Scatter factor (also known as hepatocyte growth factor) is a glycoprotein secreted by stromal cells that stimulates cef motility and proliferation. In vitro, scatter factor stimulates vascular endotheHal cell migration, proliferation, and organization into capillary-like tubes. Using two different in vivo assays, we showed that physiologic quantities ofpurified native mouse scatter factor and recombinant human hepatocyte growth factor induce angiogenesis (the formation of new blood vessels). The angiogenic activity was blocked by specific anti-scatter factor antibodies. Scatter factor induced cultured microvascular endothelHal cells to accumulate and secrete signiflcantly increased quantities of urokinase, an enzyme associated with development of an invasive endothelial phenotype during angenesis. We further showed that immunoreactive scatter factor is present surrounding sites of blood vessel formation in psorlatic skin. These findings suggest that scatter factor may act as a paracrine miator in pathologic angiogenesis aociated with human inflammatory disese.

We investigated the effect of light (0.1 MPa), moderate (1 MPa) or heavy ( 5 MPa) cyclical stresses applied continuously or intermittently for 0 to 72 h on cell death and collagen damage in adult bovine cartilage explants. No increase in cell death was observed in the cartilage loaded with a continuous cyclic stress at 0.1 MPa for up to 72 h. Cell death occurred in the uppermost superficial tangential zone (STZ) of explants after loading for 1 h at 1 MPa, and reached a maximum depth of 61 & 23 pm by 6 h (at the rate of 9 i 6 pmlh). At 5 MPa, cell death occurred in the STZ after as little as 1 min (30 cycles) of loading, and reached a maximum depth of 70 f 2 pm by 60 min (47 rt 8 pm/h). When an intermittent (with 2 s on, 2 s off) stress of 5 MPa was applied, cell death appeared in the STZ after 2 min (30 cycles) and increased to a depth of 63 f 2 pm at 60 min (45 i 11 pm/h). No significant differences were observed between the continuous and intermittent loading conditions. Both collagenase-cleaved and denatured collagen fibers were found in the STZ of explants loaded at 1 and 5 MPd. We concluded that load-induced cell death depends on load duration and magnitude, and that the chondrocytes in the STZ are more vulnerable to load-induced injury than those in the middle and deep zones.

The objective of this study was to develop an in vitro cartilage degradation model that emulates the damage seen in early-stage osteoarthritis. To this end, cartilage explants were collagenase-treated to induce enzymatic degradation of collagen fibers and proteoglycans at the articular surface. To assess changes in mechanical properties, intact and degraded cartilage explants were subjected to a series of confined compression creep tests. Changes in extracellular matrix structure and composition were determined using biochemical and histological approaches. Our results show that collagenase-induced degradation increased the amount of deformation experienced by the cartilage explants under compression. An increase in apparent permeability as well as a decrease in instantaneous and aggregate moduli were measured following collagenase treatment. Histological analysis of degraded explants revealed the presence of surface fibrillation, proteoglycan depletion in the superficial and intermediate zones and loss of the lamina splendens. Collagen cleavage was confirmed by the Col II–¾Cshort antibody. Degraded specimens experienced a significant decrease in proteoglycan content but maintained total collagen content. Repetitive testing of degraded samples resulted in the gradual collapse of the articular surface and the compaction of the superficial zone. Taken together, our data demonstrates that enzymatic degradation with collagenase can be used to emulate changes seen in early-stage osteoarthritis. Further, our in vitro model provides information on cartilage mechanics and insights on how matrix changes can affect cartilage’s functional properties. More importantly, our model can be applied to develop and test treatment options for tissue repair.

We determined the effect of cytokines on the proliferation and migration of cells isolated from the inner-third (white-white), middle-third (red-white), and outer-third (red-red) regions of bovine meniscus. Cells from the outer, or peripheral, region of the meniscus exhibited higher DNA synthesis in the presence of 10% serum compared with cells from the inner or central regions. Recombinant human platelet-derived growth factor-AB, hepatocyte growth factor/scatter factor, and bone morphogenic protein-2 stimulated DNA synthesis of all meniscal cells in a dose-dependent manner, with a two- to threefold maximal stimulation at 10 ng/ml. Cell migration was also stimulated by addition of cytokines. Platelet-derived growth factor and hepatocyte growth factor caused an increase in the migration of cells derived from all three zones, while interleukin-1 selectively stimulated the migration of outer-zone meniscal cells. Epidermal growth factor was much less effective and stimulated the migration of cells in the inner and outer zones by 40% to 50%, while bone morphogenic protein-2 and insulin-like growth factor-1 stimulated the migration of meniscal cells from the middle zone by 40% to 50%. The identification of cytokines that stimulate both the growth and migration of meniscal cells may provide new tools for modulation of meniscal healing.