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Cartilage tissue engineering is making progress, but the competing available strategies still leave room for improvement and consensual overviews regarding the best combinations of scaffolds and cell sources are limited by the capacity to compare them directly. In addition, because most strategies involve autologous cell transfer, once these are optimized, the resulting implants require individual quality control prior to grafting in order to emphasize patient-to-patient differential responsiveness to engineering processes. Here, cartilage substitutes prepared from human mesenchymal stem cells undergoing chondrogenic differentiation within distinct scaffolds were used as pilot samples to investigate the pertinence of a novel method with the aim of characterizing the implants. The limits and advantages of analysing, by label-free liquid chromatography-coupled matrix-assisted laser desorption and ionization (LC-MALDI) mass spectrometry, the secreted proteome released into culture medium by engineered cartilage tissues were investigated and compared with more classically used methods for biomaterial characterization. This method did not require sacrificing the biomaterials and robustly evidenced their chondrogenic statuses. In more detail, the method highlighted differences between batches prepared from distinct donors. It was adapted to distinct scaffolds and allowed a comparison of the influence of individual engineering steps, such as growth factor combinations and oxygen tension. Finally, it evidenced subtle changes between replicate substitutes within a series, thereby distinguishing the least and most accomplished ones. We conclude that relative quantification of secreted proteins through label-free LC-MALDI will be useful, not only to orientate engineering methodologies, but also to ultimately provide non-invasive quality control of engineered tissue substitutes for the repair of cartilage and possibly other connective tissues.

International audience

International audience; BACKGROUND: Osteoarthritis (OA) is a chronic joint disease characterized by a progressive and irreversible degeneration of articular cartilage. Among the environmental risk factors of OA, tobacco consumption features prominently, although, there is a great controversy regarding the role of tobacco smoking in OA development. Among the numerous chemicals present in cigarette smoke, nicotine is one of the most physiologically active molecules.OBJECTIVE: The aim of the study was (i) to measure the impact of nicotine on the proliferation and chondrogenic differentiation of mesenchymal stem cells from the human Wharton's jelly (hWJ-MSCs) into chondrocytes, (ii) to investigate whether the alpha 7 nicotinic acetylcholine receptors (nAChRs) was expressed in hWJ-MSCs and could play a role in the process. The project benefits from the availability of an umbilical cord bank from which hWJ-MSCs were originated.METHODS: The hWJ-MSCs were cultured and used up to passage 5. The proliferation of hWJ-MSCs with 5 mu M nicotine was measured by the MTT assay on the 1st, 2nd, 3rd, and 6th day. Flow cytometry analysis was used to detect cell apoptosis/necrosis by Annexin V/PI double-staining. The chondrogenic differentiation grade of hWJ-MSCs induced by TGF beta 3 was assessed by the Sirius red and Alcian blue staining. The expression of markers genes was followed by quantitative real-time PCR. The expression of nAChRs was followed by RT-PCR. The functional activity of alpha 7 nAChR was evaluated by calcium (Ca2+) influx mediated by nicotine using the Fluo-4 NW Calcium assay.RESULTS: The proliferation of hWJ-MSCs was significantly impaired by nicotine (5 mu M) from the 3rd day of treatment, but nicotine did not significantly induce modifications on the viability of hWJ-MSCs. Alcian blue staining indicated that the amount of proteoglycan was more abundant in control group than in the nicotine group, but no difference was observed on the total collagen amount using Sirius red staining. The mRNA expression of Sox9, type II collagen (Col2a1), aggrecan in control group was higher than in the nicotine group. We found that hWJ-MSCs expressed alpha 7 nAChR. The receptor agonist nicotine caused calcium (Ca2+) influx into hWJ-MSCs suggesting that the calcium ion channel alpha 7 homopolymer could mediate this response.CONCLUSIONS: At the concentration used, nicotine had an adverse effect on the proliferation and chondrogenic differentiation of hWJ-MSCs which was probably impaired through a alpha 7 nAChR mediation.

International audience; Cucurbitacins are a class of natural compounds known for their numerous ă potential pharmacological effects. The purpose of this work was to ă compare the cytotoxicity of three cucurbitacins I, D, E on the ă chondrosarcoma SW 1353 cancer cell line and to investigate their ă biotransformation in man. Cucurbitacins I and D showed a very strong ă cytotoxicity, which was higher than that of cytochalasin D, used as a ă drug reference. Almost 100% of the cells were apoptotic as observed by ă DNA fragmentation (TUNEL assay) after 12 h with cucurbitacins I and D (1 ă mu M) and cucurbitacin E (10 mu M). In terms of IC50 values, ă cucurbitacins I and E presented a higher toxicity compared to that of ă cucurbitacin D (MTT assay). Cucurbitacin E was readily hydrolyzed by ă human hepatic microsomes, leading to cucurbitacin I (K-m 22 mu M, V-max ă 571 nmol/mg proteins/min). On the other hand, the three cucurbitacins ă were hydroxylated at a very low extent, but they were sulfated and ă glucuronidated. In terms of V-max/K-m, the cucurbitacin E was the best ă substrate of UDP-glucuronosyltransferases. This study shows that ă cucurbitacins I, D and E present a potent cytotoxic activity toward the ă chondrosarcoma SW 1353 cell line and are metabolized as sulfate and ă glucuronide conjugates. (C) 2012 Elsevier Ireland Ltd. All rights ă reserved.

International audience

The extracellular matrix (ECM) has long been viewed primarily as an organized network of solid-phase ligands for integrin receptors. During degenerative processes, such as osteoarthritis, the ECM undergoes deterioration, resulting in its remodeling and in the release of some of its components. Matrilin-3 (MATN3) is an almost cartilage specific, pericellular protein acting in the assembly of the ECM of chondrocytes. In the past, MATN3 was found required for cartilage homeostasis, but also involved in osteoarthritis-related pro-catabolic functions. Here, to better understand the pathological and physiological functions of MATN3, its concentration as a circulating protein in articular fluids of human osteoarthritic patients was determined and its functions as a recombinant protein produced in human cells were investigated with particular emphasis on the physical state under which it is presented to chondrocytes. MATN3 down-regulated cartilage extracellular matrix (ECM) synthesis and up-regulated catabolism when administered as a soluble protein. When artificially immobilized, however, MATN3 induced chondrocyte adhesion via a α5β1 integrin-dependent mechanism, AKT activation and favored survival and ECM synthesis. Furthermore, MATN3 bound directly to isolated α5β1 integrin in vitro. TGFβ1 stimulation of chondrocytes allowed integration of exogenous MATN3 into their ECM and ECM-integrated MATN3 induced AKT phosphorylation and improved ECM synthesis and accumulation. In conclusion, the integration of MATN3 to the pericellular matrix of chondrocytes critically determines the direction toward which MATN3 regulates cartilage metabolism. These data explain how MATN3 plays either beneficial or detrimental functions in cartilage and highlight the important role played by the physical state of ECM molecules.