The Hepatic Tissue Engineering Research Based On Macromolecule Biomaterials

We evaluated the regeneration potential of differentiated bone mesenchymal stem cells (dBMSCs) cultured on hepatocyte growth factor (HGF)-loaded collagen chitosan scaffolds (HCCs) for liver tissue engineering purposes. The solutions to the discrepancy of donor livers are needed to further research optimal organ source including the use of organ regeneration in laboratory.3D printing could expand the opportunities for engineering organs. This model had great potential in liver tissue engineering and liver disease model studying in vitro. Three-dimensional-printed BMSCs after differentiation were used as in vitro seeds to synthesize minimal functional liver units. A model was developed for enabling three-dimensional (3D) regular seeding and culturing of dBMSCs through the use of bioprinting technology to promote and maintain 3D liver tissue-like cellular morphology and cell-specific functionality in vitro with the addition of hydrogels.HCCs scaffolds were constructed using crosslinked collagen and chitosan, combined with HGF and we assessed compositional characteristics. Differentiation of BMSCs was assayed by measuring gene expression of AFP, ALB and HNF4a. Glycogen synthesis was evaluated by periodic and Schiff staining. CK 18 and ALB expression was measured with immunofluorescence after differentiation. In vivo experiments were performed by engrafting dBMSCs-HCCs subcutaneously in back. ALB, CYP2C9 and UGT2 synthesis in different engrafted tissue were quantified at different time points. Grafted dBMSCs-HCCs tissue was observed with immunohistochemistry for CK18 and immunofluorescence for CK19. The 3D hydrogels scaffolds were flbricated by the bioprinter. The biocompatibility of 3D hydrogels scaffold was tested. The in vivo experiments were performed on SD rats. Groups of control, hydrogels, hydrogels with L02 (cell line HL-7702), and hydrogels with HGF were subsequently engrafted into the liver after partial hepatectomy. The engrafted tissues were observed after 2 weeks. The levels of alanine aminotransferase (ALT), albumin (ALB), glutamic-oxalacetic transaminase (AST), total bilirubin, CYP1A2, CYP2C9, glutathione S-transferase (a-GST) and UDP-glucuronosyl transferase (UGT-2) were compared. Hematoxylin-Eosin (H.E.) staining, immunohistochemical of cytokeratinl8(ck18) and ckit of engrafted tissues were observed. The survival curves of groups were described. qPCR was used to detect the expression of ALB, HNF4a and AFP. The synthesis of glycogen was evaluated by periodic acid-Schiff staining. The expression of CK18 was observed under immunofluorescence after differentiation. The biocompatibility of the hydrogels was evaluated by MTT. The concentrations of GST, ALB and CYP2C9 in vitro were evaluated at 3 days,7 days and 10 days. An in vivo experiment was performed by engrafting the printed tissue subcutaneously. The concentrations of ALB, CYP2C9 and GST in different engrafted tissues were quantified at different time points. The expressions of mRNA ALB, AFP and HNF4a in different groups were compared at 2 weeks and 4 weeks.After differentiation, mRNA of AFP, ALB and HNF4a elevated significantly. ALB, CYP2C9 and UGT2 elevated as well in dBMSCs-HCCs and dBMSCs-CCs. New tissue sections were observed under a polarized light microscope. 3D hydrogels scaffold did not impact the viability of cells. Using 3D printing liver tissue, the levels of ALT, ALB, AST, total bilirubin, CYP1A2, CYP2C9, a-GST and UGT-2 significantly improved in vivo experiments (p<0.05).H.E. staining, immunohistochemical of ck18+ and ckit+ were observed clearly in engrafted tissue. The results of the comparison of survival curves between 3D printing and control groups indicated 3D printing and hydrogels groups were significantly different (p< 0.05). From the differentiation process of BMSCs, we demonstrated that after several days of culturing, the mRNA concentrations of ALB, HNF4a and AFP changed significantly (p<0.05). The marker of CK18 was expressed, and PSA staining was positive after differentiation. The biocompatibility of the 3D printing of hydrogels showed no significant difference from the 2D culture and mix culture. After the 3D printing, the concentrations of ALB, GST and CYP2C9 improved significantly after 3 days,7 days and 10 days (p<0.05). Liver tissue was formed after 4 weeks by 3D printing. The mRNAs of ALB, AFP and HNF4a were improved significantly in the printing culture group. The concentrations of ALB, GST and CYP2C9 improved significantly after 2 weeks and 4 weeks in in vivo experiments.Thus, dBMSCs-HCCs may be offered a promising approach for tissue-engineered liver development.3D bioprinting has the potential of recapitulating liver tissue and partial liver functions and can be used in reconstruction of hepatic tissues and in vitro liver disease model studies. Three-dimensional printing of dBMSCs can be used as a model of liver tissue engineering and in liver disease model research.