i. b. b. m. e. 6 th International Meeting December 10-13 th , 2003 Orlando, Florida. Institute of Biomaterials and Biomedical Engineering. University of Toronto, CANADA. Figure 1. Scanning electron micrograph of an empty PLGA-CaP scaffold viewed longitudinally. D. C. 11 Days.
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6th International Meeting
December 10-13th, 2003
Institute of Biomaterials and Biomedical Engineering
University of Toronto, CANADA
Figure 1.Scanning electron micrograph of an empty PLGA-CaP scaffold viewed longitudinally.
Fibrin Filled Scaffolds (Low T)
Fibrin Filled Scaffolds (High T)
Table 1.Number of defects per group
Fibrin Filled Scaffolds for Bone Tissue Engineering: An in vivo Study
Jeffrey M. Karp, Feryal Sarraf, Molly S. Shoichet and John E. Davies
Methods and Results
The main goal of this work was to determine how filling bone engineering scaffolds with fibrin sealant effects bony wound healing and to examine whether the structural properties of the fibrin are important to consider. Tisseel VH was used as supplied by Baxter Bioscience Canada. To create fibrin matrices with different structural properties, fibrinogen was combined with different concentrations of thrombin. Biodegradable scaffolds filled with the different fibrin matrices were implanted into the distal femur of adult inbred Brown Norway rats and examined histomorphometrically after 2, 5 and 11 days. The results from the 5 day time point support many published in vitro cell migration studies where various cells types were demonstrated to migrate more rapidly into fibrin matrices with larger pores and thicker strands. This work demonstrates this phenomenon for the first time in vivo. However, results from the 11 day time point showed that filling scaffolds with commercially available fibrin sealants significantly delayed bony wound healing. Therefore, fibrin sealants, in their present state, are likely not ideal for bony wound healing applications.
Figure 4. Histomorphometric analysis of reparative bone after 5 days in vivo. No statistical difference was found between empty scaffolds and fibrin filled scaffolds containing fibrin(low T). However, significantly less bone was found in defects containing fibrin(high T) compared to empty scaffolds. These results correlate with decrease in fibrin sealant amount between the 2 day and 5 day time points. (Low T ~ 62% reduction, high T ~ 34 %, p<0.06)
1. Scaffolds filled with fibrin sealant will enhance bone tissue invasion in comparison to empty scaffolds.
2. Fibrin matrices with large pores and thick strands will enhance bone tissue invasion in vivo in comparison to matrices with smaller pores and thinner fibrin strands.
Figure 2. Scanning electron micrographs of polymerized Tisseel fibrin sealant. (A) Fibrin polymerized with a low thrombin concentration (1.75 NIH U/ml) contained thick fibrin strands with large pores compared to (B) fibrin polymerized with a high thrombin concentration (220 NIH U/ml), which contained thin fibrin strands with small pores.
Figure 5. Histomorphometric analysis of reparative bone after 11 days in vivo. Both scaffolds filled with fibrin contained significantly less bone then the empty scaffolds (p<0.003).
Figure 3.(A) Bone was observed invading at the periphery of (low T) fibrin filled scaffolds whereas (B) much less reparative bone was identified in (high T) fibrin filled scaffolds. Large areas occupied by residual fibrin sealant (black arrow) were observed.(C) Reparative bone at periphery of defects was bright red-orange (arrows), which indicates presence of thick, mature collagen fibers. (D) Collagen fibers at the periphery of defects were green (white arrows), which indicates thin and less mature. In comparison to empty scaffolds, which were completely filled with bone(not shown) (E,F), bone was only observed at the periphery of both fibrin filled scaffolds groups. (A,B,E,F) Masson’s Trichrome stained sections. (C,D) Picro Sirus Red stained sections.