96-Well Plate-Based Method for Total Collagen Analysis of Cell Cultures

Total collagen assays are often laborious and use large quantities of consumables. We have developed a new method of assaying total 3H-proline-labeled collagen from cultured cells. Cells and media are harvested from 96-well plates directly onto fiberglass filtermats and counted in the Wallac 1205 flat-bed scintillation counter (BetaPlate™). The assay was validated by comparison with a traditional total collagen assay. The resulting assay provides a rapid one-step method for quantifying collagen synthesis, which, unlike many collagen assays, does not require extensive dialysis or precipitation of proteins.

Osteoarthritic cartilage loses its ability to remain avascular

OBJECTIVE

To determine whether human osteoarthritic (OA) cartilage loses its ability to remain avascular when placed into the in-vivo model of angiogenesis, the chick embryo chorio-allantoic membrane (CAM), and to determine specific changes that occur in the cartilage matrix when the cartilage is exposed to an active vasculature.

DESIGN

Articular cartilage from OA and non-OA joints was grafted onto the CAM for up to 5 days before fixing and processing for histological, histochemical and immunological examination for specific changes in proteoglycan and collagen.

RESULTS

OA cartilage, but not non-OA cartilage, showed invasion of its matrix by blood vessels from the CAM to various extents. Associated with these blood vessels was a loss of staining for proteoglycans and cartilage specific glycosaminoglycans (GAG). A deposition of collagen types I and X was also visualized around the invasive vessels.

CONCLUSIONS

OA cartilage loses or has already lost its ability to remain avascular when placed onto the chick CAM. Changes occur in the matrix around the invasive blood vessels, specifically a loss of proteoglycan and GAG, and the deposition of new collagen types, notably I and X.

Intrinsic control of vascularization in developing cartilage rudiments

The vascularization of developing cartilage rudiments is temporally and spatially defined. By using an in vivo angiogenesis model, the chorioallantoic membrane (CAM) of the chick embryo and chick embryo cartilage rudiments, we conclude that the factors controlling the vascular invasion of cartilage rudiments are intrinsic. Intact rudiments, separate hypertrophic zones and separate rounded cell zones, when grafted onto the CAM, become vascularized in the same temporal and spatial manner as occurs in ovo. When grown as organ cultures prior to CAM grafting, rudiments still become vascularized in the same temporal and spatial manner. The integrity of the extracellular matrix and the presence of the periosteum are two physical factors regulating the control of vascularization. Removal of the periosteum from hypertrophic regions caused a cessation of the invasion. Insults to the matrix via brief enzymatic degradation of extracellular matrix components resulted in invasion and erosion of rounded cell zones at an earlier time than is ordinarily seen both in ovo and on the CAM.