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Background and purposeDegenerating cartilage releases potential danger signals that react with Toll-like receptor (TLR) type danger receptors. We investigated the presence and regulation of TLR1, TLR2, and TLR9 in human chondrocytes.MethodsWe studied TLR1, TLR2, TLR4, and TLR9 mRNA (qRT-PCR) and receptor proteins (by immunostaining) in primary mature healthy chondrocytes, developing chondrocytes, and degenerated chondrocytes in osteoarthritis (OA) tissue sections of different OARSI grades. Effects of a danger signal and of a pro-inflammatory cytokine on TLRs were also studied.ResultsIn primary 2D-chondrocytes, TLR1 and TLR2 were strongly expressed. Stimulation of 2D and 3D chondrocytes with a TLR1/2-specific danger signal increased expression of TLR1 mRNA 1.3- to 1.8-fold, TLR2 mRNA 2.6- to 2.8-fold, and TNF-α mRNA 4.5- to 9-fold. On the other hand, TNF-α increased TLR1 mRNA] expression 16-fold, TLR2 mRNA expression 143- to 201-fold, and TNF-α mRNA expression 131- to 265-fold. TLR4 and TLR9 mRNA expression was not upregulated. There was a correlation between worsening of OA and increased TLR immunostaining in the superficial and middle cartilage zones, while chondrocytes assumed a CD166× progenitor phenotype. Correspondingly, TLR expression was high soon after differentiation of mesenchymal stem cells to chondrocytes. With maturation, it declined (TLR2, TLR9).InterpretationMature chondrocytes express TLR1 and TLR2 and may react to cartilage matrix/chondrocyte-derived danger signals or degradation products. This leads to synthesis of pro-inflammatory cytokines, which stimulate further TLR and cytokine expression, establishing a vicious circle. This suggests that OA can act as an autoinflammatory disease and links the old mechanical wear-and-tear concept with modern biochemical views of OA. These findings suggest that the chondrocyte itself is the earliest and most important inflammatory cell in OA.

We report on craniomicromelic syndrome in a male fetus. This case had the previously reported features of prenatal onset growth retardation, underossified cranial bones, wide sutures and fontanels, small face as compared to head, small palpebral fissures, pinched nose, microstomia, micrognathia, and narrow thorax. The consistent combination of these features with short appearing limbs as observed in this case establishes this syndrome as a distinct entity. © 2011 Wiley‐Liss, Inc.

Enzymatic crosslinking has immense appeal for tissue engineers as one of the most biocompatible methods of hydrogel crosslinking. Sortase A has a number of unique advantages over previous systems. We show an impressive and tunable range of crosslinking kinetics, from almost instantaneous gelation to several minutes. We also demonstrate that Sortase A crosslinked hydrogels have good cytocompatibility and cause no immune reaction when implanted in vivo. With its additional benefits of excellent stability in solution and easy large-scale synthesis available to any lab, we believe this novel crosslinking modality will find multiple applications in high throughput screening, tissue engineering, and biofabrication.

Intra-articular administration of glucocorticoids such as dexamethasone is a common treatment for osteoarthritic inflammation and pain. Despite its potent anti-inflammatory properties, multiple barriers hinder the drug's effectiveness in the articular space. In particular, the high turnover rate of the synovial fluid and the dense cartilage extracellular matrix (ECM) lead to poor drug penetration into cartilage. In order to increase the infiltration and retention time, two dexamethasone prodrugs were developed. Firstly, dexamethasone was conjugated to polycationic chitosan, which led to deep and sustained infiltration of the drug into full thickness cartilage, due to its strong electrostatic interactions with the high negative fixed charge of the cartilage ECM. Secondly, dexamethasone was conjugated to a collagen type II-binding peptide, WYRGRL, and this prodrug was shown to be retained in the deep zones of cartilage through specific interactions with cartilage-specific collagen type II bundles. In both cases, active dexamethasone was released from the carrier by ester linkage hydrolysis. Complexing dexamethasone with either chitosan or collagen type II-affinity carriers increased its binding and therapeutic efficacy inside cartilage, compared to free drug. Both dexamethasone conjugates significantly reduced levels of inflammatory markers and slowed the loss of glycosaminoglycans in an ex vivo model. A single dose of a cartilage-targeting dexamethasone prodrug represents a promising alternative to the repetitive glucocorticoid injections needed to compensate for its rapid clearance from the joint cavity.