Whole-Heart Tissue Engineering and Cardiac Patches: Challenges and Promises.

Despite all the advances in preventing, diagnosing, and treating cardiovascular disorders, they still account for a significant part of mortality and morbidity worldwide. The advent of tissue engineering and regenerative medicine has provided novel therapeutic approaches for the treatment of various diseases. Tissue engineering relies on three pillars: scaffolds, stem cells, and growth factors. Gene and cell therapy methods have been introduced as primary approaches to cardiac tissue engineering. Although the application of gene and cell therapy has resulted in improved regeneration of damaged cardiac tissue, further studies are needed to resolve their limitations, enhance their effectiveness, and translate them into the clinical setting. Scaffolds from synthetic, natural, or decellularized sources have provided desirable characteristics for the repair of cardiac tissue. Decellularized scaffolds are widely studied in heart regeneration, either as cell-free constructs or cell-seeded platforms. The application of human- or animal-derived decellularized heart patches has promoted the regeneration of heart tissue through in vivo and in vitro studies. Due to the complexity of cardiac tissue engineering, there is still a long way to go before cardiac patches or decellularized whole-heart scaffolds can be routinely used in clinical practice. This paper aims to review the decellularized whole-heart scaffolds and cardiac patches utilized in the regeneration of damaged cardiac tissue. Moreover, various decellularization methods related to these scaffolds will be discussed.

Esophagus tissue engineering: from decellularization to in vivo recellularization in two sites.

To produce an esophageal scaffold with suitable features and evaluate the result of in vivo cell seeding after its implantation in the omentum and near its original anatomical position in the rat model. The esophagus of twelve rats were resected, cannulated, and decellularized via a peristaltic pump. After confirmation of decellularization and preservation of extracellular matrix, decellularized scaffolds were implanted either in the abdominal cavity (group I, n = 6) or cervical area (group II, n = 6). Histological evaluations were performed after 3 and 6 months of implantation. The results of histological evaluations, scanning electron microscopy, and the tensile test confirmed the maintenance of extracellular matrix and removal of all cellular constituents. At the time of biopsy, no evidence of inflammation was detected and the implanted scaffolds appeared normal. Histopathological evaluations of implanted tissues revealed that undifferentiated cells were seen in scaffolds of all follow-ups in both groups. Epithelial cell seeding was more advanced in biopsies of group II obtained after 6 months of operation and was accompanied by angiogenesis in surrounding adventitia. It seems that the implantation of scaffold near its original place may have an important role in further cell seeding. This method may be surpassing in comparison with traditional implantation techniques for perfecting esophageal transplantation.

Cardiac Extracellular Matrix as a Platform for Heart Organ Bioengineering: Design and Development of Tissue-Engineered Heart.

The field of tissue engineering and regenerative medicine is able to depict the mechanism of cardiac repair and development of cardiac function as well, in order to reveal findings to new therapeutic designs for clinical treatment. The foremost approach of this scientific field is the fabrication of scaffolds, which contain cells that can be used as cardiac grafts in the body, to have the preferred recovery. Cardiac tissue engineering has not been completely organized for routine clinical usages. Hence, engineering innovations hold promise to character research and treatment options in the years to come. Our group has extensive experience with regard to the structure of the heart, which makes us to our decision to continue with the preparation of heart, with the aim of developing a new ECM scaffold. Herein, we aim to assess the state-of-the-art fabrication methods, advances in decellularization and recellularization techniques. We also highlight the major achievements toward the production of a bioengineered heart obtained from decellularization and recellularization techniques.

Selective Trafficking of Light Chain-Conjugated Nanoparticles to the Kidney and Renal Cell Carcinoma.

