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

Introduction. Osteoarthritis (OA) is a progressively debilitating disease that affects mostly cartilage, with associated changes in the bone. The increasing incidence of OA and an ageing population, coupled with insufficient therapeutic choices, has led to focus on the potential of stem cells as a novel strategy for cartilage repair. Methods. In this study, we used scaffold-free mesenchymal stem cells (MSCs) obtained from bone marrow in an experimental animal model of OA by direct intra-articular injection. MSCs were isolated from 2.8 kg white New Zealand rabbits. There were ten in the study group and ten in the control group. OA was induced by unilateral transection of the anterior cruciate ligament of the knee joint. At 12 weeks post-operatively, a single dose of 1 million cells suspended in 1 ml of medium was delivered to the injured knee by direct intra-articular injection. The control group received 1 ml of medium without cells. The knees were examined at 16 and 20 weeks following surgery. Repair was investigated radiologically, grossly and histologically using haematoxylin and eosin, Safranin-O and toluidine blue staining. Results. Radiological assessment confirmed development of OA changes after 12 weeks. Rabbits receiving MSCs showed a lower degree of cartilage degeneration, osteophyte formation, and subchondral sclerosis than the control group at 20 weeks post-operatively. The quality of cartilage was significantly better in the cell-treated group compared with the control group after 20 weeks. Conclusions. Bone marrow-derived MSCs could be promising cell sources for the treatment of OA. Neither stem cell culture nor scaffolds are absolutely necessary for a favourable outcome. Cite this article: Bone Joint Res 2014;3:32–7

Introduction. PIEZO mechanoreceptors are increasingly recognized to play critical roles in fundamental physiological processes like proprioception, touch, or tendon biomechanics. However, their gating mechanisms and downstream signaling are still not completely understood, mainly due to the lack of effective tools to probe these processes. Here, we developed new tailor-made nanoswitches enabling wireless targeted actuation on PIEZO1 by combining molecular imprinting concepts with magnetic systems. Method. Two epitopes from functionally relevant domains of PIEZO1 were rationally selected in silico and used as templates for synthesizing molecularly imprinted nanoparticles (MINPs). Highly-responsive superparamagnetic zinc-doped iron oxide nanoparticles were incorporated into MINPs to grant them magnetic responsiveness. Endothelial cells (ECs) and adipose tissue-derived stem cells (ASCs) incubated with each type of MINP were cultured under or without the application of cyclical magnetomechanical stimulation. Downstream effects of PIEZO1 actuation on cell mechanotransduction signaling and stem cell fate were screened by analyzing gene expression profiles. Result. Nanoswitches showed sub-nanomolar affinity for their respective epitope, binding PIEZO1-expressing ECs similarly to antibodies. Expression of genes downstream of PIEZO1 activity significantly changed after magnetomechanical stimulation, demonstrating that nanoswitches can transduce this stimulus directly to PIEZO1 mechanoreceptors. Moreover, this wireless actuation system proved effective for modulating the expression of genes related to musculoskeletal differentiation pathways in ASCs, with RNA-sequencing showing pronounced shifts in extracellular matrix organization, signal transduction, or collagen biosynthesis and modification. Importantly, targeting each epitope led to different signaling effects, implying distinct roles for each domain in the sophisticated function of these channels. Conclusion. This innovative wireless actuation technology provides a promising approach for dissecting PIEZO-mediated mechanobiology and suggests potential therapeutic applications targeting PIEZO1 in regenerative medicine for mechanosensitive tissues like tendon. Acknowledgements. EU's Horizon 2020 ERC under grant No. 772817 and Horizon Europe under grant No. 101069302; FCT/MCTES for PD/BD/143039/2018, COVID/BD/153025/2022, 10.54499/2020.03410.CEECIND/CP1600/CT0013, 10.54499/2022.05526.PTDC, 10.54499/UIDB/50026/2020, 10.54499/UIDP/50026/2020, and 10.54499/LA/P/0050/2020

