This 1996 study found that human cartilage cells (chondrocytes) make and release collagenase-3, now called MMP13, while cells from the joint lining (synoviocytes) did not. Osteoarthritic cartilage made about 9.5 times more of the protein than normal cartilage, and two inflammatory signals changed how much the cells produced.
Researchers searched joint tissues for the genetic message of collagenase-3 using reverse transcriptase PCR, comparing chondrocytes with synoviocytes, the cells of the joint lining. They measured message levels in normal and osteoarthritic cartilage with Northern blots, used two specific antibodies to detect the protein the cells made, compared its speed on type II collagen with collagenase-1 (MMP-1), and tested two inflammatory cytokines, IL-1 beta and TNF-alpha.
Collagenase-3 was expressed by chondrocytes but not by synoviocytes. Its two main message forms were significantly higher in osteoarthritic cartilage than in normal cartilage, and the protein was about 9.5 times higher. Chondrocytes made it as an inactive proenzyme and as a glycosylated doublet. On type II collagen it worked about five times faster than collagenase-1. IL-1 beta and TNF-alpha changed how much the cells made, depending on dose and time.
The abstract does not say how many donors were studied. Finding more enzyme in damaged cartilage shows an association, not that the enzyme caused the damage. The fivefold speed figure comes from lab measurements and differs from the tenfold figure in Mitchell's paper the same year, which used different methods. The cytokine effects were tested on cells, not in a living joint.
Published the same year as Mitchell's study, this paper placed MMP13 inside the cartilage cell itself. If cartilage cells make their own collagen-cutting enzyme, then the cell that maintains cartilage can also take part in breaking it down. Much of the later MMP13 research rests on that idea.
MMP13, short for matrix metalloproteinase-13 and also called collagenase-3, is an enzyme that cuts collagen. Cartilage cells make it, and of the collagen-cutting enzymes...
MMP13 cuts type II collagen, the rope-like fibre that gives cartilage its strength. It cleaves each three-stranded collagen molecule at one spot, leaving a three-quarter...
Yes, in lab studies. The inflammatory messenger IL-1 raised MMP13 in human cartilage and cartilage cells in several studies, and TNF-alpha did too. To switch the MMP13...