Bone and cartilage differentiation of a single stem cell population driven by material interface

Inhibition of miR‑98‑5p promotes high glucose‑induced suppression of preosteoblast proliferation and differentiation via the activation of the PI3K/AKT/GSK3β signaling pathway by targeting BMP2

Osteoporosis (OP) is a bone metabolic disease, in which low bone mass and the microarchitectural deterioration of bone tissue contribute to the fragility of bones and increase the risk of fracture. The aim of the present study was to determine the role of microRNA (miR)-98-5p in high glucose (HG)-induced preosteoblasts. HG was used to induce preosteoblasts treated in a differentiation medium to establish an in vitro OP model. Next, miR-98-5p expression was determined using reverse transcription-quantitative PCR. Following the transfection of an miR-98-5p inhibitor into HG-treated osteoblasts, cell viability was assessed using a Cell Counting Kit-8 assay, while alkaline phosphatase (ALP) activity, differentiation ability and the expression of differentiation-regulated genes osteocalcin and osteopontin were measured using the corresponding ALP, Alizarin red staining, reverse transcription-quantitative PCR and western blotting assays. The association between miR-98-5p and the PI3K/AKT/GSK3β signaling pathway was determined using western blotting. Next, the binding relationship between miR-98-5p and bone morphogenetic protein 2 (BMP2) was predicted and verified, and the role of BMP2 in the regulation of the PI3K/AKT/GSK3β signaling pathway was explored using western blotting. The results revealed that miR-98-5p expression was upregulated in HG-induced osteoblasts, and the inhibition of miR-98-5p resulted in enhanced cell viability, alkaline phosphatase activity and differentiation in osteoblasts following HG induction. It was also discovered that miR-98-5p inhibition activated PI3K/AKT/GSK3β signaling, while knockdown of BMP2, which binds to miR-98-5p, enhanced the activation of this signaling pathway and the differentiation ability of osteoblasts. In conclusion, the findings of the present study suggested that the inhibition of miR-98-5p expression may activate PI3K/AKT/GSK3β signaling to promote HG-induced suppression of preosteoblast viability and differentiation by targeting BMP2, which provides a novel insight into future potential molecular markers for OP treatment.

Fabrication of nanocomposite/nanofibrous functionally graded biomimetic scaffolds for osteochondral tissue regeneration

One of the main challenges in treating osteochondral lesions via tissue engineering approach is providing scaffolds with unique characteristics to mimic the complexity. It has led to application of heterogeneous scaffolds as a potential candidate for engineering of osteochondral tissues, in which graded multilayered-structure should promote bone and cartilage growth. By designing three-dimensional (3D)-nanofibrous scaffolds mimicking the native extracellular matrix's nanoscale structure, cells can grow in controlled conditions and regenerate the damaged tissue. In this study, novel 3D-functionality graded nanofibrous scaffolds composed of five layers based on different compositions containing polycaprolactone(PCL)/gelatin(Gel)/nanohydroxyapatite (nHA) for osteoregeneration and chitosan(Cs)/polyvinylalcohol(PVA) for chondral regeneration are introduced. This scaffold is fabricated by electrospinning technique using spring as collector to create 3D-nanofibrous scaffolds. Fourier-transform infrared spectroscopy, X-ray diffraction, energy dispersive X-ray spectroscopy, scanning electron microscopy, mechanical compression test, porosimetry, and water uptake studies were applied to study each layer's physicochemical properties and whole functionally graded scaffold. Besides, biodegradation and biological studies were done to investigate biological performance of scaffold. Results showed that each layer has a fibrous structure with continuous nanofibers with improved pore size and porosity of novel 3D scaffold (6-13 μm and 90%) compared with two-dimensional (2D) mat (2.2 μm and 19.3%) with higher water uptake capacity (about 100 times of 2D mat). Compression modulus of electrospun scaffold was increased to 78 MPa by adding nHA. The biological studies revealed that the layer designed for osteoregeneration could improve cell proliferation rate in comparison to the layer designed for chondral regeneration. These results showed such structure possesses a promising potential for the treatment of osteochondral defects.