Objectives. Mesenchymal stem cells have the ability to differentiate into various cell types, and thus have emerged as promising alternatives to chondrocytes in cell-based cartilage repair methods. The aim of this experimental study was to investigate the effect of bone marrow derived mesenchymal stem cells combined with platelet rich fibrin on osteochondral defect repair and articular cartilage regeneration in a canine model. Methods. Osteochondral defects were created on the medial femoral condyles of 12 adult male mixed breed dogs. They were either treated with stem cells seeded on platelet rich fibrin or left empty. Macroscopic and histological evaluation of the repair tissue was conducted after four, 16 and 24 weeks using the International Cartilage Repair Society macroscopic and the O’Driscoll histological grading systems. Results were reported as mean and standard deviation (. sd. ) and compared at different time points between the two groups using the Mann-Whitney U test, with a value < 0.05 considered statistically significant. Results. Higher cumulative macroscopic and histological scores were observed in stem cell treated defects throughout the study period with significant differences noted at four and 24 weeks (9.25, . sd. 0.5 vs 7.25, . sd. 0.95, and 10, . sd. 0.81 vs 7.5, . sd. 0.57; p < 0.05) and 16 weeks (16.5, . sd. 4.04 vs 11, . sd. 1.15; p < 0.05), respectively. Superior gross and histological characteristics were also observed in stem cell treated defects. Conclusion. The use of autologous culture expanded bone marrow derived mesenchymal stem cells on platelet rich fibrin is a novel method for articular cartilage regeneration. It is postulated that platelet rich fibrin creates a suitable environment for proliferation and differentiation of stem cells by releasing endogenous growth factors resulting in creation of a hyaline-like reparative tissue. Cite this article: D. Kazemi, K. Shams Asenjan, N. Dehdilani, H. Parsa. Canine articular cartilage regeneration using mesenchymal stem cells seeded on platelet rich fibrin: Macroscopic and histological assessments. Bone Joint Res 2017;6:98–107. DOI: 10.1302/2046-3758.62.BJR-2016-0188.R1

Tendon diseases are prevalent health concerns for which current therapies present limited success, in part due to the intrinsically low regenerative ability of tendons. Therefore, tissue engineering presents a potential to improve this outcome. Here, we hypothesize that a concurrent control over both biophysical and biochemical stimuli will boost the tenogenic commitment of stem cells, thus promoting regeneration. To achieve this, we combine molecularly imprinted nanoparticles (MINPs), which act as artificial amplifiers for endogenous growth factor (GF) activity, with bioinspired anisotropic hydrogels. 2. to manufacture 3D tenogenic constructs. MINPs were solid phase-imprinted using a TGF-β3 epitope as template and their affinity for the target was assessed by SPR and dot blot. Magnetically-responsive microfibers were produced by cryosectioning electrospun meshes containing iron oxide nanoparticles. The constructs were prepared by encapsulating adipose tissue-derived stem cells (ASCs), microfibers, and MINPs within gelatin hydrogels, while aligning the microfibers with an external magnetostatic field during gelation. This allows an effective modulation of hydrogel fibrillar topography, mimicking the native tissue's anisotropic architecture. Cell responses were analyzed by multiplex immunoassay, quantitative polymerase chain reaction, and immunocytochemistry. MINPs showed an affinity for the template comparable to monoclonal antibodies. Encapsulated ASCs acquired an elongated shape and predominant orientation along the alignment direction. Cellular studies revealed that combining MINPs with aligned microfibers increased TGF-β signaling via non-canonical Akt/ERK pathways and upregulated tendon-associated gene expression, contrasting with randomly oriented gels. Immunostaining of tendon-related proteins presented analogous outcomes, corroborating our hypothesis. Our results thus demonstrate that microstructural cues and biological signals synergistically direct stem cell fate commitment, suggesting that this strategy holds potential for improving tendon healing and might be adaptable for other biological tissues. The proposed concept highlights the GF-sequestering ability of MINPs which allows a cost-effective alternative to recombinant GF supplementation, potentially decreasing the translational costs of tissue engineering strategies. Acknowledgements: The authors acknowledge the funding from the European Union's Horizon 2020 under grant No. 772817; from FCT/MCTES for scholarships PD/BD/143039/2018 & COVID/BD/153025/2022 (S.P.B.T.), and PD/BD/129403/2017 (S.M.B.), co-financed by POCH and NORTE 2020, under the Portugal 2020 partnership agreement through the European Social Fund, for contract 2020.03410.CEECIND (R.M.A.D.) and project 2022.05526.PTDC; and from Xunta de Galicia for grant ED481B2019/025 (A.P.)

