Engraftment of Prevascularized, Tissue Engineered Constructs in a Novel Rabbit Segmental Bone Defect Model

Abstract

The gold standard treatment of large segmental bone defects is autologous bone transfer, which suffers from low availability and additional morbidity. Tissue engineered bone able to engraft orthotopically and a suitable animal model for pre-clinical testing are direly needed. This study aimed to evaluate engraftment of tissue-engineered bone with different prevascularization strategies in a novel segmental defect model in the rabbit humerus. Decellularized bone matrix (Tutobone) seeded with bone marrow mesenchymal stromal cells was used directly orthotopically or combined with a vessel and inserted immediately (1-step) or only after six weeks of subcutaneous “incubation” (2-step). After 12 weeks, histological and radiological assessment was performed. Variable callus formation was observed. No bone formation or remodeling of the graft through TRAP positive osteoclasts could be detected. Instead, a variable amount of necrotic tissue formed. Although necrotic area correlated significantly with amount of vessels and the 2-step strategy had significantly more vessels than the 1-step strategy, no significant reduction of necrotic area was found. In conclusion, the animal model developed here represents a highly challenging situation, for which a suitable engineered bone graft with better prevascularization, better resorbability and higher osteogenicity has yet to be developed.

Regeneration of segmental defects in metatarsus of sheep with vascularized and customized 3D-printed calcium phosphate scaffolds

“…Proof of concept has been demonstrated at the pre-clinical level by ectopic implantation in the ewe of a chamber containing the BCP biomaterial and an arteriovenous fistula (vascular loop). After 6 and 12 weeks of implantation, abundant microvasculature was observed in the chamber contents [37][38][39][40][41][42] . Large defects at the mandibular level have been successfully reconstructed in a few patients using this technique of transplanting a pre-vascularized biomaterial from an intramuscular site 43,44 .…”

Bimodal morphological analyses of native and engineered tissues

“…Macromass pellets formed by human articular chondrocytes used for the analyses described below were derived from a previous study [6]. We selectively assessed samples resulting in Different microscopy techniques have been employed to detect the structural changes in engineered osteogenic constructs intended to repair bone defects [30,8,31]. In the present study, Histo-SEM was validated as an alternative method to characterize patterns of a developing bone tissue in cell-ceramic constructs.…”

Contrast-Enhanced Microtomographic Characterisation of Vessels in Native Bone and Engineered Vascularised Grafts Using Ink-Gelatin Perfusion and Phosphotungstic Acid

“…Although our concrete example may not be meaningful in a broader context of bone vascularisation, our method allowed a comparison of vascular branches and average branch diameter, both crucial aspects for tissue perfusion. For a more thorough evaluation of graft vascularisation, dedicated studies with greater statistical power are required, featuring previously published approaches such as vascular bundles of artery and vein [ 18 , 36 ], vascular loops [ 15 , 37 ], or wrapping with well-vascularised muscle tissue [ 38 ]. Though granulation tissue with rudimentary vasculature, sufficient for demonstration purposes in this study, formed after one week, longer in vivo incubation may be necessary for full maturation of the vascular tree.…”