear. Here we addressed these unmet scientific needs by using intravital molecular imaging to monitor the development of tissue-engineered vascular grafts (TEVG) implanted in mouse carotid artery. Methods and Results: Green fluorescent protein-labeled human bone marrow-derived mesenchymal stem cells and cord blood-derived endothelial progenitor cells were seeded on polyglycolic acid-poly-L-lactic acid scaffolds to construct small-caliber TEVG that were subsequently implanted in the carotid artery position of nude mice (n ¼ 9). Mice were injected with near-infrared agents and imaged using intravital fluorescence microscope at 0, 7, and 35 days to validate in vivo the TEVG remodeling capability (Prosense680; VisEn, Woburn, MA) and patency (Angiosense750; VisEn). Imaging coregistered strong proteolytic activity and blood flow through anastomoses at both 7 and 35 days postimplantation. In addition, image analyses showed green fluorescent protein signal produced from mesenchymal stem cell up to 35 days postimplantation. Comprehensive correlative histopathological analyses corroborated intravital imaging findings. Conclusions: Multispectral imaging offers simultaneous characterization of in vivo remodeling enzyme activity, functionality, and cell fate of viable small-caliber TEVG.
Purposes: We investigated whether circulating endothelial progenitor cells (EPCs) can be used as ... more Purposes: We investigated whether circulating endothelial progenitor cells (EPCs) can be used as a cell source for the creation of a tissue-engineered heart valve (TEHV). Methods: Trileaflet valved conduits were fabricated using nonwoven polyglycolic acid=poly-4-hydroxybutyrate polymer. Ovine peripheral blood EPCs were dynamically seeded onto a valved conduit and incubated for 7, 14, and 21 days. Results: Before seeding, EPCs were shown to express CD31 þ , eNOS þ , and VE-Cadherin þ but not a-smooth muscle actin. Histological analysis demonstrated relatively homogenous cellular ingrowth throughout the valved conduit. TEHV constructs revealed the presence of endothelial cell (EC) markers and a-smooth muscle actin þ cells comparable with native valves. Protein levels were comparable with native valves and exceeded those in unseeded controls. EPC-TEHV demonstrated a temporal pattern of matrix metalloproteinases-2=9 expression and tissue inhibitors of metalloproteinase activities comparable to that of native valves. Mechanical properties of EPC-TEHV demonstrated significantly greater stiffness than that of the unseeded scaffolds and native valves. Conclusions: Circulating EPC appears to have the potential to provide both interstitial and endothelial functions and could potentially serve as a single-cell source for construction of autologous heart valves.
Tissue-engineered heart valves are prone to early structural deterioration. We hypothesize that c... more Tissue-engineered heart valves are prone to early structural deterioration. We hypothesize that cell-scaffold interaction and mechanical deformation results in upregulation of genes related to osteogenic/chondrogenic differentiation and thus changes extracellular matrix (ECM) composition in human bone marrow mesenchymal stem cell (hBMSC)-derived tissue-engineered grafts. hBMSC were expanded and seeded onto poly-glycolic acid/poly-lactic acid scaffold for 14 days. Seeded tissue-engineered constructs (TEC) were subjected to cyclic flexure for 24 h, whereas control TEC was maintained in roller bottles for the same duration. hBMSC, TEC, and mechanically deformed TEC were subjected to gene-array and histological analysis. Expression levels of RNA and/or protein markers related to chondrogenesis (Sox9, MGP, RunX2, Col II, Col X, and Col XI) and osteogenesis (ALPL, BMP2, EDN1, RunX1, and Col I) were increased in TEC compared to unseeded hBMSC. Histological sections of TEC stained positive for Saffranin O, alkaline phosphatase activity, and calcium deposits. The expression levels of the above gene and protein markers further increased in deformed TEC compared to static TEC. Cell-scaffold interactions and mechanical stress results in gene expression suggestive of endochondral-ossification that impact upon ECM composition and may predispose them to eventual calcification.
