Tissue engineering of heart valves by recellularization of glutaraldehyde-fixed porcine valves using bone marrow-derived cells

To increase the biocompatibility and durability of glutaraldehyde (GA)-fixed valves, a biological coating with viable endothelial cells (ECs) has been proposed. However, stable EC layers have not been formed successfully on GA-fixed valves due to their inability to repopulate. In this study, to improve cellular adhesion and proliferation, the GA-fixed prostheses were detoxified by treatment with citric acid to remove free aldehyde groups. Canine bone marrow mononuclear cells (MNCs) were differentiated into EC-like cells and myofibroblast-like cells in vitro. Detoxified prostheses were seeded and recellularized with differentiated bone marrow-derived cells (BMCs) for seven days. Untreated GA-fixed prostheses were used as controls. Cell attachment, proliferation, metabolic activity, and viability were investigated and cell-seeded leaflets were histologically analyzed. On detoxified GA-fixed prostheses, BMC seeding resulted in uninhibited cell proliferation after seven days. In contrast, on untreated GA-fixed prostheses, cell attachment was poor and no viable cells were observed. Positive staining for smooth muscle a-actin, CD31, and proliferating cell nuclear antigen was observed on the luminal side of the detoxified valve leaflets, indicating differentiation and proliferation of the seeded BMCs. These results demonstrate that the treatment of GA-fixed valves with citric acid established a surface more suitable for cellular attachment and proliferation. Engineering heart valves by seeding detoxified GA-fixed biological valve prostheses with BMCs may increase biocompatibility and durability of the prostheses. This method could be utilized as a new approach for the restoration of heart valve structure and function in the treatment of end-stage heart valve disease.

In Vivo Experiment of Tissue-Engineered Artificial Vessel / 대한흉부외과학회지

BACKGROUND: The number of patients with coronary artery disease and peripheral vascular disease are increasing, and the need of small diameter vessel is also increasing. We developed small diameter artificial vessel and experimented in vivo. MATERIAL AND METHOD: We got allogenic valve from mongrel dogs, and removed all cells from the allogenic valve. Then, we seeded autologous bone marrow cells onto the decellularized scaffold. After implantation of artificial vessel into the canine carotid artery, we performed angiography regularly. In case of vessel occlusion or at 8 weeks after operation, we euthanized dogs, and retrieved the implanted artificial vessels. RESULT: Control vessels were all occluded except one (which developed aneurysmal dilatation). But autologous cell seeded vascular graft were patent by 4 weeks in one, by 6 in one and by 8 weeks in two. Histologic examination of patent vessel revealed similar structure to native artery. CONCLUSION: Tissue-engineered vascular graft manufactured with decellularized allogenic matrix and autologous bone marrow cells showed that tissue engineered graft had similar structure to native artery.

Regeneration of Renal Tissue Using Cell Transplantation in a Renal Failure Rat Model / 대한이식학회지

PURPOSE: Dialysis and renal transplantation, the current therapies for end-stage renal disease (ESRD), have limitations including severe complications, donor organ shortage, and graft failure. The present study investigated the possibility of using a tissue engineering technique for renal tissue reconstruction as a new method to replace the current treatments for ESRD. We restored renal structure in vivo by transplanting isolated renal cells in renal failure animal models. METHODS: Renal failure was surgically induced by 5/6 nephrectomy using silk tie method in Sprague-Dawley (SD) rats. Renal failure was confirmed by measuring the concentrations of blood urea nitrogen (BUN) and creatinine from blood samples. Renal cells were freshly isolated from newborn SD rat kidneys and implanted into renal failure- induced kidneys with fibrin gel matrix for 4 weeks. Retrieved specimens were examined by histological analyses. RESULTS: Renal failure-induced rats exhibited higher concentrations of BUN and creatinine compared to those of normal rats. Four weeks after cell transplantation, histological examination showed the reconstitution of vascular tufts of glomerular structures. CONCLUSION: Renal failure rat models were successfully created by 5/6 nephrectomy. This study showed a possibility of restoring the renal structures by transplanting renal cells with fibrin gel matrix in renal failure rat models. Further studies, such as investigation on renal function recovery by cell transplantation, are necessary to determine the clinical utility of this method for partial or full replacement of renal structure and function in the treatment of ESRD.

Development of a Tissue-Engineered Vascular Graft Using Autologous Bone Marrow-Derived Cells and Biodegradable Polymer Scaffold

PURPOSE: The objective of this study is to develop a tissue-engineered vascular graft using autologous bone marrow-derived cells (BMCs) and biodegradable polymer scaffold. METHOD: Autologous canine BMCs were isolated from bone marrow aspirate and cultured. A tubular scaffold was fabricated by immersing polyglycolic acid (PGA) sheet in poly (glycolide-co-caprolactone) (PGCL) solution and wrapping it around a cylindrical mold. The expanded BMCs were seeded onto the PGA/PGCL tubular scaffold (internal diameter: 7 mm, length: 35 mm) and further cultured in vitro for 1 week. The graft was anastomosed to the abdominal artery in a canine model. One week after implantation, the retrieved graft was investigated by histological and immunohistochemical analyses. RESULT: Cultured BMCs differentiated into endothelial-like and smooth muscle-like cells. The PGA tubular scaffold reinforced with PGCL was successfully implanted in an animal model without graft rupture. The vascular graft engineered with BMCs was occluded at 1 week after implantation due to thrombus formation. Histological and immunohistochemical analyses of the retrieved graft revealed that extracellular matrix proteins such as smooth muscle alpha-actin, smooth muscle myosin heavy chain and collagen were produced partially in the graft media. CoNCLUSION: The tissue-engineered vascular graft developed in this study led to graft failure due to early occlusion. Nevertheless, it is confirmed that the PGA/PGCL scaffold has microstructures appropriate for cell proliferation and good mechanical properties. This result suggests the possibile application of this scaffold as a material for engineering of diseased vascular tissues.

Implantation of Renal Segments on Biodegradable Polymer Scaffolds / 대한이식학회지

PURPOSE: Dialysis and renal transplantation, the current therapies for end-stage renal disease (ESRD), have limitations including severe complications, donor organ shortage, and allograft failure. The present study investigated the possibility of using a tissue engineering technique for renal reconstruction as a new method to replace the current suboptimal treatments for ESRD. We reconstituted renal units in vivo by transplanting isolated renal segments on three-dimensional, biodegradable polymer scaffolds. METHODS: Renal segments were freshly isolated from Sprague-Dawley rat kidneys and seeded onto porous mesh matrices fabricated from polyglycolic acid, a biodegradable synthetic polymer. The renal segment-seeded scaffolds were implanted into subcutaneous spaces of athymic mice for two and four weeks. Retrieved specimens were examined by histological analyses. RESULTS: The tubular structures with hollow centers and vascular tufts of glomerulus-like structures were identified by histological analyses of the 2 and 4 week specimens. In contrast, no renal-like structures were observed from unseeded polymer implants (negative controls). CONCLUSION: These results suggest a possibility of reconstituting the renal structures by transplanting renal segments on polymer scaffolds and could be applid for partial or full replacement of kidney function in the treatment of ESRD.