Functional State of Mesenchymal Stem Cells upon Exposure to Bioactive Coatings on Titanium Alloys

Bioactive coatings on implants affect osteogenic differentiation of mesenchymal stem cells (MSC). We studied the morphofunctional state of bone marrow MSC cultured on the surface of calcium phosphate coatings on titanium formed by plasma electrolytic oxidation (PEO). The biocompatible properties of the coatings manifested in the absence of the cytotoxic effect on cells. High expression of receptors (CD90, CD29, and CD106), enhanced synthesis of osteocalcin and osteopontin, and changes in surface architectonics of MSC adherent to the samples confirmed osteoinductive properties of the calcium phosphate PEO coating.

Designing stem cell niches for differentiation and self-renewal

Mesenchymal stem cells, characterized by their ability to differentiate into skeletal tissues and self-renew, hold great promise for both regenerative medicine and novel therapeutic discovery. However, their regenerative capacity is retained only when in contact with their specialized microenvironment, termed the stem cell niche Niches provide structural and functional cues that are both biochemical and biophysical, stem cells integrate this complex array of signals with intrinsic regulatory networks to meet physiological demands. Although, some of these regulatory mechanisms remain poorly understood or difficult to harness with traditional culture systems. Biomaterial strategies are being developed that aim to recapitulate stem cell niches, by engineering microenvironments with physiological-like niche properties that aim to elucidate stem cell-regulatory mechanisms, and to harness their regenerative capacity in vitro In the future, engineered niches will prove important tools for both regenerative medicine and therapeutic discoveries.

Controlled Nanoscale Topographies for Osteogenic Differentiation of Mesenchymal Stem Cells

Nanotopography with length scales of the order of extracellular matrix elements offers the possibility of regulating cell behavior. Investigation of the impact of nanotopography on cell response has been limited by the inability to precisely control geometries, especially at high spatial resolutions and across practically large areas. In this paper, we demonstrate well-controlled and periodic nanopillar arrays of silicon and investigate their impact on osteogenic differentiation of human mesenchymal stem cells (hMSCs). Silicon nanopillar arrays with critical dimensions in the range of 40-200 nm, exhibiting standard deviations below 15% across full wafers, were realized using the self-assembly of block copolymer colloids. Immunofluorescence and quantitative polymerase chain reaction measurements reveal clear dependence of osteogenic differentiation of hMSCs on the diameter and periodicity of the arrays. Further, the differentiation of hMSCs was found to be dependent on the age of the donor. While osteoblastic differentiation was found to be promoted by the pillars with larger diameters and heights independent of donor age, they were found to be different for different spacings. Pillar arrays with smaller pitch promoted differentiation from a young donor, while a larger spacing promoted those of an old donor. These findings can contribute for the development of personalized treatments of bone diseases, namely, novel implant nanostructuring depending on patient age.

Differential chondro- and osteo-stimulation in three-dimensional porous scaffolds with different topological surfaces provides a design strategy for biphasic osteochondral engineering

Bone/cartilage interfacial tissue engineering needs to satisfy the differential properties and architectures of the osteochondral region. Therefore, biphasic or multiphasic scaffolds that aim to mimic the gradient hierarchy are widely used. Here, we find that two differently structured (topographically) three-dimensional scaffolds, namely, "dense" and "nanofibrous" surfaces, show differential stimulation in osteo- and chondro-responses of cells. While the nanofibrous scaffolds accelerate the osteogenesis of mesenchymal stem cells, the dense scaffolds are better in preserving the phenotypes of chondrocytes. Two types of porous scaffolds, generated by a salt-leaching method combined with a phase-separation process using the poly(lactic acid) composition, had a similar level of porosity (~90%) and pore size (~150 μm). The major difference in the surface nanostructure led to substantial changes in the surface area and water hydrophilicity (nanofibrous ≫ dense); as a result, the nanofibrous scaffolds increased the cell-to-matrix adhesion of mesenchymal stem cells significantly while decreasing the cell-to-cell contracts. Importantly, the chondrocytes, when cultured on nanofibrous scaffolds, were prone to lose their phenotype, including reduced chondrogenic expressions (SOX-9, collagen type II, and Aggrecan) and glycosaminoglycan content, which was ascribed to the enhanced cell-matrix adhesion with reduced cell-cell contacts. On the contrary, the osteogenesis of mesenchymal stem cells was significantly accelerated by the improved cell-to-matrix adhesion, as evidenced in the enhanced osteogenic expressions (RUNX2, bone sialoprotein, and osteopontin) and cellular mineralization. Based on these findings, we consider that the dense scaffold is preferentially used for the chondral-part, whereas the nanofibrous structure is suitable for osteo-part, to provide an optimal biphasic matrix environment for osteochondral tissue engineering.

