Molecular differentiation between osteophytic and articular cartilage--clues for a transient and permanent chondrocyte phenotype.

OBJECTIVE: To identify the molecular differences between the transient and permanent chondrocyte phenotype in osteophytic and articular cartilage. METHODS: Total RNA was isolated from the cartilaginous layer of osteophytes and from intact articular cartilage from knee joints of 15 adult human donors and subjected to cDNA microarray analysis. The differential expression of relevant genes between these two cartilaginous tissues was additionally validated by quantitative reverse transcriptase polymerase chain reaction (RT-PCR) and by immunohistochemistry. RESULTS: Among 47,000 screened transcripts, 600 transcripts were differentially expressed between osteophytic and articular chondrocytes. Osteophytic chondrocytes were characterized by increased expression of genes involved in the endochondral ossification process [bone gamma-carboxyglutamate protein/osteocalcin (BGLAP), bone morphogenetic protein-8B (BMP8B), collagen type I, alpha 2 (COL1A2), sclerostin (SOST), growth arrest and DNA damage-induced gene 45ß (GADD45ß), runt-related transcription factor 2 (RUNX2)], and genes encoding tissue remodeling enzymes [matrix metallopeptidase (MMP)9, 13, hyaluronan synthase 1 (HAS1)]. Articular chondrocytes expressed increased transcript levels of antagonists and inhibitors of the BMP- and Wnt-signaling pathways [Gremlin-1 (GREM1), frizzled-related protein (FRZB), WNT1 inducible signaling pathway protein-3 (WISP3)], as well as factors that inhibit terminal chondrocyte differentiation and endochondral bone formation [parathyroid hormone-like hormone (PTHLH), sex-determining region Y-box 9 (SOX9), stanniocalcin-2 (STC2), S100 calcium binding protein A1 (S100A1), S100 calcium binding protein B (S100B)]. Immunohistochemistry of tissue sections for GREM1 and BGLAP, the two most prominent differentially expressed genes, confirmed selective detection of GREM1 in articular chondrocytes and that of BGLAP in osteophytic chondrocytes and bone. CONCLUSIONS: Osteophytic and articular chondrocytes significantly differ in their gene expression pattern. In articular cartilage, a prominent expression of antagonists inhibiting the BMP- and Wnt-pathway may serve to lock and stabilize the permanent chondrocyte phenotype and thus prevent their terminal differentiation. In contrast, osteophytic chondrocytes express genes with roles in the endochondral ossification process, which may account for their transient phenotype.

Quantitative ultrasound biomicroscopy for the analysis of healthy and repair cartilage tissue.

The increasing spectrum of different cartilage repair strategies requires the introduction of adequate non-destructive methods to analyse their outcome in-vivo, i.e. arthroscopically. The validity of non-destructive quantitative ultrasound biomicroscopy (UBM) was investigated in knee joints of five miniature pigs. After 12 weeks, six 5-mm defects, treated with different cartilage repair approaches, provided tissues with different structural qualities. Healthy articular cartilage from each contralateral unoperated knee joint served as a control. The reflected and backscattered ultrasound signals were processed to estimate the integrated reflection coefficient (IRC) and apparent integrated backscatter (AIB) parameters. The cartilage repair tissues were additionally assessed biomechanically by cyclic indentation, histomorphologically and immunohistochemically. UBM allowed high-resolution visualisation of the structure of the joint surface and subchondral bone plate, as well as determination of the cartilage thickness and demonstrated distinct differences between healthy cartilage and the different repair cartilage tissues with significant higher IRC values and a steeper negative slope of the depth-dependent backscatter amplitude AIBslope for healthy cartilage. Multimodal analyses revealed associations between IRC and the indentation stiffness. Furthermore, AIBslope and AIB at the cartilage-bone boundary (AIBdC) were associated with the quality of the repair matrices and the subchondral bone plate, respectively. This ex-vivo pilot study confirms that UBM can provide detailed imaging of articular cartilage and the subchondral bone interface also in repaired cartilage defects, and furthermore, contributes in certain aspects to a basal functional characterization of various forms of cartilage repair tissues. UBM could be further established to be applied arthroscopically in-vivo.

