Improvement of Vascularization of PLGA Scaffolds by Inosculation of In Situ-Preformed Functional Blood Vessels With the Host Microvasculature

Abstract

Objective: We analyzed, in vivo, whether the establishment of blood supply to implanted scaffolds can be accelerated by inosculation of an in situ-preformed microvascular network with the host microvasculature. Background: A rapid vascularization is crucial for the survival of scaffold-based transplanted tissue constructs. Methods: Poly-lactic-glycolic acid scaffolds were implanted into the flank of balb/c or green fluorescent protein (GFP)-transgenic mice for 20 days to create in situ a new microvascular network within the scaffolds. The prevascularized scaffolds were then transferred into the dorsal skinfold chamber of isogeneic recipient mice. Nonvascularized poly-lactic-glycolic acid scaffolds served as controls. Vascularization, blood perfusion, and cell survival of the implants were analyzed over 14 days using intravital fluorescence microscopy, histology, and immunohistochemistry. Results: Our results demonstrate that establishment of blood perfusion of prevascularized scaffolds is significantly accelerated and improved (136.7 Ϯ 23.2 pl/s) when compared with controls (6.9 Ϯ 1.9 pl/s), because the in situ-preformed microvessels were reperfused by forming interconnections to the host microvasculature. Apoptotic cell death within the implants was found only during the first 3 to 6 days after scaffold implantation during lack of blood perfusion, but not during the further 14-day observation period. Conclusions: Inosculation of in situ-preformed functional blood vessels represents a promising approach to improve the blood supply to implanted tissue constructs. (Ann Surg 2008;248: 939 -948)

Implanted Cell-Dense Prevascularized Tissues Develop Functional Vasculature That Supports Reoxygenation After Thrombosis

“…20 In vitro and in vivo prevascularization are promising methodologies for creating engineered tissues that quickly form a functional vascular network after implantation. [21][22][23][24] We previously showed that fibrin-only engineered tissues which have been prevascularized in vitro and implanted into dorsal window chambers surgically prepared on immunodeficient mice will anastomose with the host circulation in as short as *20 h after implantation. 25 However, thrombosis can occur rapidly ( < 1 h) after anastomosis, resulting in nonfunctional vasculature.…”

The dorsal skinfold chamber: window into the dynamic interaction of biomaterials with their surrounding host tissue

“…However, this is not associated with an improved material incorporation. In fact, the granulation tissue surrounding the Vicryl ® mesh is instable due to low collagen content and massive infi ltration of histiocytes, multinucleated giant cells and polymorphonuclear granulocytes (Laschke et al, 2009a). These results indicate that a stronger angiogenic and infl ammatory response to an implanted surgical mesh does not necessarily result in a better incorporation into the host tissue.…”

“…Prolene ® , Ultrapro ® and Vicryl ® meshes are commonly used meshes, which differ in polymer composition, mesh architecture and resorbability. After their implantation into the hamster dorsal skinfold chamber, it was found that the multifilament Vicryl ® mesh induces a more pronounced angiogenic and inflammatory host tissue response when compared to the monofi lament Prolene ® MW Laschke et al Biomaterials research with the skinfold chamber and Ultrapro ® mesh (Laschke et al, 2009a). However, this is not associated with an improved material incorporation.…”

“…After implantation of in situ prevascularised PLGA scaffolds from green fl uorescent protein (GFP)-transgenic mice into dorsal skinfold chambers of wild-type recipient animals, intravital fluorescence microscopy demonstrates that GFP-positive vessels grow out from the scaffolds into the surrounding host tissue, where external inosculation occurs (Laschke et al, 2008b). Furthermore, the GFP-positive preformed vessels contribute to sprouting angiogenesis in the centre of the scaffolds, further increasing the microvessel density of the implants (Laschke et al, 2008b). However, even this approach does not result in adequate blood perfusion of the scaffolds during the very fi rst days after implantation.…”

The Effect of Human Recombinant Erythropoietin (rHuEPO) and Tacrolimus (FK506) in Autologous and Homologous Full Thickness Skin Graft (FTSG) Take and Viability in a Rat Model

“…According to our findings it was noted that the center of the graft contains a higher density of vascular buds and vessels suggesting that angiogenesis begins there and continuous outwardly towards the periphery of the graft. It is controversial whether angiogenesis takes place before the 2-3td postgrafting day since there are authors who claim that the graft on its own has the physiologic potential to perform angiogenesis much earlier (Laschke et al, 2008;Shepherd et al, 2004). However, it is generally accepted that revascularization is a process that involves the presence of both the recipient bed and the graft itself since it is their interaction which leads to effective angiogenesis.…”