Dysfunctional pericellular hyaluronan deposition contributes to attenuated CD44/EGFR co-localization and impaired myofibroblast differentiation in chronic wound fibroblasts

Abstract

Non-healing chronic wounds, such as venous ulcers and pressure sores, represent significant causes of patient morbidity and financial burden to Healthcare Services worldwide. During normal healing, dermal fibroblasts (DFs) mediate numerous responses to promote wound closure. However, phenotypic changes induced within chronic wound environments lead to dysfunctional fibroblast functions, which facilitate non-healing. Although the processes underlying impaired proliferative and migratory responses in chronic wound fibroblasts (CWFs) are established, the mechanisms that mediate impaired CWF-myofibroblast differentiation remain poorly understood. Fibroblast-myofibroblast differentiation is induced by transforming growth factor-β₁ (TGF-β₁) and downstream classical Smad2/3 and non-classical epidermal growth factor receptor (EGFR)/ERK1/2 signaling, initiated through hyaluronan (HA) receptor (CD44) binding to EGFR and dependent on elevated HA synthesis and its pericellular accumulation. Here, we demonstrate that these signaling pathways are dysregulated in venous ulcer- and pressure sore-derived CWFs, compared to DFs. CWFs exhibit increased susceptibilities to cellular senescence and impaired myofibroblast differentiation, accompanied by defective lysosomal/endosomal activities and dysfunctional activation of the HA/CD44/EGFR pathway. Irrespective of wound source, CWFs exhibited increased HAS1 versus HAS2 expression, altered HAS1 and HAS2 intracellular localization, and deregulated hyaladherin (CD44, TSG-6, and IαI heavy chain motifs, HC3, HC4 and HC5) induction, following TGF-β₁ stimulation. These events attenuated HA pericellular coat formation and CD44/EGFR co-localization within membrane lipid rafts, essential for myofibroblast development. Our findings suggest that aberrant HAS1 and HAS2 expression and distributions cause reduced pericellular hyaluronan deposition, leading to attenuated CD44/EGFR co-localization and dysfunctional CWF-myofibroblast differentiation, which contributes to the impaired closure and healing of chronic wounds.