in: A Closer Look at Metalloproteinases, Lena Goodwin, Editor, NOVA Science Publishers Inc. , New-York, pp.153-249, 2019
Bone has a dynamic structure, since it is remodelled during the lifespan to sustain its structure and function. Extracellular matrix (ECM) is playing a tremendously important role, such as cell adhesion, immobilization of growth factors and nucleation of mineralization in bone development phase. It consists of proteins and leads the bone remodelling by the combined osteoblast (bone-forming cells) and osteoclast (bone-resorbing cells) activities. Besides, ECM behaves as a scaffold for mineral deposition. Matrix metalloproteinases (MMPs), a family of zinc-depended proteolytic enzymes, are the most important enzymes used for the degradation of unrelated proteins and structural components present in ECM. MMPs are highly expressed in mammalian bone and cartilage cells and are able to cleave collagens, thus function as collagenases. Furthermore, they lead remodelling of ECM in connection with tissue specific and cell anchored inhibitors. Functions of MMPs may vary bone quality via bone resorption and formation, i.e., osteoblast recruitment and survival, angiogenesis, osteocyte viability and function, chondrocyte proliferation and differentiation. Abnormal expression of MMPs can be related to pathological conditions such as unstable bone remodelling, particularly osteoporosis, rheumatoid arthritis and osteoarthritis. In this chapter, bone tissue components, MMP properties and functions, bone modelling, remodelling and resorption, repair and regeneration, and pathological bone resorption will be discussed.