Chondrogenic differentiation of growth factor-stimulated precursor cells in cartilage repair tissue is associated with increased HIF-1alpha activity.

OBJECTIVE: To investigate the chondrogenic potential of growth factor-stimulated periosteal cells with respect to the activity of Hypoxia-inducible Factor 1alpha (HIF-1alpha). METHODS: Scaffold-bound autologous periosteal cells, which had been activated by Insulin-like Growth Factor 1 (IGF-1) or Bone Morphogenetic Protein 2 (BMP-2) gene transfer using both adeno-associated virus (AAV) and adenoviral (Ad) vectors, were applied to chondral lesions in the knee joints of miniature pigs. Six weeks after transplantation, the repair tissues were investigated for collagen type I and type II content as well as for HIF-1alpha expression. The functional role of phosphatidylinositol 3-kinase (PI3K)/mammalian target of rapamycin (mTOR) and mitogen-activated protein kinase (MEK)/extracellular signal-regulated kinase (ERK) signaling on BMP-2/IGF-1-induced HIF-1alpha expression was assessed in vitro by employing specific inhibitors. RESULTS: Unstimulated periosteal cells formed a fibrous extracellular matrix in the superficial zone and a fibrocartilaginous matrix in deep zones of the repair tissue. This zonal difference was reflected by the absence of HIF-1alpha staining in superficial areas, but moderate HIF-1alpha expression in deep zones. In contrast, Ad/AAVBMP-2-stimulated periosteal cells, and to a lesser degree Ad/AAVIGF-1-infected cells, adopted a chondrocyte-like phenotype with strong intracellular HIF-1alpha staining throughout all zones of the repair tissue and formed a hyaline-like matrix. In vitro, BMP-2 and IGF-1 supplementation increased HIF-1alpha protein levels in periosteal cells, which was based on posttranscriptional mechanisms rather than de novo mRNA synthesis, involving predominantly the MEK/ERK pathway. CONCLUSION: This pilot experimental study on a relatively small number of animals indicated that chondrogenesis by precursor cells is facilitated in deeper hypoxic zones of cartilage repair tissue and is stimulated by growth factors which enhance HIF-1alpha activity.

[The vacuum-assisted closure (V.A.C.) and instillation dressing: limb salvage after 3 degrees open fracture with massive bone and soft tissue defect and superinfection]. / Der Vacuum-assisted closure and instillation-" (VAC-Instill-)Verband: Extremitätenerhalt bei drittgradig offener superinfizierter Femurfraktur mit massivem Knochen- und Weichteildefekt.

We report the case of a 17-year-old boy who was hit by a high velocity train. The polytraumatized patient suffered a 3 degrees open femur defect fracture with a substantial loss of the lateral femoral muscles and significant disruption of the soft tissue of the lower leg. The enormous wound areas on the thigh and the lower leg were infected by Pseudomonas aeruginosa, Enterobacter cloacae, and Stenotrophomonas maltophilia. The enormous tissue defects and the superinfection did not leave any hope for saving the limb from amputation. After rapid aggressive debridement and pulsatile lavage, we covered the wounds as a last resort with a new technique of vacuum-assisted closure (V.A.C) and instillation (V.A.C. Instill(R)) dressings. In sequences of 1 min we instilled Lavasept, kept it for 20 min on the wound surface, and exhausted the liquid. We repeated this for 6 consecutive days and then changed the dressing. In the follow-up examinations the number of germs was significantly reduced. During follow-up care we used the V.A.C. treatment without instillation and finally we transplanted skin onto the clean wound surface and were able to save the leg of this young patient. We discharged him with a good function of his lower leg. This technique of V.A.C. Instill seems to offer great possibilities in critically infected wound situations.

[Generalized compartment syndrome after excessive drinking. A rare complication of psychological disorders?]. / Das generalisierte Kompartmentsyndrom nach exzessivem Trinken. Seltene Komplikation psychischer Erkrankungen?

Psychogenic polydipsia can lead to compartment syndromes, which is too infrequently considered in psychiatric patients who binge-drink on hypotonic fluids. If masked by the leading clinical presentation of cerebral edema, compartment syndromes of the extremities may be diagnosed too late or remain undetected. Based on a literature review and case report, we discuss additional factors and the specific features of diagnosis and treatment.