Specific delivery platforms for drugs to the kidney and diagnostic agents to renal cell carcinoma (RCC) constitute urgent but unfulfilled clinical needs. To address these challenges, we engineered nanocarriers that interact selectively for the first time with proximal tubule epithelial cells (PTECs) in the kidney and with RCC through the interplay between lambda light chains (LCs) attached to PEGylated polylactic-co-glycolic acid (PLGA) nanoparticles and the membrane protein megalin. Systemic administration of these light chain-conjugated nanoparticles (LC-NPs) to mice resulted in their specific retention by megalin-expressing PTECs for seven days. Repetitive dosing of LC-NPs demonstrated no renal toxicity. LC-NPs also localized selectively to megalin-expressing RCC tumors in mice. Moreover, we confirmed that both the primary tumor and lymph node metastases of human RCC express megalin, reinforcing the potential of LC-NPs for clinical use. Thus, LC-NPs can contribute potentially to improving the management of both non-oncologic and oncologic renal disorders.

Preparation and characterization of human size whole heart for organ engineering: scaffold microangiographic imaging.

Definitive treatment for end-stage heart failure is heart transplantation, however, this is associated with several limitations. Aim: We decellularized and assessed ovine hearts through coronary perfusion. To evaluate in situ recellularization, a decellular graft was transplanted hetrotopically into the omental wrap. Results: Cell removal was confirmed by DNA count (11.68 ± 3.42 ng/mg dry weight). Elastic, reticular and collagen fiber were well preserved. There was a slight change in both glycosaminoglycan (7.01 ± 1.36 to 8.37 ± 0.32 µg/mg) and collagen (32.37 ± 2.3 to 36.31 ± 2.1) µg/mg (p > 0.05). Angiography and blood circulation revealed an intact vascular network. Implantation led to proper vascularization. Image J indicated CD31: 23.98 ± 12.3; CD34: 48.67 ± 19.5 and αSMA: 78.33 ± 27.8 inch/cm. Conclusion: Bio-scaffold of human size heart is achievable for future steps employing this technique.

Decellularised whole ovine testis as a potential bio-scaffold for tissue engineering.

The aim of this study was to determine an efficient whole-organ decellularisation protocol of a human-sized testis by perfusion through the testicular arteries. In the first step of this study, we determined the most efficient detergent agent, whereas the second phase delineated the optimal time required for the decellularisation process. Initially sheep testes were decellularised by one of three different detergent agents: sodium dodecyl sulphate (SDS), Triton X-100 and trypsin-ethylenediamine tetraacetic acid (EDTA) solutions, each perfused for 6h. In the second phase, the selected detergent agent was applied for different time periods. A total number of 20 organs were processed during this investigation. The efficacy of the decellularisation process and the preservation of the extracellular matrix components and structure were evaluated by histopathological examinations, 4',6'-diamidino-2-phenylindole (DAPI) staining, DNA quantification, hydroxyproline measurement, magnetic resonance imaging and scanning electron microscopy. Organ perfusion with 1% SDS solution for 6 to 8h demonstrated the most desirable outcomes regarding decellularisation and extracellular matrix preservation. The 3-[4, 5-dimethylthiazol-2-yl]-2, 5-diphenyltetrazolium bromide (MTT) assay was used to determine the toxicity of the scaffold and its potential for further application in tissue-engineering investigations. This investigation introduces an efficient method to produce a three-dimensional testicular bio-scaffold resembling the properties of the native organ that could be employed in tissue-engineering studies.

Whole organ sheep kidney tissue engineering and in vivo transplantation: Effects of perfusion-based decellularization on vascular integrity.

