[Influence of mechanical stress on chondrogenesis of in vitro cultured porcine bone marrow stem cells: a preliminary study].
OBJECTIVE
To evaluate the influence of mechanical stress on chondrogenesis of in vitro cultured porcine bone marrow stem cells (BMSC).


METHODS
Porcine BMSC of passage 2 were seeded onto a cylinder-shaped PGA/PLA scaffold, 8mm in diameter and 3mm in thickness, at a density of 5 x 10(7)/cm(3). After the cell-scaffold constructs were cultured for one week, the primary medium, high-glucose DMEM medium with 10% fetal bovine serum (FBS), was replaced by chondrogenically inductive medium containing TGFbeta(1) (10 ng/ml), IGF-I (50 ng/ml), and dexamethasone (40 ng/ml) in addition to DMEM+10% FBS. The constructs were randomly divided into three groups according to the imposed stress: experimental group A in which a centrifugal stress was imposed at 100 g, 30 min, 2/d; experimental group B in which a rotative stress was imposed at 80 rpm, 8 h/d by a shaker; and control group in which the constructs were statically cultured. The gross view, histology, histochemistry, immunohistochemistry and glycosaminoglycan (GAG) content were evaluated after 4 and 8 weeks respectively.


RESULTS
Four weeks later, the constructs in both experimental groups maintained their original sizes and shapes. Histology showed nodular lacuna-like structures, in company with GAG deposition and collagen synthesis. In addition, collagen type II was detected by immunohistochemistry. In the control group, however, the constructs shrunk to a little smaller size than those in the experimental groups, and histological staining showed a little amount of lacuna. Eight weeks later, the constructs in both experimental groups still maintained the original sizes and shapes with good elasticity. HE staining showed massive lacuna-like structures in most areas of the construct and extracellular matrix deposited evenly. Fibrous tissues were only observed in some areas. Safranin-O staining showed massive GAG formation and Masson staining showed much more collagen formation than those in the control group. Immunohistochemical staining of collagen type II showed strong positive expression. In the control group the constructs showed massive fibrous tissues, with a small amount of lacuna-like structures in the peripheral areas. GAG contents in the 2 experimental groups were 5.98 mg/g and 5.62 mg/g respectively, both significantly higher than that in the control group (4.73 mg/g) without a difference between the 2 experimental groups.


CONCLUSIONS
Mechanical stress promotes chondrogenesis and cartilage maturation of BMSC in vitro.
Liu
Tian-yi
TY
Department of Plastic Surgery, Ninth People's Hospital, Shanghai Second Medical University, Shanghai Tissue Engineering Research Center, Shanghai 200011, China.
Zhou
Guang-dong
GD
Miao
Chun-lei
CL
Wei
Xian
X
Chen
Fu-guo
FG
Cui
Lei
L
Liu
Wei
W
Cao
Yi-lin
YL
D000818:Animals; D001854:Bone Marrow Cells / Q000166:cytology*; D002454:Cell Differentiation; D002478:Cells, Cultured; D019902:Chondrocytes / Q000166:cytology; D020219:Chondrogenesis; D005260:Female; D008297:Male; D059630:Mesenchymal Stem Cells / Q000166:cytology*; D011897:Random Allocation; D013314:Stress, Mechanical; D013552:Swine; D023822:Tissue Engineering