Tissue-engineered Pericardium Research Articles

Aortic valve construction using pericardial tissue: short-term single-centre outcomes†

Aortic valve construction using pericardial tissue has been known since the late 1960s. The procedure was re-introduced by Ozaki in 2010 and is currently used to treat specific aortic valve diseases. The exact sizing of the neo-cusps and the insertion of the commissures remain the keys to success when performing this procedure. We evaluated our experience using modified custom-made templates. In this prospective single-centre study, we evaluated 52 consecutive patients who underwent aortic valve construction between September 2015 and March 2017 using either autologous (16 patients, 30.8%) or tissue-engineered pericardium (36 patients, 69.2%). Most patients (34, 65.4%) presented with aortic stenosis or endocarditis (5, 9.6%). Twenty patients had bicuspid and 5 had unicuspid valves. A modified sizing technique with specially designed templates was used. The primary end point was early death; the secondary end points were major adverse cardiac and cerebrovascular events, freedom from reoperation and overall mortality rate. Echocardiographic follow-up was performed intraoperatively and at 12-month intervals. The mean age was 60 ± 14 years; 63.5% were men; and 34 (65.4%) patients had combined procedures. The mean cross-clamp time was 99 ± 17 min. Early outcomes included 1 stroke, 2 patients needing short-term dialysis and 1 death. During follow-up (mean 11.2 ± 4.8 months), trace aortic regurgitation was observed in 4 patients; the mean pressure gradient was 6.8 ± 2.9 mmHg. Three patients died later (of non-cardiac reasons), and 5 patients needed reoperation due to endocarditis. Aortic valve construction using pericardial tissue could be an alternative in middle-age patients presenting with aortic valve disease in whom valve repair was not possible. The newly designed templates allow exact sizing of the neo-cusps and optimal commissure implantation; however, long-term follow-up in a larger cohort is warranted to assess the durability of the neo-valves.

Application of Different Scaffolds for Bladder Wall Regeneration: The Bladder as a Natural Bioreactor

We investigated the potential of different scaffolds for in vivo construction of bladder muscular and urothelial wall. Bladder wall was used as a bioreactor to create a model of the natural environment for cellular interactions, growth, and differentiation. Forty rabbits were divided into 10 groups. Different scaffolds were implanted between bladder mucosa and seromuscular layer. Scaffolds used in each group were one layer or a three-layered combination of tissue-engineered pericardium (TEP), biofilm, and polyglycolic acid (PGA). In all groups, a biopsy of full thickness of bladder was dissected. Muscular and urothelial layers were separated and minced into small fragments. Fragments were seeded above the urothelial layer and urothelial fragments were placed on the scaffold under the seromuscular layer. One group served as control and no scaffold was inserted between the separated bladder layers. After 2 and 6 weeks, biopsies were performed for histologic examinations (trichrome, smooth muscle α-actin, and pancytokeratin AE1/AE3, CD34, CD31). Histopathological examinations showed granulomatous reaction and severe inflammation in biofilm-containing groups. Samples with TEP alone and with PGA-coated TEP as scaffolds revealed more organized bladder wall in two different layers with mature urothelial and smooth muscle cells. The number of CD34+ cells and CD31+ microvessels increased continuously during 6 weeks. Our results demonstrated the effective role of PGA-coated TEP as a potential scaffold for muscular and urothelial fragment seeding in bladder wall acting as a natural bioreactor. Biodegradable scaffolds could be helpful in association with acellular matrices to optimize the cell attachment and in vivo bladder wall construction.

In-vivo autologous bladder muscular wall regeneration: Application of tissue-engineered pericardium in a model of bladder as a bioreactor

Purpose Tissue-engineered pericardium (TEP) is a collagen-rich matrix that has previously been shown to promote in vivo and in vitro tissue regeneration. We evaluated the potential of TEP as a source for the in-vivo creation of bladder muscular wall grafts. We used bladder wall as a bioreactor to create a natural environment for cellular growth and differentiation. Materials and methods Sixteen rabbits were divided into four groups. A control group underwent classical bladder autoaugmentation. Other groups underwent insertion of TEP between bladder mucosa and muscular layer: group 2 with insertion of TEP, group 3 with TEP over autologous bladder muscular wall fragments, and group 4 with autologous bladder smooth muscle cells (SMCs) seeded on TEP. After 4 and 8 weeks, grafts were biopsied for histopathological evaluations. Results Frames from groups 3 and 4 demonstrated more organized muscular wall generation with a significantly higher number of CD34 + endothelial progenitor cells and CD31 + microvessels, and maintenance of α-smooth muscle actin expression through immunohistochemistry. Group 4 showed significant enhancement of SMC penetration to TEP. Although the fragment-seeded group required a simpler procedure, the cell-seeded group showed superior organization of the muscular layer on histopathology. We found a semi-organized muscular layer and new vessels in the margins of TEP in group 3, while there was a homogeneous pattern of SMCs and new vessels in both the margins and center of TEP in group 4. Conclusions This preliminary work has important functional and clinical implications, as it indicates that use of the autologous SMC seeding method may enhance the properties of TEP in terms of bladder wall regeneration.

