Glycosaminoglycans (GAGs) are a group of heteropolysaccharides, which include: chondroitin sulfates, dermatan sulfates, heparan sulfates, heparin, keratan sulfates, and hyaluronic acid. GAGs are composed of negatively charged polysaccharide chains composed of repeating disaccharide units, which include N-acetylated hexosamine residues – D-glucosamine or D-galactosamine – or N-sulfated D-glucosamine and hexuronic acid residues – D-glucuronic or L-iduronic acid – or galactose. All GAGs, except for hyaluronic acid, have a sulfate group and form proteoglycans (PGs) when attached to the core proteins. GAGs have many important biological functions influencing PGs functions. PGs are present in all types of tissues and participate in cell migration, proliferation, and differentiation. They occur mainly in the extracellular matrix (ECM), where they participate in ECM organization, structure formation and mechanical properties. They play an important role in maintaining homeostasis and also influence metabolic processes, such as bone mineralization and blood coagulation. PGs (due to the strongly negative charge of the glycan chains) are involved in the selective permeability of cell membranes. Components of the ECM, including GAGs, play a structural and functional role during the healing of tissue damage. They regulate the healing process by acting as a reservoir and modulator for cytokines and growth factors and perform structural functions by filling tissue defects during the repair process.