Objectives. The molecular mechanism of rheumatoid arthritis (RA) remains elusive. We conducted a protein-protein interaction network-based integrative analysis of genome-wide association studies (GWAS) and gene expression profiles of RA. Methods. We first performed a dense search of RA-associated gene modules by integrating a large GWAS meta-analysis dataset (containing 5539 RA patients and 20 169 healthy controls), protein interaction network and gene expression profiles of RA synovium and peripheral blood mononuclear cells (PBMCs). Gene ontology (GO) enrichment analysis was conducted by DAVID. The protein association networks of gene modules were generated by STRING. Results. For RA synovium, the top-ranked gene module is HLA-A, containing TAP2, HLA-A, HLA-C, TAPBP and LILRB1 genes. For RA PBMCs, the top-ranked gene module is GRB7, consisting of HLA-DRB5, HLA-DRA, GRB7, CD63 and KIT genes. Functional enrichment analysis identified three significant GO terms for RA synovium, including antigen processing and presentation of peptide antigen via major histocompatibility complex class I (false discovery rate (FDR) = 4.86 × 10 – 4), antigen processing and presentation of peptide antigen (FDR = 2.33 × 10 – 3) and eukaryotic translation initiation factor 4F complex (FDR = 2.52 × 10 – 2). Conclusion. This study reported several RA-associated gene modules and their functional association networks. Cite this article: X. Xiao, J. Hao, Y. Wen, W. Wang, X. Guo, F. Zhang. Genome-wide association studies and gene expression profiles of rheumatoid arthritis: an analysis. Bone Joint Res 2016;5:314–319. DOI: 10.1302/2046-3758.57.2000502

Background. Hyaluronan (HA) promotes extracellular matrix (ECM) production and inhibits the activity of matrix degrading enzymes in chondrocytes. The meniscus is composed of the avascular inner and vascular outer regions. Inner meniscus cells have a chondrocytic phenotype compared with outer meniscus cells. In this study, we examined the effect of HA on chondrocytic gene expression in human meniscus cells. Methods. Human meniscus cells were prepared from macroscopically intact lateral meniscus. Inner and outer meniscus cells were obtained from the inner and outer halves of the meniscus. The proliferative activity of meniscus cells was evaluated by WST-1 assay in the presence or absence of HA (MW = 600–1200 kDa; Seikagaku). Gene expression of SOX9, COL2A1, and COL1A1 was assessed by a quantitative real-time PCR analysis. The effect of HA on the gene expression and cellular proliferation was investigated under the treatment of interleukin (IL)-1α. Meniscal samples perforated by a 2-mm-diameter punch were maintained for 3 weeks in HA-supplemented media. Cultured meniscal samples were evaluated by histological analyses. Results. HA treatments stimulated cellular proliferation in both inner and outer meniscus cells. HA also increased COL2A1 expression in inner meniscus cells. On the other hand, HA did not induce COL2A1 expression in outer meniscus cells. Although IL-1α treatment decreased COL2A1 expression in inner meniscus cells, the decrease of COL2A1 expression was prevented by HA treatments. In addition, HA treatments increased cellular counts along the perforated surface of organ-cultured meniscal samples. Conclusion. The present study demonstrated that HA activated the proliferation and chondrocytic gene expression of inner meniscus cells. In addition, IL-1α-dependent decrease of COL2A1 expression was prevented by HA treatment. Our results suggest that intra-articular HA injection may be useful in the treatment of inner meniscal injury. Level of evidence. in vitro study, level IV. Disclosure. The authors have no conflicts of interest

Introduction. Bone morphogenetic proteins (BMPs) are members of the TGF-beta superfamily of growth factors and are known to regulate proliferation and expression of the differentiated phenotype of chondrocytes, osteoblasts, and osteoclasts. To investigate the osteoblastic differentiation gene expressions that contribute to BMP-7 dependent ostogenesis, we performed gene expression profiling of BMP-7-treated mouse bone marrow stromal cells. Methods. D1 cells (mouse bone marrow stromal cells) were cultured in osteogenic differentiation medium (ODM) for 3 days, and then treated with BMP-7 for 24 hr. Total RNA was extracted using Trizol, purified using RNeasy columns. Total RNA was amplified and purified using the Ambion Illumina RNA amplification kit to yield biotinylated cRNA. The data analysis up- and down-regulation developmental processes (anterior/posterior patterning, ectoderm development, embryogenesis, gametogenesis, mesoderm development, other development process, and segment specification) genes expression fold. Results. We detected 18 mRNAs (Id2, Igf2, Pparg, S100a10, Foxn3, Tulp3, Mycbp2, Notch3, Ptk7, Lrp4, Tnfrsf11b, Ogn, Cyr61, Mglap, Akp2, Ltbp4, Ibsp, and Thbs1) that were differentially up-regulated after BMP-7 stimulation. 3 mRNAs (Wars, Adss and Trim35) were differentially down-regulated after BMP-7 stimulation. Conclusion. The data indicate that BMP-7 regulate various developmental processes genes expression during osteoblastic differentiation. Though further studies are needed in relation to each expression gene profiles and osteoblastic differentiation, this information may serve as a point of comparison for osteoblastic differentiation of BMP-7. Furthermore, the data should facilitate the informed use of BMP-7 as a therapeutic agent and tissue engineering tool. Acknowledgement. This work was supported by the Korea Science and Engineering Foundation (KOSEF) grant funded by the Korea government (MEST) (No. R01-2008-000-10089-0)

