Bone regeneration in Ds-Red pig calvarial defect using allogenic transplantation of EGFP-pMSCs – a comparison of host cells and seeding cells in the scaffold

Abstract

26 2 27 28 Keywords: mesenchymal stem cell, bone regeneration, enhanced green fluorescent, DsRed pig, 29 pig calvarial defect model 30 31 Abstract 32 Background: Cells, scaffolds, and factors are the triad of regenerative engineering;33 however, it is difficult to distinguish whether cells in the regenerative construct are from the 34 seeded cells or host cells via the host blood supply. We performed a novel in vivo study to 35 transplant enhanced green fluorescent pig mesenchymal stem cells (EGFP-pMSCs) into calvarial 36 defect of DsRed pigs. The cell distribution and proportion were distinguished by the different 37 fluorescent colors through the whole regenerative period. 38Method/Results: Eight adult domestic Ds-Red pigs were treated with five modalities:39 empty defects without scaffold (group 1); defects filled only with scaffold (group 2); defects 40 filled with osteoinduction medium-loaded scaffold (group 3); defects filled with 5 x 10 3 41 cells/scaffold (group 4); and defects filled with 5 x 10 4 cells/scaffold (group 5). The in vitro cell 42 distribution, morphology, osteogenic differentiation, and fluorescence images of groups 4 and 543 were analyzed. Two animals were sacrificed at 1, 2, 3, and 4 weeks after transplantation. The in 44 vivo fluorescence imaging and quantification data showed that EGFP-pMSCs were represented 45 in the scaffolds in groups 4 and 5 throughout the whole regenerative period. A higher seeded cell 46 density resulted in more sustained seeded cells in bone regeneration compared to a lower seeded 47 cell density. Host cells were recruited by seeded cells if enough space was available in the 48 scaffold. Host cells in groups 1 to 3 did not change from the 1st week to 4th week, which 3 49 indicates that the scaffold without seeded cells cannot recruit host cells even when enough space 50 is available for cell ingrowth. The histological and immunohistochemical data showed that more 51 cells were involved in osteogenesis in scaffolds with seeded cells. 52Conclusion: Our in vivo results showed that more seeded cells recruit more host cells and 53 that both cell types participate in osteogenesis. These results suggest that scaffolds without 54 seeded cells may not be effective in bone transplantation. 55 4 56 Introduction 57 Skeletal defects require surgery using bone grafts. Autografts are the gold standard for 58 bone grafting [1]; however, donor site morbidity and the limited amount of available donor tissue 59 restrict their application [2, 3]. Regenerative tissue engineering using cells, scaffolds, factors and 60 blood supply [4] has become an alternative method to treat skeletal bone defects. 61 Allografts may provide the same osteoconductive conduit for bony fusion as traditional 62 autografts and may have comparable biomechanical properties without amount restriction [5, 6]. 63 Although depleted of osteoprogenitor cells like mesenchymal stem cells (MSCs), the fusion rate 64 still reaches 73% to 100% in instrumented spinal fusion [7-16], making allograft a clinically 65 feasibl...

Novel Composites for Bone Tissue Engineering

“…d) The second layer of the composite strip kept away from the corticotomy had profuse infiltration of fibrocytes. e) The fibrous changeover in the superficial layer of the composite had abundant neovascularization These changes confirm the osteo induction potential of the composite, the ability of the composite to go for bioconversion, and high bioactivity of the composite [37][38][39].…”