EFFECT OF SCAFFOLDS WITH BONE GROWTH FACTORS ON NEW BONE FORMATION - Intelligent Scaffolds for Tissue Engineering and Regenerative Medicine - page 893

predifferentiationpriortoimplantation,whichhasbeenshowntobe
very important to achieve the best therapeutic result. Under the in
vitro culture condition, without the vasculature network, the tradi-
tionalstaticculturecannotfulfillthespecialrequirementofnutrient
and oxygen supply for culturing large-dimension 3D scaffold con-
structs, because of the limited diffusion capacities and high demand
in nutrient and gas exchange created by high cellular density. Many
studies have demonstrated that the effective distance for nutrient
andgastransportisonlylimitedtoadepthofafewhundredmicrons
under the static culture. 60 , 61 Therefore, bioreactors have been
widely used in the TE field because they can not only increase the
mass transfer to maintain the viability of large 3D cellular scaffolds
but also provide certain mechanical stimulation, which can pro-
motethecelldifferentiationbytriggeringthemechanotransduction-
signaling pathway. 62 − 64 The rotating wall vessel (RWV) bioreactor
hasbeenutilizedforBTEandisknownforitsadvancedcharacteris-
tics of low shear, three dimensionality, and high mass transfer 65 − 69 ;
however, it has a problem that the single axial rotation may lead
to the nonhomogenous distribution of the cell and extracellular
matrix. 63 , 70 , 71 We developed a novel type of RWV bioreactor (biax-
ial rotating bioreactor), which can rotate simultaneously in two
perpendicularaxesandincorporatetheperfusionsystem. 72 , 73 Com-
putational simulation analysis has demonstrated that it can achieve
manifold increases of fluid velocity with significant improvements
of fluid transport through the scaffolds compared with the conven-
tional uniaxial rotating bioreactor and static culture. 72 Our further
laboratoryinvestigationshoweditmaintainedhighcellularviability
in the core of a thick scaffold, which was 2,000 mm from the sur-
face, throughout a 28-day culture, while the traditional static cul-
tureresultedinthelargenecroticcoreofthethickscaffold,asdeter-
minedbyflorosceindiacetate/propidiumiodine(FDA/PI)live/dead
staining(Fig.43.18).Comparedtothestaticculture,thecellularscaf-
fold under the biaxial rotating bioreactor culture proliferated faster
and reached cellular confluence earlier (7 days vs. 28 days), with
greater cellularity (2x, p < 0.01). Furthermore, the biaxial bioreac-
tor culture was associated with greater osteogenic induction, ALP
expression (1.5x, p < 0.01), calcium deposition (5.5x, p < 0.001) and
bonynoduleformationonSEM,and in vivo ectopicboneformationin