Injectable hyaluronic acid-dextran hydrogels and effects of implantation in ferret vocal fold

Abstract

Injectable hydrogels may potentially be used for augmentation/regeneration of the lamina propria of vocal fold tissue. In this study, hyaluronic acid (HA) and dextran were chemically modified and subsequently crosslinked via formation of hydrazone bonds in phosphate buffer. Swelling ratios, degradation, and compressive moduli of the resulting hydrogels were investigated. It was found that the properties of HA-dextran hydrogels were variable and the trend of variation could be correlated with the hydrogel composition. The biocompatibility of three injectable HA-dextran hydrogels with different crosslinking density was assessed in the vocal fold region using a ferret model. It was found that HA-dextran hydrogels implanted for three weeks stimulated mild foreign-body reactions. Distinct tissue-material interactions were also observed for hydrogels made from different formulations: the hydrogel with the lowest crosslinking density was completely degraded in vivo; while material residues were visible for other types of hydrogel injections, with or without cell penetration into the implantation depending on the hydrogel composition. The in vivo results suggest that the HA-dextran hydrogel matrices can be further developed for applications of vocal fold tissue restoration.

FIGURE 1

Illustration of HA and dextran derivatives for synthesis of injectable hydrogels: (a) HA-ADH and (b) dextran-aldehyde derived from periodate oxidization.

FIGURE 2

(a) Swelling ratios of HA-dextran hydrogels (mean ± standard deviation, n = 4); (b), in vitro degradation study (in 50 U/mL hyaluronidase solution) using the carbazole assay shows that the degradation rate of HA-dextran hydrogels decreases with increasing dextran content (mean ± standard deviation, n = 3).

FIGURE 3

(a) Compressive moduli of fully swollen HA-dextran hydrogels (mean ± standard deviation, n = 3); (b), Representative stress-strain curves of HA-dextran hydrogels. Hydrogel moduli were derived from the linear strain range between 5% and 25%.

FIGURE 4

The ferret vocal fold injected with HA-dex 0.5, showing the normal histology of ferret vocal fold tissue with no residue of hydrogel materials. Regions of epithelium and muscle tissue are indicated by letters E and M, respectively (scale bar: 200 µm).

FIGURE 5

H&E stained tissue slides of HA-Dextran crosslinked hydrogel implanted in the ferret vocal fold at week 3. Regions of epithelium, injected gel and muscle tissue are indicated by letters E, G, and M, respectively. (a) HA-dex0.75 in the host tissue (scale bar: 200 µm); (b), the interface of the host tissue and HA-dex0.75 gel (scale bar: 50 µm); (c), HA-dex1 in the host tissue (scale bar: 200 µm); (d) the interface of the host tissue and HA-dex1 gel (scale bar: 50 µm). Cell types were visually identified in b and pointed by arrows (yellow horizontal arrow: macrophage; yellow vertical arrow: foam cell; black vertical arrow: neutrophil; black horizontal arrows: fibroblasts).