Objectives. Cellular movement and relocalisation are important for many physiologic properties. Local mesenchymal stem cells (MSCs) from injured tissues and circulating MSCs aid in fracture healing. Cytokines and chemokines such as Stromal cell-derived factor 1(SDF-1) and its receptor chemokine receptor type 4 (CXCR4) play important roles in maintaining mobilisation, trafficking and homing of stem cells from bone marrow to the site of injury. We investigated the differences in migration of MSCs from the femurs of young, adult and ovariectomised (OVX) rats and the effect of CXCR4 over-expression on their migration. Methods. MSCs from young, adult and OVX rats were put in a Boyden chamber to establish their migration towards SDF-1. This was compared with MSCs transfected with CXCR4, as well as MSCs differentiated to osteoblasts. Results. MSCs from OVX rats migrate significantly (p < 0.05) less towards SDF-1 (9%, . sd. 5%) compared with MSCs from adult (15%, . sd. 3%) and young rats (25%, . sd. 4%). Cells transfected with CXCR4 migrated significantly more towards SDF-1 compared with non-transfected cells, irrespective of whether these cells were from OVX (26.5%, . sd. 4%), young (47%, . sd. 17%) or adult (21%, . sd. 4%) rats. Transfected MSCs differentiated to osteoblasts express CXCR4 but do not migrate towards SDF-1. Conclusions. MSC migration is impaired by age and osteoporosis in rats, and this may be associated with a significant reduction in bone formation in osteoporotic patients. The migration of stem cells can be ameliorated by upregulating CXCR4 levels which could possibly enhance fracture healing in osteoporotic patients. Cite this article: A. Sanghani-Kerai, M. Coathup, S. Samazideh, P. Kalia, L. Di Silvio, B. Idowu, G. Blunn. Osteoporosis and ageing affects the migration of stem cells and this is ameliorated by transfection with CXCR4. Bone Joint Res 2017;6:–365. DOI: 10.1302/2046-3758.66.BJR-2016-0259.R1

The extracellular matrix (ECM)-based biomaterials provide a platform to mimic the disc microenvironment in facilitating stem cell transplantation for tissue regeneration. However, little is known about in vitro preconditioning human umbilical cord Wharton Jelly-derived mesenchymal stem cells (MSCs) on 3D hyaluronic acid (HA)/type II collagen (COLII) hydrogel for nucleus pulposus (NP) phenotype and pain modulation. We developed a tuneable 3D HA/COLII by fabricating HA/COLII hydrogel at 2 mg/ml COLII and various weight ratios of HA:COLII, 1:9 and 4.5:9. The hydrogel was characterized for degradability, stability, and swelling capacity. The viability of hWJ-MSC encapsulated on hydrogel supplemented with TGF-β3 was assessed. The implantation of HA/COLII hydrogel was done in surgically induced disc injury model of pain in the rat tail. The general health status in rats was monitored. The nociceptive behaviour in rats was performed for mechanical allodynia using von Frey test. The HA/COLII 4.5:9 hydrogel showed higher swelling capacity than weight ratio 1:9, suggesting that a higher amount of HA can absorb a large amount of water. Both HA/COLII 4.5:9 and 1:9 hydrogel formulations had a similar degradation profile, stable to the hydrolytic process. The hWJ-MSC-encapsulated on hydrogel marked higher cell viability with round morphology shape of cells in vitro. The surgically induced disc injury in the rat tail evoked mechanical allodynia, without affecting general health status in rats. The implantation of HA/COLII 1:9 hydrogel was observed to slightly alleviate injury-induced mechanical allodynia. Fine-tuning HA/COLII-based hydrogel provides the optimal swelling capacity, stability, degradability, and non-cytotoxic, mimicking the 3D NP niche in guiding hWJ-MSCs towards NP phenotype. The HA/COLII hydrogel could be employed as an advanced cell delivery system in facilitating stem cell transplantation for intervertebral disc regeneration targeting pain

Adipose-derived stem cells (ADSCs) are an effective alternative for Teno-regeneration. Despite their applications in tendon engineering, the mechanisms promoting tendon healing still need to be understood. Since there is scattered information on ovine ADSCs, this research aims to investigate in vitro their teno-differentiation for potential use in preclinical tendon regeneration models. Ovine ADSCs were isolated from the tail region according to FAT-STEM laboratories, expanded until passage six (P6), and characterized in terms of stemness, adhesion and MHC markers by Flow Cytometry (FCM) and immunocytochemistry (ICC). Cell proliferation and senescence were evaluated with MTT and Beta-galactosidase assays, respectively. P1 ADSCs’ teno-differentiation was assessed by culturing them with teno-inductive Conditioned Media (CM) or engineering them on tendon-mimetic PLGA scaffolds. ADSCs teno-differentiation was evaluated by morphological, molecular (qRT-PCR), and biochemical (WesternBlot) approaches. ADSCs exhibited mesenchymal phenotype, positive for stemness (SOX2, NANOG, OCT4), adhesion (CD29, CD44, CD90, CD166) and MHC-I markers, while negative for hematopoietic (CD31, CD45) and MHC-II markers, showing no difference between passages. ICC staining confirmed these results, where ADSCs showed nuclear positivity for SOX2 (≅ 56%) and NANOG (≅ 67%), with high proliferation capacity without senescence until P6. Interestingly, ADSCs cultured with the teno-inductive CM did not express tenomodulin (TNMD) protein or gene. Conversely, ADSCs seeded on scaffolds teno-differentiated, acquiring a spindle shape supported by TNMD protein expression at 48h (p<0.05 vs. ADSCs 48h) with a significant increase at 14 days of culture (p<0.05 vs. ADSCs + fleece 48h). Ovine ADSCs respond differently upon distinct teno-inductive strategies. While the molecules on the CM could not trigger a teno-differentiation in the cells, the scaffold's topological stimulus did, resulting in the best strategy to apply. More insights are requested to better understand ovine ADSCs’ tenogenic commitment before using them in vivo for tendon regeneration. Acknowledgements: This research is part of the P4FIT project ESR5, under the H2020MSCA-ITN-EJD-P4 FIT-Grant Agreement ID:955685

