1. Isolation and culture of human adipose and bone marrow stem cells:
Human adipose tissue is collected by needle biopsy or liposuction aspiration at surgery ward of Shariati Hospital, Tehran, Iran. The protocol was performed in accordance with the Declaration of Helsinki and approved by the Cellular Transplantation Ethics Committee of Iranian public hospitals and also Zabol University of Medical Sciences ethics committee. All participants informed about the proposed intervention and we emphasized their roles in our decision-making process and also all of the participants informed about the risks of proposed intervention. Adipose tissue was washed extensively with sterile phosphate-buffered saline (PBS) and 1% penicillin-streptomycin to remove red blood cells. Washed tissue fragments placed in a sterile tissue culture plate with 0.075% Collagenase Type I (Sigma-Aldrich, USA) prepared in PBS containing 2% penicillin-streptomycin for tissue digestion. After incubation for 30 min at 37 °C and 5% CO2, collagenase activity was neutralized by adding 5 ml of α-MEM containing 20% heat inactivated fetal bovine serum (Gibco, Thermo Fisher Scientific, USA) and centrifuged in 4000 g for 10 minutes. To lyse remaining red blood cells, pellet was re-suspended in 160 mM NH4Cl at room temperature for 10 minutes and then centrifuged at 1,200×g for 10 min to pellet the MSC-rich dense cell fraction. Afterward, the collected cells were filtered through 100-μm cell strainer (Grainer, USA) and incubated for 48 h at 37 °C in 5 % CO2 in culture medium with serum and antibiotics. Bone marrow was isolated from one patient in hematology ward of Shariati hospital, Tehran, Iran under aseptic condition and dispersed into single cell suspension, L-DMEM cells were cultured in a density of 1.5 × 105 /cm2 in alpha-MEM (Sigma, USA), 10 % FBS, 1% penicillin-streptomycin and incubated at 37 °C and 5 % CO2 for 3 days and later the medium was refreshed every 48 h till confluence was reached.
2. Characterization of cultured adipose and bone marrow stem cells
Flow cytometry analysis was used to determine positive (CD29 and CD105) and negative (CD18 and CD34) markers. The cells were washed with PBS containing 2 % FBS. FITC conjugated anti human CD18, CD29, CD34 and CD105 monoclonal antibodies (Cell Signaling Technology, USA). The fluorescence of the cells was immediately determined by a FACS-Calibur flow cytometry (Becton Dickinson, San Jose, USA). The FACs flow cytometry data were analyzed using freely available WinMDI software ver.2.9 (http://facs.scripps.edu/software.html).
3. Differentiation of MSCs into functional islet beta cells
At passage 3, adipose and bone marrow derived stem cells were induced to differentiate into functional pancreatic cells. According to previous reports about beta cell differentiation, we used design of experiment (DOE) to find cause-and-effect relationships and to determine the relationship between factors affecting our differentiation process. Among our designed experiments we decided to choose our best quality method. Therefore, cells were plated in L-DMEM medium supplemented with 20% FBS and 1% penicillin-streptomycin for 10 days at 37°C and 5% CO2. Second, the cells were cultured in differentiation medium containing L-DMEM supplemented with 10% FBS, 2% B27, b-FGF, and 10 mM nicotinamide (all purchased from Sigma-Aldrich) for 7 days and finally, the cells were cultured in induction medium containing H-DMEM supplemented with 2% B27, b-FGF, 10 ng/ml activin A, 10 mM nicotinamide, and 1 mM 2-mercaptoethanol (Sigma-Aldrich) for another 6 days. Cells cultured in L-DMEM medium without an inducer were used as controls.
4. Real-time PCR analysis
Total RNA was isolated utilizing the high pure RNA isolation kit (Roche, Mannheim, Germany), according to the manufacturer’s instructions. For synthesis of first strand cDNA, total RNA (0.2 µg) from each sample, before and after differentiation was used in a random primed reverse transcription (RT) reaction utilizing the RevertAid™ First Strand cDNA Synthesis Kit (Fermentas, Lithuania). Quantitative real-time PCR using custom made gene specific primers (Invitrogen, Carlsbad, CA) was performed to evaluate mRNA expression before and after differentiation. Target genes and the primer sequences used for qRT-PCR were described in Table 1. Quantitative real-time PCR (qPCR) reactions were carried out using the HOT MOLPol EvaGreen qPCR Mix Plus (Solis BioDyne, Estonia) in a total volume of 20 µl on ABI Prism 7900 Sequence Detector System (Applied Biosystems) according to the manufacturer’s instructions. The following thermal profile was used: One cycle at 95 °C for 15 min and 40 cycles of denaturation at 95 °C for 15 s, annealing at 60–65 °C for 20 s and elongation at 72 °C for 20 s. All qRT-PCR results were normalized to GAPDH gene as reference gene. The results were expressed as the target/reference ratio of differentiated cells divided by the target/reference ratio of the calibrators (undifferentiated control samples) [28].
