Tissue Engineering Skin Flaps: Which Vascular Carrier, Arteriovenous Shunt Loop or Arteriovenous Bundle, Has More Potential for Angiogenesis and Tissue Generation?

Abstract

This study was designed to clarify which vascular carrier, the arteriovenous shunt loop or the arteriovenous bundle, has more potential as a vascular carrier for an artificial skin flap in rats. An arteriovenous shunt loop was constructed between the femoral artery and vein using an interpositional artery (group I) or vein (group II) graft. For arteriovenous bundle groups, the femoral artery and vein were used and subdivided into two groups: distal ligation type (group III) and flow-through type (group IV). The vascular pedicle was wrapped with an artificial dermis and implanted beneath the inguinal skin for 4 weeks. For the control group, a folded sheet of artificial dermis without any vascular carrier was embedded. In experiment 1, the volumes of generated tissue within the artificial dermis were measured in the experimental and control groups (n = 5 in each group). In experiment 2, the origin of new blood vessels sprouting from the arteriovenous shunt loop and arteriovenous bundle were evaluated histologically. The volume of generated tissue in the shunt groups was significantly greater than that in the bundle groups (p < 0.01). However, the bundle groups also showed a great potential for producing new tissue. Serial histological studies showed that new capillaries were derived not only from the vasa vasorum of the femoral vessels but directly from the femoral vein in both the shunt and the bundle groups. This "sprouting" was extensively exhibited in the group III. Although the arteriovenous shunt loop showed a greater potential for producing new tissue and capillaries, the distal ligation type of bundle was thought to be an effective and practical vascular carrier for producing a tissue-engineered skin flap.

A new approach to tissue engineering of vascularized skeletal muscle

“…The model was enhanced by Morrison and coworkers who inserted the loop into isolation chambers resulting in a successful vascularisation of polymer-and gel matrices [11,17]. This group also demonstrated the superiority of the AV loop as vascular carrier in comparison to the vascular bundle in terms of vascular density and capacity for generation of new tissue [18]. Based on these findings we decided to generate AV loops for induction of vascularisation instead of the distally ligated femoral pedicle (as used by Birla and coworkers [13]), though microsurgical preparation of the loop is far more challenging and meticulous.…”

Cardiac Tissue Engineering in an In Vivo Vascularized Chamber

“…The mean thickness of compact cardiac tissue is similar to that of the adult rat right ventricular wall, 41 is many times larger than all heart tissues engineered in vitro to date, 4,5,8 -10 and is comparable to the thickness attained by polysurgery of cell sheet grafts. 14 This approach has recently been adopted in the flow-through pedicle model, 42 which is less angiogenic than the AV loop model, 43 which perhaps explains why up to 20 million cells generated only small amounts of tissue. 42 The concept of tissue engineering in situ with a dedicated blood supply permits the implanted cells, aided by the invasion of inflammatory cells, fibroblasts, and endothelial cells, to orchestrate their own endogenous cascade of appropriate cytokines, chemokines, and matrix production.…”

Evaluation of Angiogenesis of Bioactive Glass in the Arteriovenous Loop Model

“…It has been shown that the arterovenous loop enhanced neovascularization in a higher degree than an arteriovenous shunt. 23 The Teflon isolation chamber prevents the scaffolds from extrinsic vascularization from the surrounding tissue. 24 Therefore, the constructs are exclusively vascularized from the vascular axis.…”