Abstract: Objective To explore the biocompatibility of three-dimensional printed polylactic acid-hydroxyapatite（3D printed PLA-HA） as the composite scaffolds with bone marrow stromal cells for selecting the suitable scaffold in bone tissue engineering. Methods GPF positive bone marrow stromal cells were seeded on three-dimensional printed polylactic acidhydroxyapatite composite scaffolds and beta-tricalcium phosphate（β-TCP） and then cultured in vitro. The cell adhesion and proliferation were observed by fluorescence microscope, and cell morphology was scrutinized by scanning electron microscopy. Cell Counting Kit 8（CCK8） were used to test the adhesion rate and proliferation of cells on two kinds of scaffolds at different time points; Alkaline phosphatase（ALP） activity were detected on the third, seventh and fourteenth day.Results Bone marrow stromal cells exhibited the adhesion and proliferation ability well in both three-dimensional printed polylactic acid-hydroxyapatite composite scaffolds and beta-tricalcium phosphate; The adhesion rate in β-TCP group was higher than in PLA-HA group（P〈0.05）, while the adhesion rate in PLA-HA group was still more than 60% after cultured for12 hours; The amount of cell proliferation（the value of OD） 4 and 7 days after culture in PLA-HA group were both higher than in β-TCP and control group respectively（P〈0.05） in vitro. The secretion of ALP 7 and 14 days after culture in groupPLA-HA as well as β-TCP were both higher than in control group 3（P〈0.05）. Meanwhile, the ALP secretion in PLA-HA group was higher on the third day compared with β-TCP group（P〈0.05）. Conclusion Three-dimensional printed polylactic acid-hydroxyapatite composite scaffolds present good biocompatibility in vitro and it can be selected as biomaterials in bone tissue engineering.

Key words: Three-dimensional printing, Bone tissue engineering, Polylactic acid, Hydroxyapatite, Bone marrow stromal cells