INTRODUCTION: During the past decade, increased efforts have been made to develop alternative management options instead of dialysis and homograft renal transplantation for end-stage renal disease. State-of-the-art methods employ tissue engineering to produce natural acellular scaffolds that could resolve the concern of allograft rejection and obviate the need for immunosuppressive therapy. Complete decellularization of kidney with intact extracellular matrix is crucial for in vivo compatibility and success of transplantation. Herein, we evaluate the efficacy of two different whole organ decellularization protocols, vasculature integrity, and in vivo transplantation of sheep kidneys. MATERIALS AND METHODS: Eight sheep kidneys were decellularized by perfusion-based method utilizing two different protocols (Protocol 1: 1% Triton X-100 and 0.5% SDS vs. Protocol 2: 1% SDS). The samples were evaluated by histopathology in terms of decellularization and extracellular matrix preservation. Computerized tomography angiography was performed to evaluate vasculature. Subsequently, both methods were transplanted in four sheep and monitored for vascular integrity and extravasations in short-term. RESULTS: Scaffolds obtained from both protocols were entirely decellularized. However; the extracellular matrix was better preserved in protocol 1 compared to protocol 2. In addition, the vascular integrity was intact in decellularized scaffolds treated with Triton X-100 plus SDS (protocol 1). After transplantation, the samples treated with protocol 2 showed extravasation of fluid in the interstitial space while the samples treated with protocol 1 showed intact extracellular matrix and vasculature. CONCLUSIONS: This study demonstrated the efficacy of well-preserved acellular scaffold and vasculature network in post renal transplant outcome in a sheep model. These results have potential to pave the road for further investigations in acellular whole organ transplantation.

Decellularized Pancreas Matrix Scaffolds for Tissue Engineering Using Ductal or Arterial Catheterization.

INTRODUCTION: Diabetes is known as a worldwide disease with a great burden on society. Since therapeutic options cover a limited number of target points, new therapeutic strategies in the field of regenerative medicine are considered. Bioscaffolds along with islet cells would provide bioengineered tissue as a substitute for ß-cells. The perfusion-decellularization technique is considered to create such scaffolds since they mimic the compositional, architectural, and biomechanical nature of a native organ. In this study, we investigated 2 decellularization methods preserving tissue microarchitecture. METHODS: Procured pancreas from Sprague-Dawley rats was exposed to different percentages of detergent for 2, 4, and 6 h after cannulation via the common bile duct or aorta. RESULTS: High concentrations of sodium dodecyl sulfate (SDS), i.e., > 0.05%, resulted in tissue disruption or incomplete cell removal depending on the duration of exposure. In both methods, 6-h exposure to 0.05% SDS created a bioscaffold with intact extracellular matrices and proper biomechanical characteristics. Tissue-specific stainings revealed that elastic, reticular, and collagen fiber concentrations were well preserved. Quantitative findings showed that glycosaminoglycan content was slightly different, but hydroxyproline was in the range of native pancreas tissue. Dye infusion through ductal and vascular cannulation proved that the vascular network was intact, and scanning electron microscopy indicated a homogeneous porous structure. CONCLUSIONS: Using the detergent-based method, an effective and time-efficient procedure, a whole pancreas extracellular matrix bioscaffold can be developed that can be used as a 3D structure for pancreas tissue engineering-based studies and regenerative medicine applications.

Heart valve tissue engineering: an overview of heart valve decellularization processes.

Despite recent advances in medicine and surgery, many people still suffer from cardiovascular diseases, which affect their life span and morbidity. Regenerative medicine and tissue engineering are novel approaches based on restoring or replacing injured tissues and organs with scaffolds, cells and growth factors. Scaffolds are acquired from two major sources, synthetic materials and naturally derived scaffolds. Biological scaffolds derived from native tissues and cell-derived matrix offer many advantages. They are more biocompatible with a higher affinity to cells, which facilitate tissue reconstruction. Interestingly, xenogeneic recipients generally tolerate their components. Therefore, heart valve tissue engineering is increasingly benefiting from naturally derived scaffolds. In this review, we investigated the different protocols and methods that have been used for heart valve decellularization.

In vivo regeneration of bladder muscular wall using decellularized colon matrix: an experimental study.

