Increasing the Volume of Vascularized Tissue Formation in Engineered Constructs: An Experimental Study in Rats

Abstract

The authors have previously described a model of in vivo tissue generation based on an implanted, microsurgically created vessel loop in a plastic chamber (volume, 0.45 ml) containing a poly(DL-lactic-co-glycolic acid) (PLGA) scaffold. Tissue grew spontaneously in association with an intense angiogenic sprouting from the loop and almost filled the chamber, resulting in a mean amount of tissue in chambers of 0.23 g with no added matrix scaffold and 0.33 g of tissue in PLGA-filled chambers after 4 weeks of incubation. The aim of the present study was to investigate whether a greater volume of tissue could be generated when the same-size vessel loop was inserted into a larger (1.9 ml) chamber. In four groups of five rats, an arteriovenous shunt sandwiched between two disks of PLGA, used as a scaffold for structural support, was placed inside a large polycarbonate growth chamber. Tissue and PLGA weight and volume, as well as histological characteristics of the newly formed tissue, were assessed at 2, 4, 6, and 8 weeks. Tissue weight and volume showed a strong linear correlation. Tissue weight increased progressively from 0.13 +/- 0.04 g at 2 weeks to 0.57 +/- 0.06 g at 6 weeks (p < 0.0005). PLGA weight decreased progressively from 0.89 +/- 0.07 g at 2 weeks to 0.20 +/- 0.09 g at 8 weeks (p < 0.0005). Histological examination of the specimens confirmed increased tissue growth and maturation over time. It is concluded that larger quantities of tissue can be grown over a longer period of time by using larger-size growth chambers.

Fibrin Gel-Immobilized VEGF and bFGF Efficiently Stimulate Angiogenesis in the AV Loop Model

“…In this study we were able to demonstrate the feasibility of using VEGF and bFGF immobilized in a fibrin-based drug delivery system in the AVL model in the rat. This model was first described by Erol and Spira 1979 (21) and enhanced by Morrison et al, who inserted the AVL into polycarbonate isolation chambers (6,22). Lokmic et al showed that the AVL without any matrix is able to produce a highly vascularized construct (29).…”

“…In (6,22). This concept allows vascularization and subsequent transfer of biomaterials independent of local conditions at the recipient site.…”

Tissue engineering of bone: the reconstructive surgeon's point of view

“…Morrison and co-workers augmented this model and implanted the AV-loop into polycarbonate isolation chambers. Furthermore they induced vascularization in polymer matrices and managed to generate large volumes of axially vascularized tissue [133][134][135]. In the era of tissue engineering this concept met with great interest.…”

Polycaprolactone nanofibrous mesh reduces foreign body reaction and induces adipose flap expansion in tissue engineering chamber

“…9 In 2011, the initial 5 mL of adipose flap successfully expanded to 56.5 mL using large volume chamber (78.5 mL) in pig model, providing clinically relevant volumes of tissue for soft tissue construction. 10 Despite the advancement of tissue engineering chamber technique in recent years, [11][12][13] the final maximum volume of the flap was still unable to fill the chamber thoroughly for unknown reasons.…”