(554d) Tissue-Engineered Perfusable Small Diameter Blood Vessels for Vascular Applications

Cardiovascular disease is one of the most leading causes of mortality in the USA. The limited availability of implantable blood vessels with appropriate physical and biological properties has led to the fabrication of prosthetic vascular conduits. During the last decades various approaches and biomaterials have been applied to solve the problems associated with small diameter blood vessels, particularly the biomechanical mismatch with the host vessel. Quantification of the mechanical properties of native blood vessels including stiffness, elongation, and ultimate strength are required for designing biomimetic synthetic blood vessels. In this study, we engineered highly elastic blood vessel made of gelatin methacryloyl (GelMA) and poly(e-caprolactone) (PCL) by using electrospinning technique¹ combined with a mandrel with a diameter of 2 mm. The engineered tube was then endothelialized in vitro by using human umbilical vein endothelial cells (HUVECs) and perfused by culture media to form a functional blood vessel.

Materials and Methods:

The 3D fibrous composite scaffolds were engineered by dissolving various concentrations of GelMA in the range of 5 to 15 %(w/v) and PCL ranging from 0 to 5 %(w/v) in hexafluoro-2-propanol (HFIP) and electrospinning of resulting solutions. The engineered fibrous composites were then photocrosslinked by using UV light at the intensity of 6.9 mW/cm² for 10 min to form stable GelMA/PCL fibrous scaffolds. We then characterized the mechanical properties of the fibrous scaffolds and elastic tubes by using an Instron 5542 mechanical tester. The mechanical properties of the engineered fibrous scaffolds were optimized by using different ratios of GelMA/PCL and compared with that of native small diameter porcine blood vessels. Both native blood vessels and GelMA/PCL fibrous scaffolds were stretched to failure in the longitudinal direction. Also, scanning electron microscopy (SEM) performed to characterize the fibers diameter and porosity of the engineered materials. For the in vitro study, we characterized the viability and proliferation of HUVECs inside the engineered vessels using Live/Dead and Actin/DAPI assays², respectively.

Results:

We found that the stiffness and elongation of the GelMA/PCL composites significantly increased as compared to pure GelMA scaffolds. For instance, at 10%(w/v) GelMA, by increasing the concentration of PCL from 0 to 5 %(w/v), the stiffness of the scaffolds increased from 1.2 to 6.5 MPa; and the elongation increased from 10 to 220 %. The porosity, degradability, and swellability of the engineered electrospun fibrous scaffolds could be also tuned by altering the ratio of GelMA/PCL ratio. Based on our results, of the 6 various compositions, 10%GelMA/5%PCL composite provided a well-balance of mechanical property, swelling capability, and degradation rate which are suitable for blood vessel formation. The engineering GelMA/PCL scaffolds supported the adhesion, growth and proliferation of HUVECs on the scaffolds, leading to the formation of biologically relevant endothelial layer on both side of the scaffolds. Furthermore, we utilized perfusion system using a pulsatile pump to culture HUVECS on the best composite tube and showed that cells could spread and proliferate on both the surface and inside the tubes.

Conclusion:

Our results revealed that the engineered tubes have the same mechanical property of that native vessel. The engineered GelMA/PCL tube has potential to be used as synthetic blood vessel for cardiovascular tissue engineering applications.

References:

[1] Zhao, Xin, Xiaoming Sun, Lara Yildirimer, Qi Lang, Zhi Yuan William Lin, Reila Zheng, Yuguang Zhang, Wenguo Cui, Nasim Annabi, and Ali Khademhosseini. "Cell infiltrative hydrogel fibrous scaffolds for accelerated wound healing." Acta biomaterialia, 2017; 49; 66-77.

[2] Annabi N, Mithieux SM, Zorlutuna P, Camci-Unal G, Weiss AS, Khademhosseini A. “Engineered cell-laden human protein-based elastomer”. Biomaterials. 2013;34(22):5496-505.

Acknowledgement: This work is supported by Northeastern University and the American Heart Association (AHA, 16SDG31280010).