Novel In Situ Gelling Hydrogels Loaded with Recombinant Collagen Peptide Microspheres as a Slow-Release System Induce Ectopic Bone Formation

New solutions for large bone defect repair are needed. Here, in situ gelling slow release systems for bone induction are assessed. Collagen-I based Recombinant Peptide (RCP) microspheres (MSs) are produced and used as a carrier for bone morphogenetic protein 2 (BMP-2). The RCP-MSs are dispersed in three hydrogels: high mannuronate (SLM) alginate, high guluronate (SLG) alginate, and thermoresponsive hyaluronan derivative (HApN). HApN+RCP-MS forms a gel structure at 32 ºC or above, while SLM+RCP-MS and SLG+RCP-MS respond to shear stress displaying thixotropic behavior. Alginate formulations show sustained release of BMP-2, while there is minimal release from HApN. These formulations are injected subcutaneously in rats. SLM+RCP-MS and SLG+RCP-MS loaded with BMP-2 induce ectopic bone formation as revealed by X-ray tomography and histology, whereas HApN+RCP-MS do not. Vascularization occurs within all the formulations studied and is significantly higher in SLG+MS and HApN+RCP-MS than in SLM+RCP-MS. Inflammation (based on macrophage subset staining) decreases over time in both alginate groups, but increases in the HApN+RCP-MS condition. It is shown that a balance between inflammatory cell infiltration, BMP-2 release, and vascularization, achieved in the SLG+RCP-MS alginate condition, is optimal for the induction of de novo bone formation.

Intra-articular biomaterials-assisted delivery to treat temporomandibular joint disorders

The temporomandibular joint disorder, also known as myofascial pain syndrome, is considered one of the prevalent chronic pain diseases caused by muscle inflammation and cartilage degradation in head and neck, and thus influences even biopsychosocial conditions in a lifetime. There are several current treatment methodologies relieving inflammation and preventing degradation of the joint complex. One of the promising non-surgical treatment methods is an intra-articular injection of drugs such as corticosteroids, analgesics, and anti-depressants. However, the side effects of drugs due to frequent injections and over-doses, including dizziness, dry mouth, and possible drug dependency are considered limitations. Thus, the delivery of therapeutic molecules through the use of nano/microparticles is currently considered as a promising strategy primarily due to the controlled release. This review highlights the nano/microparticle systems for effective intra-articular therapeutics delivery to prevent cartilage degradation and protect subchondral bone in a temporomandibular joint.

Efficacy of collagen and alginate hydrogels for the prevention of rat chondrocyte dedifferentiation

Dedifferentiation of chondrocytes remains a major problem in cartilage tissue engineering. The development of hydrogels that can preserve chondrogenic phenotype and prevent chondrocyte dedifferentiation is a meaningful strategy to solve dedifferentiation problem of chondrocytes. In the present study, three gels were prepared (alginate gel (Alg gel), type I collagen gel (Col gel), and their combination gel (Alg/Col gel)), and the in vitro efficacy of chondrocytes culture while preserving their phenotypes was investigated. While Col gel became substantially contracted with time, the cells encapsulated in Alg gel preserved the shape over the culture period of 14 days. The mechanical and cell-associated contraction behaviors of Alg/Col gel were similar to those of Alg. The cells in Alg and Alg/Col gels exhibited round morphology, whereas those in Col gel became elongated (i.e. fibroblast-like) during cultures. The cells proliferated with time in all gels with the highest proliferation being attained in Col gel. The expression of chondrogenic genes, including SOX9, type II collagen, and aggrecan, was significantly up-regulated in Alg/Col gel and Col gel, particularly in Col gel. However, the chondrocyte dedifferentiation markers, type I collagen and alkaline phosphatase (ALP), were also expressed at significant levels in Col gel, which being contrasted with the events in Alg and Alg/Col gels. The current results suggest the cells cultured in hydrogels can express chondrocyte dedifferentiation markers as well as chondrocyte markers, which draws attention to choose proper hydrogels for chondrocyte-based cartilage tissue engineering.