Mesenchymal stem cell-based tissue engineering of small-diameter blood vessels.

The aim of the study was to construct small-diameter vascular grafts using canine mesenchymal stem cells (cMSCs) and a pulsatile flow bioreactor. cMSCs were isolated from canine bone marrow and expanded ex vivo. cMSCs were then seeded onto the luminal surface of decellularized arterial matrices, which were further cultured in a pulsatile flow bioreactor for four days. Immunohistochemical staining and scanning electron microscopy was performed to characterize the tissue-engineered blood vessels. cMSCs were successfully seeded onto the luminal surface of porcine decellularized matrices. After four-day culture in the pulsatile flow bioreactor, the cells were highly elongated and oriented to the flow direction. Immunohistochemistry demonstrated that the cells cultured under pulsatile flow expressed Von Willebrand factor, an endothelial cell marker. In conclusion, cMSCs seeded onto decellularized arterial matrices could differentiate into endothelial lineage after culturing in a pulsatile flow bioreactor, which provides a novel approach for tissue engineering of small-diameter blood vessels.

Preliminary investigation of seeding mesenchymal stem cells on biodegradable scaffolds for vascular tissue engineering in vitro.

We used epsilon-caprolactone/L-lactide (PCLA) as a biodegradable scaffold and bone marrow (BM) mesenchymal stem cells (MSCs) as seeding cells for vascular tissue engineering: we expected MSCs to grow in the scaffolds in a bioreactor. The MSCs we used were from the BM of dogs, and vascular scaffolds were carried out on the electrospinning process of PCLA copolymers. MSCs expressed CD44 and CD105 but did not express CD34 or CD14 at an identical time point. Scaffolds were nontoxic to cells and were favorable for the growth and migration of MSCs. After culture in a bioreactor with mechanical stimulation, cells completely covered the surfaces of PCLA scaffolds and penetrated or infiltrated into the inside of the scaffold structure.

Electrospinning of synthesized triblock copolymers of epsilon-caprolactone and L-lactide for the application of vascular tissue engineering.

Biodegradable triblock copolymers of epsilon-caprolactone and L-lactide with varying compositions and molecular weights have been synthesized. They were then used to fabricate compliant small-diameter tissue engineered vascular scaffolds by using an electrospinning technique. The in vitro and in vivo degradation of the ultrafine fabrics was monitored to be faster than their counterpart cast films. A favorable interaction between the scaffolds and the mouse fibroblast L929 cells was demonstrated via MTT assay. A confluent, adherent monolayer of canine mesenchymal stem cells was observed in the tubular scaffold lumen after culture in a bioreactor for 3 days. The scaffold mechanical strength was strong enough to be transplanted into the canine carotid artery.

Response of mesenchymal stem cells to shear stress in tissue-engineered vascular grafts.

AIM: Recent studies have demonstrated that mesenchymal stem cells (MSCs) can differentiate into endothelial cells. The effect of shear stress on MSC differentiation is incompletely understood, and most studies have been based on two-dimensional systems. We used a model of tissue-engineered vascular grafts (TEVGs) to investigate the effects of shear stress on MSC differentiation. METHODS: MSCs were isolated from canine bone marrow. The TEVG was constructed by seeding MSCs onto poly-epsilon-caprolactone and lactic acid (PCLA) scaffolds and subjecting them to shear stress provided by a pulsatile bioreactor for four days (two days at 1 dyne/cm(2) to 15 dyne/cm(2) and two days at 15 dyne/cm(2)). RESULTS: Shear stress significantly increased the expression of endothelial cell markers, such as platelet-endothelial cell adhesion molecule-1 (PECAM-1), VE-cadherin, and CD34, at both the mRNA and protein levels as compared with static control cells. Protein levels of alpha-smooth muscle actin (alpha-SMA) and calponin were substantially reduced in shear stress-cultured cells. There was no significant change in the expression of alpha-SMA, smooth muscle myosin heavy chain (SMMHC) or calponin at the mRNA level. CONCLUSION: Shear stress upregulated the expression of endothelial cell-related markers and downregulated smooth muscle-related markers in canine MSCs. This study may serve as a basis for further investigation of the effects of shear stress on MSC differentiation in TEVGs.

[Tissue engineering of vascular graft from decellularized arterial matrix and mesenchymal stem cells.].

OBJECTIVE: To investigate the method of constructing small-diameter vascular grafts from xenogenic decellularized arterial matrices and mesenchymal stem cells (MSCs). METHODS: Porcine iliac arteries were decellularized by detergent and trypsin treatment. Histology, mechanical strength and porosity experiments were performed to evaluate the properties of decellularized matrices. MSCs were isolated from bone marrow of dogs and expanded ex vivo. Decellularized matrices were seeded with MSCs and further cultured in a pulsatile bioreactor. Morphological features of the tissue engineered grafts were assayed by HE staining and scanning electron microscopy. RESULTS: After cell extraction, absence of cellular components and preservation of extracellular matrix were verified. Mechanical strength of decellularized matrices was slightly reduced compared with native arteries. Porosity of decellularized matrices was 94.9%. Decellularized matrices were successfully seeded with MSCs, which grew to a near-confluent monolayer under flow conditions and MSCs were highly elongated and oriented to the flow direction. CONCLUSION: Small-diameter vascular grafts can be constructed by seeding MSCs onto xenogenic decellularized arterial matrices and culturing in a pulsatile bioreactor.