Summary. Shear stress and hydrostatic effects on the hMSCs early mechano gene response were similar. For the same magnitude gene response, the hydrostatic compression (1.5×10. 5. Pascal) is a 200000 times greater than the force exerted by shear stress (0.7 Pascal). Introduction. In the lab, a perfusion bioreactor designed to automate the production of bone constructs was developed. The proof of concept was established in a large animal model of clinical relevance. The cells perfused in the bioreactor are likely to perceive 2 types of stresses: shear stress and hydrostatic pressure. Optimization of this bioreactor implies a better understanding of the effects of these forces on the cells in order to have better proliferation and differentiation. An understanding of the response of one cell layer submit to various strength is relevant. The primary objective of this study was to test the hypothesis that hMSCs have the fundamental ability to distinguish between different types of mechanical signals as evidenced by distinct gene expression. The effect of shear stress on one cell layer cultures of hMSCs will be evaluated using a commercially available system called Ibidi. For the hydrostatic pressure as there is no commercial device available, our group has developed a prototype capable of delivering a well-defined mechanical loading to cells in culture. Validation of the techniques: In order to validate the systems (shear stress and cyclic pressure apparatus) used in this study, we have used an osteocytes-like cell line, MLO-Y4. When stimulated by a 30 minutes PFF at 7 dyn/cm. 2. or hydrostatic compression at 1.5 bar, cells responded by producing NO in the culture media. NO release after mechanical stimulation of hMSCs: hMSCs were subjected to increased PFF (7 to 42 dyn/cm. 2. ) for 30 minutes. This stimulation resulted in an increased release of NO in the media compared to non-stimulated cells (p<0.05). Interestingly the level of NO was maximal at 7 dyn/cm. 2. and decreased with higher flow rate. Similar observation was made after hMSCs stimulation by hydrostatic pressure for 30 minutes: a peak of NO release at 1.5 bar was observed. Early gene expression of known mechano-sensitive genes: Gene expression analysis immediately after stimulation (PFF or hydrostatic compression) was performed on a range of known mechano-sensitive genes: NOS2, PTGS2, PTGES, IER3 and EGR1. Immediately after stimulation by PFF at 7 dyn/cm. 2. or hydrostatic pressure at 1.5 bars, the expression of all the genes of interest appear to be up regulated in stimulated cells. Conclusions. In the present study, hMSCs cells responses to two different treatments, shear stress and hydrostatic pressure, were monitored in parallel to study the difference in sensitivity to both mechanical stresses. Both systems used ensure a stable and reproducible strain condition in a well-controlled environment. We demonstrated that the shear stress and the hydrostatic pressure effects on the hMSCs were similar. We note that, for the same magnitude response, force exerted by the hydrostatic compression (1.5×10. 5. Pascal) on the cells is a 200000 times greater than the force exerted by shear stress (0.7 Pascal). This shows that the direct effect of hydrostatic compression on the hMSCs is negligible compared to the shear stress

