TGF-beta Activity Related to the Use of Collagen Membranes: In Vitro Bioassays

Abstract

Collagen membranes commonly used in guided bone regeneration are supposed to actively influence tissue regeneration and are not exclusively serving as passive barriers shielding away the soft tissue. The molecular mechanisms by which collagen membranes might affect tissue regeneration might involve the activation of transforming growth factor beta (TGF-beta) signaling pathways. Here, we determined the TGF-beta activity of supernatants and proteolytic lysates of five commercially available collagen membranes. The expression of TGF-beta target genes interleukin 11 (IL11), NADPH oxidase 4 (NOX4), and proteoglycan 4 (PRG4) was evaluated by reverse transcriptase polymerase chain reaction and IL11 immunoassay in gingival fibroblasts. TGF-beta signaling activation was further assessed by blocking the TGF-beta receptor I kinase, a TGF-beta neutralizing antibody, and showing the nuclear localization of phosphorylated Smad3 and total Smad2/3. We could identify two collagen membranes whose supernatants and lysates caused a robust increase of TGF-beta receptor I kinase-dependent expression of IL11 in gingival fibroblasts. Moreover, the supernatant of a particular one membrane caused the nuclear localization of phosphorylated Smad3 and Smad2/3 in the fibroblasts. These results strengthen the evidence that some collagen membranes possess an intrinsic TGF-beta activity that might actively influence the process of guided bone regeneration.