Hyaluronan Controls the Deposition of Fibronectin and Collagen and Modulates TGF-β1 Induction of Lung Myofibroblasts

Abstract

The contribution of hyaluronan-dependent pericellular matrix to TGF-β1-driven induction and maintenance of myofibroblasts is not understood. Hyaluronan is an extracellular matrix (ECM) glycosaminoglycan important in cell adhesion, proliferation and migration, and is implicated in myofibroblast formation and maintenance. Reduced turnover of hyaluronan has been linked to differentiation of myofibroblasts and potentiation of lung fibrosis. Fibronectin is a fibril forming adhesive glycoprotein that is also upregulated following induction with TGF-β1. Although they are known to bind each other, the interplay between hyaluronan and fibronectin in the pericellular matrix during myofibroblast induction and matrix assembly is not clear. This study addresses the role of hyaluronan and its interaction with fibrillar matrix components during myofibroblast formation. Hyaluronan and fibronectin were increased and co-localized in the ECM following myofibroblast induction by TGF-β1. Inhibition of hyaluronan synthesis in TGF-β1-induced lung myofibroblasts over a 4 day period with 4-methyl umbelliferone (4-MU) further enhanced myofibroblast morphology, caused increased deposition of fibronectin and type I collagen in the ECM, and increased expression of alpha-smooth muscle actin and hyaluronan synthase 2 (HAS2) mRNA. Hyaluronan oligosaccarides or hyaluronidase treatment, which more effectively disrupted the pericellular matrix, had similar effects. CD44 and β1 integrins co-localized in the cell membrane and along some stress fibers. However, CD44 and hyaluronan were specifically excluded from focal adhesions, and associated primarily with cortical actin. Time-lapse imaging of the immediate effects of hyaluronidase digestion showed that hyaluronan matrix primarily mediates attachment of membrane and cortical actin between focal contacts, suggesting that surface adhesion through hyaluronan and CD44 is distinct from focal adhesion through β1 integrins and fibronectin. Fluorescein-labeled hyaluronan bound regularly along fibronectin fibers and co-localized more with β1 integrin and less with CD44. Therefore, the hyaluronan matrix can interfere with the assembly of fibrillar ECM components, and this interplay regulates the degree of myofibroblast formation. These data also suggest that adhesion through hyaluronan matrix impacts cytoskeletal organization, and is potentially part of a clutch mechanism that regulates stick and slip of myofibroblasts by affecting the adhesion to and organization of fibronectin and collagen.

Hyaluronan as a therapeutic target in human diseases

“…Both CD44 [148] and HMMR [57] have been shown to have a role in fibroblast migration during tissue injury. Furthermore, myofibroblast migration can be regulated by HA [149]. These studies suggested a role for HA in tissue injury and fibrosis.…”

The effect of hyaluronan on the motility of skin dermal fibroblasts in nanofibrous scaffolds

“…7A), while the majority of CD44 was associated with the cortical actin network between stress fibers. The cortical actin network gives rise to lamellipodia and filopodia, suggesting that adhesion via CD44 and hyaluronan might be a precursor to the formation of these structures in fibroblasts [37].…”

Biology and biotechnology of hyaluronan

“…Usually, the presence of HA in inflammation is followed by tissue repair and new collagen deposition. This phenomenon should be carefully tuned as the excess of inflammation due to high amount of HA oligosaccharides or excess of fibroblasts stimulation by HA oligosaccharides may drive to fibrosis [84]. The relationship between HA production and chronic inflammation is evident in gut pathologies as Crohn disease and ulcerative colitis.…”

“…The healing processes in all tissues are typically characterized by a complete alteration of ECM and the first step of the healing process is characterized by the synthesis of HA which favours inflammatory cell migration, a correct macrophage, fibroblast migration, new synthesis of collagen and neoangiogenesis [18,57,84]. In all of these processes, HA plays a pivotal role and altered HA content affects wound healing altering a normal scar formation [92].…”