Cell culture and transfection. hPMSCs were cultured as before18. In details, cells were cultured in complete medium (DMEM with 10% FBS and 1% PS). When the cell density fusion was 80–90%, the digestive passage culture was conducted with 0.25% trypsin. The surface markers of hPMSCs were analyzed by flow cytometry, including CD29, CD90 and CD45 (Abcam, UK). The osteogenic differentiation of hPMSCs were cultured with conditional medium (DMEM with 10%FBS, 20 mmol/L β-glycerophosphate, 50 g/mL vitamin C and 10 mol/L dexamethasone). The 8 x 104 cells were subcultured into 6-well plates into 6-well plates, the medium was changed every two to three days, and protein /RNA samples were collected at different time points. When the cell density approached 80 percent, 100pM miRNA mimics and NC were transfected to cells followed by the protocol of Lipofectamine™ 2000 Transfection Reagent (Thermo Fisher Scientific, USA). The mimics were synthesised from Genepharma. ALP staining was performed followed by the TRAP/ALP Stain kit (Wako, Japan). Alizarin Red staining was performed to detect calcium deposits after 14 days of induction culture in accordance with the instructions of the kit (Cyagen, China).
Preparation of scaffolds and cell seeded. The HAG scaffold was produced and cleaned by referring to previous description [18]. The scaffolds were incubated overnight in DMEM prior to the cell experiment at 37°C. The surface micromorphology and cell adhesion of HAG were confirmed by ZEISS Gemini 300 scanning electron microscopy (SEM). In details,20µL cell suspension (4 × 106 /mL) were seeded onto the surface of HAG scaffolds༌and cultured for 3 day. Then, scaffolds were fixed with 15% glutaraldehyde overnight after washed three times with PBS. Dehydration was performed according to the following alcohol concentration gradient (25%, 50%, 60%, 70%, 75%, 80%, 90%, 95%, 100% 15min each time). The sample after vacuum drying was used for SEM detection。
Osteogenic differentiation of hPMSCs with HAG and quantitative real-time PCR (qRT-PCR). 20µL cell suspension (4 × 106 /mL) were seeded in a HAG. Then, the cells co-culture with the scaffold in incubator. After osteogenic induction for different time point, extracted the total RNAs (TRIzol™ Reagent, Invitrogen), and reversed to cDNAs (M-MLV, Invitrogen™. Quantitative fluorescence detection was performed using 2X ChamQ Universal SYBR Master Mix (Vazyme, China). ABI 7500 was applied for qRT-PCR. Primers specific for human miRNAs and internal control U6 were designed and synthesized from Tsingke, China. (5’-3’ALP: F-CTTGAAGTGTTGCATGGGC, R-CAAGTCTCAGGGTGGAAGG; OCN: F-CAGCGAGGTAGTGAAGAGAC, R-TGAAAGCCGATGTGGTCAG; BMP2: F-CTATCAGGACATGGTTGTGGAG, R-GGGAAATATTAAAGTGTCAACTGGG)
Western blotting. The proteins were isolated by 10% SDS-PAGE gel, which transferred with NC membranes (BD). After incubation with GAPDH, ALP, OCN, Runx2 (Huabio, China) primary antibodies overnight, the membranes were washed for 5 times with PBST (2‰ Tween). Then, the HRP- conjugated secondary antibody was incubated for 1h. Finally, Super ECL kit (biosharp, China) was used to detect the protein bands. The Tanon-5200 was applied for exposure.
Experimental animals and implantation. All experimental protocols were approved by Medical Ethics Committee of Sichuan Provincial People's Hospital, Affiliated Hospital of UESTC. Male SD rats (8 weeks) were purchased from Chengdu Dossy Experimental Animals CO.,LTD. After a week of acclimatization, 6 rats were randomly allocated for HAG implantation, and the lateral femoral muscles of HAG-free were made the wound surface of the same size and depth used as the control. Then,each animal was given intramuscular injections of penicillin per day to combat infection for three days.
Immunochemistry. Paraffin sections were washed with xylene, repeated 3 times, then passed through alcohol gradient, and finally into distilled water. Nuclear were stained by Hematoxylin for 5min, and washed with distilled water, differentiated with 70% hydrochloric acid and alcohol, Distilled water wash to return blue. Sections were stained with Masson Lichun red acid solution for 5 min and soaked in 0.2% glacial acetic acid solution. 1% phosphotungstic acid aqueous solution after differentiation for 5 min, then they were directly dyed with toluidine blue for 5 min without washing and soaked in 0.2% glacial acetic acid solution for 5s. At last, 95% ethanol and anhydrous ethanol were used, slices were dehydrated, slices were transparent with xylene and sealed with neutral gum. The pictures were captured by BA200Digital and analysed by Image-Pro Plus 6.0 and SPSS17.0.
Microarray Assays. Microarray Assays were completed by Aksomics, China. Total RNA were extracted using Trizol™ reagent and used to build a miRNA library. The library quality was determined by Agilent 2100 Bioanalyzer. It was eventually sequenced on an Illumina NextSeq 500 sequencer.
Bioinformatics Analysis. Edge R was used to analyze the differential expression of miRNA between groups. Based on the database of TargetScan7.1 and mirdbV6, target genes were screened for the Top 10 miRNA up and down regulated in significant difference. Then the function enrichment analysis of target genes was performed by Gene Ontology, including Molecular function, Cellular component and Biological process. The miRNA-mRNA networks were constructed using Cytoscape.
Statistical Analysis. Three independent repeated experiments were used to perform and analysis related results (mean ± SD). The T test was used to analyze differences between groups. P values < 0.05 were considered significant.
We confirmed that all methods were carried out in accordance with relevant guidelines and regulations in the manuscript, and the study was carried out in compliance with the ARRIVE guidelines in the manuscript.