It is supposed that disturbed vascularization is a major cause for the development of an atrophic non-union. However, an actual study revealed normal vessel formation in human non-union tissues [1]. An animal study using an atrophic non-union model should clarify the influence of the inhibition of angiogenesis by the inhibitor Fumagillin on bone healing and the underlying processes including inflammation, chondrogenesis, angiogenesis and osteogenesis. For each group and time point (3, 7, 14, 21 and 42 days) 5–6 adult female Sprague Dawley rats were analyzed. The tibia was osteotomized and stabilized intramedullary with a k-wire coated with the drug carrier PDLLA (control group) or PDLLA +10% Fumagillin (atrophy group). Microarrays: Total-RNA were pooled per group, labeled with the Agilent single-color Quick-Amp Labeling Kit Cy3 and hybridized on Agilent SurePrint G3 Rat Gene Expression microarrays. After feature extraction and quantile normalization, relevant biological processes were identified using GeneOntology. Genes with an expression value below the 25. percentile were excluded. Heatmaps were used for visualization. The analysis of inflammatory genes revealed an upregulation of monocyte/macrophage- relevant factors such as the chemokines Ccl2 and Ccl12 and the surface marker CD14. Other factors involved in the early inflammation process such as Il1a, Tnf and Il6 were not affected. Chondrogenic markers including Collagen Type II, -IX, -X, Mmp9, Mmp13, Hapln1, Ucma, Runx2, Sox5 and -9 were downregulated in this group. Furthermore, osteogenic factors were less regulated within the middle stage of healing (day 14–21). This gene panel included Bmps, Bmp antagonists, Bmp- and Tgfb receptors, integrines and matrix proteins. qPCR analysis of angiogenic genes showed an upregulation of Angpt2, Fgf1 and -2, but not for Vegfa over the later healing time points. We demonstrated in a previous study that inhibiting angiogenesis in an osteotomy model led to a reduction in vessel formation and to the development of an atrophic non-union phenotype [2]. The microarray analysis indicated no prolonged inflammatory reaction in the atrophy group. But the upregulation of chemokines together with a delay in hematoma degradation signs to a mismatch between recruitment and demand of macrophages from the vessel system. Furthermore, chondrogenesis was completely blocked, which was shown by a downregulation of chondrogenic but also osteogenic markers being involved in chondrogenic processes. A reduced recruitment of MSCs might be a possible explanation. Although, microarray data revealed only minor expression changes regarding angiogenic genes, validation by q-PCR showed an upregulation of Angpt2, Fgf1 and -2 over the later healing time points. Due to the heterogeneity of the callus tissue it might be that variations of gene expression of a single tissue type will be masked by the expression levels of other tissue types. This issue is even more pronounced when analyzing different time points and by pooling the samples

Introduction. Parathyroid hormone-related peptide (PTHrP) has been shown to be an important regulator of bone remodelling1. The aim of this study was to investigate the effect of the N-terminal domain of PTHrP (1–36) on osteogenic and angiogenic gene expression in human osteoblasts (HOB) and human bone marrow stromal cells (hBMSCs). Materials and Methods. Primary hBMSC's and HOBs were cultured in standard or osteogenic media with different concentrations of PTHrP, either continuously for 8, 24, 48 h and 9 days, or with 3 cycles of intermittent exposure (24 h with PTHrP, 24 h without) over 6 days. Cell lysates were then processed for analysis of gene expression. Expression of the osteogenic markers runt-related transcription factor 2 (RUNX-2), alkaline phosphatase (ALP) and Collagen 1, and the angiogenic marker; vascular endothelial growth factor (VEGF), were measured. Results. Exposure to PTHrP for ≤ 48 hours resulted in an upregulation of the angiogenic marker VEGF and the osteogenic markers RUNX-2, ALP and Collagen 1 in both cell types, peaking at a 1 nM PTHrP. Conversely, continuous exposure for 9 days, resulted in a downregulation of all osteogenic and angiogenic gene expression. HOB cells exposed intermittently to PTHrP showed an upregulation in VEGF and ALP, peaking at 10nM PTHrP. Discussion and Conclusion. Continuous exposure for short durations (<48 hours) and intermittent exposures of both HOB cells and BMSC's to PTHrP upregulated both osteogenic and angiogenic gene expression. Continuous exposure to 9 days however had the opposite effect, with a downregulation in gene transcription

INTRODUCTION. Bone marrow derived mesenchymal stem cells are a potential source of cells for the repair of articular cartilage defects. Hypoxia has been shown to improve chondrogenesis in adult stem cells. In this study we characterised bone marrow derived stem cells and investigated the effects of hypoxia on gene expression changes and chondrogenesis. MATERIALS AND METHODS. Adherent colony forming cells were isolated and cultured from the stromal component of bone marrow. The cells at passage 2 were characterised for stem cell surface epitopes, and then cultured as cell aggregates in chondrogenic medium under normoxic (20% oxygen) or hypoxic (5% oxygen) conditions for 14 days. Gene expression analysis, glycosoaminoglycan and DNA assays, and immunohistochemical staining were determined to assess chondrogenesis. RESULTS. Bone marrow derived adherent colony forming cells stained strongly for markers of adult mesenchymal stem cells including CD44, CD90 and CD105, and they were negative for the haematopoietic cell marker CD34 and for the neural and myogenic cell marker CD56. Interestingly, a high number of cells were also positive for the pericyte marker 3G5. Cell aggregates showed a chondrogenic response and in lowered oxygen there was increased matrix accumulation of proteoglycan, but less cell proliferation, which resulted in 3.2-fold more glycosoaminoglycan per DNA after 14 days of culture. In hypoxia there was increased expression of key transcription factor SOX6, and the expression of collagens II and XI, and aggrecan was also increased. DISCUSSION. Pericytes are a candidate stem cell in many tissue and our results show that bone marrow derived mesenchymal stem cells express the pericyte marker 3G5. The response to chondrogenic culture in these cells was enhanced by lowered oxygen tension, which up-regulated SOX6 and increased the synthesis and assembly of matrix during chondrogenesis. This has important implications for tissue engineering applications of bone marrow derived stem cells

Objectives

Effects of insulin-like growth factor 1 (IGF1), fibroblast growth factor 2 (FGF2) and bone morphogenetic protein 2 (BMP2) on the expression of genes involved in the proliferation and differentiation of osteoblasts in culture were analysed. The best sequence of growth factor addition that induces expansion of cells before their differentiation was sought.