Optimization of cell seeding and culturing is an important step for the successful tissue enginee... more Optimization of cell seeding and culturing is an important step for the successful tissue engineering of vascular conduits. We evaluated the effectiveness of using a hybridization oven for rotational seeding and culturing of ovine vascular myofibroblasts onto biodegradable polymer scaffolds suitable for replacement of small-and large-diameter blood vessels. Large tubes (12 mm internal diameter and 60 mm length, n 5 4) and small tubes (5 mm internal diameter and 20 mm length, n 5 4) were made from a combination of polyglycolic acid/poly-4-hydroxybutyrate and coated with collagen solution. Tubes were then placed in culture vessels containing a vascular myofibroblast suspension (10 6 cells/cm 2 ) and rotated at 5 rpm in a hybridization oven at 37°C. Light and scanning electron microscopy analyses were performed after 5, 7, and 10 days. Myofibroblasts had formed confluent layers over the outer and inner surfaces of both large and small tubular scaffolds by day 5. Cells had aligned in the direction of flow by day 7. Multiple spindle-shaped cells were observed infiltrating the polymer mesh. Cell density increased between day 5 and day 10. All conduits maintained their tubular shape throughout the experiment. We conclude that dynamic rotational seeding and culturing in a hybridization oven is an easy, effective, and reliable method to deliver and culture vascular myofibroblasts onto tubular polymer scaffolds.
The Journal of Thoracic and Cardiovascular Surgery, 2015
We pursued a multimodality approach to the treatment of patients with pulmonary vein stenosis, in... more We pursued a multimodality approach to the treatment of patients with pulmonary vein stenosis, incorporating sutureless surgical repair, catheter interventions, and adjunctive chemotherapy. We report our outcomes after surgery. Between January 2007 and August 2013, 49 patients with multivessel pulmonary vein stenosis underwent operations at our institution. We retrospectively reviewed data from a pulmonary vein stenosis registry and the medical records. At the time of the index operation, the median patient age was 6 months (range, 32 days-48 months) and weight was 4.9 kg (range, 2.1-13.4 kg). Fourteen patients (28%) died during the follow-up period (median follow-up was 0.5 years [range, 0.04-4.9 years]). There were 2 deaths (4%) within 30 days. Age at repair <6 months, weight at repair <3 kg, and a preoperative right ventricular systolic pressure < ¾ systemic were found to be associated with mortality. One patient required repeat operation for recurrent stenosis. Thirty-nine patients (80%) underwent postoperative catheterizations. The median number of catheterizations per patient was 2 (range, 0-14). Twenty-nine patients (59%) underwent catheterizations with pulmonary vein intervention. The median number of catheterizations with intervention per patient was 1 (range, 0-14). There were no identifiable associations with need for or number of catheterizations with intervention. Ten patients were listed for lung transplantation: 4 patients were de-listed, 3 patients died waiting, and 3 patients underwent transplant. Using a multimodality approach, we observed acceptable early survival after operation in patients with pulmonary vein stenosis, despite the need for catheter reinterventions. Lung transplantation remains a viable option.
Other uses, including reproduction and distribution, or selling or licensing copies, or posting t... more Other uses, including reproduction and distribution, or selling or licensing copies, or posting to personal, institutional or third party websites are prohibited.
Page 1. IMAGINATION, COGNITION AND PERSONALITY, Vol. 26(1-2) 3-41, 2006-2007 THE LIFE SPACE: A FR... more Page 1. IMAGINATION, COGNITION AND PERSONALITY, Vol. 26(1-2) 3-41, 2006-2007 THE LIFE SPACE: A FRAMEWORK AND METHOD TO DESCRIBE THE INDIVIDUAL'S EXTERNAL TRAITS MARC A. BRACKETT Yale University ...
The Journal of thoracic and cardiovascular surgery, 2005
This study was undertaken to evaluate the effect of triiodothyronine replacement on the early pos... more This study was undertaken to evaluate the effect of triiodothyronine replacement on the early postoperative course of neonates undergoing aortic arch reconstruction. We performed a randomized, double-blind, placebo-controlled trial of triiodothyronine supplementation in neonates undergoing either a Norwood procedure or two-ventricle repair of interrupted aortic arch and ventricular septal defect. Patients were assigned to receive a continuous infusion of triiodothyronine (0.05 micro/kg/h) or placebo for 72 hours after cardiopulmonary bypass. Primary end points were a composite clinical outcome score and cardiac index at 48 postoperative hours. We enrolled 42 patients (triiodothyronine n = 22, placebo n = 20). Baseline characteristics were similar in the treatment groups. Study drug was discontinued prematurely because of hypertension (n = 1) and ectopic atrial tachycardia (n = 1), both cases in the triiodothyronine group. Free and total triiodothyronine levels were higher in the tri...
