Reagents
Anti-mouse CD11b (# 12-0112-85), anti-mouse Sca-1 (# 11-5981-82), anti-mouse CD105 (# 12-0900-81), anti-mouse CD34 (# 11-0341-82), anti-mouse CD45 (#14-0451-82), anti-mouse CD31 (# 3-0311-82), anti-human CD73 (# 12-0739-42), anti-human CD34 (# 11-0341-82), anti-human CD105 (# 12-1051-82), anti-human CD45 (# 11-0451-82), anti-human HLA-DR (# 11-9952-42), anti-humanCD166 (# 12-1668-42) were purchased from eBioscience. Mouse anti-ICAM-1 (# sc-8439) was purchased from Santan Cruz biotechnology. Rabbit Anti-TSG101 (# ab125011) and Rabbit Anti-CD63 (# Ab217345) were purchased from Abcam. CellTracker™ CM-Dil (# C7000), cellTracker™ green CMFDA (# C7025), IFN-α Mouse enzyme linked immunosorbent assay (ELISA) Kit (# BMS6027TEN), TNF–α Mouse ELISA Kit (# BMS607HS), IL-17 Mouse ELISA Kit (# BMS6001) were purchased from Invitrogen. Protease/phosphatase Inhibitor Cocktail (# 5872S) was purchased from Cell Signaling. HiFiScript gDNA Removal RT MasterMix (# CW2020) and UltraSYBR One Step RT-qPCR Kit (High ROX, # CW2624) were purchased from CWBIO. ExoEasy Maxi Kit (# 76064) was purchased from QIAGEN. Luciferase®Reporter Assay System (# E1910) was purchased from Promega. CD4 microbeads (# L3T4) were purchased from Miltenyi Biotech. Purified anti-mouse CD3ε (# 145-2C11) and purified anti-mouse IL-4 (# 504101) were purchased from Biolegend, and purified anti-mouse IL-12 (# 505202), purified anti-mouse IFN-γ (# 505701) were purchased from Peprotech. The miRNA agomiR was purchased from RIOBIO. Primers were purchased from Sangon Biotech. HEK 293T (# CRL-1573) and human umbilical vein endothelial cells (HUVECs) (# CRL-1730) were purchased from ATCC. C57BL/6 Mouse Primary Lymphatic Endothelial cells (# C57-6092) were purchased from Cell Biologics.
Mice
Male BALB/c mice served as the recipient mice [8-week-old, specific pathogen free (SPF)]. The donor mice were 6-week-old SPF-grade female C57BL/6j mice (H2kb). Mice were purchased from Beijing Vital River Laboratory Animal Technology [license SCXK (Beijing) 2016-0001]. All the mice were reared in SPF animal rooms in the Experimental Animal Center at the Beijing Academy of Military Medical Sciences. The recipient mice were fed with sterilized food and water containing gentamicin (320 mg/L) and erythromycin (250 mg/L).
Cell preparation
MSCs, isolated from human umbilical cords and murine compact bone, were cultured in alpha-MEM containing 10% fetal bovine serum (FBS), 100 U/ml penicillin, and 100 mg/ml streptomycin according to the previous description[25, 26]. The cells were cultured to the third passage.
Bone marrow cells and splenocytes were isolated from 6-week-old C57BL/6j mice. Mice were euthanized (carbon dioxide), followed by obtaining the spleen and bone marrow tissues. Erythrocytes were lysed by using erythrocyte lysis buffer. Fresh splenocytes and bone marrow were obtained and washed twice with PBS. These cells were used for transplantation into the irradiated recipient mice.
For the splenocyte staining, the splenocytes for transplantation were labeled with CellTracker™ CM-DiI dye. This was achieved by adding CM-Dil (2 µl) to a splenocyte suspension and incubating at 37 °C in dark for 5 min, followed by incubating at 4 °C in dark for 15 min. PBS was used to remove the unbound dye.
