CELL - BASED NANOCOMPOSITES AND BIOMOLECULES FOR BONE TISSUE ENGINEERING - Advanced Biomaterials: Fundamentals, Processing, and Applications - page 555

solid-walled scaffolds. These observations seemed to have an impact on osteo-
blastic phenotype and cellular signaling, suggesting that nanofi brous materials
were superior than solid-walled materials 97 .
Improved mechanical properties and wettability were demonstrated on elec-
trospun gelatin/PCL fi brous membranes than on pure gelatin or PCL membranes.
Not only were bone marrow stromal cells favorably attached on the gelatin/PCL,
but also the cells migrated into the scaffolds up to 114

μ m after one week of

culture 98 .

16.3.5 Cell-Material Constructs (e.g. Stem Cell or
Osteoblast/Material Constructs)
After material selection, factors such as the type of pre-treatment of the sub-
strate, choice of cells to be seeded and culture environment (dynamic/static
conditions, cyclic/static loading) have to be considered. To create a more favor-
able environment for in vivo osteogenesis, many have attempted to pre-seed
osteoblasts or MSCs on the bone-graft materials. Essentially, bone is made up of
two main cell types, namely osteoblasts and osteoclasts. These bone cells, which
are connected by gap junctions, allow cellular communications between the bone
surface and the mineral matrix. Osteoblasts are involved in the production of
Type I collagen and mineralization. The secretion of prostaglandin E 2 and inter-
leukin-6 by osteoblasts stimulates osteoclasts, leading to bone resorption. In
recent years, MSCs seem to be an attractive cell source because they are capable
of differentiating into an osteoblastic lineage when induced in the appropriate
conditions. The ECM secreted by MSCs can involved in several cellular processes
such as the recruitment, proliferation, differentiation and maturation of progeni-
tor cells. Physiologically, MSCs differentiates into mature matrix-secreting osteo-
blasts, which progressively become osteocytes.

16.3.5.1 Mesenchymal Stem Cells (MSCs)-Material Constructs. For
instance, coral, which has a natural architecture that resembles spongy bone, is
said to be suitable as a bone graft material owing to its porosity (with an average
pore size of 150

m) because blood vessels and the deposition of the ECM and
other cellular constituents can be intertwined within the graft, giving rise to an
enhancement of material properties and stability. In this particular study, the
authors have illustrated that the use of low level laser irradiation applied to a
MSC/coral construct stimulated the proliferation and differentiation of MSC into
an osteoblastic phenotype during the initial culture period and signifi cantly
induced in vitro osteogenesis over time. Higher levels of calcium deposition were
seen in irradiated-treated samples at early (days three and six) and late culture
periods (days 21 and 28).
On the other hand, phosphate deposition was enhanced in samples that were
laser-treated in later culture periods (days 14, 21 and 28). The coral construct with
MSC did not undergo laser irradiation. In addition, as an indicator of early osteo-
blast differentiation, ALP activity was observed.

μ