The Journal of thoracic and cardiovascular surgery, 2014
In a previous study of infants less than 6 month old, we found that delayed revision of residual ... more In a previous study of infants less than 6 month old, we found that delayed revision of residual lesions resulted in worse patient outcomes compared with intraoperative revision. We explored a larger cohort to determine if this finding persisted. A prospective cohort followed from index surgery to discharge from January 2011 to September 2013 were divided into 4 groups: (1) intraoperative revisions (IO) of residual lesions, (2) delayed postoperative revision (PO) of residual lesions during the same hospital stay, (3) both intraoperative and delayed (BOTH) revision of residual lesions, (4) no intraoperative or postoperative revision (NO). Linear and logistic regression analyses were used to compare outcomes of postoperative hospital length of stay, postoperative adverse events (AE), hospital costs, and mortality, after adjusting for age, prematurity, presence of extracardiac anomalies, and RACHS-1 (Risk Adjustment for Congenital Heart Surgery-1) risk category known to affect outcomes...
Arterial conduits are increasingly preferred for surgical bypass because of inherent functional p... more Arterial conduits are increasingly preferred for surgical bypass because of inherent functional properties conferred by arterial endothelial cells, especially nitric oxide production in response to physiologic stimuli. We tested whether endothelial progenitor cells can replace arterial endothelial cells and promote patency of tissue-engineered small diameter blood vessels (4 mm). To address this, endothelial progenitor cells were isolated non-invasively from peripheral blood of sheep, expanded ex vivo, and subsequently seeded onto decellularized porcine iliac vessels. Endothelial progenitor cell-seeded grafts remained patent for 130 days as a carotid interposition graft in sheep, while non-seeded grafts occluded within 15 days. Importantly, the endothelial progenitor cellexplanted grafts exhibited contractile activity and nitric oxide-mediated vascular relaxation that was similar to native carotid arteries but which has not been reported previously for tissue-engineered small diameter grafts. These results suggest that endothelial progenitor cells can function similarly to arterial endothelial cells and thereby confer longer vascular graft survival. Due to their unique properties, endothelial progenitor cells may have more general applications for other tissueengineered structures and also in treating vascular diseases.
Journal of molecular and cellular cardiology, Jan 26, 2015
Thickening of mitral leaflets, endothelial-to-mesenchymal transition (EndMT), and activated myofi... more Thickening of mitral leaflets, endothelial-to-mesenchymal transition (EndMT), and activated myofibroblast-like interstitial cells have been observed in ischemic mitral valve regurgitation. We set out to determine if interactions between mitral valve endothelial cells (VEC) and interstitial cells (VIC) might affect these alterations. We used in vitro co-culture in Transwell™ inserts to test the hypothesis that VIC secrete factors that inhibit EndMT and conversely, that VEC secrete factors that mitigate the activation of VIC to a myofibroblast-like, activated phenotype. Primary cultures and clonal populations of ovine mitral VIC and VEC were used. Western blot, quantitative reverse transcriptase PCR (qPCR) and functional assays were used to assess changes in cell phenotype and behavior. VIC or conditioned media from VIC inhibited transforming growth factorβ (TGFβ)-induced EndMT in VEC, as indicated by reduced expression of EndMT markers α-smooth muscle actin (α-SMA), Slug, Snai1 and M...
