The high number of vascular diseases demand for vascular grafts in various clinical application. Nonetheless, a big hurdle for the use of autologous tissue-engineered vascular grafts (TEVG) is represented by the usually long manufacturing time.Therefore, we here present a biohybrid vascular graft and a bioreactor that can provide distinct conditions such as flow, pressure, and temperature allowing the in vitro bioreactor conditioning of TEVG within four days. For in situ monitoring, we established reliable non-invasive imaging methods to monitor the degradation of the synthetic structural elements, ECM production, and signs of inflammation by molecular magnetic resonance imaging and ultrasound.
A polyvinylidene fluoride (PVDF) tubular textile mesh was used as a permanent scaffold and coated with biodegradable superparamagnetic iron oxide nanoparticles (SPIONs) labeled PLGA fibers. TEVGs were prepared by a molding process which consists of the scaffold, fibrin gel, and arterial smooth muscle cells (SMCs). After molding an endothelialization process and bioreactor conditioning mimicking physiological blood flow and pressure values followed. Burst strength and suture retention strength of TEVG were measured and compared before and after bioreactor conditioning. The ECM production was studied in TEVG after 14 days of maturation using elastin- and collagen type I-targeted MR molecular gadolinium-based probes and immunohistology. The αvβ3 integrin expression as a marker of inflamed endothelium was assessed by molecular targeted US using RGD-poly(butyl cyanoacrylate) microbubbles and compared to RAD-control microbubbles1.
After four days of conditioning in a close loop bioreactor, 617±85 mm Hg of burst pressure and 2.24±0.3 N of suture retention strength were achieved. The bioreactor provided a suitable environment to the TEVG in which the cells could proliferate and produce extracellular matrix. The immunohistological findings proved the development of smooth muscle actin, Collagen I, Collagen IV, and continuous endothelial linings within the TEVG’s lumen. The presence of collagen was further identified by MRIusing a targeted contrast agent. The expression of integrin in TEVG was identified by selective binding of RGD microbubbles only after mimicking an inflammatory state..
We introduce a biohybrid TEVG with a coated scaffold for longitudinal monitoring by non-invasive molecular imaging methods. After 4 days of bioreactor cultivation, this graft provides sufficient stability for implantation and the possibility of longitudinal monitoring in situ.
- Rama, E. et al., Adv. Sci. in publication (2022).