Flap Prefabrication and Prelamination with Tissue-Engineered Cartilage

Abstract

In reconstructive surgery, the integration of tissue-engineered cartilage in a prefabricated free flap may make it possible to generate flaps combining a variety of tissue components, to meet the special requirements of particular defects. One aim of the present study was to investigate prefabrication of a microvascular free flap by implanting a vessel loop under a skin flap in a rabbit model. A second aim was to report on the authors' preliminary experiences in prelaminating prefabricated flaps with autologous tissue-engineered cartilage, in terms of matrix development, inflammatory reaction, and host-tissue interaction. The flap was prefabricated by implanting a vessel loop under a random-pattern abdominal skin flap. The tissue-engineered cartilage constructs were made by isolating chondrocytes from auricular biopsies. Following a period of amplification, the cells were seeded onto a non-woven scaffold made of a hyaluronic-acid derivative and cultivated for 2 weeks. One cell-biomaterial construct was placed beneath the prefabicated flap, and two additional constructs were placed subcutaneously and intramuscularly. In addition, a biomaterial sample without cells was placed subcutaneously to provide a control. All implanted specimens were left in position for 6 or 12 weeks. Neovascularization in the prefabricated flap and biomaterial construct was analyzed by angiography. After explantation, the specimens were examined by histologic and immunohistochemical methods. The prefabricated flaps showed a well-developed network of blood vessels between the implanted vessel loop and the original random-pattern blood supply. The tissue-engineered constructs remained stable in size and showed signs of tissue similar to hyaline cartilage, as evidenced by the expression of cartilage-specific collagen type II and proteoglycans. No inflammatory reactions were observed. The physiologic environment of the autologous rabbit model provided favorable conditions for matrix deposition and maturation of the cell-biomaterial constructs. These initial results demonstrated the potential of prefabricating an axial perfused flap, combined with tissue-engineered cartilage, thus creating functionally competent tissue components for reconstructive surgery with minimal donor-site morbidity.

Vascularization of engineered cartilage constructs in a mouse model

“…The mouse model presented here works with the combination of a flow-through model with later transposition of the construct to confirm the sole dependence of the vascularized construct on the implanted vessels and to answer questions concerning transposition or perform pre-studies prior to free microsurgical transfer in rats or rabbits. According to the findings of Staudenmaier et al (2004) and Nguyen et al (2005), we performed a transposition after 3 weeks with vascularization being sufficient after this time. This is also consistent with the practice of other investigators who have described sufficient vascularization after 3 weeks (Takato et al 1993;Itoh 1992).…”

“…Others have introduced rat models to solve problems concerning prefabrication (Tan et al 2004;Tanaka et al 2003). Staudenmaier et al (2004) and Hoang et al (2005b) demonstrated in a rabbit model that flaps could be well vascularized by an arteriovenous vessel loop. Hoang et al (2009) even simulated a free microsurgical transfer of the prefabricated, prelaminated flaps.…”

“…In contrast, only a few studies have been published dealing with the prefabrication of in vitro cartilage-engineered scaffolds to ensure survival, function and shape in vivo (Staudenmaier et al 2004, Neumeister et al 2006). Shen was the first to describe the term "prefabrication" (Shen 1982), meaning the implantation of a vascular pedicle under a skin flap.…”

“…Nevertheless, newly engineered voluminous three-dimensional (3D) cartilage constructs require a hyperoxic environment for adequate growth and proliferation (Staudenmaier et al 2004). In reconstructive surgery, cartilage is needed in large quantities to rebuild structures like the ear, nose, larynx or trachea.…”

Tissue-engineered trachea: History, problems and the future☆

“…Between the epithelial layer and the hyaline cartilage tissues we can find a submucosal layer of capillary networks. Normal cartilage tissue preventing the in-growth of capillary vessels is separated from other connective tissues (i.e., submucosa) by a fibrous membrane [71,72]. Unlike parenchymal organs, the trachea is supplied with a network of small vessels inaccessible to direct revascularization through vessel anastomosis.…”