The Cell-Multilayered Periosteal Sheet —A Promising Osteogenic and Osteoinductive Grafting Material - New Trends in Tissue Engineering and Regenerative Medicine - page 20

Figure 1. Cultured periosteal sheet application to infrabony defects in patients with periodontitis
2. Biological characteristics of the cultured periosteal sheet
Our periosteal sheets are prepared using static explant cultures of small pieces of alveolar
periosteum tissue. The number of cells can be expanded at least by 1000 times by the end of
the 6-week preparation, and the resulting periosteal sheet is mechanically tough enough to be
picked up by forceps [Kawase et al ., 2009]. In our experience preparing more than 2000
periosteal sheets, we confirmed that the growth is not significantly dependent either on age
or sex. The successful preparation is rather dependent on the cell density in excised periosteum
tissue segments. It is also important to handle the excised periosteum tissue in a timely manner,
especially in the initial preparation of the “cut and paste” onto culture dishes because this
procedure includes a time-sensitive semi-drying process for facilitating tissue segment
attachment onto the plastic surface.
We developed this grafting material as a substitute for crushed autologous bone, a gold
standard osteogenic grafting material. Therefore, the periosteal sheets are expected to express
osteogenic and osteoinductive capabilities besides (or rather than) the osteoconductive
capability displayed by most recent bone filler made of bioactive ceramics.
In our basic studies using in vitro cell culture systems and in vivo animal implantation systems,
we have demonstrated several remarkable characteristics of the periosteal sheet, which are
summarized below:
Tissue-like thickness: The periosteal sheet displays a unique structure that is composed of
cell-multilayers and abundantly deposited extracellular matrices (ECM).
Osteogenicity: Periosteal cells within the periosteal sheet differentiate to osteogenic cells
slowly but spontaneously with time of expansion using a conventional medium.
Osteoinduction: The periosteal sheet produces the major growth factors involved in bone
metabolism.