The elastic system fibers comprise oxytalan, elaunin, and elastic fibers, differing in their relative microfibril and elastin contents. Among them, human periodontal ligament (PDL) contains only oxytalan fibers (pure microfibrils). Elastin microfibril interface-located protein-1 (EMILIN-1) is localized at the interface between microfibrils and elastin. We hypothesized that EMILIN-1 may contribute to the formation of oxytalan fibers. We used a small interfering RNA (siRNA) for EMILIN-1 in PDL cell culture to examine the extracellular deposition of fibrillin-1 (the major component of microfibrils). EMILIN-1 was labeled on microfibrils positive for fibrillin-1 and was colocalized with fibrillin-1 upon immunoprecipitation assay. EMILIN-1 suppression reduced the level of fibrillin-1 deposition to 23% of the control, and this was responsible for the diminution of fibrillin-1 deposition revealed by immunofluorescence. These results suggest that EMILIN-1 may regulate the formation of oxytalan fibers and play a role in their homeostasis.

The elastic system fibers comprise oxytalan, elaunin and elastic fibers, which differ in their relative microfibril and elastin content. Human periodontal ligaments (PDL) contain only oxytalan fibers (pure microfibrils) among them. Since fibulin-5 regulates the organization of elastic fibers to link the fibers to cells, we hypothesized that fibulin-5 may contribute to the formation of oxytalan fibers. We used siRNA for fibulin-5 in PDL cell culture to examine the extracellular deposition of fibrillin-1 and -2, which are the major components of microfibrils. Fibulin-5 was labeled on microfibrils positive for fibrillin-1 and -2. Fibulin-5 suppression reduced the level of fibrillin-1 and -2 deposition to 60% of the control level. These results suggest that fibulin-5 may control the formation of oxytalan fibers, and play a role in the homeostasis of oxytalan fibers.

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