We have examined the process of fusion of the intertransverse processes and bone graft in the rabbit by in situ hybridisation and evaluated the spatial and temporal expression of genes encoding pro-α1 (I) collagen (COL1A1), pro-α1 (II) collagen (COL2A1) and pro-α1 (X) collagen (COL10A1). Beginning at two weeks after operation, osteogenesis and chondrogenesis occurred around the transverse process and the grafted bone at the central portion of the area of the fusion mass. Osteoblasts and osteocytes at the newly-formed woven bone expressed COL1A1. At the cartilage, most chondrocytes expressed COL2A1 and some hypertrophic chondrocytes COL10A1. In some regions, co-expression of COL1A1 and COL2A1 was observed. At four weeks, such expressions for COL1A1, COL2A1 and COL10A1 became prominent at the area of the fusion mass. From four to six weeks, bone remodelling progressed from the area of the transverse processes towards the central zone. Osteoblasts lining the trabeculae expressed a strong signal for COL1A1. At the central portion of the area of the fusion mass, endochondral ossification progressed and chondrocytes expressed COL2A1 and COL10A1. Our findings show that the fusion process begins with the synthesis of collagens around the transverse processes and around the grafted bone independently. Various spatial and temporal osteogenic and chondrogenic responses, including intramembranous, endochondral and transchondroid bone formation, progress after bone grafting at the intertransverse processes. Bone formation through cartilage may play an important role in posterolateral spinal fusion

This study aimed to investigate the effect of irisin on human nucleus pulposus cells (hNPCs) in vitro. Our hypothesis was that irisin would improve hNPC metabolism and proliferation. hNPCs were isolated from intervertebral discs and cultured in alginate beads. hNPCs were exposed to phosphate-buffered saline (PBS) or recombinant irisin (r-irisin) at 5, 10 and 25 ng/mL (n=4). Each experiment was performed in triplicate. Cell proliferation was assessed with trypan blue staining-automated cell counting and PicoGreen assay. Glycosaminoglycan (GAG) content was measured using the DMMB assay. Metabolic activity was assessed with the MTT assay and the Griess Reagent System. Gene expression of collagen type II (COL2), matrix metalloproteinase (MMP)-13, tissue inhibitor of matrix metalloproteinase (TIMP)-1 and −3, aggrecan, interleukin (IL)-1β, a disintegrin and metalloproteinase with thrombospondin motifs (ADAMTS)-5 was measured by RT-PCR. MTT assay and ADAMTS-5, COL2, TIMP-1 and IL-1β gene expression were evaluated following incubation with 5, 10 and 25 ng/mL r-irisin for 24 hours and subsequent culture with 10 ng/ml IL-1β and vice versa (incubation for 24 hours with IL-1β and subsequent culture with r-irisin). Irisin increased hNPC proliferation (p<0.001), metabolic activity (p<0.05), GAG content (p<0.01), as well as COL2 (p<0.01), aggrecan (p<0.05), TIMP-1 and −3 (p<0.01) gene expression, while decreasing MMP-13 (p<0.05) and IL-1β (p<0.001) mRNA levels. r-irisin pretreatment of hNPCs cultured in pro-inflammatory conditions resulted in a rescue of metabolic activity (p<0.001) and a decrease of IL-1β (p<0.05) levels. Similarly, incubation of hNPCs with IL-1β and subsequent exposure to r-irisin increased hNPC metabolic activity (p<0.001), COL2 gene expression (p<0.05) and decreased IL-1β (p<0.05) and ADAMTS-5 levels (p<0.01). Irisin stimulates hNPC proliferation, metabolic activity, and anabolism by reducing IL-1β and catabolic enzyme expression while promoting matrix synthesis

