The binding of native biglycan and decorin to pepsinextracted collagen VI from human placenta was examined by solid phase assay and by measurement of surface plasmon resonance in the BIAcore TM 2000 system. Both proteoglycans exhibited a strong affinity for collagen VI with dissociation constants (K D ) of ϳ30 nM. Removal of the glycosaminoglycan chains by chondroitinase ABC digestion did not significantly affect binding. In coprecipitation experiments, biglycan and decorin bound to collagen VI and equally competed with the other, suggesting that biglycan and decorin bind to the same binding site on collagen VI. This was confirmed by electron microscopy after negative staining of complexes between gold-labeled proteoglycans and collagen VI, demonstrating that both biglycan and decorin bound exclusively to a domain close to the interface between the N terminus of the triple helical region and the following globular domain. In solid phase assay using recombinant collagen VI fragments, it was shown that the ␣2(VI) chain probably plays a role in the interaction.Collagens are a large family of extracellular structural proteins made up of three ␣ chains that are intracellularly associated and folded into specific structures including characteristic triple helical domains (1). The major class, recognized as the fibril-forming collagens, contains molecules with one large uninterrupted triple helical domain (for review, see Refs. 1 and 2). Other members of the collagen family have one or more non-triple helical domains, which may constitute the major part of the protein. Most of these collagens do not form prominent lateral aggregates in a manner similar to that of the fibril-forming collagens. Instead, they form complex aggregates together with other matrix macromolecules. Collagen VI is one example, forming multimolecular filamentous beaded structures after secretion from the cell (for review, see Ref. 3). This collagen is composed of three different peptide chains (␣1(VI), ␣2(VI), and ␣3(VI)), which form the basic unit consisting of a relatively short triple helical domain flanked by two large multidomain globular regions (4). These are composed primarily of repeating units of von Willebrand type A domains (5). Collagen VI assembles intracellularly into antiparallel, overlapping dimers that then align and form tetramers (6). These structures are stabilized by disulfide bonds. Secreted tetramers assemble extracellularly in a characteristic end-to-end fashion into thin (3-10 nm) beaded filaments with a periodicity of about 100 nm (7-9). Further supramolecular assembly includes lateral associations of the beaded filaments into microfibrils (8, 9).Collagen VI is ubiquitous. It can be found intermingled with fibril-forming collagens and is often enriched in the pericellular matrix (for review, see Refs. 3 and 10). Decreased amounts of secreted collagen VI resulting from mutations in COL6A1 have been shown in Bethlem myopathy (11, 12), a dominantly inherited disorder characterized by progressive muscle weakness and wasting....

Arthritic diseases cause enormous burdens in terms of pain, crippling, and disability. Osteoarthritis (OA), the most common form of arthritis, is characterized by a slow progressive degeneration of articular cartilage. The exact etiology of OA is not known, but the degradation of cartilage matrix components is generally agreed to be due to an increased synthesis and activation of extracellular proteinases, mainly matrix metalloproteinases. Insufficient synthesis of new matrix macromolecules is also thought to be involved, possibly as a consequence of deficient stimulation by growth factors. Although OA is defined as a noninflammatory arthropathy, proinflammatory cytokines such as interleukin-1 have been implicated as important mediators in the disease. In response to interleukin-1, chondrocytes upregulate the production of nitric oxide and prostaglandin E2, two factors that have been shown to induce a number of the cellular changes associated with OA. The generation of these key signal molecules depends on inducible enzymes and can be suppressed by pharmacological inhibitors.

The osteogenic potential of autogenous bone grafts is superior to that of allografts and xenografts because of their ability to release osteoinductive growth factors and provide a natural osteoconductive surface for cell attachment and growth. In this in vitro study, autogenous bone particles were harvested by four commonly used techniques and compared for their ability to promote an osteogenic response. Primary osteoblasts were isolated and seeded on autogenous bone grafts prepared from the mandibles of miniature pigs with a bone mill, piezo-surgery, bone scraper, and bone drill (bone slurry). The osteoblast cultures were compared for their ability to promote cell attachment, proliferation, and differentiation. After 4 and 8 hrs, significantly higher cell numbers were associated with bone mill and bone scraper samples compared with those acquired by bone slurry and piezo-surgery. Similar patterns were consistently observed up to 5 days. Furthermore, osteoblasts seeded on bone mill and scraper samples expressed significantly elevated mRNA levels of collagen, osteocalcin, and osterix at 3 and 14 days and produced more mineralized tissue as assessed by alizarin red staining. These results suggest that the larger bone graft particles produced by bone mill and bone scraper techniques have a higher osteogenic potential than bone slurry and piezo-surgery.

We have demonstrated that synovial MSCs derived from the knee joints of aging human donors possess chondrogenic potential. Under serum-free culturing conditions and in the absence of dexamethasone, BMP-2 and BMP-7 were the most potent inducers of this transformation process.

These data can provide a scientific basis to better understand the impact of harvesting techniques on the number and activity of transplanted cells, which might contribute to the therapeutic outcome of the augmentation procedure.