Plain-English definitions of the terms that come up in MMP13 and cartilage research, each linked to a fuller explanation.
ADAMTS5 is the main enzyme that cuts aggrecan, the cushioning molecule in cartilage. It is a separate enzyme family from MMP13, which cuts the collagen.
Aggrecan is the large water-holding molecule packed into cartilage's collagen network, which lets cartilage resist being squashed. Its loss is described as early and reversible.
AKBA is the boswellic acid most studied in boswellia resin research. In rats it suppressed MMP13 and raised the MMP inhibitor TIMP-1.
An animal model is a laboratory animal, usually a rat or mouse, used to study a process such as cartilage damage that can't be tested the same way in people.
Articular cartilage is the smooth, firm tissue that covers the ends of bones where they meet in a joint. It is built from a type II collagen network holding the water-retaining molecule aggrecan.
Boswellic acids are compounds in the gum resin of Boswellia trees, the source of frankincense. AKBA is the most studied of them.
A chondrocyte is the cell that lives inside cartilage and maintains it. Chondrocytes make cartilage's building materials and also the enzymes, including MMP13, that break it down.
Chondroitin sulphate is a sugar chain found in cartilage, bone, skin and other connective tissue. In a human cartilage cell line it lowered MMP-2 and MMP-9 and raised the inhibitors TIMP-1 and TIMP-2.
A collagenase is an enzyme that can cut intact collagen, the tightly wound protein that gives tissues their strength. Humans have three main collagenases: MMP-1, MMP-8 and MMP-13.
Curcumin is a compound from the root of turmeric, Curcuma longa. In lab and rat studies it lowered MMP13, and one of its metabolites blocked MMP13 directly.
An explant is a small piece of living tissue, such as cartilage, taken from the body and kept alive in a dish for experiments. It keeps cells in their natural matrix.
The extracellular matrix is the material cells build around themselves. In cartilage it is the collagen network and aggrecan gel that make up almost all of the tissue.
Glucosamine is an amino sugar that is a building block of the glycosaminoglycans in cartilage. Lab studies of its effect on MMP13 have given mixed results.
A half-life is the time it takes for half of something to be replaced, broken down or cleared. Cartilage collagen's half-life has been estimated at 117 years.
Hyaluronic acid is a long sugar molecule found in joint fluid and cartilage. In human cartilage cells it lowered IL-1 beta-driven MMP13, more at higher doses.
IL-1 beta is a messenger protein, or cytokine, released during inflammation. It is the trigger most cartilage studies use to switch on MMP13 in cells.
In vitro means done outside a living body, in a dish or test tube. Most MMP13 research is in vitro, using cartilage cells or purified enzymes.
Matrix metalloproteinases, or MMPs, are a family of zinc-dependent enzymes that break down proteins in the material around cells. MMP13 is one of them.
MMP13 is an enzyme made by cartilage cells that cuts type II collagen, the main fibre of joint cartilage. Of the collagen-cutting enzymes it has the highest activity against type II collagen.
N-acetyl-cysteine, or NAC, is an antioxidant compound. Given by mouth to rats, it held back MMP13 and the loss of type II collagen in a joint damage model.
NF-kB is a control protein inside cells that switches on inflammation-related genes when it moves into the nucleus. MMP13 is one of the genes it helps switch on.
Piperine is the compound in black pepper that slows the body's breakdown of some other compounds. Taken with curcumin, it raised curcumin absorption by 2000% in human volunteers.
A randomised controlled trial assigns people by chance to a treatment or a comparison such as a placebo, so differences in outcome can be credited to the treatment. Double-blind means neither participants nor researchers know who got which.
TIMPs, tissue inhibitors of metalloproteinases, are the body's own blockers of MMPs and related enzymes. Humans have four, TIMP-1 to TIMP-4.
Type II collagen is the main collagen in joint cartilage, forming the fibre network that gives cartilage its strength. In adults it is barely replaced.