Isolation of exosomes
Serum-free culture medium was used to culture P2 passages huc-MSCs and mb-MSCs. When the cell density of 80% was reached, the supernatant was collected and centrifuged at 700 g for 10 min. The supernatant was collected and centrifuged at 9,000 g at 4 °C for 30 min to remove cell debris. The supernatant was collected, and an exoEasy Maxi kit (Qiagen) was used to isolate the exosomes that were finally resuspended in 100 µL PBS. Then sequencing was performed, which revealed the high expression of miR-223 that was used for the subsequent analysis.
MSC transplantation into C57BL/6j mice
For the experimental group (n = 5), P3 passages MSCs (1 × 106) were injected into mice through the tail vein. An equal volume of PBS was injected into the control group (n = 5). About 48 hrs after treatment, peripheral blood was isolated and centrifuged at 3,000 g for 15 min. The serum was collected to isolate the serum exosomes according to the manufacturer’s instructions.
Co-culture of exosomes and HUVECs
HUVECs (2 × 105) were seeded into each well in 6-well plates. The exosomes (2 µg/well) were added to the experimental group, and an equal volume of PBS buffer was added to the control group as previously described[27]. The cells were cultured in RPMI 1640 medium containing 10% FBS for 24 hrs. The supernatant was discarded, and the cells were washed twice with PBS to remove residual exosomes. Finally, 0.25% trypsin was used for digestion, followed by cell collection.
Transient transfection experiment
In total, HUVECs or mouse primary lymphatic endothelial cells (mLECs) were seeded onto 24-well plates (2 × 105/well) and cultured using complete RPMI 1640 medium containing 10% FBS. Upon a cell density of 50–70%, the jetPrime transfection reagent was used to separately transfect miR-223 mimic (100 nM) and negative control. Cells were collected after 48 hrs.
Luciferase
The 293T cells were transfected using Jetprime with pGL3-ICAM-1-3’UTR plasmid, Co-reporter vector pRL-TK (containing renilla) and miR-223 mimic (100 nM). After 48 hrs, the culture supernatant was discarded, and cells were washed once with PBS. The passive lysis buffer from the Dual-Luciferase®Reporter Assay System (Promega) was used to lyse cells, and luciferase activity was measured according to the manufacturer’s instructions.
Th1 cell differentiation in vitro
CD4+ Th1 differentiation was induced according to the previous study[28]. Briefly, mouse spleen was homogenized followed by filtering through a filter (mesh, 40 µm). Erythrocytes were lysed by using erythrocyte lysis buffer. CD4 (L3T4) microbeads were used to isolate CD4 T-cells, which were then cultured in a 24-well plate coated with anti-CD3ε (3 µg/ml) and anti-CD28 (5 µg/ml). The culture medium contained IFN-γ (20 ng/ml), IL-12 (5 ng/ml), and anti-IL4 (5 µg/ml). Upon cell culture for 3–5 days, flow cytometry was used to measure the expression of IFN-γ and IL-4.
Th1 cells staining
The cells were resuspended gently in CellTracker™ (1:1000, Invitrogen) staining solution. The mixture was incubated at 37 °C for 30 min followed by centrifugation to remove the CellTracker™ Working Solution. The stained cells resuspended with culture media were used for the following assays.
In vitro cell crawling assays
Cultured C57BL/6 mLECs were seeded into coated channeled chamber slides (µ-Slide VI0.4, #1709291, IBIDI). Monolayers were transfected with miR-223 mimic and normal control until 24 hrs, and then stained Th1 cells (3 × 104) were added. About 20 min later, chambers were rinsed twice to remove non-adherent Th1 cells. After a further 10 min equilibration at 37 °C, time-lapse imaging was performed on Operetta CLS™ (PerkinElmer Operetta CLS). The images were analyzed using Operetta primarily software.
In vitro transmigration assay
Transferred miR-223 mimic and negative control to mLECs until 24 hrs were seeded onto the upper side of coated Transwell membrane inserts with a pore size of 5 µm (#PIMP12R48, Millipore), followed by culturing until confluence. On the day of the assay, stained Th1 cells (5 × 104) were added in the upper well of the Transwell insert. After 4 hrs, the medium in the bottom well was collected and the number of Th1 cells was quantified by cell counter (Luna).