Tissue-Engineered Pericardium as a Potential Natural Scaffold for Bladder Muscular Wall Construction

Purpose To investigate the potential of tissue-engineered pericardial (TEP) matrixes to form effective sources for in-vivo creation of urinary bladder wall grafts. Material and Methods Sixteen rabbits were divided into 4 groups. The control Group underwent classical autoaugmentation (Group 1). Other groups underwent insertion of 2x1cm2 frame acellular pericardium as a natural tissue expander between bladder mucosa and seromuscular layer. Group 2 underwent insertion of acellular pericardium. In group 3, inserted scaffold was implanted with autologous tissue fragments; biopsy of 10x5mm2 smooth muscle cell (SMC) layer of bladder was dissected and minced into 20 fragments. The fragments were coated on bladder mucosal layer. In group 4 the SMCs were isolated and cultured from dissected SMC layer and seeded on acellular pericardium. After 6 weeks, the in-vivo constructed muscular layer was grafted to remaining bladder host muscular layer. Before grafting and at 30d intervals after grafting, bladder biopsies were obtained for determination of CD31/34, SMC α-actin, and cytokeratin AE1/AE3 following cystometric evaluations. Results The frames containing fragment-seeded and cell-seeded tissue expanders, demonstrated more organized muscular wall generation with mature muscular layers, while number of CD34+ endothelial progenitor cells and CD31+ microvessels were significantly higher(P Conclusions The results demonstrate the bladder wall acted as an in-situ bioreactor; preserved autologous bladder tissue culture with seeded fragments and cells on a tissue expander provided a histologically organized muscular wall. Application of decellularized pericardium was an effective method for in-vivo constructed grafts in augmentation cystoplasty.

In-Vivo Autologus Bladder Wall Generation; Application of Different Scaffolds for Bladder Autoaugmentation in a Model of Bladder as a Bioreactor

Purpose To investigate the potential of different scaffolds in bladder wall construction, using bladder as a bioreactor. Material and Methods Forty rabbits were divided into 10 groups. The control group underwent classical autoaugmentation (G1). In all other groups, different scaffolds were implanted between bladder mucosa and seromuscular layer. A biopsy of 10x5 mm2 full thickness of bladder was dissected. The smooth muscle cell (SMC) and urothelial cell (UC) layers were separated and minced into 20 fragments. The SMC fragments were seeded on mucosal layer and UC fragments were placed on 2x1cm2 framed scaffold under seromuscular layer.The scaffolds used in each groups were as follow: G2:acellular pericardium, G3:biofilm, G4:Polyglycolic Acid (PGA) as a biodegradable scaffold, G5:biofilm-coated acellular pericardium, G6:PGA-coated pericardium, G7:Pericardium-coated Biofilm, G8:PGA-coated Biofilm, G9:Pericarduim-coated PGA, and G10:Biofilm-coated PGA. After 2 and 6 weeks, biopsies were performed for histologic examinations and then the recombinant bladder tissue layers were grafted to the remaining host bladder. Biopsies at 1month intervals were obtained for determination of CD31/34, SMC α-actin, and cytokeratin AE1/AE3, following cystometry. Results Histopathological examinations revealed granulation in G3, 5, 7, 8, and 10.Bladder wall frames in G2 and 6 demonstrated organized bladder wall generation in two different expanded layers with mature UCs and SMCs and showed a significant bladder capacity increment as compared with other groups(P Conclusions Our results demonstrated effective role of tissue-engineered pericardium as a potential scaffold for SMC and UC seeding in bladder wall acting as a natural bioreactor. The biodegradable scaffolds could be also helpful in association with acellular matrixes in improvement of cell attachment and optimizing the in-vivo bladder wall construction for bladder auto augmentation.

Development and Characterization of an Acellular Human Pericardial Matrix for Tissue Engineering

This study aimed to produce an acellular human tissue scaffold with a view to recellularization with autologous cells to produce a tissue-engineered pericardium that can be used as a patch for cardiovascular repair. Human pericardia from cadaveric donors were treated sequentially with hypotonic buffer, SDS in hypotonic buffer, and a nuclease solution. Histological analysis of decellularized matrices showed that the human pericardial tissue retained its histioarchitecture and major structural proteins. There were no whole cells or cell fragments. There were no significant differences in the hydroxyproline (normal and denatured collagen) and glycosaminoglycan content of the tissue before and after decellularization (p > 0.05). There were no significant changes in the ultimate tensile strength after decellularization (p > 0.05). However, there was an increased extensibility when the tissue strips were cut parallel to the visualized collagen bundles (p = 0.005). No indication of contact or extract cytotoxicity was found when using human dermal fibroblasts and A549 cells. In summary, successful decellularization of the human pericardium was achieved producing a biocompatible matrix that retained the major structural components and strength of the native tissue.