ObjectiveTo study the preparation method of acellular dermal matrix (ADM) for cartilage tissue engineering and analyze its biocompatibility. MethodsThe dermal tissues of the calf back were harvested, and decelluarized with 0.5% SDS, and the ADM was reconstructed with 0.5% trypsin, cross-linked with formaldehyde, and modified with 0.5% chondroitin sulfate which can promote the proliferation of chondrocytes. And the porosity, cytotoxicity, and biocompatibility were determined. Co-cultured 2nd passage chondrocytes and bone marrow stromal cells in a proportion of 3 to 7 were used as seed cells. The cells were seeded on ADM (experimental group) for 48 hours to observe the cell adhesion. The expressions of mRNA and protein of collagen type Ⅱ were tested by RT-PCR and Western blot methods, respectively. And the expressions were compared between the cells seeded on the scaffold and cultured in monolayer (control group). ResultsAfter modification of 0.5% trypsin, the surface of ADM was smooth and had uniform pores; the porosity (85.4%±2.8%) was significantly higher than that without modification (72.8%±5.8%) (t=-4.384, P=0.005). The cell toxicity was grade 1, which accords to the requirements for cartilage tissue engineering scaffolds. With time passing, the number of inflammatory cells decreased after implanted in the back of the rats (P<0.05). The scanning electron microscope observation showed that lots of seed cells adhered to the scaffold, the cells were well stacked, displaying surface microvilli and secretion. The expressions of mRNA and protein of collagen type Ⅱ were not significantly different between experimental and control groups (t=1.265, P=0.235;t=0.935, P=0.372). ConclusionThe ADM prepared by acellular treatment, reconstruction, cross-linking, and modification shows perfect characters. And the seed cells maintain chondrogenic phenotype on the scaffold. So it is a proper choice for cartilage tissue engineering.
ObjectiveTo investigate the effects and mechanisms of differentiation of bone marrow mesenchymal stem cells (BMSCs) into insulin producing cells (IPCs) induced by injured pancreatic tissue extract of rat. MethodsEighty 6-week-old Sprague Dawley rats were selected. Forty rats underwent removal of 60% pancreas and the injured pancreas tissue was obtained after 48 hours to prepare the injured pancreatic tissue extract; and normal pancreatic tissue extract was prepared from the other 40 rats. The BMSCs were isolated from the tibia and femur of 4-week-old Sprague Dawley rats. BMSCs at passage 3 were co-cultured with rat injured pancreatic tissue extract as experimental group, with rat normal pancreatic tissue extract as normal control group, and with cell culture medium as blank control group for 14 days. The expressions of pancreas development related genes and proteins were detected, and cell morphological changes were observed. Then the C peptide positive cell rate was detected by flow cytometry analysis and insulin secretion levels were detected by glucose stimulation experiment at 14 days. ResultsInjured pancreatic tissue extract can induced BMSCs differentiating into IPCs. The pancreatic development related genes of pancreatic duodenal homeobox 1 (PDX-1), islet 1, Nkx6.1, glucose transporter type 2, proprotein convertase 2, neurogenin 3, and somatostatin were expressed sequentially in the differentiation process of experimental group; mature pancreatic proteins of PDX-1, insulin, C peptide, Nkx6.1 also were expressed. But there was no morphological changes and expression of pancreatic development related genes and proteins in normal control and blank control groups. The C peptide positive cell rate of experimental group (13.8%±1.8%) were significantly higher than those of normal control and blank control groups (1.6%±0.4%) (P<0.05). The insulin secretion of experimental group was significantly higher than that of normal control and blank control groups (P<0.05), but it was 1/40 and 1/47 of natural islet cells (P<0.05). ConclusionAfter pancreatic injury, injured pancreas would secrete transcription proteins related to development, differentiation, and repair of pancreas, which can promote the differentiation of BMSCs into IPCs.