ABSTRACT
[Objective]To investigate the osteogenic ability in vivo of mesenchymal stem cells(MSCs).[Method]Ten-fifteen ml bone marrow aspirates were harvested from the iliac crest of sheep and enriched for MSCs by density gradient centrifugation over a Percoll cushion(1.073 g/ml).After cultured and proliferated,the tissue-engineered bones were constructed with these cells and seeded onto porous 13-tricalcium phosphate ceramics(13-TCP).Then,the constructs were implanted into left metatarsus defect(21 mm in length)of 8 sheep as an experimental group.Porous ?-TCP composed with bone marrow was implanted into defects of same size and position in 8 sheep as a control group.Sheep were sacrificed in the 6th,12th,and 24th week postoperatively,and the implanted samples were examined by radiograph,histology,and biomechanical analysis.[Result]New bone tissue was observed either radiographically or histologically at the defect area of experimental group as early as the 6th week postoperatively;but was not observed in the control group.Because of the new bone formed in a direct manner without progression through a cartilaginous process intermediately,osteoid tissue,woven bone and lamellar bone,occurred earlier in the experimental group than in the control group,in which the bone defects were repaired in a "creep substitution" manner.At the 24th week,radiographs and biomechanical tests revealed an almost complete repair of the defect in experimental group,but only a partial repair in the control group.[Conclusion]MSCs have good reproductive activity not only in vitro,but also in vivo.The new bone formed in a direct manner without progression through a cartilaginous process intermediately when MSCs were transplanted in vivo.The results demonstrated that MSCs was an excellent seed cells for bone tissue engineering.
ABSTRACT
Tissue-engineering bone with porous β-tricalcium phosphate (β-TCP) ceramic and autologous bone marrow mesenchymal stem cells (MSC) was constructed and the effect of this composite on healing of segmental bone defects was investigated. 10-15 ml bone marrow aspirates were harvested from the iliac crestof sheep, and enriched for MSC by density gradient centrifugation over a Percoll cushion (1. 073 g/ml). After cultured and proliferated, tissue-engineering bones were constructed with these cells seeded onto porous β-TCP, and then the constructs were implanted in 8 sheep left metatarsus defect (25 mm in length) as experimental group. Porous β-TCP only were implanted to bridge same size and position defects in 8 sheep as control group, and 25 mm segmental bone defects of left metatarsus were left empty in 4 sheep as blank group. Sheep were sacrificed on the 6th, 12th, and 24th week postoperatively and the implants samples were examined by radiograph, histology, and biomechanical test. The 4 sheep in blank group were sacrificed on the 24th week postoperatively. The results showed that new bone tissues were observed either radiographic or histologically at the defects of experimental group as early as 6th week postoperatively, but not in control group, and osteoid tissue, woven bone and lamellar bone occurred earlier than in control group in which the bone defects were repaired in "creep substitution" way, because of the new bone formed in direct manner without progression through a cartilaginous intermediate. At the 24th week, radiographs and biomechanical test revealed an almost complete repair of the defect of experimental group, only partly in control group. The bone defects in blank group were non-healing at the 24th week. It was concluded that engineering bones constructed with porous β-TCP and autologous MSC were capable of repairing segmental bone defects in sheep metatarsus beyond "creep substitution" way and making it healed earlier. Porous β-TCP being constituted with autologous MSC may be a good option in healing critical segmental bonedefects in clinical practice and provide insight for future clinical repair of segmental defect.