The Influence of Extracellular Matrix on the Generation of Vascularized, Engineered, Transplantable Tissue

Abstract

In a recently described model for tissue engineering, an arteriovenous loop comprising the femoral artery and vein with interposed vein graft is fabricated in the groin of an adult male rat, placed inside a polycarbonate chamber, and incubated subcutaneously. New vascularized granulation tissue will generate on this loop for up to 12 weeks. In the study described in this paper three different extracellular matrices were investigated for their ability to accelerate the amount of tissue generated compared with a no‐matrix control. Poly‐d,l‐lactic‐co‐glycolic acid (PLGA) produced the maximal weight of new tissue and vascularization and this peaked at two weeks, but regressed by four weeks. Matrigel was next best. It peaked at four weeks but by eight weeks it also had regressed. Fibrin (20 and 80 mg/ml), by contrast, did not integrate with the generating vascularized tissue and produced less weight and volume of tissue than controls without matrix. The limiting factors to growth appear to be the chamber size and the capacity of the neotissue to integrate with the matrix. Once the sides of the chamber are reached or tissue fails to integrate, encapsulation and regression follow. The intrinsic position of the blood supply within the neotissue has many advantages for tissue and organ engineering, such as ability to seed the construct with stem cells and microsurgically transfer new tissue to another site within the individual. In conclusion, this study has found that PLGA and Matrigel are the best matrices for the rapid growth of new vascularized tissue suitable for replantation or transplantation.

Zymosan-induced inflammation stimulates neo-adipogenesis

“…To date, studies that report on the longterm stability of in vivo adipose constructs have been disappointing with many identifying tissue regression at later time points. 27,57,58 Macrophage foreign body reactions have been implicated in the late loss of maturing tissue constructs. 59 It is significant that here macrophage recruitment did not appear to result in tissue loss.…”

“…The volumes of patent tissue constructs were determined by volume displacement in normal saline at room temperature. 27 Constructs were fixed in 4% paraformaldehyde, dehydrated through a graded alcohol series and paraffin embedded. Each construct was serially sectioned along its longitudinal axis to completion.…”

Cell Proliferation and Oxygen Diffusion in a Vascularising Scaffold

“…An in vivo model has recently been developed for this purpose (Cassell et al, 2001). An arteriovenous (A-V) loop from a rat or mouse is placed on a scaffold base and then a dome-shaped scaffold placed on top.…”

Neural ECM mimetics

“…As a biodegradable implant, Matrigel ™ resembles the complex extracellular environment found in many healthy tissues (Kleinman and Martin, 2005) and is widely used as a substrate for cell culture, which forms a nonporous hydrogel at physiological temperature. It has been described as a suitable matrix for tissue generation (Cassell et al, 2001) and has led to neuronal regeneration of varying degrees from only limited growth to extensive axonal sprouting in several studies (Iannotti et al, 2003;Novikova et al, 2006). Scaffolds of Matrigel ™ allow only limited axonal growth after spinal cord trauma (Estrada et al, 2014;Sakiyama-Elbert et al, 2012;Someya et al, 2008).…”