الفهرس 
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Abstract
Stem cell biology has become an important field in
regenerative medicine and tissue engineering therapy since the
discovery and characterization of mesenchymal stem cells
(MSCs). MSCs can be isolated from many tissues, including
bone marrow, adipose tissue, placenta and umbilical cord. All
of these MSCs show fibroblast-like cell morphology, selfrenewal
capacities and multilineage differentiation
potentiality.
MSCs have also been isolated from human dental
tissues, including dental pulp stem cells, stem cells from
human exfoliated deciduous teeth, stem cells from apical
papilla, dental follicle cells and periodontal ligament stem
cells. Those dental tissue-derived stem cells have potent
capacities to differentiate into chondrogenic, osteogenic and
odontogenic lineages and generate dental tissue structures.
Many people have an impacted third molar that does
not cause occlusion and have that impacted tooth extracted to
avoid inflammation or orthodontic therapy. Such extracted
teeth usually contain dental follicle and are commonly
discarded as medical waste. Dental follicle contains MSCs in
the tooth germ at various stages of development in different
species. Therefore, the DF is a candidate source for isolating
MSCs. Comparatively, a population of stem cells within
gingival tissue, termed gingiva-derived mesenchymal stem
cells constitutes more attractive alternatives to other dentalderived
MSCs for the accessibility and availability and
minimal discomfort.
This research was performed to assess and compare
stem cells isolated from dental follicle and gingiva with regard
to their characterization, proliferation and capability to
differentiate into osteogenic and odontogenic lineages.
The gingival tissue sample was obtained from healthy
patient undergoing gingivectomy for crown lengthening above
20 years, under local anesthesia after providing written
informed consent. Human dental follicle sample was obtained
from patient above 20 years undergoing surgical removal of
impacted wisdom, under local anesthesia after providing
written informed consent.
MSCs isolation procedures of both gingival and dental
follicle tissues were done. The minced pieces were
collected in sterile, labeled 15 ml Falcon tubes to which a
digesting solution consisting of collagenase type II and
dispase mixture was added. The digested solution used was 3
mg/ml collagenase type II and 4 mg/ml dispase (SigmaAldrich,
USA)
for
60 minutes
at
37°C.
Propagation was performed when the primary cell
culture of adherent cells reached 70% confluence and was
named passage zero (P0). Later passages were named accordingly. Cells were sub-cultured every other week and the
culture medium was replaced every 2 - 3 days over a 12 - 14
day period.
Cells were identified as being MSCs by their
morphology (fibroblast like cells) and plastic adherence.
Adherent cells were trypsinized and adjusted to 1×106
cells/ml. Then were incubated with 10μl of monoclonal
antibodies: CD45, CD90 and CD105, (Beckman coulter,
USA) at 4 ◦C in the dark. The results show that successful
isolation of stem cells from dental follicle and gingiva based
on their ability to adhere to plastic plates was achieved. Cells
were successfully sub-cultured and expanded up to passage
three. Cells positively expressed CD90 and CD105 and
negatively expressed CD45.
Cells were allowed to proliferate and then the
proliferation capacity was assessed using MTT assay to
compare the proliferation of the two cell types. Although the
highest mean was found for DFSCS, there was no significant
difference between GMSCs and DFSCs in their proliferative
capability.
Then the cells were induced for differentiation:
odontogenic differentiation by placing the cells in odontogenic
induction media for 21 days and osteogenic differentiation by
placing the cells in osteogenic induction media for 30 days.
Odontogenic and osteogenic differentiation were
evaluated by Alizarin red stain. By the 14th day, the