Phenotypic drift of stem cells and insufficient production of extracellular matrix (ECM) are frequently observed in tissue-engineered cartilage substitutes, posing major weaknesses of clinically relevant therapies targeting cartilage repair. Microenvironment plays an important role for stem cell maintenance and differentiation and therefore an optimal chondrogenic differentiation protocol is highly desirable. Macromolecular crowding (MMC) is a biophysical phenomenon that accelerates biological processes by several orders of magnitude. MMC was recently shown to significantly increase ECM deposition and to promote chondrogenic differentiation of stem cells. We hypothesise that the addition of sulphated high-molecular weight polysaccharides (carrageenan) to the media positively affects stem cell maintenance and chondrogenic differentiation. Herein, we venture to assess the impact of MMC on the maintenance of stem cell phenotype and multipotency, and ECM deposition in xeno-free human bone marrow mesenchymal stem cell (BMSCs) cultures. We investigate different xeno- and serum-free stem cell media with MMC for expansion of BMSCs, assessing multipotency maintenance (FACS analysis), cell viability, metabolic activity, proliferative capacity and matrix deposition (SDS-PAGE, ICC) at day 4 and day 10. Experiments will be conducted at 2 different passages (p3, p7). Medium without MMC will be used as control. Based on these results, cells expanded with the best protocol will be subsequently investigated for chondrogenic differentiation comparing different xeno-/serum-free and serum containing differentiation media. Chondrogenic differentiation will be assessed via Alcian blue and Safranin O stainings, gene expression for chondrogenic marker genes and quantification of GAG content. Finally, these findings will pave the way for developing more effective strategies for cartilage tissue engineering

The current treatment for osteoporosis such as bisphosphonates inhibits the catabolic activity of osteoclasts and subsequent bone resorption, but does not increase bone formation. There is therefore interest in using anabolic factors such as stem cells to augment fracture repair. The poor bone formation in postmenopausal women could be due to poor retention and function of Mesenchymal stem cells (MSCs) resulting into delayed unions. Another factor associated with fracture healing is the retention and migration of stem cells to the site of injury (1–3). The aim of this study was to isolate stem cells from osteopenic rats and investigate and compare the CD marker expression, proliferation, migration, osteogenic and adipogenic differentiation. The hypothesis of this study is that the migration of MSCs from young, adult and ovariectomised (OVX) rats will have different proliferation, differentiation and migratory abilities. Ovariectomy was performed in 6–9 month old Wistar rats and osteopenia developed over a 4 month post-op period. MSCs were harvested from the femora of young, adult and osteopenic Wistar rats. Proliferation of the these MSCs from the three group of rats was measured using Alamar blue, osteogenic differentiation was measured using ALP expression at day 0, 7, 14 and 21 and alizarin red at day 21. Adipogenic differentiation was measured at day 7, 14 and 21 using Oil red O. Cells were incubated in Boyden chambers to quantify their migration towards SDF1. For analysis, the number of cells migrating across the membrane was expressed as a percentage of the cells remaining on the upper membrane surface. Data was analysed using a Student t-test where p values < 0.05 were considered significant. The stem cells from all 3 groups of rats expressed on average the same amount of CD29 (>90%), CD90 (>96%), CD34 (<5%) and CD45 (approx 10%). The proliferation rate measured by Alamar blue normalised against DNA was also similar at day 3, 7, 10 and 14. However, interestingly the migration and differentiation ability was significantly different between the MSCs from the 3 groups of rats. The young MSCs were not only better at differentiating into bone and fat as well, but they also migrated significantly more towards SDF1. The migration of SDF-1 doubled with young rats compared to the adult rats (p = 0.023) and it was four times higher when compared to cells isolated from OVX rats (p = 0.013). MSCs from OVX rats are similar to MSCs from young rats. However when induced to turn into bone, fat and migrate towards SDF1, young MSCs are significantly more responsive than MSCs from OVX and adult control rats. The poor homing ability and differentiation of the stem cells and their retention may result in a reduction in bone formation leading to delayed union in fractures of osteoporotic patients(4)

