hADSCs culture and labeling
Frozen hADSCs from the previous study (Bakhtiari et al. 2021) were thawed and cultured with Dulbecco's modified Eagle's medium DMEM/ F12 (Bioidia, BI1027) containing 10% fetal bovine serum (FBS) (Gibco, 10270106) and 1% penicillin/streptomycin (Bioidia, BI1036) based on a previous study at 37 ◦C in a humidified 5% CO2 incubator . After 80% cell confluency, hADSCs were detached by 0.25% trypsin and 0.02% ethylenediaminetetraacetic acid (EDTA) (Bioidia, BI 1601). 72 hours before cell transplantation, the hADSCs which obtained from passages 3–5, were labeled using PKH26 (a red florescent dye) (Sigma-Aldrich, MINI26) according to our previous study (Ganji et al. 2020).
Behavioral test
During the study, hanging-wire test was performed to assess motor function and muscle stretch. To this end, the mice were hung from a 2-mm-thick metal hanger for 3 min after starting the timer. If the mice fell to the ground before the end of the test period, they were placed on the wire up to two more times, and finally the average maximum hanging time was recorded (Yamazaki et al. 2021).
Animal grouping
Sixty female C57BL/6 mice, 8 weeks old and 18 - 22 g weight, were purchased from the Royan Center, Isfahan, Iran, and maintained on alike light/dark cycles and at stable room temperature in polypropylene cages. In order to induce demyelination, cuprizone dissolved in corn oil according to previous study (Bakhtiari et al. 2021) and the mice were gavaged with 0.5 ml cuprizone 0.2% for 5 weeks (Zhu et al. 2017). Next, in order to prove the destruction of myelin and mice grouping, the results of the behavioral test were examined. Mice with significant or slight motor damage were included in this study. In these mice, the hanging time was reduced by at least 30 seconds compared to the before the study (Yamazaki, Ohno, and Huang 2021). These mice were randomly assigned to five experimental groups including, cuprizone (Cup, n=8) sham (n=8, treated with intra-peritoneal normal saline for 4 weeks), human Adipose Derived Stem Cell (n=8, treated with 1× 106 labeled hADSC, iv) (Lykhmus et al. 2019), lithium chloride (Li, n=8, treated with 50 mg/kg/day intra-peritoneal lithium) (Makoukji et al. 2012) and Li+ hADSC (n=8, treated simultaneously with 50 mg/kg/day lithium for 4 weeks and 1× 106 labeled hADSC) groups. In addition, a control group (n=8) with normal feeding was considered for compare the results.
Histological Examination
At the endpoint of experiment, the mice were sacrificed by performing deep anesthesia using ketamine/xylazine and fixation was done by cardiac perfusion method using normal saline and 4% formaldehyde (Merck, 1,040,021,000) (PH 7.4). In the following, the brains were immediately removed and post-fixed with same fixative for 24 h. After tissue processing, 5 μm sections were prepared by rotating microtome (Leitz1512, Germany) and after staining with toluidine blue, the sections were examined with an Olympus Provis light microscope (Hou et al. 2018).
Immunohistochemistry Technique
In order to oligodendrocytes evaluation, 3 μm-thick sections from corpus callosum were prepared and after antigen retrieval using sodium citrate buffer and 1 mM EDTA buffer (Gibco, USA), the slices were incubated with primary antibodies including anti-Olig2 antibody (1:1000; Abcam, Cambridge, MA, USA) and anti-myelin oligodendrocyte glycoprotein (MOG) antibody (1:1000; Abcam, Cambridge, MA, USA) at 4 °C overnight. Afterwards, the slices were washed with PBS, and were treated with FITC - conjugated secondary antibodies (1:500; Abcam, Cambridge, MA, USA) at room temperature for 1 h, and then, with 4′,6-diamidino-2-phenylindole (DAPI) (SigmaAldrich, D9542) for 2 min. Finally, the mean percentage of MOG and Olig2 positive cells was calculated in a minimum total of 200 cells per slide using a fluorescent microscope and Image j software (Bakhtiari et al. 2021).
Real-Time Reverse Transcription Polymerase Chain Reaction (Real Time RT-PCR) Analysis
To determine the expression β-Catenin, human and mouse myelin and oligodendrocyte specific genes in corpus callosum, the samples were evaluated using real-time RT-PCR technique. Total RNA was isolated from the tissue samples using the Total RNA Prep kit (BIOFACT, RP101–050, Korea) according to the instructions. The RNA was reverse transcribed using the BioFact™ 5X RT Pre-Mix cDNA Synthesis Kit (BIOFACT, 25081) and oligo dT primers. To remove DNA from the samples, the extracted RNA was treated with the RNase-free DNase kit (Qiagen, ID79254 Germany). The real-time PCR was performed using the BioFact™2X Real-Time PCR Master mix kit (BIOFACT, DQ385–40) and the Step One Plus™ quantitative real time PCR detection system (Applied Biosystems). The expression level of each target gene was calculated as 2-ΔΔCt. It should be noted that the primers (Table 1) were designed by Allele ID 7.6 and checked against the mice genome using the BLAST site. Also, the β-actin was considered as housekeeping gene to normalize gene expression (Dong et al. 2017).
Table 1. The list of primers used in this study.
Gene
|
Primer sequences
|
В-actin-m-F
|
5′-CGGTTCCGATGCCCTGAGGCTCTT-3′
|
В-actin-m-R
|
5′-CGTCACACTTCATGATGGAATTGA-3′
|
В-ACTIN-H-F
|
5′-AGCCTCGCCTTTGCCGATCC-3′
|
В-ACTIN-H-R
|
5′-ACATGCCGGAGCCGTTGTCG-3′
|
Mbp-m-F
|
5′-AACATTGTGACACCTCGAACA-3′
|
Mbp-m-R
|
5′-TGTCTCTTCC TCCCCAGCT-3′
|
MBP-H-F
|
5′-ACTATCTCTTCCTCCCAGCTTAAAAA-3′
|
MBP-H-R
|
5′-TCCGACTATAAATCGGCTCACA-3′
|
Mog-m-F
|
5′-TGATTTCCCTCCCTCAACTG-3′
|
Mog-m-R
|
5′-CGTATCCTGGTTGGCAGAAT-3′
|
MOG-H-F
|
5′-ACCAGGCACCTGAATATCGG-3′
|
MOG -H-R
|
5′-CAGGGCTCACCCAGTAGAAAG-3′
|
Olig2-m-F
|
5′-TGGAGAGATGCGTTCGTTCC-3′
|
Olig2-m-R
|
5′-GTGCTCTGCGTCTCGTCTAA -3′
|
OLIG2-H-F
|
5′-AGATCGACGCGACACCAGCG-3′
|
OLIG2-H-R
|
5′-TCGGACCCGAAAATCTGGATGCG-3′
|
β-Catenin-m-F
|
5′-GTACGCACCATGCAGAATAC-3′
|
β-Catenin-m-R
|
5′-TGGAGCAGGAGATTATGCAG-3′
|
Statistical Analysis
Statistical analysis was done using the software SPSS (IBM, SPSS Statistics Version 25). One-way analysis of variance (ANOVA) and LSD post-hoc test were conducted in order to find significant differences between experimental groups. All data were presented as mean ± standard error of the mean (mean ± SEM).