Upregulation of osteogenesis of mesenchymal stem cells with virus-based thin films

Identification of a Specific Phage as Growth Factor Alternative Promoting the Recruitment and Differentiation of MSCs in Bone Tissue Regeneration

Inefficient use and loss of exogenously implanted mesenchymal stem cells (MSCs) are major concerns in MSCs-based bone tissue engineering. It is a promising approach to overcome the above issues by recruiting and regulation of endogenous MSCs. However, there are few substances that can recruit MSCs effectively and specifically to the site of bone injury. In this study, we identified a phage clone (termed P11) with specific affinity for MSCs through phage display biopanning, and further investigated the effects of P11 on the cytological behavior of MSCs and macrophages. The results showed that P11 could bind MSCs specifically and promote the proliferation and migration of MSCs. Meanwhile, P11 could polarize macrophages to the M1 phenotype and significantly changed their morphology, which further enhanced the chemotaxis of MSCs. Additionally, RNA-seq results revealed that P11 could promote the secretion of osteogenesis-related markers in MSCs through the TPL2-MEK-ERK signaling pathway. Altogether, P11 has great potential to be used as growth factor alternatives in bone tissue engineering, with the advantages of cheaper and stable activity. Our study also advances the understanding of the effects of phages on macrophages and MSCs, and provides a new idea for the development in the field of phage-based tissue engineering.

Biocompatibility study of tobacco mosaic virus nanoparticles on human alveolar bone cells

One of the most important factors in a dental implant's success is an adequate quantity of supporting bone. However, there are still some limitations for the bone substitution material. Previous studies found that tobacco mosaic virus (TMV) had the potential for bone formation induction. The aim of this study was to evaluate the biocompatibility of TMV with primary human alveolar bone cells. Primary human alveolar bone cells were cultured on TMV coated substrates. Cell viability, alkaline phosphatase activity, calcium matrix mineralization forming ability, immunofluorescence staining for osteocalcin synthesis and cell morphology were assessed. The results showed that primary human alveolar bone cells cultured on the TMV coated substrates had a higher metabolic rate than the non-TMV coated control group at days 1, 3, 7 and 14. Moreover, the calcium deposition was positive and the alkaline phosphatase activity assay was found significantly greater than the control group at day 14 (p < 0.05). The osteocalcin protein synthesis was found in both the TMV coated substrates and the control group. The immunofluorescence study revealed that in the TMV coated substrates group, the cell morphology changed into a polygonal shape and aggregated more quickly than the control group. The present findings conclude that TMV is biocompatible with primary human alveolar bone cells and also shows osteoinduction potential.

Hyaluronic acid-based hydrogels with tobacco mosaic virus containing cell adhesive peptide induce bone repair in normal and osteoporotic rats

Tobacco mosaic virus (TMV) has been studied as a multi-functional agent for bone tissue engineering. An osteo-inductive effect of wild-type TMV has been reported, as it can significantly enhance the bone differentiation potential of bone marrow stromal cells both on a two-dimensional substrate and in a three-dimensional (3D) hydrogel system. A TMV mutant (TMV-RGD1) was created which featured the adhesion peptide arginyl-glycyl-aspartic acid (RGD), the most common peptide motif responsible for cell adhesion to the extracellular matrix, on the surface of the virus particle to enhance the bio-functionality of the scaffold material. We hypothesised that the incorporation of either wild-type TMV or TMV-RGD1 in the 3D hydrogel scaffold would induce bone healing in critical size defects of the cranial segmental bone. We have previously tested the virus-functionalised scaffolds, in vitro, with a hyaluronic acid-based system as an in-situ hydrogel platform for 3D cell encapsulation, culture, and differentiation. The results of these experiments suggested the potential of the virus-functionalised hydrogel to promote in vitro stem cell differentiation. The hydrogel-forming system we employed was shown to be safe and biocompatible in vivo. Here, we further explored the physiological responses regarding bone regeneration of a calvarial defect in both normal and osteoporotic ovariectomized rat models. Our results, based on histological analysis in both animal models, suggested that both wild-type TMV and TMV-RGD1 functionalised hydrogels could accelerate bone regeneration, without systemic toxicity, evaluated by blood counts. New bone formation was intensified by the incorporation of the RGD-mutant viral particles. This finding increased the potential for use of the rod-shaped plant virus as a platform for the addition of powerful biofunctionality for tissue engineering applications. This study was approved by the Ethics Committee on Animal Use of the Zhenjiang Affiliated First People's Hospital affiliated to Jiangsu University.

