IntroductionThe present study examined the effect of collagen fragments on anabolic and catabolic activities by chondrocyte/agarose constructs subjected to dynamic compression.MethodsConstructs were cultured under free-swelling conditions or subjected to continuous and intermittent compression regimes, in the presence of the N-terminal (NT) and C-terminal (CT) telopeptides derived from collagen type II and/or 1400 W (inhibits inducible nitric oxide synthase (iNOS)). The anabolic and catabolic activities were compared to the amino-terminal fibronectin fragment (NH2-FN-f) and assessed as follows: nitric oxide (NO) release and sulphated glycosaminoglycan (sGAG) content were quantified using biochemical assays. Tumour necrosis factor-α (TNFα) and interleukin-1β (IL-1β) release were measured by ELISA. Gene expression of matrix metalloproteinase-3 (MMP-3), matrix metalloproteinase-13 (MMP-13), collagen type II and fibronectin were assessed by real-time quantitative polymerase chain reaction (qPCR). Two-way ANOVA and the post hoc Bonferroni-corrected t-test was used to examine data.ResultsThe presence of the NT or CT peptides caused a moderate to strong dose-dependent stimulation of NO, TNFα and IL-1β production and inhibition of sGAG content. In some instances, high concentrations of telopeptides were just as potent in stimulating catabolic activities when compared to NH2-FN-f. Depending on the concentration and type of fragment, the increased levels of NO and cytokines were inhibited with 1400 W, resulting in the restoration of sGAG content. Depending on the duration and type of compression regime employed, stimulation with compression or incubation with 1400 W or a combination of both, inhibited telopeptide or NH2-FN-f induced NO release and cytokine production and enhanced sGAG content. All fragments induced MMP-3 and MMP-13 expression in a time-dependent manner. This effect was reversed with compression and/or 1400 W resulting in the restoration of sGAG content and induction of collagen type II and fibronectin expression.ConclusionsCollagen fragments containing the N- and C-terminal telopeptides have dose-dependent catabolic activities similar to fibronectin fragments and increase the production of NO, cytokines and MMPs. Catabolic activities were downregulated by dynamic compression or by the presence of the iNOS inhibitor, linking reparative activities by both types of stimuli. Future investigations which examine the signalling cascades of chondrocytes in response to matrix fragments with mechanical influences may provide useful information for early osteoarthritis treatments.

Due to the poor self-healing capacities of cartilage, innovative approaches are a major clinical need. The use of in vitro expanded mesenchymal stromal cells (MSCs) in a 2-stage approach is accompanied by cost-, time-, and personnel-intensive good manufacturing practice production. A 1-stage intraoperative procedure could overcome these drawbacks. The aim was to prove the feasibility of a point-of-care concept for the treatment of cartilage lesions using defined MSC subpopulations in a collagen hydrogel without prior MSC monolayer expansion. We tested 4 single marker candidates (MSCA-1, W4A5, CD146, CD271) for their effectiveness of separating colony-forming units of ovine MSCs via magnetic cell separation. The most promising surface marker with regard to the highest enrichment of colony-forming cells was subsequently used to isolate a MSC subpopulation for the direct generation of a cartilage graft composed of a collagen type I hydrogel without the propagation of MSCs in monolayer. We observed that separation with CD271 sustained the highest enrichment of colony-forming units. We then demonstrated the feasibility of generating a cartilage graft with an unsorted bone marrow mononuclear cell fraction and with a characterized CD271 positive MSC subpopulation without the need for a prior cell expansion. A reduced volume of 6.25% of the CD271 positive MSCs was needed to achieve the same results regarding chondrogenesis compared with the unseparated bone marrow mononuclear cell fraction, drastically reducing the number of nonrelevant cells. This study provides a proof-of-concept and reflects the potential of an intraoperative procedure for direct seeding of cartilage grafts with selected CD271 positive cells from bone marrow.

No abstract