In vitro adhesion assay
The miR-223 mimic and normal control were transferred to mLECs for 24 hrs, followed by seeding onto a coated 96-well clear bottom (Corning Costar®). Then in vitro generated Th1 cells (1 × 104) were added to the mLECs. About 45 min later, non-adherent cells were collected and the number of Th1 cells was measured by cell counter.
Construction of mouse aGvHD model
BALB/C mice (8-week-old) were irradiated with a single dose of 800 cGy total body irradiation (TBI, Co60γ source). The aGvHD model mice were infused with nucleated bone marrow cells (1 × 107) and splenocytes (1 × 107) isolated from C57BL/6 mice (6-week-old) through tail vein injection. After 24 hrs of irradiation, MSCs (P3, 5 × 105/mouse), chemically synthesized miR-223Agomir and micrONTMAgo NControl#22 were used to treat aGvHD.
The miR-223Agomir and micrONTMAgo NControl#22 served as the negative control were centrifuged transiently to achieve miRNA powder aggregation at the bottom of the centrifuge tube. Subsequently, PBS buffer (1 ml) was added to dissolve the powder until a concentration of 50 mol/L, and was administered to recipient mice 1 day before irradiation, as well as 1, 4, and 7 days after irradiation by tail vein injection (10 nmol/mouse).
Western blot
RIPA lysis buffer containing protease inhibitors/phosphatase inhibitors were added to cell pellets (or exosomes) and incubated at 4 °C for 30 min for lysis. Proteins were subject to SDS-PAGE. Next, proteins were transferred onto a PVDF membrane at a constant current of 200 mA for 120 min. The membranes were blocked with 5% skimmed milk-TBST for 1 hr, and CD63, TSG101, and then ICAM-1 antibodies were added. The membranes were incubated overnight at 4 °C. The next day, the membranes were washed with TBST thrice for 10 min. HRP-labeled secondary antibodies were added, and the membranes were incubated at room temperature for 1 hr. Subsequently, the membranes were washed with TBST thrice for 10 min each before imaging.
ELISA
Serum IFN-γ, TNF–α and IL-17 were measured using a commercially available ELISA kit (Invitrogen, USA). All protocols were conducted according to the manufacturer’s instructions.
Quantitative qPCR
Total RNA was extracted from exosomes and cells using Trizol reagent. The cDNA synthesis was conducted using the commercial reverse transcription kit (CWBIO). The stem-loop method was used for reverse transcription of miRNA. qPCR was carried out using the UltraSYBR One-Step Kit was according to the manufacturer’s instructions. PCR amplification was conducted on the 7500 Real-Time system with GAPDH serving as a reference gene. The specific primers were listed in Table 1.
Table 1
Gene | Primer sequence (5’-3’) |
miR-223 Forward | ACACTCCAGCTGGGTGTCAGTTTGTCAA |
miR-223 Reverse | CTCAACTGGTGTCGTGGAGTCGGCAATTCAGTTGAGTGGGGTAT |
snoRNA202 Forward | ACACTCCAGCTGGGGCTGTACTGACTTGATG |
snoRNA202 Reverse | CTCAACTGGTGTCGTGGAGTCGGCAATTCAGTTGAGCATCAGAT |
URP | TGGTGTCGTGGAGTCG |
human ICAM Forward | ACCATCTACAGCTTTCCGG |
human ICAM Reverse mouse GAPDH Forward mouse GAPDH reverse human GAPDH Forward human GAPDH Reverse | ACACTTCACTGTCACCTCG ACTCTTCCACCTTCGATGC CCGTATTCATTGTCATACCAGG TCAAGATCATCAGCAATGCC CGATACCAAAGTTGTCATGGA |
Statistical analysis
Data were presented as mean ± standard error of mean. When comparing two groups with a sample size of ≥ 3, an unpaired two-tailed Student’s t-test was used. Mann–Whitney nonparametric tests were used to compare two independent groups with a sample size of ≥ 3. When data were paired and samples size was ≥ 3, Wilcoxon matched-pairs tests were used. One-way ANOVA were used to compensate for multiple testing procedures. A value of P < 0.05 was considered to be statistically significant.