Collagen barrier membranes adsorb growth factors liberated from autogenous bone chips

Collagen membranes serve as barriers to separate bone grafts from soft tissues. Bone grafts harvested with a bone scraper release growth factors activating transforming growth factor-β (TGF-β) signaling in mesenchymal cells. The aim of the present pilot study was to determine whether collagen membranes adsorb molecules from bone-conditioned medium (BCM) with the capacity to provoke the expression of TGF-β target genes in vitro.

Collagen membranes were soaked in aqueous extracts from fresh and demineralized bone chips placed in cell culture medium. Recombinant human TGF-β1 served as control. Gingival fibroblasts were seeded onto the washed collagen membranes and evaluated for the expression of adrenomedullin, pentraxin 3, interleukin 11, and proteoglycan 4. Cell viability and morphology with phalloidin staining were also determined.

Incubation of collagen membranes with BCM for at least one minute caused fibroblasts to decrease the expression of adrenomedullin and pentraxin 3, and to increase the expression of interleukin 11 and proteoglycan 4. Four different membrane treatments - incubated with recombinant TGF-β1, pre-wetted with saline solution, exposed to UV light, and dry out and stored one week at room temperature - also provoked significant changes in gene expression. Likewise, conditioned medium from demineralized bone chips caused gene expression changes. BCM did not alter the viability or morphology of gingival fibroblasts.

These findings demonstrate that collagen membranes rapidly adsorb the TGF-β activity released from bone chips, a molecular process that might contribute to guided bone regeneration.