BACKGROUND: Finding a proper scaffold for augmentation is a serious challenge in bladder tissue engineering. We hereby aimed to determine the histological aspects of a decellularized colon graft for bladder augmentation in healthy rats. METHODS: Rat colon tissues were decellularized using perfusion-based method. After partial cystectomy, bladders were grafted with a patch of decellularized colon. Bladder specimens were investigated in 12 rats at 1, 3, and 9 months postoperatively for further histological changes and immunohistochemistry analyses were also performed. RESULTS: One month after implantation, partial seeding of new cells was observed. After 3 months continuity of transitional epithelium of natural bladder on the decellularized grafted colon tissue was confirmed with histological and immunohistochemical examinations. All augmented bladders demonstrated a spherical shape without stone formation, necrosis or graft rejection. The presence of urothelium with similar morphology to the natural urothelium and visible blood vessels were found within 3 months of operation. All immunohistochemical markers (except markers of colonic stem cells) were expressed in biopsies obtained 3 months after surgery demonstrating a progressive vascular and smooth muscle cell infiltration into the graft after implantation. CONCLUSION: This study suggests that decellularized colon may provide a viable material for bladder augmentation in rats to pave the road for future applications of this natural collagen scaffold.

A novel technique for simultaneous whole-body and multi-organ decellularization: umbilical artery catheterization as a perfusion-based method in a sheep foetus model.

The aim of this study was to develop a method to generate multi-organ acellular matrices. Using a foetal sheep model have developed a method of systemic pulsatile perfusion via the umbilical artery which allows for simultaneous multi-organ decellularization. Twenty sheep foetuses were systemically perfused with Triton X-100 and sodium dodecyl sulphate. Following completion of the whole-body decellularization, multiple biopsy samples were taken from different parts of 21 organs to ascertain complete cell component removal in the preserved extracellular matrices. Both the natural and decellularized organs were subjected to several examinations. The samples were obtained from the skin, eye, ear, nose, throat, cardiovascular, respiratory, gastrointestinal, urinary, musculoskeletal, central nervous and peripheral nervous systems. The histological results depicted well-preserved extracellular matrix (ECM) integrity and intact vascular structures, without any evidence of residual cellular materials, in all decellularized bioscaffolds. Scanning electron microscope (SEM) and biochemical properties remained intact, similar to their age-matched native counterparts. Preservation of the collagen structure was evaluated by a hydroxyproline assay. Dense organs such as bone and muscle were also completely decellularized, with a preserved ECM structure. Thus, as shown in this study, several organs and different tissues were decellularized using a perfusion-based method, which has not been previously accomplished. Given the technical challenges that exist for the efficient generation of biological scaffolds, the current results may pave the way for obtaining a variety of decellularized scaffolds from a single donor. In this study, there have been unique responses to the single acellularization protocol in foetuses, which may reflect the homogeneity of tissues and organs in the developing foetal body.

Whole-organ tissue engineering: decellularization and recellularization of three-dimensional matrix liver scaffolds.

To report the results of whole liver decellularization by two different methods. To present the results of grafting rat and sheep decellularized liver matrix (DLM) into the normal rat liver and compare natural cell seeding process in homo/xenograft of DLM. To compare the results of in vitro whole liver recellularization with rats' neonatal green fluorescent protein (GFP)-positive hepatic cells with outcomes of in vivo recellularization process. Whole liver of 8 rats and 4 sheep were resected and cannulated via the hepatic vein and perfused with sodium dodecyl sulfate (SDS) or Triton + SDS. Several examinations were performed to compare the efficacy of these two decellularization procedures. In vivo recellularization of sheep and rat DLMs was performed following transplantation of multiple pieces of both scaffolds in the subhepatic area of four rats. To compare the efficacy of different scaffolds in autologous cell seeding, biopsies of homograft and xenograft were assessed 8 weeks postoperatively. Whole DLMs of 4 rats were also recellularized in vitro by perfusion of rat's fetal GFP-positive hepatic cells with pulsatile bioreactor. Histological evaluation and enzymatic assay were performed for both in vivo and in vitro recellularized samples. The results of this study demonstrated that the triton method was a promising decellularization approach for preserving the three-dimensional structure of liver. In vitro recellularized DLMs were more similar to natural ones compared with in vivo recellularized livers. However, homografts showed better characteristics with more organized structure compared with xenografts. In vitro recellularization of liver scaffolds with autologous cells represents an attractive prospective for regeneration of liver as one of the most compound organs. In vivo cell seeding on the scaffold of the same species may have more satisfactory outcomes when compared with the results of xenotransplantation. This study theoretically may pave the road for in situ liver regeneration probably by implantation of homologous DLM or in vitro recellularized scaffolds into the diseased host liver.

