Adult stem cells, such as human mesenchymal stem cells (hMSCs), show limited proliferative capacity and, after long-term culture, lose their differentiation capacity and are therefore not an optimal cell source for tissue engineering. Human embryonic stem cells (hESCs) constitute an important new resource in this field, but one major drawback is the risk of tumor formation in the recipients. One alternative is to use progenitor cells derived from hESCs that are more lineage restricted but do not form teratomas. We have recently derived a cell line from hESCs denoted hESC-derived mesodermal progenitors (hES-MPs), and here, using genome-wide microarray analysis, we report that the process of hES-MPs derivation results in a significantly altered expression of hESC characteristic genes to an expression level highly similar to that of hMSCs. However, hES-MPs displayed a significantly higher proliferative capacity and longer telomeres. The hES-MPs also displayed lower expression of HLA class II proteins before and after interferon-g treatment, indicating that these cells may somewhat be immunoprivileged and potentially used for HLA-incompatible transplantation. The hES-MPs are thus an appealing alternative to hMSCs in tissue engineering applications and stem-cell-based therapies for mesodermal tissues.

Herein, we provide evidence of a previously unknown link between GDF5 signaling and canonical Wnt signaling that may contribute to the understanding of the molecular mechanisms of OA.

BackgroundOsteoarthritis (OA) is a destructive joint disease and there are no known biomarkers available for an early diagnosis. To identify potential disease biomarkers and gain further insight into the disease mechanisms of OA we applied quantitative proteomics with SILAC technology on the secretomes from chondrocytes of OA knees, designated as high Mankin (HM) scored secretome. A quantitative comparison was made between the secretomes of the medial and lateral femur condyle chondrocytes in the same knee since the medial femur condyle is usually more affected in OA than the lateral condyle, which was confirmed by Mankin scoring. The medial/lateral comparison was also made on the secretomes from chondrocytes taken from one individual with no clinically apparent joint-disease, designated as low Mankin (LM) scored secretome.ResultsWe identified 825 proteins in the HM secretome and 69 of these showed differential expression when comparing the medial and lateral femoral compartment. The LM scored femoral condyle showed early signs of OA in the medial compartment as assessed by Mankin score. We here report the identification and relative quantification of several proteins of interest for the OA disease mechanism e.g. CYTL1, DMD and STAB1 together with putative early disease markers e.g. TIMP1, PPP2CA and B2M.ConclusionsThe present study reveals differences in protein abundance between medial/lateral femur condyles in OA patients. These regulatory differences expand the knowledge regarding OA disease markers and mechanisms.

Pluripotent human embryonic stem cell (hESC) lines are a promising model system in developmental and tissue regeneration research. Differentiation of hESCs towards the three germ layers and finally tissue specific cell types is often performed through the formation of embryoid bodies (EBs) in suspension or hanging droplet culture systems. However, these systems are inefficient regarding embryoid body (EB) formation, structural support to the EB and long term differentiation capacity. The present study investigates if agarose, as a semi solid matrix, can facilitate EB formation and support differentiation of hESC lines. The results showed that agarose culture is able to enhance EB formation efficiency with 10% and increase EB growth by 300%. The agarose culture system was able to maintain expression of the three germ layers over 8 weeks of culture. All of the four hESC lines tested developed EBs in the agarose system although with a histological heterogeneity between cell lines as well as within cell lines. In conclusion, a 3-D agarose culture of spherical hESC colonies improves EB formation and growth in a cost effective, stable and non-laborious technique.

Background:There is a need for tools to predict the chondrogenic potency of autologous cells for cartilage repair.Purpose:To evaluate previously proposed chondrogenic biomarkers and to identify new biomarkers in the chondrocyte transcriptome capable of predicting clinical success or failure after autologous chondrocyte implantation.Study Design:Controlled laboratory study and case-control study; Level of evidence, 3.Methods:Five patients with clinical improvement after autologous chondrocyte implantation and 5 patients with graft failures 3 years after implantation were included. Surplus chondrocytes from the transplantation were frozen for each patient. Each chondrocyte sample was subsequently thawed at the same time point and cultured for 1 cell doubling, prior to RNA purification and global microarray analysis. The expression profiles of a set of predefined marker genes (ie, collagen type II α1 [COL2A1], bone morphogenic protein 2 [BMP2], fibroblast growth factor receptor 3 [FGFR3], aggrecan [ACAN], CD44, and activin receptor–like kinase receptor 1 [ACVRL1]) were also evaluated.Results:No significant difference in expression of the predefined marker set was observed between the success and failure groups. Thirty-nine genes were found to be induced, and 38 genes were found to be repressed between the 2 groups prior to autologous chondrocyte implantation, which have implications for cell-regulating pathways (eg, apoptosis, interleukin signaling, and β-catenin regulation).Conclusion:No expressional differences that predict clinical outcome could be found in the present study, which may have implications for quality control assessments of autologous chondrocyte implantation. The subtle difference in gene expression regulation found between the 2 groups may strengthen the basis for further research, aiming at reliable biomarkers and quality control for tissue engineering in cartilage repair.Clinical Relevance:The present study shows the possible limitations of using gene expression before transplantation to predict the chondrogenic and thus clinical potency of the cells. This result is especially important as the chondrogenic potential of the chondrocytes is currently part of quality control measures according to European and American legislations regarding advanced therapies.

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