Sulfated Glycosaminoglycans As Promising Artificial Extracellular Matrix Components to Improve the Regeneration of Tissues

Glycosaminoglycans (GAG) such as hyaluronan (HA) or chondroitin/dermatan sulfate (CS/DS) occur in many connective tissues, for instance, in bone, cartilage and skin. Due to their significant water-binding capacity, GAG are essential for the biomechanical properties of these tissues. However, there is also increasing evidence that the sulfation of GAG does not occur at random, but a "sulfation code" exists that mediates the physiological functions of GAG. Thus, the biological properties of these biomacromolecules are strongly influenced by the degree of sulfation (ds) and the sulfate group distribution along the polymer. Therefore, certain GAG might also have interesting pharmacological properties. It is, thus, commonly accepted that GAG represent promising biomaterials in the field of tissue engineering as well as to design new bioactive materials for tissue repair and reconstruction. In this review we will focus on chemically sulfated GAG and provide a survey of these compounds on four different levels. First, we will provide an overview on chemical functionalization strategies of naturally occurring HA and CS/DS with special emphasis on regioselective methods to introduce a defined number of sulfate residues into the carbohydrate backbone. Second, chemical and biochemical methods to characterize the synthesized compounds will be introduced with the focus on methods based on nuclear magnetic resonance (NMR) and mass spectrometry (MS). In the third part, we will discuss the interaction of natural and chemically sulfated GAG with proteins and other biomolecules with regulatory functions. Additionally, biological consequences of these interactions regarding healing processes of skin and bone will be presented by discussing selected cell culture experiments. Finally, in vivo effects of GAG as components of artificial extracellular matrices will be discussed.