In-vivo trachea regeneration: fabrication of a tissue-engineered trachea in nude mice using the body as a natural bioreactor.

PURPOSE: To investigate the outcomes of implanting rat decellularized trachea scaffold (DTS) between the paravertebral muscles of nude mice using the body as a bioreactor for total graft recellularization. METHODS: The tracheas of four rats were aseptically resected and decellularized. To assess the efficiency of the decellularization procedure, all decellularized scaffolds and native control tissues were evaluated with scanning electron microscopy (SEM), DAPI staining, DNA quantification, biomechanical analyses and hydroxyproline measurement. They were then implanted between the paravertebral muscles of four nude mice. The biopsies were precisely evaluated at 1, 3, 6 and 12 months postoperatively for tracheal cartilage and soft tissue recellularization by staining for TTF1, CD34, S100 and leukocyte common antibody. RESULTS: Hematoxylin and eosin (H&E) staining, SEM and the tensile test confirmed the preservation of the tissue structure and the biophysical and biochemical properties of the DTS. The present study clearly demonstrated that the hydroxyproline content of the DTS was similar to that of the native tissue. On the other hand, in biopsy samples obtained after 12 months, histological evaluation showed superior organization and cell seeding in both the cartilage and connective tissues. CONCLUSION: This study demonstrated the feasibility of using a natural bioreactor for recellularizing DTS; this may have the potential to facilitate homologous transplantation for repairing segmental trachea defects.

Congenital urethral polyps in girls: as a differential diagnosis of interlabial masses.

STUDY OBJECTIVE: To present the clinical appearance, differential diagnosis, long-term follow-up, and the surgical result of single-center experience with female urethral polyps presenting as an interlabial mass, and to report the common causes of interlabial masses in infants. DESIGN: All 12 girls who presented with an interlabial mass and intermittent bleeding have been included in this study; however, the benign urethral polyps are discussed in detail and are the subject of this study. SETTING: All patients were referred to our national referral pediatric urology center with initial impression of vaginal bleeding; however, rhabdomyosarcoma of bladder and urethra (n = 2) or vagina (n = 3) and urethral polyp (n = 7) was the final diagnosis. PARTICIPANTS: The records of 12 girls who presented with external genitalia bleeding were retrospectively reviewed. Among them, 7 had fibroepithelial polyps and underwent initial polypectomy between 2001 and 2011with mean age of 21.5 months (range: 1-90 mo). All girls underwent endoscopic surgical removal of polyps. MAIN OUTCOME MEASURES: No postoperative polyp recurrence was observed following endoscopic polyp resection. RESULTS: The postoperative period was uneventful except in 1 girl who had immediate postoperative urethral bleeding which stopped spontaneously. There was no major complication or polyp recurrence after operation during the long-term follow-up. CONCLUSIONS: The interlabial mass must be considered as a urethral polyp and should be differentiated from the vaginal rhabdomyosarcoma with protrusion of vaginal tumor from the vaginal outlet or other benign lesions. Physical examination in frog legged position or examination under anesthesia with urethrocystoscopy may confirm the final diagnosis.

Effect of three decellularisation protocols on the mechanical behaviour and structural properties of sheep aortic valve conduits.

