[Preliminary study on transgenic cell sheet with cartilage-derived morphogenetic protein].

Objective: To construct a transgenic cell sheet of cartilage-derived morphogenetic protein 1 (CDMP1) by adenovirus vector in vitro and to identify its biological activity.

Methods: The bone mesenchymal stem cells (BMSCs) were isolated from bone marrow of 1-month-old rabbit, and cultured in vitro. The 3rd-6th generation of BMSCs were used for experiment. The experiment was divided into 3 groups: BMSCs transfected by adenovirus (Ad)-cytomegalovirus (CMV)-human CDMP1 (hCDMP1)-internal ribosome entry site (IRES)-enhanced green fluorescent protein (EGFP) in group A, BMSCs transfected by Ad-CMV-EGFP in group B, and untransfected BMSCs in group C. The expression of green fluorescence was observed in 3 groups under fluorescent inverted microscope. MTT assay was used to detect the proliferation of the cells. The cell sheet was obtained by means of temperature-responsive culture dish for 14 days. The morphological and HE staining observations of the cell sheet were carried out. RT-PCR and Western blot were used to detect the expressions of hCDMP1 and collagen type II at gene and protein levels, while alcian blue staining was used to detect the expression of glycosaminoglycans (GAG).

Results: Bright green fluorescence was observed in transfected cells at 72 hours under fluorescent inverted microscope, and the transfection efficiency was up to 90%. MTT assay showed approximate S-shaped growth curves in 3 groups, showing no significant difference in the absorbance (A) value among 3 groups within 9 days (P > 0.05). The three-dimensional cell sheets were successfully harvested in vitro. The RT-PCR and Western blot showed that there were positive expressions of hCDMPl and collagen type II in group A and negative expression in other 2 groups. HE staining and alcian blue staining showed that there were rich fibrous tissues, mass extracellular matrix, and dark blue metachromatic granules in group A, but there was less fibrous tissues and no specific blue metachromatic granules in other 2 groups; and the positive expression area was significantly lower and gray scale of GAG was significantly higher in group A than that in groups B and C (P < 0.05).

Conclusion: A transgenic cell sheet of exogenous recombinant hCDMP1 by adenovirus vector can express collagen type II and GAG, so it has chondrogenic capacity. This technology that overcomes limitations in traditional tissue engineering, such as low cell-attachment efficiency and inflammatory reaction, may be a new tissue engineering approach for hard tissue reconstruction and is hopeful to build a large density of tissue engineered cartilage.