Cartilage lesions often undergo irreversible progression due to low self-repair capability of this tissue. Tissue engineered approaches based in extrusion bioprinting of constructs loaded with stem cell spheroids may offer valuable alternatives for the treatment of cartilage lesions. Human mesenchymal stromal cell (hMSC) spheroids can be chondrogenically differentiated faster and more efficiently than single cells. This approach allows obtaining larger tissues in a rapid, controlled and reproducible way. However, it is challenging to control tissue architecture, construct stability, and cell viability during maturation. In this study we aimed at the development of a reproducible bioprinting process followed by post-bioprinting chondrogenic differentiation procedure using large quantities of hMSC spheroids encapsulated in a xanthan gum-alginate hydrogel. Multi-layered constructs were bioprinted, ionically crosslinked, and chondrogenically differentiated for 28 days. The expression of glycosaminoglycan, collagen II and IV were observed. After 56 days in culture, the bioprinted constructs were still stable and show satisfactory cell metabolic activity with profuse extracellular matrix production. These results showed a promising procedure to obtain 3D cartilage-like constructs that could be potential use as stable chondral tissue implants for future therapies. Acknowledgments: The National Council for Scientific and Technological Development (CNPq, Brazil – Grants # 314 724/2021-4, 307 829/2018-9, 430 860/2018-8, 142 050/2018-0 and 465 656/2014-5), the Coordination for the Improvement of Higher Educational Personnel (CAPES, Brazil – PrInt 88 887.364849/2019-00 and PrInt 88 887.310405/2018-00), the Fund for Support to Teaching, Research and Extension from the University of Campinas (FAEPEX/UNICAMP, Brazil – Grants # 2921/18, 2324/21), and the European Union's Horizon 2020 JointPromise project – Precision manufacturing of microengineered complex joint implants, under grant agreement 874 837 are acknowledged for the financial support of this study

Introduction. Tendon is prone to degeneration through ageing and injury and current therapies are largely ineffective. The recent identification of a cell population within tendon with stem cell-like characteristics holds potential for regeneration of tendon. The local stem cell environment (niche) is important for stem cell maintenance and function. This study aims to characterize extracellular matrix (ECM) components of the stem cell niche in equine tendon, which is prone to age-related degeneration and rupture. Materials and Methods. Putative tendon stem cells (TSCs) were isolated from equine superficial digital flexor tendon by low-density plating and differential adhesion to fibronectin. Cells were analysed by flow cytometry using antibodies to mesenchymal stem cell markers, as well as qRT-PCR for stem cell and tenogenic markers. The multipotency of cells was assessed using tri-lineage differentiation assays. ECM components of the tenocyte and TSC niche were analysed using radio-isotope labelling, immunohistochemistry and histology. Results. Putative TSCs were able to form colonies, and both tenocytes and TSCs expressed CD90, CD105 and CD73 as determined by flow cytometry. However, TSCs did not exhibit increased expression of stem cell marker genes when compared with tenocytes. TSCs and tenocytes both displayed osteogenic and chondrogenic differentiation, however not adipogenic differentiation. Tenocytes and TSCs labelled with 14C-labelled amino acids both displayed similar labelling profiles. Histological analysis of tendon tissue highlighted the varied structure and composition of tendon, with tenascin C expression confined to the interfascicular matrix. Discussion. TSCs do not highly express stem cell markers when compared with tenocytes, indicating that these cells may not be true stem cells. In addition the similar labelling profiles of the two cell types indicates that a stem cell population has not been differentially isolated, however the tri-lineage differentiation assays suggest the cells may possess some stem cell-like properties. It is possible that the equine tendon cell population consists of a heterogeneous mixture of cells at different stages of differentiation

Background. Osteoporosis and bone fractures lead to immobility, chronic pain and high patient care costs. Mesenchymal stem cells (MSCs) from postmenopausal women have a slower growth rate and osteogenic differentiation ability causing lower bone density and reduced fracture healing capacity compared to MSCs from premenopausal women. Cellular movement and relocalisation are necessary for many physiologic properties. Local MSCs from injured tissues and circulating MSCs are involved in fracture healing. Cytokines and chemokines such as SDF-1 and its receptor CXCR4 play important roles in maintaining mobilisation, trafficking and homing of stem cells from bone marrow to the site of injury. This study investigated the effect of CXCR4 over-expression on the migration of MSCs from ovariectomised, normal and young rats. Methods. MSCs were harvested from femora of young, normal and OVX rats, genetically modified to over-express CXCR4and put in a Boyden chamber to establish their migration towards SDF-1. This was compared to the non-transfected stem cells. Results. MSCs from OVX rats migrate less towards SDF1 compared to MSCs from normal and juvenile rats. When the MSCs were differentiated to osteoblasts their migration towards SDF1 reduced as well and this was not enhanced by over-expression of CXCR4. Cell transfected with CXCR4 migrated more towards SDF-1 compared to non-transfected cells irrespective of whether these cells were from OVX, young or normal rats. Conclusions. MSCs migration is impaired by age and osteoporosis explaining the significant reduction in bone formation in osteoporotic patients. The migration of stem cells can be ameliorated by up regulating the CXCR4 levels which could possibly enhance fracture healing in osteoporotic patients. Level of Evidence. IIb