Osteoarthritis (OA) is the most common joint disease, which is characterized by a progressive loss of proteoglycans and the destruction of extracellular matrix (ECM), leading to a loss of cartilage integrity and joint function. During OA development, chondrocytes alter ECM synthesis and change their gene expression profile including upregulation of hypertrophic markers known from the growth plate. Although physiological mechanical loading can support cartilage formation and maintenance, mechanical overload represents one major risk factor for OA development. To date, little is known on how an OA-like hypertrophic chondrocyte phenotype alters the response of cartilage tissue to mechanical loading. The aim of this study was to investigate whether a hypertrophic phenotype change of chondrocytes affects the response to physiological mechanical loading and to reveal differences compared to normal control cartilage. Cartilage replacement tissue was generated using human articular chondrocytes (normal control cartilage, n=3–5) or human mesenchymal stromal cells which develop a hypertrophic phenotype similar to the one observed in OA (OA cartilage model, n=3–6). Cells were seeded in a collagen type I/III carrier and attached to a beta-TCP bone replacement phase, building an osteochondral unit for simulation of natural conditions. After 21 and 35 days of chondrogenic (re)differentiation, a single physiological mechanical compression episode (1 Hz, 25 %, 3 h) was applied, imitating three hours of normal walking in ten-minute intervals. Proteoglycan and collagen synthesis, gene expression and activation of signaling pathways were assessed. Cartilage replacement tissue of both groups had similar proteoglycan and collagen type II content as well as hardness properties. During (re)differentiation, both cell types showed a comparable upregulation of the chondrogenic marker genes COL2A1 and ACAN. As expected, hypertrophic marker genes (COL10A1, ALPL, MEF2C, IBSP) were only upregulated in the OA cartilage model. Mechanotransduction in both tissues was confirmed by load-induced activation of pERK1/2 signaling. While the 3 h loading episode significantly increased proteoglycan synthesis in normal control cartilage at day 35, the same protocol resulted in a suppression of proteoglycan and collagen synthesis in the OA cartilage model, which was accompanied by a downregulation of COL2A1 gene expression. In addition, hypertrophic marker genes COL10A1, ALPL and IBSP were significantly reduced after loading. Along lower load-induced SOX9 mRNA and protein stimulation in the OA cartilage tissue, a weaker induction of mechanosensitive BMP2, BMP6, FOS and FOSB gene expression was observed. While stable cartilage showed anabolic effects after physiological loading, the hypertrophic chondrocytes reacted with a reduced extracellular matrix synthesis. This could be explained by a lower mechanoinduction of the BMP signaling cascade and insufficient SOX9 stimulation. Progressive OA development could thus be influenced by a reduced mechanocompetence of osteoarthritic chondrocytes

Nitric oxide is a free radical which in vivo is solely produced during the conversion of the amino acid arginine into citrulline by nitric oxide synthase enzymes. Recently, the importance of nitric oxide on inflammation and bone metabolism has been investigated. However, the knowledge regarding possible in vitro effects of arginine supplementation on chondrogenic differentiation is limited. ATDC5, a cell line which is derived from mouse teratocarcinoma cells and which is characterized as chondrogenic cell line, were proliferated in Dulbecco's Modified Eagle Medium (DMEM)/F12 and subsequently differentiated in proliferation medium supplemented with insulin, transferrin and sodium-selenite and where arginine was added in four different concentrations (0, 7.5, 15 and 30 mM). Samples were harvested after 7 or 10 days and were stored at −80 °C for subsequent RNA isolation for qPCR analysis. To determine chondrogenic differentiation, Alcian Blue staining was performed to stain the proteoglycan aggrecan, which is secreted by differentiated ATDC5 cells. All measurements were performed in triplo. Alcian Blue staining showed a qualitative increase of proteoglycan aggrecan secretion in differentiated ATDC5 cells after treatment with 7 and 15 mM arginine, with additional increased expression of ColII, ColX, Bmp4 and Bmp6. Treatment with 30 mM arginine inhibited chondrogenic differentiation and expression of aforementioned genes, however, Cox-2 and Vegfa gene expression were increased in these samples. Bmp7 was not significantly expressed in any experimental condition. The obtained results are suggestive for a dose-dependent effect of arginine supplementation on chondrogenic differentiation and associated gene expression, with 7.5 and 15 mM as most optimal concentrations and implications for apoptosis after incubation with 30 mM arginine. A future recommendation would be to investigate the effects of citrulline in a similar experiment, as this shows even more promising results to enhance the nitric oxide metabolism in sepsis and bone healing

To design slow resorption patient-specific bone graft whose properties of bone regeneration are increased by its geometry and composition and to assess it in in-vitro and in-vivo models. A graft composed by hydroxyapatite (HA) and β-TCP was designed as a cylinder with 3D gyroid porosities and 7 mm medullary space based on swine's anatomy. It was produced using a stereolithography 3D-printing machine (V6000, Prodways). Sterile bone grafts impregnated with or without a 10µg/mL porcine BMP-2 (pBMP-2) solution were implanted into porcine femurs in a bone loss model. Bone defect was bi-weekly evaluated by X-ray during 3 months. After sacrifice, microscanner and non-decalcified histology analysis were conducted on biopsies. Finally, osteoblasts were cultured inside the bone graft or in monolayer underneath the bone graft. Cell viability, proliferation, and gene expression were assessed after 7 and 14 days of cell culture (n=3 patients). 3D scaffolds were successfully manufactured with a composition of 80% HA and 20% β-TCP ±5% with indentation compressive strength of 4.14 MPa and bending strength of 11.8MPa. In vivo study showed that bone regeneration was highly improved in presence of pBMP-2. Micro-CT shows a filling of the gyroid sinuses of the implant (Figure 1). In vitro, the presence of BMP2 did not influence the viability of the osteoblasts and the mortality remained below 3%. After 7 days, the presence of BMP2 in the scaffold significantly increased by 85 and 65% the COL1A1 expression and by 8 and 33-fold the TNAP expression by osteoblasts in the monolayer or in the scaffold, respectively. This BMP2 effect was transient in monolayer and did not modify gene expression at day 14. BMP2-impregnated bone graft is a promising patient-personalized 3D-printed solution for bone defect regeneration, by promoting neighboring host cells recruitment and solid new bone formation. For any figures and tables, please contact the authors directly