PURPOSE: To determine the best method for decellularisation of aortic valve conduits (AVCs) that efficiently removes the cells while preserving the extracellular matrix (ECM) by examining the valvular and conduit sections separately. MATERIAL/METHODS: Sheep AVCs were decellularised by using three different protocols: detergent-based (1% SDS+1% SDC), detergent and enzyme-based (Triton+EDTA+RNase and DNase), and enzyme-based (Trypsin+RNase and DNase) methods. The efficacy of the decellularisation methods to completely remove the cells while preserving the ECM was evaluated by histological evaluation, scanning electron microscopy (SEM), hydroxyproline analysis, tensile test, and DAPI staining. RESULTS: The detergent-based method completely removed the cells and left the ECM and collagen content in the valve and conduit sections relatively well preserved. The detergent and enzyme-based protocol did not completely remove the cells, but left the collagen content in both sections well preserved. ECM deterioration was observed in the aortic valves (AVs), but the ultrastructure of the conduits was well preserved, with no media distortion. The enzyme-based protocol removed the cells relatively well; however, mild structural distortion and poor collagen content was observed in the AVs. Incomplete cell removal (better than that observed with the detergent and enzyme-based protocol), poor collagen preservation, and mild structural distortion were observed in conduits treated with the enzyme-based method. CONCLUSIONS: The results suggested that the detergent-based methods are the most effective protocols for cell removal and ECM preservation of AVCs. The AVCs treated with this detergent-based method may be excellent scaffolds for recellularisation.

Congenital urethral polyps in children: report of 18 patients and review of literature.

BACKGROUND/PURPOSE: To evaluate the presentation, diagnosis and management of congenital urethral polyps (CUP) in children and to report the results of the endoscopic resection of polyp with long-term follow-up. METHODS: Between April 1995 to March 2010, 18 children (14 boys, 4 girls) with CUP were treated. The most common presentation was urinary outflow obstruction/retention, hematuria or protruding polyp from the urethra meatus in girls. Six patients presented with vesicoureteral reflux (VUR). All children (except one) underwent a transurethral resection of the CUP. RESULTS: Following the endoscopic resection of the polyps, there was no polyp recurrence, and all patients became symptom-free. The children exhibited no reflux, urinary retention, hematuria or urinary tract infection (UTI) following endoscopic management. Abnormal uroflowmetry patterns returned to normal following the resection of the polyp for one year after the operation. CONCLUSIONS: Urethral polyps must be considered in every child with history of triad of recurrent intermittent urinary retention, hematuria and lower urinary tract symptoms. The cure can be achieved in all cases by an endoscopic approach. This type of tumor is always benign and very rarely recurs, unless the pedicle stalk is not resected. The endoscopic management of reflux is unnecessary in this group of patients due to their natural history of secondary reflux.

Sheep colon acellular matrix: Immunohistologic, biomechanical, scanning electron microscopic evaluation and collagen quantification.

Colon decellularization provides three-dimensional biologic scaffold without any cell elements with preservation of extracellular matrix in order to enable autologous cell seeding for tissue augmentation without any immunological response. This study was performed to investigate the safety and feasibility of sheep colon decellularization as a first step of colon tissue engineering. The process of sheep colon decellularization was done in four stages which included scaffold preparation, histologic examination and microscopic investigations to reveal the remaining cellular deposits, biomechanical evaluation and collagen quantification studies by measurement of hydroxyproline content of normal and decellularized sheep colon. Decellularized colon scaffold revealed complete cell removal under a light microscope while 4',6-diamidino-2-phenylindole, di-hydrochloride (DAPI) staining confirmed no deoxyribonucleic acid (DNA) residues. Decellularized colon displayed preserved ultrastructure, comparable biophysical properties (resistance to unidirectional stretch forces) and higher hydroxyproline content. The results of biomechanical tests proved that the decellularized matrix did not bear any unexpected damages or structural changes which would make it unable to tolerate in vivo forces and stretches. The microscopic images captured after staining the tissue with Picro-sirius red also showed that the collagen in extracellular matrix is well preserved; this was confirmed by scanning electron microscopy. This implies that the scaffold prepared by this method is suitable for tissue augmentation or transplantation.