title: Combination of extrinsic and intrinsic pathways significantly accelerates axial vascularization of bioartificial tissues.
abstract: BACKGROUND
  In this study, the authors present a modification of the arteriovenous loop model that combines extrinsic and intrinsic vascularization modes to enhance vascularization of bioartificial matrices.
  
  
  METHODS
  An arteriovenous loop was created in the medial thighs of 24 rats. The loop was placed in a newly developed titanium chamber, which was fabricated with an electron beam melting facility, and was embedded in a hydroxyapatite/β-tricalcium phosphate/fibrin matrix. At the explantation time points (2, 4, 6, and 8 weeks), constructs were perfused by differently colored dyes to determine the amount of tissue vascularized by either the intrinsic or the extrinsic vascular pathway. Specimens were investigated by means of micro-computed tomography and histologic and morphometric analysis.
  
  
  RESULTS
  Although there was an equal number of blood vessels originating from the center and the periphery, 83 percent of all vessels displayed a connection to the arteriovenous loop already at 2 weeks. There was a continuous increase of the relative proportion of vessels connected to the arteriovenous loop over time detectable. At 8 weeks, communications between the newly formed vessels and the arteriovenous loop were visible in 97 percent of all vessels.
  
  
  CONCLUSIONS
  This study demonstrates for the first time the enhancement of angiogenesis in an axially vascularized tissue by an additional extrinsic vascular pathway. By 2 weeks, both pathways showed connections, allowing transplantation of the entire construct using the arteriovenous loop pedicle. This approach will allow for reduction of the time interval between arteriovenous loop implantation and transplantation into the defect site and limitation of operative interventions.
authors.affiliation: Erlangen, Germany From the Department of Plastic and Hand Surgery, University of Erlangen Medical Center, and the Institute of Science and Technology of Metals, University of Erlangen-Nürnberg.
authors.forename: Andreas
authors.initials: A
authors.lastname: Arkudas
authors.forename: Galyna
authors.initials: G
authors.lastname: Pryymachuk
authors.forename: Justus P
authors.initials: JP
authors.lastname: Beier
authors.forename: Linda
authors.initials: L
authors.lastname: Weigel
authors.forename: Carolin
authors.initials: C
authors.lastname: Körner
authors.forename: Robert F
authors.initials: RF
authors.lastname: Singer
authors.forename: Oliver
authors.initials: O
authors.lastname: Bleiziffer
authors.forename: Elias
authors.initials: E
authors.lastname: Polykandriotis
authors.forename: Raymund E
authors.initials: RE
authors.lastname: Horch
authors.forename: Ulrich
authors.initials: U
authors.lastname: Kneser
mesh_terms: D000818:Animals; D001166:Arteriovenous Shunt, Surgical; D001808:Blood Vessels / Q000254:growth & development*; D005263:Femoral Artery / Q000601:surgery; D005268:Femoral Vein / Q000601:surgery; D006882:Hydroxyapatites; D008297:Male; D018919:Neovascularization, Physiologic / Q000502:physiology*; D010477:Perfusion; D019736:Prostheses and Implants; D051381:Rats; D011917:Rats, Inbred Lew; D023822:Tissue Engineering / Q000295:instrumentation / Q000379:methods*; D014025:Titanium; D055114:X-Ray Microtomography
chemical_list: D006882:Hydroxyapatites; C074950:hydroxyapatite-beta tricalcium phosphate; D014025:Titanium