Osteogenic differentiation of mesenchymal stem cells on the bimodal polymer polyurethane/polyacrylonitrile containing cellulose phosphate nanowhisker

Cellulose-based composite scaffolds for bone tissue engineering and localized drug delivery

Natural bone constitutes a complex and organized structure of organic and inorganic components with limited ability to regenerate and restore injured tissues, especially in large bone defects. To improve the reconstruction of the damaged bones, tissue engineering has been introduced as a promising alternative approach to the conventional therapeutic methods including surgical interventions using allograft and autograft implants. Bioengineered composite scaffolds consisting of multifunctional biomaterials in combination with the cells and bioactive therapeutic agents have great promise for bone repair and regeneration. Cellulose and its derivatives are renewable and biodegradable natural polymers that have shown promising potential in bone tissue engineering applications. Cellulose-based scaffolds possess numerous advantages attributed to their excellent properties of non-toxicity, biocompatibility, biodegradability, availability through renewable resources, and the low cost of preparation and processing. Furthermore, cellulose and its derivatives have been extensively used for delivering growth factors and antibiotics directly to the site of the impaired bone tissue to promote tissue repair. This review focuses on the various classifications of cellulose-based composite scaffolds utilized in localized bone drug delivery systems and bone regeneration, including cellulose-organic composites, cellulose-inorganic composites, cellulose-organic/inorganic composites. We will also highlight the physicochemical, mechanical, and biological properties of the different cellulose-based scaffolds for bone tissue engineering applications.

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Cellulose and its derivatives are renewable and biodegradable natural polymers that with great potential for bone tissue engineering.

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Cellulose-based materials can be used various therapeutics directly to the bone to achieve bone regeneration.

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Bioinks made of cellulose-based materials hold great promise to develop patient specific solutions for bone repair using 3D printing.

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Challenges associated with inaccuracies in existing preclinical models, sterilization regulatory barriers still need to be addressed before clinical translation.

Nanotopography in directing osteogenic differentiation of mesenchymal stem cells: potency and future perspective

Severe bone injuries can result in disabilities and thus affect a person's quality of life. Mesenchymal stem cells (MSCs) can be an alternative for bone healing by growing them on nanopatterned substrates that provide mechanical signals for differentiation. This review aims to highlight the role of nanopatterns in directing or inducing MSC osteogenic differentiation, especially in bone tissue engineering. Nanopatterns can upregulate the expression of osteogenic markers, which indicates a faster differentiation process. Combined with growth factors, nanopatterns can further upregulate osteogenic markers, but with fewer growth factors needed, thereby reducing the risks and costs involved. Nanopatterns can be applied in scaffolds for tissue engineering for their lasting effects, even in vivo, thus having great potential for future bone treatment.

Coculture of Endothelial and Stromal Cells to Promote Concurrent Osteogenesis and Vasculogenesis

A key challenge in the treatment of large bone defects is the need to provide an adequate and stable vascular supply as new tissue develops. Bone tissue engineering applies selected biomaterials and cell types to create an environment that promotes tissue formation, maturation, and remodeling. Mesenchymal stromal cells (MSCs) have been widely used in these strategies because of their established effects on bone formation, and their ability to act as stabilizing pericytes that support vascular regeneration by endothelial cells (ECs). However, the creation of vascularized bone tissue in vitro requires coupling of osteogenesis and vasculogenesis in a three-dimensional (3D) biomaterial environment. In the present study, 3D fibrin hydrogels containing MSCs and ECs were prevascularized in vitro for 7 days to create an endothelial network in the matrix, and were subsequently cultured for a further 14 days under either continued vasculogenic stimulus, a combination of vasculogenic and osteogenic (hybrid) stimulus, or only osteogenic stimulus. It was found that ECs produced robust vessel networks in 3D fibrin matrices over 7 days of culture, and these networks continued to expand over the 14-day treatment period under vasculogenic conditions. Culture in hybrid medium resulted in maintenance of vessel networks for 14 days, while osteogenic culture abrogated vessel formation. These trends were mirrored in data representing overall cell viability and cell number in the 3D fibrin constructs. MSCs were found to colocalize with EC networks under vasculogenic and hybrid conditions, suggesting pericyte-like function. The bone marker alkaline phosphatase increased over time in hybrid and osteogenic media, but mineral deposition was evident only under purely osteogenic conditions. These results suggest that hybrid media compositions can support some aspects of multiphase tissue formation, but that alternative strategies are needed to obtain robust, concomitant vascularization, and osteogenesis in engineered tissues in vitro. Impact statement The combined use of mesenchymal stromal cells (MSCs) and endothelial cells to concomitantly produce mature bone and a nourishing vasculature is a promising tissue engineering approach to treating large bone defects. However, it is challenging to create and maintain vascular networks in the presence of osteogenic cues. This study used a 3D fibrin matrix to demonstrate that prevascularization of the construct can lead to maintenance of vessel structures over time, but that osteogenesis is compromised under these conditions. This work illuminates the capacity of MSCs to serve as both supportive pericytes and as osteoprogenitor cells, and motivates new strategies for coupling osteogenesis and vasculogenesis in engineered bone tissues.