The effect of stiffness variation of electrospun fiber meshes of multiblock copolymers on the osteogenic differentiation of human mesenchymal stem cells

Osteoblast responsive biosilica-enriched gelatin microfibrillar microenvironments

Engineering of scaffolds for bone regeneration is often inspired by the native extracellular matrix mimicking its composite fibrous structure. In the present study, we used low loadings of diatomite earth (DE) biosilica to improve the bone regeneration potential of gelatin electrospun fibrillar microenvironments. We explored the effect of increasing the DE content from 1 % to 3 % and 5 %, respectively, on the physico-chemical properties of the fibrous scaffolds denoted FG_DE1, FG_DE3, FG_DE5, regarding the aqueous media affinity, stability under simulated physiological conditions, morphology characteristics, and local mechanical properties at the surface. The presence of biosilica generated composite structures with lower swelling degrees and higher stiffness when compared to gelatin fibers. Increasing DE content led to higher Young modulus, while the stability of the protein matrix in PBS, at 37 °C, over 21 was significantly decreased by the presence of diatomite loadings. The best preosteoblast response was obtained for FG_DE3, with enhanced mineralization during the osteogenic differentiation when compared to the control sample without diatomite. 5 % DE in FG_DE5 proved to negatively influence cells' metabolic activity and morphology. Hence, the obtained composite microfibrillar scaffolds might find application as osteoblast-responsive materials for bone tissue engineering.

How Mechanical and Physicochemical Material Characteristics Influence Adipose-Derived Stem Cell Fate

Adipose-derived stem cells (ASCs) are a subpopulation of mesenchymal stem cells. Compared to bone marrow-derived stem cells, they can be harvested with minimal invasiveness. ASCs can be easily expanded and were shown to be able to differentiate into several clinically relevant cell types. Therefore, this cell type represents a promising component in various tissue engineering and medical approaches (e.g., cell therapy). In vivo cells are surrounded by the extracellular matrix (ECM) that provides a wide range of tissue-specific physical and chemical cues, such as stiffness, topography, and chemical composition. Cells can sense the characteristics of their ECM and respond to them in a specific cellular behavior (e.g., proliferation or differentiation). Thus, in vitro biomaterial properties represent an important tool to control ASCs behavior. In this review, we give an overview of the current research in the mechanosensing of ASCs and current studies investigating the impact of material stiffens, topography, and chemical modification on ASC behavior. Additionally, we outline the use of natural ECM as a biomaterial and its interaction with ASCs regarding cellular behavior.

A comparison between β-tricalcium phosphate verse chitosan poly-caprolactone-based 3D melt extruded composite scaffolds

Melt extrusion 3D printing has become an attractive additive manufacturing technology to construct degradable scaffolds as tissue precursors in order to create clinically relevant medical devices. Towards this end, a commonly used synthetic polyester, poly-caprolactone (PCL), was used to make scaffolds composed of different biomaterial compositions to increase bioactivity using 3D melt pneumatic extrusion technology. Varying ratios of the natural biopolymer, chitosan, or the bioceramic, β-tricalcium phosphate (TCP) were blended with PCL to fabricate support scaffolds with three-dimensional (3D) architecture for human bone-marrow derived mesenchymal stem cell (hBMSC) growth for potential bone regeneration application. In this study, basic printing requirements as well as biomaterial dynamic mechanical (DMA), elemental, and thermogravimetric (TGA) analysis results demonstrate material homogeneity as well as thermal stability. Scaffold morphology and microarchitecture were assessed using scanning electron microscopy (SEM) alongside in vitro scaffold degradation and biological characterisation. Human BMSC proliferation was assessed using fluorescence imaging, and quantitated via the 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) colorimetric assay. These in vitro cell viability studies revealed that the highest chitosan concentration blend of 20% favoured the most hBMSC growth, exhibited the most swelling, and showed minimal degradation after 28 days. The 20% TCP blend had the second highest hBMSC growth, exhibited moderate swelling, and the fastest degradation rate. Overall, this study demonstrates the first direct comparison of a natural biopolymer-based, that is, chitosan, 3D melt extruded PCL composite with that of a bioceramic-based, that is, β-TCP, PCL composite and their effects on hBMSC 3D proliferation. 3D melt extruded PCL-based composite scaffolds methodology offers a straightforward way to print scaffolds with good shape fidelity, interconnected porosities and enhanced bioactivity; and demonstrates their potential use for regenerative, bone repair applications.

Multiblock copolymers type PDC- a family of multifunctional biomaterials for regenerative medicine1

Multiblock copolymers type PDC are polyetheresterurethanes composed of poly(ɛ-caprolactone) and poly(p-dioxanone) segments. They were designed as degradadable shape-memory polymers for medical devices, which can be implanted minimally-invasively. While providing structural support in the initial phase after implantation, they are capable to modulate soft tissue regeneration while degradation. In this perspective, we elucidate cell-material interactions, compatibility both in-vitro and in-vivo and biofunctionality of PDC, which represents a promising candidate biomaterial family especially for cardiovascular applications.

Effect of Polymeric Matrix Stiffness on Osteogenic Differentiation of Mesenchymal Stem/Progenitor Cells: Concise Review

Mesenchymal stem/progenitor cells (MSCs) have a multi-differentiation potential into specialized cell types, with remarkable regenerative and therapeutic results. Several factors could trigger the differentiation of MSCs into specific lineages, among them the biophysical and chemical characteristics of the extracellular matrix (ECM), including its stiffness, composition, topography, and mechanical properties. MSCs can sense and assess the stiffness of extracellular substrates through the process of mechanotransduction. Through this process, the extracellular matrix can govern and direct MSCs' lineage commitment through complex intracellular pathways. Hence, various biomimetic natural and synthetic polymeric matrices of tunable stiffness were developed and further investigated to mimic the MSCs' native tissues. Customizing scaffold materials to mimic cells' natural environment is of utmost importance during the process of tissue engineering. This review aims to highlight the regulatory role of matrix stiffness in directing the osteogenic differentiation of MSCs, addressing how MSCs sense and respond to their ECM, in addition to listing different polymeric biomaterials and methods used to alter their stiffness to dictate MSCs' differentiation towards the osteogenic lineage.