Human cultured periosteal sheets, which are developed from small excised periosteum tissue segments (PTSs) in culture dishes by simple expansion culture, have been applied as a promising autologous osteogenic grafting material for periodontal regenerative therapy. However, the weak initial adhesion of PTSs to dish surfaces often hampers cellular outgrowth and limits the number of preparations. To correct this weakness and still avoid the use of animal-derived adhesion biomolecules, we have developed a novel, biodegradable, porous poly(L-lactic acid) (pPLLA) membrane. Freshly excised PTSs bound well to the highly porous pPLLA membrane, possibly due to the presence of semihemispheric 20-30 μm diameter openings on the upper surface. Global gene expression analysis demonstrated that periosteal sheets cultured on pPLLA membranes upregulated expression of many adhesion molecules. Osteogenic induction stimulated the production of proteoglycans by these cells and concomitantly enhanced their expansion and penetration into the deep pore regions of the membrane in parallel with the progression of in vitro mineralization. These findings suggest that our pPLLA membranes not only facilitate initial adhesion, primarily mediated by adsorbed proteins, but also enhance biological adhesion by inducing endogenous adhesion molecules in periosteal sheet cultures. Therefore, the efficacy of periosteal sheets in therapy should be greatly enhanced by using this new pPLLA membrane.
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