Summary Statement. Umbilical cord derived stem cell secretion could enhance the osteogenic differentiation of human bone marrow stem cells. It may promote bone, cartilage and tendon regeneration in rat models, but the effect was not significant up to now. Introduction. Mesenchymal stem cells (MSCs) are multipotent cells that have extensive proliferative capacity. MSCs synthesise various exosomes, growth factors and cytokines. Stem cell secretions were made from serum free conditioned medium of stem cells collected from different human tissues, such as adipose tissue and dental pulp. Our hypothesis is umbilical cord stem cell secretion could promote multiple proliferation and differentiation of MSCs, also enhance the regeneration of musculoskeletal tissues. Methods. In vitro: Human bone marrow mesenchymal stem cells (hBMSCs) were cultured in high glucose dulbecco's modified eagle medium with 10% serum. hBMSCs were treated by differential medium for osteogenic, tenogenic and chondrogenic differentiation. Alizarin red S staining, alcian blue staining and sirius red staining were used to test osteogenesis, chondrogenesis and tenogenesis of hBMSCs after treated by secretion. RNA expression level of hBMSCs were detected by real-time reverse transcriptase polymerase chain reaction. In vivo: 10 weeks male Sprague-Dawley rats were used in all the animal studies. Rat calvarial bone defect model, rat femoral closed fracture model with internal fixation, rat articular cartilage defect model and rat patella tendon window defect model were used in animal experiments. Radiography analysis, micro-computed tomography imaging analysis, mechanical test, ultrasound test and histology analysis were used to evaluate the regeneration of bone, cartilage and tendon. Results. Alizarin red S staining showed the minimal effective concentration of 20ug/ml umbilical cord stem cells secretion could promote strong osteogenesis of hBMSCs, with enhanced expression of osteogenic markers runx2 and ocn. 20ug/ml umbilical cord stem cells secretion could promote tenogenic differentiation. The bone defect healing study using rat calvarial defect model indicated no significant difference (p»0.05) between 0.5ug/1ug umbilical cord secretion treated group (agarose gel with secretion was implanted in defect) and control (PBS) in 4 weeks or 8 weeks time points. In the rat femoral closed fracture model, the difference of bone repair between 10ug umbilical cord secretion local injection group (injected 10ug in callus after surgery) and control (PBS injected) was not significant (p»0.05) in 4 weeks or 8 weeks. In the rat articular cartilage defect model, 1ug umbilical stem cell secretion with 20ul alginate gel group recovered better than alginate gel only group in 6 weeks(p<0.05), but the difference of cartilage healing was not significant (p»0.05) between other groups (alginate gel with BMSCs) in 6 weeks or 9 weeks. In the rat patella tendon window defect model, there were more compact collagen fibers in 1ug umbilical cord secretion group (secretion with fibrin glue), but the alignment of new tissue was not better than control (PBS with fibrin glue). Also the stress of defected area was not significantly different (p»0.05) between treated and control in 6 weeks and 9 weeks. Discussion/Conclusion. The umbilical cord stem cell secretion demonstrated osteogenic, and tenogenic effect in vitro, but the result in the healing of bone, cartilage and tendon was not significant. The optimal dosage and slow release method will be considered to improve the experiment. The mechanism of stem cell secretions will be studied in further research

Macromolecular crowding (MMC) is a biophysical phenomenon that accelerates thermodynamic activities and biological processes by several orders of magnitude. Herein, we ventured to identify the optimal crowder and to assess the influence of MMC in umbilical cord mesenchymal stem cell. 7 types of carrageenan (κ&λ, κ-LV1, κ-LV2, λ-MV, λ-HV, ι-MV, ι-HV) acted as crowder and biophysical properties were assessed respectively. Human umbilical cord mesenchymal stem cells were seeded at 15,000 cells/cm. 2. in 24 well plates and allowed to attach for 24 h. Subsequently, the medium was changed to medium with 7 types of carrageenan (10, 50, 100, 500 μg/ml) and 100 μM L-ascorbic acid phosphate (Sigma Aldrich). Medium without carrageenan was used as control. Cell morphology and SDS-PAGE analysis were conducted after 3, 5 and 7 days. Biophysical assessment showed 7 types of carrageenan have increased particle size with concentration, good polydispersity and negative charges. SDS-PAGE and densitometric analyses revealed significant increase (p < 0.001) in collagen deposition in the presence of 10 μg/ml carrageenan λ and ι at all the time points. SDS-PAGE and densitometric analysis also showed that the highest collagen deposition was observed in culture at 50 μg/ml carrageenan λ. No significant difference was observed in cell morphology between the groups. Collectively, these data primarily illustrate the beneficial effect of carrageenan λ in human umbilical cord mesenchymal stem cell culture

