Efficient in vivo bone formation by BMP-2 engineered human mesenchymal stem cells encapsulated in a projection stereolithographically fabricated hydrogel scaffold

Thomas P Lozito,Ying Tang,Bing Wang,Nicholas Oyster,Hang Lin,Rocky S Tuan

doi:10.1186/s13287-019-1350-6

Abstract

BackgroundStem cell-based bone tissue engineering shows promise for bone repair but faces some challenges, such as insufficient osteogenesis and limited architecture flexibility of the cell-delivery scaffold.MethodsIn this study, we first used lentiviral constructs to transduce ex vivo human bone marrow-derived stem cells with human bone morphogenetic protein-2 (BMP-2) gene (BMP-hBMSCs). We then introduced these cells into a hydrogel scaffold using an advanced visible light-based projection stereolithography (VL-PSL) technology, which is compatible with concomitant cell encapsulation and amenable to computer-aided architectural design, to fabricate scaffolds fitting local physical and structural variations in different bones and defects.ResultsThe results showed that the BMP-hBMSCs encapsulated within the scaffolds had high viability with sustained BMP-2 gene expression and differentiated toward an osteogenic lineage without the supplement of additional BMP-2 protein. In vivo bone formation efficacy was further assessed using an intramuscular implantation model in severe combined immunodeficiency (SCID) mice. Microcomputed tomography (micro-CT) imaging indicated rapid bone formation by the BMP-hBMSC-laden constructs as early as 14 days post-implantation. Histological examination revealed a mature trabecular bone structure with considerable vascularization. Through tracking of the implanted cells, we also found that BMP-hBMSC were directly involved in the new bone formation.ConclusionsThe robust, self-driven osteogenic capability and computer-designed architecture of the construct developed in this study should have potential applications for customized clinical repair of large bone defects or non-unions.

Highlights

Stem cell-based bone tissue engineering shows promise for bone repair but faces some challenges, such as insufficient osteogenesis and limited architecture flexibility of the cell-delivery scaffold
Both cassettes were driven by the CMV promoter, separately (Fig. 1b). enhanced green fluorescent protein (eGFP) gene expression allowed the detection of BMP-human bone marrowderived mesenchymal stem cells (MSCs) (hBMSCs) within the scaffolds and the assessment of gene transduction efficiency
Additional file 1: Figure S3 shows the same area under phase and fluorescence microscopy, showing lentiBMP-2-transduced hBMSCs cultured on tissue culture plastic (TCP)

Summary

Introduction

Stem cell-based bone tissue engineering shows promise for bone repair but faces some challenges, such as insufficient osteogenesis and limited architecture flexibility of the cell-delivery scaffold. Research advances in tissue engineering, involving a combination of cells, biomaterial scaffolds, and signaling molecules [7,8,9], have shown its potential in enhancing bone healing without the use of native bone tissue [10, 11] Owing to their osteogenic capability upon stimulation, relative ease of isolation, low immunogenicity, and lack of ethical controversial [12], mesenchymal stem cells (MSCs) isolated from various adult tissues have been tested in different animal models as a promising cell type for bone repair, including femoral defects [13, 14], mandibular defects [15,16,17], and tibial defects [18, 19]. To maintain a high concentration of BMP-2 for extended periods of time at the defect site, a large dose of BMP-2 protein is often applied at the beginning, which is costly and might cause side effects, such as edema, ectopic bone formation, and nerve root irritation [27]

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Results

Conclusion