BMP2 Genetically Engineered MSCs and EPCs Promote Vascularized Bone Regeneration in Rat Critical-Sized Calvarial Bone Defects

Abstract

Current clinical therapies for critical-sized bone defects (CSBDs) remain far from ideal. Previous studies have demonstrated that engineering bone tissue using mesenchymal stem cells (MSCs) is feasible. However, this approach is not effective for CSBDs due to inadequate vascularization. In our previous study, we have developed an injectable and porous nano calcium sulfate/alginate (nCS/A) scaffold and demonstrated that nCS/A composition is biocompatible and has proper biodegradability for bone regeneration. Here, we hypothesized that the combination of an injectable and porous nCS/A with bone morphogenetic protein 2 (BMP2) gene-modified MSCs and endothelial progenitor cells (EPCs) could significantly enhance vascularized bone regeneration. Our results demonstrated that delivery of MSCs and EPCs with the injectable nCS/A scaffold did not affect cell viability. Moreover, co-culture of BMP2 gene-modified MSCs and EPCs dramatically increased osteoblast differentiation of MSCs and endothelial differentiation of EPCs in vitro. We further tested the multifunctional bone reconstruction system consisting of an injectable and porous nCS/A scaffold (mimicking the nano-calcium matrix of bone) and BMP2 genetically-engineered MSCs and EPCs in a rat critical-sized (8 mm) caviarial bone defect model. Our in vivo results showed that, compared to the groups of nCS/A, nCS/A+MSCs, nCS/A+MSCs+EPCs and nCS/A+BMP2 gene-modified MSCs, the combination of BMP2 gene -modified MSCs and EPCs in nCS/A dramatically increased the new bone and vascular formation. These results demonstrated that EPCs increase new vascular growth, and that BMP2 gene modification for MSCs and EPCs dramatically promotes bone regeneration. This system could ultimately enable clinicians to better reconstruct the craniofacial bone and avoid donor site morbidity for CSBDs.

Hybrid Biomaterial with Conjugated Growth Factors and Mesenchymal Stem Cells for Ectopic Bone Formation

“…3 MSCs were infected with Ad-BMP2 in a serum-free medium for 4 h and then cultured overnight in the alpha-MEM medium with 2% FBS. 4 Scaffold preparation nCS was produced following the method reported previously. 36,37 Briefly, alginate was dissolved in PBS to prepare 10% alginate solution (pH 7.2).…”

“…Recent work from our laboratory demonstrated that bone marrow-derived MSCs (BM-MSCs) engineered to overexpress bone morphogenic protein 2 (BMP2) have greater bone formation potential than native MSCs. 3,4 BMPs are potent morphogens that stimulate bone formation in developed tissues 5,6 and one member of the family, BMP2, has shown promising results in orthopedic clinical trials. In addition to soluble signals, the mechanical properties of the scaffold have been shown to affect bone formation and surface stiffness has been shown to affect stem cell fate, [7][8][9][10] with harder/stiffer surfaces promoting osteogenic differentiation of MSCs.…”

“…9 To this end, our laboratory has recently shown the ability of calcium sulfate nanoparticles (nCS) to promote osteogenic differentiation. 3,4 We developed an injectable and porous nanocalcium sulfate/alginate (nCS/A) scaffold and demonstrated that nCS/A is biocompatible and promotes bone regeneration. 3,4 In addition to mechanical properties, tuning the angiogenic properties of scaffolds is essential for promoting tissue regeneration, especially for highly vascularized tissues such as bone.…”

“…3,4 We developed an injectable and porous nanocalcium sulfate/alginate (nCS/A) scaffold and demonstrated that nCS/A is biocompatible and promotes bone regeneration. 3,4 In addition to mechanical properties, tuning the angiogenic properties of scaffolds is essential for promoting tissue regeneration, especially for highly vascularized tissues such as bone. 1,[11][12][13] Decorating the scaffold with angiogenic factors may be one strategy to enhance angiogenesis.…”

Mesenchymal Stem Cells: Roles and Relationships in Vascularization

“…Bmp2-gene-modified MSCs and EPCs were delivered in injectable calcium sulfate/alginate scaffolds, providing drastic increases in osteoblast differentiation and endothelial differentiation, resulting in increased bone and vascular formation. 101 Another genetic modification strategy involved modifying MSCs to express VEGF. 102 The increased expression of VEGF led to a threefold increase of vascular density compared with control MSC-seeded grafts.…”