Meniscus tears have been treated using partial meniscectomy to relieve pain in patients, although this leads to the onset of early osteoarthritis (OA). Cell-based therapies can help preserve the meniscus, although the presence of inflammatory cytokines compromises clinical outcomes. Anti-inflammatory drugs (e.g. celecoxib), can help to reduce pain in patients and in vitro studies suggest a beneficial effect on cytokine inhibited matrix content. Previously, we have demonstrated that the inhibitory effects of IL-1β can be countered by culture under low oxygen tension or physioxia. The present study sought to understand whether physioxia, celecoxib or combined application can counter the inhibitory effects IL-1β inhibited meniscus cells. Human avascular and vascular meniscus cells (n =3) were isolated and expanded under 20% (hyperoxia) or 2% (physioxia) oxygen. Cells were seeded into collagen scaffolds (Geistlich, Wolhusen) and cultured for 28 days either in the presence of 0.1ng/mL IL-1β, 5µg/mL celecoxib or both under their expansion oxygen conditions. Histological (DMMB, collagen I and collagen II immunostaining), GAG content and gene expression analysis was evaluated for the scaffolds. Under hyperoxia, meniscus cells showed a significant reduction in GAG content in the presence of IL-1β (*p < 0.05). Celecoxib alone did not significantly increase GAG content in IL-1β treated cultures. In contrast, physioxic culture showed a donor dependent increase in GAG content in control, IL-1β and celecoxib treated cultures with corresponding histological staining correlating with these results. Additionally, gene expression showed an upregulation in COL1A1, COL2A1 and ACAN and a downregulation in MMP13 and ADAMTS5 under physioxia for all experimental groups. Physioxia alone had a stronger effect in countering the inhibitory effects of IL-1β treated meniscus cells than celecoxib under hyperoxia. Preconditioning meniscus cells under physioxia prior to implantation has the potential to improve clinical outcomes for cell-based therapies of the meniscus

Meniscal injuries affect over 1.5 million people across Europe and the USA annually. Injury greatly reduces knee joint mobility and quality of life and frequently leads to the development of osteoarthritis. Tissue engineered strategies have emerged in response to a lack of viable treatments for meniscal pathologies. However, to date, constructs mimicking the structural and functional organisation of native tissue, whilst promoting deposition of new extracellular matrix, remains a bottleneck in meniscal repair. 3D bioprinting allows for deposition and patterning of biological materials with high spatial resolution. This project aims to develop a biomimetic 3D bioprinted meniscal substitute. Meniscal tissue was characterised to effectively inform the design of biomaterials for bioprinting constructs with appropriate structural and functional properties. Histology, gene expression and mass spectrometry were performed on native tissue to investigate tissue architecture, matrix components, cell populations and protein expression regionally across the meniscus. 3D laser scanning and magnetic resonance imaging were employed to acquire the external geometrical information prior to fabrication of a 3D printed meniscus. Bioink suitability was investigated through regional meniscal cell encapsulation in blended hydrogels, with the incorporation of growth factors and assessed for their suitability through rheology, scanning electron microscopy, histology and gene expression analysis. Meniscal tissue characterisation revealed regional variations in matrix compositions, cellular populations and protein expression. The process of imaging through to 3D printing highlighted the capability of producing a construct that accurately replicated meniscal geometries. Regional meniscal cell encapsulation into hydrogels revealed a recovery in cell phenotype, with the incorporation of growth factors into the bioink's stimulating cellular re-differentiation and improved zonal functionality. Meniscus biofabrication highlights the potential to print patient specific, customisable meniscal implants. Achieving zonally distinct variations in cell and matrix deposition highlights the ability to fabricate a highly complex tissue engineered construct. Acknowledgements: This work was undertaken as part of the UK Research and Innovation (UKRI)-funded CDT in Advanced Biomedical Materials

