Vascular patches tissue-engineered with autologous bone marrow-derived cells and decellularized tissue matrices

Abstract

Synthetic polymer vascular patches used in cardiovascular surgery have shortcomings such as thrombosis, intimal hyperplasia, calcification, infection, and no growth potential. Tissue-engineered vascular patches using autologous vascular cells may solve these problems. In this study, we developed a tissue-engineered vascular patch using autologous bone marrow-derived cells (BMCs) and decellularized tissue matrices. Vascular smooth muscle cells and endothelial cells were differentiated from bone marrow mononuclear cells in vitro. Tissue-engineered vascular patches were fabricated by seeding these cells onto decellularized canine inferior vena cava matrices and implanted into the inferior vena cava of dogs. Three weeks after implantation, the tissue-engineered vascular patches were patent with no sign of thrombus formation. Histological, immunohistochemical, and electron microscopic analyses of the vascular patches retrieved 3 weeks after implantation revealed regeneration of endothelium and smooth muscle and the presence of collagen and elastin. BMCs labeled with a fluorescent dye prior to implantation were detected in the retrieved vascular patches, indicating that the BMCs survived after implantation and contributed to the vascular tissue regeneration. This study demonstrates that vascular patches can be tissue-engineered with autologous BMCs and decellularized tissue matrices.

Introduction

Vascular patches made of synthetic polymers have been clinically used to reconstruct vascular conduits [1], [2], [3]. The patch materials include expanded polytetrafluoroethylene and polyethylene terephthalate. These vascular patches have shown good mechanical properties and in vivo durability. However, these patches have potential shortcomings of thrombus formation and calcium deposition due to blood and tissue incompatibility [4]. Moreover, these patches are susceptible to infection for their life span and need the ability to grow. In surgery for pediatric patients with congenital cardiovascular diseases, an antithrombogenic living patch that would allow for growth is required. Previous studies to develop antithrombogenic, biocompatible, and durable vascular patches have focused mainly on surface modification through grafting of antithrombogenic materials, such as polyethylene oxide [5] and heparin [6]. However, these approaches still have problems of thrombus formation and no capability of growing in vivo.

Tissue-engineered vascular patches could overcome the problems of synthetic polymer vascular patches. In the tissue-engineering approach, autologous vascular cells are seeded onto biodegradable polymer scaffold and regenerate vascular tissues with endothelium in vivo. The polymer scaffolds degrade completely in vivo, resulting in natural tissue formation without foreign materials. Thus, these tissue-engineered vascular patches are antithrombogenic, biocompatible, durable, and capable of growing and repairing. These patches might be appropriate for growing child patients with congenital cardiovascular defects. Recently, a vascular patch tissue-engineered with autologous vascular cells and biodegradable synthetic polymer (poly 4-hydroxybutyric acid) has been reported [7]. In this method, however, autologous vascular cells were isolated from vascular tissue biopsies, which requires additional invasive surgical procedures from patients and may produce morbidity at the biopsy sites. Bone marrow-derived cells (BMCs) could be an alternative cell source for tissue engineering of vascular patches. Recently, it has been reported that BMCs can differentiate into endothelial cells (ECs) and smooth muscle cells (SMCs) in vivo [8], [9], [10], [11], [12] or in vitro [13], [14], [15], [16]. The use of BMCs as the cell source is generally considered as less invasive than harvest of vascular cells from autologous blood vessels. In addition, BMCs could be utilized as a cell source when patients do not have blood vessels suitable for harvest due to preexisting vascular disease or vessel use in previous procedures.

In this study, we developed tissue-engineered vascular patches using autologous BMCs and decellularized tissue matrices. BMCs were induced to differentiate into ECs and SMCs. The vascular cells were seeded onto decellularized tissue matrices and implanted in the inferior vena cava (IVC) of dogs. Three weeks after implantation, vascular tissue regeneration in the implanted patches was investigated by histological, immunohistochemical, and electron microscopic analyses.