Designing topographically textured microparticles for induction and modulation of osteogenesis in mesenchymal stem cell engineering

Mesenchymal stem cells are the focus of intense research in bone development and regeneration. The potential of microparticles as modulating moieties of osteogenic response by utilizing their architectural features is demonstrated herein. Topographically textured microparticles of varying microscale features are produced by exploiting phase-separation of a readily soluble sacrificial component from polylactic acid. The influence of varying topographical features on primary human mesenchymal stem cell attachment, proliferation and markers of osteogenesis is investigated. In the absence of osteoinductive supplements, cells cultured on textured microparticles exhibit notably increased expression of osteogenic markers relative to conventional smooth microparticles. They also exhibit varying morphological, attachment and proliferation responses. Significantly altered gene expression and metabolic profiles are observed, with varying histological characteristics in vivo. This study highlights how tailoring topographical design offers cell-instructive 3D microenvironments which allow manipulation of stem cell fate by eliciting the desired downstream response without use of exogenous osteoinductive factors.

Mineral Distribution Spatially Patterns Bone Marrow Stromal Cell Behavior on Monolithic Bone Scaffolds

Interfaces between soft tissue and bone are characterized by transitional gradients in composition and structure that mediate substantial changes in mechanical properties. For interfacial tissue engineering, scaffolds with mineral gradients have shown promise in controlling osteogenic behavior of seeded bone marrow stromal cells (bMSCs). Previously, we have demonstrated a 'top-down' method for creating monolithic bone-derived scaffolds with patterned mineral distributions similar to native tissue. In the present work, we evaluated the ability of these scaffolds to pattern osteogenic behavior in bMSCs in basic, osteogenic, and chondrogenic biochemical environments. Immunohistochemical (IHC) and histological stains were used to characterize cellular behavior as a function of local mineral content. Alkaline phosphatase, an early marker of osteogenesis, and osteocalcin, a late marker of osteogenesis, were positively correlated with mineral content in basic, osteogenic, and chondrogenic media. The difference in bMSC behavior between the mineralized and demineralized regions was most pronounced in an basic biochemical environment. In the mineralized regions of the scaffold, osteogenic markers were clearly present as early as 4 days in culture. In osteogenic media, osteogenic behavior was observed across the entire scaffold, whereas in chondrogenic media, there was an overall reduction in osteogenic biomarkers. Overall, these results indicate local mineral content of the scaffold plays a key role in spatially patterning bMSC behavior. Our results can be utilized for the development of interfacial tissue engineered scaffolds and understanding the role of local environment in determining bMSC behavior. STATEMENT OF SIGNIFICANCE: Soft tissue-to-bone interfaces, such as tendon-bone, ligament-bone, and cartilage-bone, are ubiquitous in mammalian musculoskeletal systems. These interfacial tissues have distinct, hierarchically-structured gradients of cellular, biochemical, and materials components. Given the complexity of the biological structures, interfacial tissues present unique challenges for tissue engineering. Here, we demonstrate that material-derived cues can spatially pattern osteogenic behavior in bone marrow stromal cells (bMSCs). Specifically, we observed that when the bMSCs are cultured on bone-derived scaffolds with mineral gradients, cells in contact with higher mineral content display osteogenic behavior at earlier times than those on the unmineralized substrate. The ability to pattern the cellular complexity found in native interfaces while maintaining biologically relevant structures is a key step towards creating engineered tissue interfaces.