Successful anterior cruciate ligament (ACL) reconstructions strive a firm ligament-bone integration. Therefore, the aim of this study was to address in more detail the enthesis as the thriphasic bone attachment of the ACL using a tissue engineering approach. To establish a tissue-engineered enthesis-like construct, triphasic scaffolds embroidered from poly(L-lactide-co-caprolactone) and polylactic acid functionalized with collagen foam were colonized with osteogenically differentiated human mesenchymal stromal cells (hMSCs) and lapine (L) ACL fibroblasts. These triphasic scaffolds with a bone-, a fibrocartilage transition- and a ligament phase were seeded directly after spheroid assembly or with 14 days precultured LACL fibroblast spheroids and 14 days osteogenically differentiated hMSCs spheroids (=longer preculture) and cultured for further 14 days. Cell survival was tested. Collagen type I and vimentin were immunolabeled and the content of DNA and sulfated glycosaminoglycan (sGAG) was quantified. The relative gene expression of tenascin C, type I and X collagens, Mohawk and Runx2 was analyzed. Compared to the LACL spheroids the hMSC spheroids adhered better to the scaffold surface with faster cell outgrowth on the fibers. Collagen type I and vimentin were mainly detected in the hMSCs colonizing the bone zone. The DNA content was generally higher in the bone (hMSCs) than in the ligament zones and after short spheroid preculture higher than after longer preculture whereas the sGAG content was greater after longer preculture for both cell types. The longer precultivated hMSCs expressed more type I collagen in comparison to those only shortly precultured before scaffold seeding. Type I collagen and tenascin C were higher expressed in scaffolds directly colonized with LACL compared to those seeded after longer spheroid preculture. The gene expression of ECM components and transcription factors depended on cell type and preculturing condition. Zonal colonization of triphasic scaffolds using the spheroid method is possible offering a novel approach for enthesis tissue engineering

While cell morphology has been recognized as a fundamental regulator of cell behavior, few studies have measured the complex cell morphological changes of chondrocytes using quantitative cell morphometry descriptors in relation to inflammation and phenotypic outcome. Acute vs. persistent exposure to IL-1β and how IL-1β modulated dynamic changes in cell morphology in relation to the phenotype, donor and OA grade in healthy and osteoarthritis (OA) chondrocytes was investigated. A panel of quantitative cell morphometry descriptors was measured using an automated high-throughput method. Absolute quantification of gene expression was measured by ddPCR followed by correlation analyses. In OA chondrocytes, chronic IL-1β significantly decreased COL2A1, SOX9, and ACAN, increased IL-6 and IL-8 levels and caused chondrocytes to become less wide, smaller, longer, slimmer, less round and more circular, consistent with a de-differentiated phenotype. In healthy chondrocytes, 3 days after acute (72 h) IL-1β exposure, COL1A2 and IL-6 significantly increased but had minor effects on cell morphology. However, in healthy chondrocytes, persistent IL-1β led to more profound effects in all cell morphology descriptors and chondrocytes expressed significantly less COL2A1 and more IL-6 and IL-8 vs. controls and acutely-stimulated chondrocytes. In both OA and healthy chronically-stimulated chondrocytes, area, width and circularity were sensitive to the persistent presence of the IL-1β cytokine. Moreover, there were many significant and strong correlations among the measured parameters, with several indications of an IL-1β-mediated mechanism. Cell morphology combined with gene expression analysis could guide researchers interested in understanding inflammatory effects in the complex domain of cartilage/chondrocyte biology. Use of quantitative cell morphometry could complement classical approaches by providing numerical data on a large number of cells, thereby providing a biological fingerprint for describing chondrocyte phenotype, which could help to understand how changes in cell morphology lead to disease progression

Worldwide, tendon disorders are one of the main causes of disability that decrease the quality of life of individuals and represent a substantial economic burden on society. Currently, the main therapies used for tendon injuries are not able to restore tendon functionality, and due to tendons' hypovascular and hypocellular nature, they present a reduced healing capacity, which also limits the success of the available therapies. In order to discover new therapies, extracellular vesicles (EVs), key players in cell-cell communication, have been widely explored for tissue engineering and regenerative medicine applications. Thus, the aim of this study is to assess the role of EVs derived from platelets in stem cell tenogenic commitment using a bioengineered tendon in vitro model for potential use as tendon therapeutic agents. Biomimetic platelet-derived EVs were produced by freeze-thaw cycles of platelets and isolation at different centrifugation speed. To recreate the architecture of tendons, a 3D system consisting of electrospun anisotropic nanofiber scaffolds coated with collagen encapsulating human adipose stem cells (hASCs) and different types of platelet-derived EVs, were produced. Then, the influence of the tendon-mimetic constructs and the distinct EVs populations in the hASCs tenogenic differentiation were assessed over culture time. We observed that the hASCs on the nanofibrous tendon scaffolds, show high cytoskeleton anisotropic organization that is characteristic of tenocytes. Moreover, acting as biological cues, platelet-derived EVs boosted hASCs tenogenic commitment, supported by the increased gene expression of tendon-related markers (SCX and TNMD). Additionally, EVs enhanced the deposition of tendon like extracellular matrix (ECM), as evidenced by the increased gene expression of ECM-related markers such as COL1, COL3, DCN, TNC, and MMP-3, which are fundamental for ECM synthesis and degradation balance. Moreover, EVs induced lower collagen matrix contraction on hASCs, which has been related with lower myofibroblast differentiation. Overall, the results revealed that EVs are capable of modulating stem cells' behavior boosting their tenogenic commitment, through the increased expression of healthy tendon cell markers, potentiating ECM deposition and decreasing cell contractility. Therefore, platelet EVs are a promising biochemical tool, worthy to be further explored, as paracrine signaling that might potentiate tendon repair and regeneration