There is increasing interest in using anabolic factors such as stem cells to augment fragility fracture repair. One of the factors associated with fracture healing is the retention and migration of stem cells to the site of injury (1–3). The aim of this study was to isolate stem cells from osteopenic rats and investigate and compare the CD marker expression, proliferation, migration, osteogenic and adipogenic differentiation. The hypothesis of this study is that the migration of MSCs from young, adult and ovariectomised (OVX) rats will have different proliferation, differentiation and migratory abilities. CD marker expression of MSCs from young, adult and osteopenic rats was measured using flow cytometry. Proliferation, osteogenic differentiation and adipogenic differentiation was measured using Alamar Blue, ALP expression and Alizari n Red and quantitative Oil red O respectively. Cells were incubated in Boyden chambers to quantify their migration towards SDF1. Data was analysed using a Student t-test where p values < 0.05 were considered significant. MSCs from all 3 groups of rats had similar proliferation and expression of CD29(>90%), CD90(>96%), CD34(<5%) and CD45(approx 10%). The proliferation rate was also similar. However, interestingly the migration and differentiation ability was significantly different between the MSCs from the 3 groups of rats. The young MSCs were not only better at differentiating into bone and fat, but they also migrated significantly more towards SDF1. MSCs from OVX rats are similar to MSCs from young rats. However when induced to turn into bone, fat and migrate towards SDF1, young MSCs are significantly more responsive than MSCs from OVX and adult control rats. The poor homing ability and differentiation of the stem cells and their retention may result in a reduction in bone formation leading to delayed union in fractures of osteoporotic patients(4)

Objectives. To explore the therapeutic potential of combining bone marrow-derived mesenchymal stem cells (BM-MSCs) and hydroxyapatite (HA) granules to treat nonunion of the long bone. Methods. Ten patients with an atrophic nonunion of a long bone fracture were selectively divided into two groups. Five subjects in the treatment group were treated with the combination of 15 million autologous BM-MSCs, 5g/cm. 3. (HA) granules and internal fixation. Control subjects were treated with iliac crest autograft, 5g/cm. 3. HA granules and internal fixation. The outcomes measured were post-operative pain (visual analogue scale), level of functionality (LEFS and DASH), and radiograph assessment. Results. Post-operative pain evaluation showed no significant differences between the two groups. The treatment group demonstrated faster initial radiographic and functional improvements. Statistically significant differences in functional scores were present during the first (p = 0.002), second (p = 0.005) and third (p = 0.01) month. Both groups achieved similar outcomes by the end of one-year follow-up. No immunologic or neoplastic side effects were reported. Conclusions. All cases of nonunion of a long bone presented in this study were successfully treated using autologous BM-MSCs. The combination of autologous BM-MSCs and HA granules is a safe method for treating nonunion. Patients treated with BM-MSCs had faster initial radiographic and functional improvements. By the end of 12 months, both groups had similar outcomes. Cite this article: H.D. Ismail, P. Phedy, E. Kholinne, Y. P. Djaja, Y. Kusnadi, M. Merlina, N. D. Yulisa. Mesenchymal stem cell implantation in atrophic nonunion of the long bones: A translational study. Bone Joint Res 2016;5:287–293. DOI: 10.1302/2046-3758.57.2000587

Mesenchymal stem cells (MSC) have potent immunomodulatory and regenerative effects via soluble factors. One approach to improve stem cell-based therapies is encapsulation of MSC in hydrogels based on natural proteins such as collagen and fibrin, which play critical roles in bone healing. In this work, we comparatively studied the influence of collagen and fibrin hydrogels of varying stiffness on the paracrine interactions established by MSC with macrophages and osteoblasts. Type I collagen and fibrin hydrogels in a similar stiffness range loaded with MSC from donants were prepared by modifying the protein concentration. Viability and morphology of MSC in hydrogels as well as cell migration rate from the matrices were determined. Paracrine actions of MSC in hydrogels were evaluated in co-cultures with human macrophages from healthy blood donors or with osteoblasts from bone explants of patients with osteonecrosis of the femoral head. Lower matrix stiffness resulted in higher MSC viability and migration. Cell migration rate from collagen hydrogels was higher than from fibrin matrices. The secretion of the immunomodulatory factors interleukin-6 (IL-6) and prostaglandin E. 2. (PGE. 2. ) by MSC in both collagen and fibrin hydrogels increased with increasing matrix stiffness. Tumor necrosis factor-α (TNF-α) secretion by macrophages cultured on collagen hydrogels was lower than on fibrin matrices. Interestingly, higher collagen matrix stiffness resulted in lower secreted TNF-α while the trend was opposite on fibrin hydrogels. In all cases, TNF-α levels were lower when macrophages were cultured on hydrogels containing MSC than on empty gels, an effect partially mediated by PGE. 2. Finally, mineralization capacity of osteoblasts co-cultured with MSC in hydrogels increased with increasing matrix stiffness, although this effect was more notably for collagen hydrogels. Paracrine interactions established by MSC in hydrogels with macrophages and osteoblasts are regulated by matrix composition and stiffness

