**4. Versican is a chondroitin sulfate proteoglycan and is critical for dermal viscoelasticity**

Among the ECM molecules in the dermis, versican appears to be the most important molecule for tissue viscoelasticity. Versican (also called PG-M) is a large chondroitin sulfate proteoglycan that was originally characterized in a mesenchymal condensation in chick limb bud (12). Versican binds to hyaluronan via its amino-terminal G1 domain and to fibrillin-1, fibulin-1 and fibulin-2 via its carboxyl terminal G3 domain. The distribution of versican is similar to that of elastic fiber in the dermis and in other tissues (13, 14) and is immunolocalized to microfibrils through its binding affinity to fibrillin-1 (15) as observed in Figure 3.

Thus, versican plays critical roles in the viscoelastic properties of skin. Versican 1) connects with elastic microfibrils by binding to fibrillin via its G3 domain; 2) has chondroitin sulfate chains that hold a large amount of water within the ECM space; and 3) binds to HA, which holds a large quantity of water. Figure 4 shows the proposed structural model of the elastichydrated matrix in the dermis. Furthermore, the fibrillin-versican-hyaluronan network is also observed in the ciliary body (16).

160 Viscoelasticity – From Theory to Biological Applications

MF: microfibrils (Bar = 200 nm)

**viscoelasticity** 

**Figure 2.** Electron microscopic image of dermal connective tissues. Col: collagen fiber, El: elastin core,

**4. Versican is a chondroitin sulfate proteoglycan and is critical for dermal** 

Among the ECM molecules in the dermis, versican appears to be the most important molecule for tissue viscoelasticity. Versican (also called PG-M) is a large chondroitin sulfate proteoglycan that was originally characterized in a mesenchymal condensation in chick limb bud (12). Versican binds to hyaluronan via its amino-terminal G1 domain and to fibrillin-1, fibulin-1 and fibulin-2 via its carboxyl terminal G3 domain. The distribution of versican is similar to that of elastic fiber in the dermis and in other tissues (13, 14) and is immunolocalized

Thus, versican plays critical roles in the viscoelastic properties of skin. Versican 1) connects with elastic microfibrils by binding to fibrillin via its G3 domain; 2) has chondroitin sulfate

to microfibrils through its binding affinity to fibrillin-1 (15) as observed in Figure 3.

**Figure 3.** Versican co-localizes with fibrillin-1 in the dermis. Immunofluorescent staining using specific antibodies against versican and fibrillin-1 show co-localization.

**Figure 4.** Schematic presentation of the dermal viscoelastic network linked by versican. Versican links elastic fibers to ground substance.