In relation to regenerative therapies in osteoarthritis and cartilage repair, mesenchymal stromal cells (MSCs) have immunomodulatory functions and influence macrophage behaviour. Macrophages exist as a spectrum of pro-(M1) and anti-(M2) inflammatory phenotypic subsets. In the context of cartilage repair, we investigated MSC-macrophage crosstalk, including specifically the priming of cartilage cells by macrophages to achieve a regenerative rather than fibrotic outcome. Human monocytes were isolated from blood cones and differentiated towards M1 and M2 macrophages. Monocytes (Mo), M1 and M2 macrophages were cultured directly and indirectly (trans-well system) with human bone marrow derived MSCs. MSCs were added during M1 polarisation and separately to already induced M1 cells. Outcomes (M1/M2 markers and ligands/receptors) were evaluated using RT-qPCR and flow cytometry. Influence on chondrogenesis was assessed by applying M1 and M2 macrophage conditioned media (CM) sequentially to cartilage derived cells (recapitulating an acute injury environment). RT-qPCR was used to evaluate chondrogenic/fibrogenic gene transcription. The ratio of M2 markers (CD206 or CD163) to M1 markers (CD38) increased when MSCs were added to Mo/M1 macrophages, regardless of culture system used (direct or indirect). Pro-inflammatory markers (including TNFβ) decreased. CXCR2 expression by both M1 macrophages and MSCs decreased when MSCs were added to differentiated M1 macrophages in transwell. When adding initially M1 CM (for 12 hours) followed by M2 CM (for 12 hours) sequentially to chondrocytes, there was a significant increase of Aggrecan and Collagen type 2 gene expression and decrease in fibroblastic cell surface markers (PDPN/CD90). Mo/M1 macrophages cultured with MSCs, directly or indirectly, are shifted towards a more M2 phenotype. Indirect culture suggests this effect can occur via soluble signaling mediators. Sequential exposure of M1CM followed by M2CM to chondrocytes resulted in increased chondrogenic and reduced fibrotic gene expression, suggesting that an acute pro-inflammatory stimulus may prime chondrocytes before repair

Herein we address, hyaline cartilage regeneration issue by engineering a synthetic biocompatible hydrogel scaffold capable to promote chondrogenic differentiation. In this study, the chemically crosslinked hydrogels consisting of synthetic peptides that have the collagen-like sequence Cys-Gly-(Pro-Lys-Gly)4 (Pro-Hyp-Gly)4 (Asp-Hyp-Gly)4- conjugated with RGD sequence (CLP-RGD) and crosslinked hydrogels of type I collagen (CA) were used. For cartilage formation, we used human skeletal muscle-derived stem/progenitor cells (hMDSPCs) set for differentiation towards a chondrogenic lineage by BMP-7 and TGF-ß3 growth factors. Initially 150, 100 and 75 ng of BMP-7and TGF-ß3 growth factors were inserted in each scaffold and amount of growth factors diffusing out of the scaffolds was observed by ELISA assays. In vitro experiments were performed by seeding hMDSPCs onto hydrogels loaded with growth factors (75ng/scaffold) and cultured for 28 days. Cartilage formation was monitored by ELISA and RT-PCR assays. All experiments were performed in triplicates or quadruplicates. Growth factors incorporation strategy allowed a sustained release of TGF-ß3 growth factor, 6.00.3% of the initially loaded amount diffused out after 4 h and 2.70.5% already at the second time point (24h) from CA and CLP-RGD substrates. For the BMP-7 growth factor, 13.12.3% and 15.751.6% of the initially loaded amount diffused out after 4 h, 1.70.2% and 2.450.3% at the second time point (24 h) from CA and CLP-RGD respectively. In vitro experiments shown that scaffolds with immobilized growth factors resulted in higher collagen type II accumulation when compared to the scaffolds alone. The gene expression on CLP-RGD hydrogels with growth factors has shown lower collagen type I expression and higher aggrecan expression compared to day 0. However, we also report increased collagen X gene expression on CA hydrogels (with growth factors). Our results support the potential of the strategy of combining hydrogels functionalized with differentiation factors toward improving cartilage repair