Future studies will help us to understand the precise effect of corticosteroids on fibroblasts.
In vitro studies of the use of corticosteroids show a decrease in smooth-muscle cell proliferation. The antiproliferative effect of corticosteroids can therefore benefit asthmatic patients through smooth-muscle mass reduction if it is also effective in vivo. As smooth-muscle cells produce inflammatory mediators, corticosteroids can also reduce cytokine and chemokine production at this level, but this has to be confirmed. Some studies have shown that corticosteroids have no effect on the activation of the nuclear factor-кБ transcription factor, suggesting a possible immunosuppressive effect by corticosteroids on ASM. Corticosteroids were also ineffective in reducing ECM protein production by human ASM. Thus, corticosteroids may improve asthma control through decreased smooth-muscle cell proliferation but are less effective in modulating the synthesis of ECM proteins and cytokines. add comment
Proteoglycans: Tenascin, an ECM glycoprotein, appears to be responsive to corticosteroid treatment as a short-course of ICS (4 to 6 weeks) significantly decreased tenascin immunoreactivity in the airways of chronic asthmatic patients.
Subepithelial Fibrosis: As subepithelial fibrosis is a major histologic feature of asthma with significant clinical consequences, the effect of corticosteroid treatment on this feature has been assessed. Jeffery, Lundgren et al and Boulet et al reported no change in basement membrane thickness following long (3 year, 7 year, and 10 year) or short-term (8 weeks) use of ICS. In other studies, treatment with ICS lasting 6 weeks, 4 months, or 6 months resulted in a modest decrease in basement membrane thickness. With ICS treatment of 1-year and 2-year durations, a modest decrease in basement membrane thickness was observed in asthmatic patients. Sont et al described a decrease in reticular basement membrane (RBM) thickness in a group of patients receiving a dose of ICS equivalent to 800 ^g/d of budesonide.