Human bone marrow-derived mesenchymal stem cells differentiate into chondrocytes in vitro / 中国组织工程研究

ABSTRACT

BACKGROUND:How to obtain sufficient autogeneic chondrocytes is a problem which must be answered as soon as possible in both the transplantation of chondrocytes and the development of cartilage engineering.Bone marrow-derived mesenchymal stem cells have the potential of multidirectional differentiation. Under different induced conditions, they can differentiate into multiple tissue cells, such as chondrocyte, osteoblasts , sarcoblast, nerve cells and so on. Insulin-like growth factor-I plays an important role in regulating the formation and development of limb and cartilage.OBJECTIVE:To observe the effect of the insulin-like growth factor-I and culture solution of chondrocyte on inducing bone marrow-derived mesenchymal stem cells to differentiate into chondrocytes in vitro.DESIGN:Open experiment.MATERIALSThis experiment was carried out at the Medical Study Center, Second Hospital Affiliated to Sun Yat-sen University from March to November 2003.Human bone marrow-derived mesenchymal stem cells were harvested from 4 to 6-month old embryos, all of which were from pregnant women who needed to terminate of pregnancy by induction delivery with water bag for health.METHODS:Human embryonic mesenchymal stem cells were isolated with Percoll separating medium. Subsequently, the cells were amplified in vitro,and the expression of surface makers of bone marrow-derived mesenchymal stem cells, such as CD44, CD71, CD34 and CD45 were measured with flow cytometer to identify the cells in our experiment. 100 μg/L insulin-like growth factors and culture solution of chondrocytes were added in the culture medium of bone marrow-derived mesenchymal stem cells of the fourth generation. The morphological changes of induced cells were observed with an inverted microscope. The expression of type Ⅱ cartilage matrix was observed by collogen immunohistochemistry. The proteoglycan level in the cells was detected, too.MAIN OUTCOME MEASURES:Phenotype of bone marrow-derived mesenchymal stem cells was identified through detecting the expressions of CD34, CD44 and CD4.Type Ⅱ collagen immunohistochemistry and the change of cellular ability to secrete proteoglycan after induction were observed to determine whether bone marrow-derived mesenchymal stem cells can differentiate into chondrocytes.RESULTS: ① Being observed under an inverted microscope,the bone marrow-derived mesenchymal stem cells presented a morphology like fibroblasts when they were cultured in vitro. ②Identification of surface antigen of bone marrow-derived mesenchymal stem cells These cells were detected to have good homogenicity with flow cytometer. The fourth generation of bone marrow-derived stem cells positively expressed CD44, negatively expressed CD34 and CD45, suggesting these cells had the characteristics of bone marrow-derived mesenchymal stem cells. ③Observation of the morphological change of chondrocytes induced by bone marrow-derived mesenchymal stem cells under optical microscope chondrocyte condition culture solution and insulin-like growth factors-Ⅰ were added to co-culture.During the process of culture, bone marrow-derived mesenchymal stem cells were seen to have a shape of round gradually. Fifteen days later, some cells presented a shape of short-shuttle or polygon with short mutations,which were the shape characteristics of chondrocytes. ④Immunohistochemical staining of Type Ⅱ collagen In the insulin-like growth factor group,72.5% cells had many brown granules in cytoplasm, which were weakly positive or strongly positive expression of Type Ⅱ collagen. In the control group, bone marrow-derived mesenchymal stem cells was negative expression of type Ⅱ collagen on the 15th day. ⑤ Measurement of proteoglycan level After co-culture with insulin-like growth factor-Ⅰ and chondrocyte culture solution for 15 days, proteoglycan was higher in the cells of co-culture group [ (8.92±0.91) μg/L ] than in culture group [(2.56±0.26) μg/L,P ＜ 0.05], but lower than in the chondrocyte group[(13.69±1.51) μg/L, P＜ 0.05].CONCLUSION:Insulin-like growth factor-Ⅰ and chondrocyte culture solution can induce bone marrow-derived mesenchymal stem cells to differentiate into chondrocytes.