Biomedical Engineering Reference
In-Depth Information
dicularly into the newly formed cementum-like tissue, and this orientation resembled the
native Sharpey's fibers. In addition, the regenerative potential of hPDL cell sheets cultured
with the osteoinductive medium the was confirmed, when hPDL cell sheets were trans‐
planted onto the root surface of periodontal defects in athymic rat mandibles (Flores et al.,
2008b). The results indicate that most of the specimens in the experimental group exhibited
a newly-formed cementum and a new attachment of collagen fibers to the cementum layer.
No clear cementum layer was observed in the control group (in the absence of osteoinduc‐
tive supplements). As shown in these experiments, hPDL cells cultured with osteoinductive
medium could contribute to the simultaneous regeneration of cementum and PDL.
3.2. Large animal studies
Based on the successful results from small animal studies, we next utilized canine periodon‐
tal defect models. Dog PDL (dPDL) cells were extracted using collagenase/dispase digestion.
Four individual dPDL cells were successfully isolated and expanded
ex vivo
. Cells were cul‐
tured in a standard medium with osteoinductive supplements for 5 days, because longer
cultivation induced spontaneous detachment of cell sheets from the UpCell Surfaces. Three-
layered dPDL cell sheets were fabiricated with woven polyglycolic acid (PGA) for cell sheet
transfer. This PGA product has a number of advantages, including: 1) cell sheets can be easi‐
ly peeled from temperature responsive dishes, because cell sheets can be attached to the fi‐
bers of the woven PGA, 2) the shrinkage of cell sheets can be prevented, 3) easy stacking of
multi-layered cell sheets can be achived in a short period of time (see the video attached to
the manuscript (Iwata et al., 2009)), 4) easy adjustment of different sizes of cell sheets can be
used to cover any defect shape by simply trimming the cell sheets, 5) the ability to make
contact on hard tissues and curved surfaces, and 6) the transplant is visible to the operators.
dPDL cell sheets were transplanted into the surface of dental roots containing three-wall pe‐
riodontal defects in an autologous manner, and bone defects were filled with porous beta-
tricalcium phosphate (β-TCP). Cell sheet transplantation regenerated both new bone and
cementum connecting with the well-oriented collagen fibers, while only limited bone regen‐
eration was observed in the control group where cell sheet transplantation was not per‐
formed. These results suggest that PDL cells have multiple differentiation properties that
allow for the regeneration of periodontal tissues composed of hard and soft tissues.
Next, we evaluated the safety and efficacy of PDL cell sheets in a one-wall infrabony defect
model (Tsumanuma et al., 2011), which is considered to be a severe defect model (Kim et al.,
2004). In this study, we also compared the differences in the periodontal healing of various
cell sources. PDL cells, bone marrow derived mesenchymal stem cells, and alveolar perios‐
teal cells were obtained from each animal, three-layered canine cell sheets were transplanted
in an autologous manner, and bone defects were filled with porous β-TCP with 3% type I
collagen gelto stabilize the graft shape. Eight weeks after transplantation, significantly more
periodontal regeneration was observed in the newly formed cementum and well-oriented
PDL fibers more in the PDL cell sheets group than in the other groups. These results indicate
that PDL cell sheets combined with β-TCP/collagen scaffold serve as a promising tool for pe‐
riodontal regeneration.
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