Abstract
BackgroundFibroblasts are key players in maintaining skin homeostasis and in orchestrating physiological tissue repair and skin regeneration. Dysfunctions in fibroblasts that occur with aging and the senescent process lead to the delayed healing observed in elderly people. The molecular mechanisms leading to fibroblast dysfunction during aging and the senescent process have not yet been clarified. Previously, changes in patterns of glycosylation were observed in fibroblasts in aging and the senescent process, but the effect of these changes on the function of fibroblasts has not been well documented. Here, we investigated whether changes in glycosylation during the process to senescence may have functional effects on fibroblasts.MethodsThe changes in cell surface glycans on skin fibroblasts during the process to senescence were examined in early-passage (EP) and late-passage (LP) skin fibroblasts by fluorescence-activated cell sorting analysis using lectins. The contributors to the changes in cell surface glycans were examined by real-time polymerase chain reaction or Western blot analysis. The effects of changes in glycosylation on proliferation, migration, induction of cellular senescence, and myofibroblast differentiation induced by transforming growth factor (TGF)-β1 stimulation were examined in EP fibroblasts. The changes in glycosylation were performed by GalNAc-α-O-benzyl or sialidase treatment.ResultsA decrease in sialylation of glycoproteins and an increase in sialidase NEU1 were observed in LP fibroblasts. The reduction of sialylation did not have any effect on proliferation, migration, or induction of cellular senescence. On the other hand, myofibroblast differentiation was inhibited by the reduction of sialylation, indicating that sialylation is important for myofibroblast differentiation. The localization of CD44 in lipid rafts, which is required for myofibroblast differentiation, was inhibited by the reduction of sialylation. Furthermore, reduced myofibroblast differentiation in LP fibroblasts was restored by a sialidase inhibitor.ConclusionsDesialylation of CD44 with increased sialidase during the process to senescence reduced the localization of CD44 in lipid rafts after TGF-β1 stimulation, leading to the inhibition of myofibroblast differentiation. Thus, regulation of sialylation may be an attractive strategy for the prevention and regenerative therapy of age-related skin diseases, cosmetic skin alterations, and chronic wounds caused by delayed healing in elderly people.
Highlights
Fibroblasts are key players in maintaining skin homeostasis and in orchestrating physiological tissue repair and skin regeneration
These results demonstrate that sialylation of glycoproteins on the cell surface of skin fibroblasts was decreased during the process to senescence, presumably due to a cell surface increase in the expression of NEU1
Raft localization of CD44 after transforming growth factor (TGF)-β1 stimulation is inhibited by reduced sialylation with by GalNAc-α-Obenzyl (BGN) Because activation of the mitogen-activated protein kinase (MAPK/Extracellular signal-regulated kinase (ERK)) signaling by TGF-β1 stimulation is known to be required for myofibroblast differentiation [23], we examined whether the reduction of sialylation had an effect on TGF-β1–Mitogen-activated protein kinase (MAPK)/ERK signaling
Summary
Fibroblasts are key players in maintaining skin homeostasis and in orchestrating physiological tissue repair and skin regeneration. Recent reports have demonstrated that cell surface glycans on fibroblasts change during aging and the senescent process; for instance, reduced sialylation on glycans was observed during cellular senescence in human lung fibroblasts [9,10,11,12]. Our previous glycome analysis using lectin microarrays demonstrated changes in the total membrane glycosylation of glycoproteins in human skin fibroblasts with aging and the senescent process [13]. It is not known whether the changes in glycosylation have any effects on fibroblast function and senescence
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