Influence of glycosaminoglycan identity on vocal fold fibroblast behavior

Poly(ethylene glycol) (PEG) hydrogels have recently begun to be studied for the treatment of scarred vocal fold lamina propria due, in part, to their tunable mechanical properties, resistance to fibroblast-mediated contraction, and ability to be polymerized in situ. However, pure PEG gels lack intrinsic biochemical signals to guide cell behavior and generally fail to mimic the frequency-dependent viscoelastic response critical to normal superficial lamina propria function. Recent results suggest that incorporation of viscoelastic bioactive substances, such as glycosaminoglycans (GAGs), into PEG networks may allow these gels to more closely approach the mechanical responses of normal vocal fold lamina propria while also stimulating desired vocal fold fibroblast behaviors. Although a number of vocal fold studies have examined the influence of hyaluronan (HA) on implant mechanics and vocal fold fibroblast responses, the effects of other GAG types have been relatively unexplored. This is significant, since recent studies have suggested that chondroitin sulfate C (CSC) and heparan sulfate (HS) are substantially altered in scarred lamina propria. The present study was therefore designed to evaluate the effects of CSC and HS incorporation on the mechanical response of PEG gels and vocal fold fibroblast behavior relative to HA. As with PEG-HA, the viscoelasticity of PEG-CSC and PEG-HS gels more closely approached that of the normal vocal fold lamina propria than pure PEG hydrogels. In addition, collagen I deposition and fibronectin production were significantly higher in CSC than in HA gels, and levels of the myofibroblast marker smooth muscle α-actin (SM α-actin) were greater in CSC and HS gels than in HA gels. Since collagen I, fibronectin, and SM α-actin are generally elevated in scarred lamina propria these results suggest that CSC and HS may be undesirable for vocal fold implants relative to HA. Investigation of various signaling intermediates indicated that alterations in NFκB-p50, NFκB-p65, or pERK1/2 levels may underlie the observed differences among the PEG-GAG gels.