Seminars in Thoracic and Cardiovascular Surgery, 2014
Recognition of late problems following repair of tetralogy of Fallot (TOF) with a transannular pa... more Recognition of late problems following repair of tetralogy of Fallot (TOF) with a transannular patch has stimulated modifications to preserve pulmonary valve (PV) function. This study assesses the ability of technical performance score (TPS) to determine the need for post-discharge reinterventions (RIs) in valve-sparing TOF repair. We retrospectively reviewed 157 patients following valve-sparing repair of TOF from 2007-2012. We assigned TPS as Class 1 (optimal), Class 2 (adequate), or Class 3 (inadequate) based on discharge echo and clinical criteria. Preoperative, discharge, and follow-up PV Z scores and post-discharge RIs were documented. Reasons for Class 2 or 3 designation were right ventricular outflow tract (RVOT) gradient in 52, pulmonary regurgitation in 13, residual ventricular septal defects in 7, both RVOT gradient and ventricular septal defects in 13, and both RVOT gradient and pulmonary regurgitation in 37 patients. Median follow-up was 19.6 (range: 0.1-86.1) months. Class 3 patients had a significantly longer median intensive care unit and hospital stay compared with Class 1 (3 vs 2 days [P = 0.015] and 7 vs 5 days [P < 0.001], respectively). Post-discharge RIs were significantly lower in Class 1 vs Class 2 and Class 3 (P = 0.003). Class 1 patients had significantly larger PV Z scores compared with Class 2 or Class 3 patients (P < 0.001). TPS is associated with post-discharge RI rate after valve-sparing TOF repair. Preoperative PV Z score is highly correlated with Class I TPS. Patient selection based on preoperative PV Z scores may help determine if valve-sparing approach is appropriate, thus minimizing the need for RIs.
The Journal of Thoracic and Cardiovascular Surgery, 2014
Aortic root translocation is a promising surgical option for repair of transposition of the great... more Aortic root translocation is a promising surgical option for repair of transposition of the great arteries, ventricular septal defect, and pulmonary stenosis. There are little data on the outcomes of this procedure, with no long-term follow-up available. We reviewed our experience with aortic root translocation and the impact of the type of right ventricular outflow tract reconstruction. The demographic, procedural, and outcome data were obtained for 32 patients who underwent aortic root translocation from 1997 to 2013 at Boston Children's Hospital. Patients were grouped on the basis of right ventricular outflow tract reconstruction with a valved conduit or a nonvalved anastomosis of the pulmonary artery bifurcation to the right ventricular outflow tract with anterior patch augmentation (transannular patch). The median age was 7.5 months (16 days to 42 years). Twenty-six patients had valved conduits, and 6 patients had transannular patches. There were no significant differences between groups in baseline and operative characteristics. There was 1 early death (transannular patch group). There were no late deaths during a median follow-up of 20.8 months (1 month to 16.5 years). No patients developed late left ventricular outflow tract obstruction. Transcatheter reintervention was required in 14 patients, 9 with valved conduits (34.6%) and 1 with transannular patch (20%, P > .99). Six patients (19.4%) required reoperation, all with a valved conduit (P = .34). Aortic root translocation can be done with low early and late mortality. There was preserved aortic valve function and no left ventricular outflow tract obstruction at late follow-up. The use of a transannular patch had early outcomes comparable to valved conduits, with a trend for fewer late reoperations.
Objectives: Creating functional small-diameter tissue-engineered blood vessels has not been succe... more Objectives: Creating functional small-diameter tissue-engineered blood vessels has not been successful to date. Moreover, the processes underlying the in vivo remodeling of these grafts and the fate of cells seeded onto scaffolds remain unclear. Here we addressed these unmet scientific needs by using intravital molecular imaging to monitor the development of tissue-engineered vascular grafts (TEVG) implanted in mouse carotid artery. Methods and Results: Green fluorescent protein-labeled human bone marrow-derived mesenchymal stem cells and cord blood-derived endothelial progenitor cells were seeded on polyglycolic acid-poly-L-lactic acid scaffolds to construct small-caliber TEVG that were subsequently implanted in the carotid artery position of nude mice (n ¼ 9). Mice were injected with near-infrared agents and imaged using intravital fluorescence microscope at 0, 7, and 35 days to validate in vivo the TEVG remodeling capability (Prosense680; VisEn, Woburn, MA) and patency (Angiosense750; VisEn). Imaging coregistered strong proteolytic activity and blood flow through anastomoses at both 7 and 35 days postimplantation. In addition, image analyses showed green fluorescent protein signal produced from mesenchymal stem cell up to 35 days postimplantation. Comprehensive correlative histopathological analyses corroborated intravital imaging findings. Conclusions: Multispectral imaging offers simultaneous characterization of in vivo remodeling enzyme activity, functionality, and cell fate of viable small-caliber TEVG.
