Evaluation of blood vessel ingrowth in fibrin gel subject to type and concentration of growth factors

Abstract

Our aim was to quantitatively assess the angiogenetic effects of VEGF and bFGF immobilized in a fibrin-based drug delivery system in a suitable subcutaneous rat model. After evaluation of a suitable implantation technique (6 rats), four teflon isolation chambers containing fibrin gel matrices were implanted subcutaneously in an upside-down fashion on the back of 30 Lewis rats. The matrices consisted of 500 μl fibrin gel with two different fibrinogen concentrations (10 mg/ml or 40 mg/ml fibrinogen) and 2 I.U./ml thrombin and contained VEGF and bFGF in five different concentrations (0 to 250 ng/ml each). At 3, 7 and 14 days after implantation, matrices were explanted and subjected to histological and morphometrical analysis. At 1 week, the volume of the fibrin clots was significantly smaller in the 100 and 250 ng/ml VEGF and bFGF groups in comparison to lower concentrated growth factors. At 1 and 2 weeks, the use of growth factors in low concentrations (25 ng/ml VEGF and bFGF) significantly increased the amount of fibrovascular tissue, average fraction of blood vessels and number of blood vessels at the matrix–host interface in comparison to growth factor-free controls. Higher concentrations were neither associated with further increase of tissue formation nor with increased sprouting of blood vessels in this model. This study demonstrates that fibrin gel-immobilized angioinductive growth factors efficiently stimulate generation of fibrovascular tissue and sprouting of blood vessels in a newly developed subcutaneous upside-down isolation chamber model with an optimum between 25 and 100 ng/ml.

Fibrin gels and their clinical and bioengineering applications

“…Though fibrin has been effective in vitro at promoting osteogenesis, it lacks the mechanical strength required for bone tissue engineering and in vivo studies have been disappointing even when a stiff scaffold encases the fibrin (Kneser et al 2005;Arkudas et al 2007). Fibrin has been more effective as a scaffold for cartilage, cardiovascular and nervous tissue engineering.…”

Automatic Quantitative Micro-Computed Tomography Evaluation of Angiogenesis in an Axially Vascularized Tissue-Engineered Bone Construct

“…14,16,17 Incorporation of angiogenic growth factors, such as vascular endothelial growth factor (VEGF 165 ) and basic fibroblast growth factor (bFGF), in the scaffold could also promote in vivo angiogenesis. [18][19][20][21][22][23] The aim of this study was to (1) establish an automatic quantitative analysis method of vascularization using micro-CT along with 3D reconstruction, (2) evaluate whether the micro-CT analysis of vascularization is comparable with standard histological analysis methods, (3) vascularize a clinically approved particulated porous HA/TCP matrix, and (4) analyze the angioinductive effect of 100 ng/mL VEGF 165 and bFGF on axial vessel sprouting using the rat AVL model.…”

Axial vascularization of a large volume calcium phosphate ceramic bone substitute in the sheep AV loop model

“…Among the various in vivo models of axial vascularization, the rat arteriovenous loop (AV loop) model seems most promising. It was introduced in by Erol and Spira (1979) in the context of flap prefabrication and then further developed for tissue-engineering purposes during the past decade (Bach et al, 2006;Arkudas et al, , 2008. The axial type of blood supply allows the vascularization and transfer of biomaterials independently of local conditions at the recipient site.…”