Table 1
Forward and reverse primers used for beta-cell differentiation in real-time PCR
Gene
|
Sequence
|
Annealing temperature (°C)
|
Insulin
|
Forward: 5’- AGCCTTTGTGAACCAACACC-3’
Reverse: 5’- GCTGGTAGAGGGAGCAGATG-3’
|
54
|
Nestin
|
Forward: 5’- GCGGGGCGGTGCGTGACTAC-3’
Reverse: 5’- AGGCAAGGGGGAAGAGAAGGATGT-3’
|
56
|
NGN-3
|
Forward: 5’- AGGCAGTCTGGCTTTCTCAG-3’
Reverse: 5’- GAACAAGTGCTTTTGAGGGC-3’
|
53
|
PAX-4
|
Forward: 5’- TGGAGAAAGAGTTCCAGCGTG-3’
Reverse: 5’- TGGAAAACCAGACCCTCACC-3’
|
56
|
PDX-1
|
Forward: 5’- TTCAACAAGTACATCTCACGGC-3’
Reverse: 5’- TTGTCCTCCTCCTTTTTCCA-3’
|
54
|
NeuroD1
|
Forward: 5′-GCGGCCCCAAAAAGAAGAAG-3′
Reverse: 5′-TCCGACAGAGCCCAGATGTA-3′
|
57
|
NKX6.1
|
Forward: 5’- GGGCTCGTTTGGCCTATTCGTT-3’
Reverse: 5’- CCACTTGGTCCGGCGGTTCT-3’
|
55
|
PC1/3
|
Forward: 5’- CGCTGACCTGCACAATGACT-3’
Reverse: 5’- CAGACAACCAGGTGCTGCAT-3’
|
56
|
IAPP
|
Forward: 5’- TGCTCTCTGTTGCATTGAACC- 3’
Reverse: 5’- GTTGCATTTCCGCTTTTCCA-3’
|
54
|
GAPDH
|
Forward: 5’- TGGTATCGTGGAAGGACTCATGA-3’
Reverse: 5’- ATGCCAGTGAGCTTCCCGTTCAGC-3’
|
56
|
5. Western blot analysis
Protein expression of nestin and insulin as two markers of ADSCs and BMSCs before and after differentiation to beta-islet cells was evaluated by western blot analysis. Cells before and after differentiation were homogenized in a lysis buffer containing 50 mM Tris (pH 7.4), 2 mM EDTA, 2 mM EGTA, 2 mM NaF, 1 mM Na3VO4, 10 mM B-glycerophosphate, 10 mM 2-mercaptoethanol, sodium desoxycholate, and 1 μL protease and phosphatase inhibitor cocktail and 1 mM phenylmethanesulfonyl. Proteins were separated on a 12% SDS-PAGE under reducing conditions at a constant voltage (120 v) for 1:45 h. The separated proteins were electro-transferred to the polyvinylidene difluoride (PVDF, Bio Rad) membrane. To block non-specific binding sites, membranes were incubated in 5% non-fat dry milk in TBST buffer (20 mM Tris–HCl pH 7.5, 137 mM NaCl, 0.5% Tween 20) for 1 h at room temperature. After blocking, the membranes were incubated overnight at 4°C with primary antibodies against nestin (1/1000), insulin (1/1000) and β-actin (1/1000). The blots were then incubated for 1 h at room temperature with a HRP conjugated secondary antibody (1:3000) (All antibodies were purchased from Abcam, USA). Protein bands were visualized using the enhanced chemiluminescence method (ECL detection kit, Pierce Biotech, Inc.) and Alliance 4.7 Gel Doc (UVTEC, Cambridge). Band intensities were quantified using UV BAND image analysis software (UVTEC, Cambridge).
6. Insulin and C-peptide secretion assay
To determine whether the differentiated ADSCs and BMSCs were responsive to glucose stimulation, insulin release was measured after exposure to high glucose level using human insulin ELISA kit (Abcam, Cambridge, UK). After differentiation of adipose and bone marrow stem cells, they were washed twice with PBS and incubated in low glucose DMEM culture media for 3 h and then the medium was collected and stored at -20°C. In next step, cells were washed twice with PBS and incubated for 3 h in high glucose DMEM culture media and again, the medium was collected and stored at -20°C. C-peptide content of culture medium was determined by using C-peptide ELISA kits (Abcam, Cambridge, UK) according to the manufacturer’s instructions. Briefly, 50 µl of samples was added to 100 µl C-peptide HRP and biotin conjugate in a 96-well plate and incubated for 2h at room temperature. After washing three times with 300 µl washing solution, 100 µl tetramethylbenzidine (TMB) was added and incubated for 15 minutes at room temperature in the dark. Then, 100 µl stop solution was added to the wells and mixed for 10 seconds on a shaker. Finally, the absorbance of the sample at 450 nm within 5 minutes of addition of the stop solution against a reference wavelength of 620-630 nm was measured.
7. Statistical analysis
The results obtained from the experiment were presented as means ± SD. Each experiment will be repeated for 3 times. Student’s t-test was used to compare the means of two groups. P value of less than, or equal to 0.05 was considered to be statistically significant. The statistical analysis was performed using the SPSS 16.0 software program (Statistics Package for Social Sciences, SPSS Inc. Chicago, Illinois, USA).