Purposes: We investigated whether circulating endothelial progenitor cells (EPCs) can be used as ... more Purposes: We investigated whether circulating endothelial progenitor cells (EPCs) can be used as a cell source for the creation of a tissue-engineered heart valve (TEHV). Methods: Trileaflet valved conduits were fabricated using nonwoven polyglycolic acid=poly-4-hydroxybutyrate polymer. Ovine peripheral blood EPCs were dynamically seeded onto a valved conduit and incubated for 7, 14, and 21 days. Results: Before seeding, EPCs were shown to express CD31 þ , eNOS þ , and VE-Cadherin þ but not a-smooth muscle actin. Histological analysis demonstrated relatively homogenous cellular ingrowth throughout the valved conduit. TEHV constructs revealed the presence of endothelial cell (EC) markers and a-smooth muscle actin þ cells comparable with native valves. Protein levels were comparable with native valves and exceeded those in unseeded controls. EPC-TEHV demonstrated a temporal pattern of matrix metalloproteinases-2=9 expression and tissue inhibitors of metalloproteinase activities comparable to that of native valves. Mechanical properties of EPC-TEHV demonstrated significantly greater stiffness than that of the unseeded scaffolds and native valves. Conclusions: Circulating EPC appears to have the potential to provide both interstitial and endothelial functions and could potentially serve as a single-cell source for construction of autologous heart valves.
Tissue-engineered heart valves are prone to early structural deterioration. We hypothesize that c... more Tissue-engineered heart valves are prone to early structural deterioration. We hypothesize that cell-scaffold interaction and mechanical deformation results in upregulation of genes related to osteogenic/chondrogenic differentiation and thus changes extracellular matrix (ECM) composition in human bone marrow mesenchymal stem cell (hBMSC)-derived tissue-engineered grafts. hBMSC were expanded and seeded onto poly-glycolic acid/poly-lactic acid scaffold for 14 days. Seeded tissue-engineered constructs (TEC) were subjected to cyclic flexure for 24 h, whereas control TEC was maintained in roller bottles for the same duration. hBMSC, TEC, and mechanically deformed TEC were subjected to gene-array and histological analysis. Expression levels of RNA and/or protein markers related to chondrogenesis (Sox9, MGP, RunX2, Col II, Col X, and Col XI) and osteogenesis (ALPL, BMP2, EDN1, RunX1, and Col I) were increased in TEC compared to unseeded hBMSC. Histological sections of TEC stained positive for Saffranin O, alkaline phosphatase activity, and calcium deposits. The expression levels of the above gene and protein markers further increased in deformed TEC compared to static TEC. Cell-scaffold interactions and mechanical stress results in gene expression suggestive of endochondral-ossification that impact upon ECM composition and may predispose them to eventual calcification.
Optimization of cell seeding and culturing is an important step for the successful tissue enginee... more Optimization of cell seeding and culturing is an important step for the successful tissue engineering of vascular conduits. We evaluated the effectiveness of using a hybridization oven for rotational seeding and culturing of ovine vascular myofibroblasts onto biodegradable polymer scaffolds suitable for replacement of small-and large-diameter blood vessels. Large tubes (12 mm internal diameter and 60 mm length, n 5 4) and small tubes (5 mm internal diameter and 20 mm length, n 5 4) were made from a combination of polyglycolic acid/poly-4-hydroxybutyrate and coated with collagen solution. Tubes were then placed in culture vessels containing a vascular myofibroblast suspension (10 6 cells/cm 2 ) and rotated at 5 rpm in a hybridization oven at 37°C. Light and scanning electron microscopy analyses were performed after 5, 7, and 10 days. Myofibroblasts had formed confluent layers over the outer and inner surfaces of both large and small tubular scaffolds by day 5. Cells had aligned in the direction of flow by day 7. Multiple spindle-shaped cells were observed infiltrating the polymer mesh. Cell density increased between day 5 and day 10. All conduits maintained their tubular shape throughout the experiment. We conclude that dynamic rotational seeding and culturing in a hybridization oven is an easy, effective, and reliable method to deliver and culture vascular myofibroblasts onto tubular polymer scaffolds.
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Papers by John Mayer