Background. The gradient structure of osteochondral tissue, with bone, calcified and cartilage regions, challenges the design of biomaterials for defect repair. A novel biomimetic tri-layered collagen-based scaffold, designed to replicate these 3 anatomical layers, has been developed within our group and has shown success as an off-the-shelf product in treatment of focal defects in several animal models by recruiting host cells and directing them to form bone and cartilage in the requisite layers. This study aimed to elucidate the mechanism by which the extracellular matrix macromolecules in the scaffold directed stem cell differentiation in each layer. Methods. Tri-layered scaffolds were divided into their three constituent layers. Each layer was individually seeded with rat mesenchymal stem cells (MSCs). Cell infiltration and proliferation, calcium production and sGAG formation were assessed up to 28 days. Results. The scaffold allowed cell infiltration and proliferation through all layers. The collagen hydroxyapatite layer was found to be inherently osteogenic due to the hydroxyapatite. The collagen I/hyaluronic acid layer did not encourage osteogenesis and the collagen I/II layer demonstrated chondrogenesis even without the presence of chondrogenic supplements. Conclusion. The biomaterial and microstructural properties within this tri-layered material thus show an ability to direct the response of native stem cells. The mechanisms demonstrated here explain the positive results previously observed in in vivo studies. Level of Evidence. IIb. The senior author on this abstract serves on the Scientific and Medical Advisory Board and holds stock in SurgaColl Technologies for which he receives an honorarium

Deriving autologous mesenchymal stem cells (MSCs) from adipose tissues without using enzymes requires sophisticated biomedical instruments. Applied pressure on tissues and cells are adjusted manually although centrifugation and filtration systems are frequently used. The number of derived MSCs therefore could differ between instruments. We compared the number of MSCs obtained from four commercially available devices and our newly designed and produced instrument (A2, B3, L3, M2 and T3). Three-hundred mL of adipose tissue was obtained from a female patient undergoing liposuction using the transillumination solution. Obtained tissue was equally distributed to each device and handled according to the producers' guides. After handling, 3 mL stromal vascular fraction (SVF) was obtained from each device. Freshly isolated SVF was characterized using multi-color flow cytometry (Navios Flow Cytometer, Beckman Coulter, USA). Cell surface antigens were chosen according to IFATS and ISCT. CD31-FITC, CD34-PC5,5, CD73-PE, CD90-PB and CD45-A750 (Backman Coulter, USA) fluorochrome-labeled monoclonal antibodies were assessed. Markers were combined with ViaKrome (Beckman Coulter, USA) to determine cell viability. At least 10. 5. cells were acquired from each sample. A software (Navios EX, Beckman Coulter, USA) was used to create dot plots and to calculate the cell composition percentages. The data was analyzed in the Kaluza 2.1 software package (Beckman Coulter, USA). Graphs were prepared in GraphPad Prism. CD105 PC7/CD31 FITC cell percentages were 23,9%, 13,5%, 24,6%, 11,4% and 28,8% for the A2, B3, L3, M2 and T3 devices, respectively. We conclude that the isolated MSC percentage ranged from 11,4% to 28,8% between devices. The number of MSCs in SVF are key determinants of success in orthobiological treatments. Developing a device should focus on increasing the number of MSCs in the SVF while preserving its metabolic activity. Acknowledgments: Scientific and Technological Research Council of Türkiye (TÜBİTAK)- Technology and Innovation Funding Program Directorate (TEYDEB) funded this project (#321893). Servet Kürümoğlu and Bariscan Önder of Disposet Ltd., Ankara, Türkiye (. www.disposet.com. ) contributed to the industrial design and research studies. Ali Tuncel and Feza Korkusuz are members of the Turkish Academy of Sciences (TÜBA). Nilsu Baysal was funded by the STAR Program of TÜBITAK Grant # 3210893