Effect of a gelatin hydrogel incorporating epiregulin on human keratinocyte growth

Ionic hydrogels are biocompatible interesting candidates for tissue-engineering applications, such as the creation of artificial skin, as they can also be used, along with growth factors and cells grown in vitro, for developing bioengineered tissues to be implanted. Among the growth factors that can be used to induce keratinocytes growth in vitro, epiregulin, a broad-specificity epidermal growth factor (EGF) family member, has been shown to be more effective than EGF and transforming growth factor-alpha (TGF-α) in promoting re-epithelization in vitro. To produce a drug-delivery hydrogel for epiregulin, bovine gelatin was cross-linked with poly(glutamic acid) (PLG) in the presence of epiregulin (5-50 ng/ml). Spontaneously immortalized human keratinocytes (HaCaT) were seeded on unloaded and epiregulin-loaded hydrogels and cell adhesion was evaluated after 6 h. Moreover, cell proliferation and stratification, cytokeratins (K5, K10), differentiation markers (filaggrin and transglutaminase-1 (TG-1)) and matrix metalloproteinases (MMP-2, MMP-9 and MMP-28) expression were evaluated after 7 days. The presence of epiregulin induced an increase in cell proliferation, stratification and K5 expression along with MMP-9 and MMP-28 expression, while all differentiation markers expression (K10, filaggrin, TG-1) was decreased. These data indicated that a simple hydrogel loaded with epiregulin could be an effective tool for skin tissue engineering.