2022, Vol. 26 ›› Issue (34): 5454-5460

3D bio-printing methylacrylated gelatin hydrogel scaffolds promote the repair of subchondral bone defects

Lu Dongdong1, Zhu Tianfeng1, Zhang Yijian1, Zhao Zhijian1, Liu Yang1, Shen Xu2, Zhu Xuesong1   

Abstract: BACKGROUND: Subchondral bone plays an important role in normal physiological activities of joints and is difficult to repair once it is damaged. Traditional bone cement and autologous bone grafting treatment methods have certain limitations.
OBJECTIVE: To explore the efficacy of bone marrow mesenchymal stem cells or chondroprogenitor cells encapsulated in 3D bio-printing methylacrylated gelatin hydrogel scaffolds to repair subchondral bone defects.
METHODS: Chondroprogenitor cells were obtained by fibronectin sorting method and rabbit bone marrow mesenchymal stem cells were obtained by whole bone marrow adherent method. The proliferation, osteogenic, chondrogenic, and adipogenic differentiation abilities were compared between the two groups. Methylacrylated gelatin hydrogel scaffolds loaded with bone marrow mesenchymal stem cells and chondroprogenitor cells were prepared by 3D bio-printing. After osteogenic induction and culture, the survival rate of cells in the scaffold was analyzed by live-dead staining. The osteogenic gene expression of the scaffold was detected by qRT-PCR. Subchondral bone defects with a diameter of 5 mm and a depth of 5 mm were prepared at the bilateral knee joints of 16 New Zealand white rabbits. They were divided into four groups. Group A was not treated. Group B was implanted with methylacrylated gelatin hydrogel scaffold. Group C was implanted with a hydrogel scaffold loaded with bone marrow mesenchymal stem cells. Group D was implanted with a hydrogel scaffold loaded with chondroprogenitor cells. Micro-CT scanning and histological observation of the bone defect area were performed at 6 and 12 weeks after surgery.  
RESULTS AND CONCLUSION: (1) The proliferation, osteogenic and adipogenic differentiation of bone marrow mesenchymal stem cells were higher than those of chondroprogenitor cells. The chondrogenic differentiation of bone marrow mesenchymal stem cells was weaker than that of chondroprogenitor cells. (2) Bone marrow mesenchymal stem cells and chondroprogenitor cells in the hydrogel scaffolds showed good viability. The mRNA expression of osteogenic related genes of bone marrow mesenchymal stem cells including osteocalcin, osteopontin and runt-related transcription factor 2 in the scaffold was higher than that of chondroprogenitor cells (P < 0.05). (3) The micro-CT scan of the animal repair experiment showed that the bone tissue formed in Group C was the most, and the trabecular bone structure was formed at 12 weeks after the operation. The shape of the new bone was similar to the surrounding natural cancellous bone; the new bone tissue in groups A and B was the least. The Safranin O/fast green staining results showed that at 6 weeks after surgery, only a small amount of new bone was formed in the subchondral bone area of Groups C and D. At 12 weeks after surgery, bone matrix was formed in Groups A and B. Group C showed massive repairs of subchondral bone. More new bone formation was found in Group C compared with Group D. (4) Results suggested that bone marrow mesenchymal stem cells and 3D bio-printing methylacrylated gelatin hydrogel scaffold were suitable for seed cells and scaffolds for bone tissue engineering.
Key words: methylacrylated gelatin, hydrogel, bone marrow mesenchymal stem cells, chondroprogenitor cells, 3D bio-printing, scaffold, subchondral bone