Mice

C57BL/6J (CD45.2) and C57BL6.SJL (CD45.1) mice were purchased from The Jackson Laboratory and housed under specific pathogen-free conditions. Male and female mice from 8 to 12 weeks were used in experiments and provided with a suitable environment and sufficient water and food. After a week of acclimatization, each mouse was randomly divided into groups, given 100L pure water, 0.01mg/100L, or 0.1mg/100L MPs by oral gavage every two days for five weeks in a gavage experiment (n=5 for each group). For the intravenous injection experiment, MPs were administered into mouse blood via the tail vein at a rate of 0.1g/100L per week for a duration of 4 weeks (n=5 for each group). All animal experiments were first approved by the Laboratory Animal Welfare and Ethics Committee of Zhejiang University (AP CODE: ZJU20220108).

Indocyanine green polystyrene (ICG-PS), polystyrene (PS) and polymethyl methacrylate (PMMA) particles were obtained from Suzhou Mylife Advanced Material Technology Company (China). Polyethylene (PE) particles were purchased from Cospheric (USA). Scanning electron microscopy (SEM, Nova Nano 450, FEI) was used to characterize the primary sizes and shapes of different MPs20. MPs were dispersed in ultrapure water with sonication before dynamic light scattering analysis (Zetasizer, Malvern, UK) to determine the hydrodynamic sizes and zeta potentials49.

Mice were sacrificed and organs were removed within six hours of ICG-PS gavage, including the heart, lung, kidney, spleen, liver, gastrointestinal tissues and bone marrow. Feces were collected 1h before the mice were sacrificed. Both organs and feces were monitored by ex vivo bioluminescence imaging with a small-animal imaging system50 (IVIS Spectrum, PerkinElmer).

For flow cytometry analysis and isolation of hematopoietic stem and progenitor cells, cells were stained with relevant antibodies51 in PBS with 2% fetal bovine serum for 3045min on ice. Antibody clones that were used: Sca-1-PE-Cy7, c-Kit-APC, CD150-PE, CD48-BV421, CD45.1-FITC, CD45.2 PE-Cy5, Gr-1-PE-Cy5, Mac1-PE-Cy5, IgM-PE-Cy5, CD3-PE-Cy5, CD4- PE-Cy5, CD8-PE-Cy5, CD45R-PE-Cy5 and Ter-119-PE-Cy5. Detailed antibody information is summarized in Supplementary Table S6. HSPCs were stained with a lineage antibody cocktail (Gr-1, Mac1, CD3, CD4, CD8, CD45R, TER119 and B220), Sca-1, c-Kit, CD150 and CD48. Cell types were defined as followed: LSK compartment (LinSca-1+c-Kit+), LT-HSC (LSK CD150+CD48), ST-HSC (LSK CD150CD48), MPP2 (LSK CD150+CD48+) and MPP3/4 (LSK CD150CD48+). B cells (CD45.2+Mac1Gr-1+B220+), T cells (CD45.2+Mac1Gr-1+CD3+) and myeloid cells (CD45.2+Mac1+Gr-1). Samples were analyzed on a flow cytometer (CytoFLEX LX, Beckman). For sorting HSCs, lineage antibody cocktail-conjugated paramagnetic microbeads and MACS separation columns (Miltenyi Biotec) were used to enrich Lin cells before sorting. Stained cells were re-suspended in PBS with 2% FBS and sorted directly using the Beckman moflo Astrios EQ (Beckman). Flow cytometry data were analyzed by FlowJo (BD) software.

Apoptosis of cells was detected by Annexin V staining (Yeason, China). After being extracted from the bone marrow of mice, 5106 cells were labeled with different surface markers for 30 to 45min at 4C and then twice rinsed with PBS. Subsequently, the cells were reconstituted in binding buffer and supplemented with Annexin V. After 30min of incubation, flow cytometry was detected in the FITC channel. Cell cycle analysis was performed with the fluorescein Ki-67 set (BD Pharmingen, USA), following the directions provided by the manufacturer. Briefly, a total of 5106 bone marrow cells were labeled with corresponding antibodies, as previously stated. Afterward, the cells were pre-treated with a fixation/permeabilization concentrate (Invitrogen, USA) at 4C overnight and subsequently rinsed with the binding buffer. The cells were stained with Ki-67 antibody for 1h in the dark and then with DAPI (Invitrogen) for another 5min at room temperature. Flow cytometry data were collected by a flow cytometer (CytoFLEX LX, Beckman, USA).

HSCs were sorted by flow cytometry according to the experimental group (ctrl and PSH mice, Rikenellaceae treatment or hypoxanthine treatment). 150 HSCs were seeded in triplicate on methylcellulose media52 (M3434, Stemcell Technologies, Inc.). After 8 days, the number of colonies was counted by microscopy. In addition, 5000 BM cells were seeded and analyzed the same way as HSCs. The cell culture media was diluted in PBS and subjected to centrifugation at 400g for 5min to determine the total cell number.

Recipient mice (CD45.1) were administered drinking water with Baytril (250mg/L) for 7 days pre-transplant and 10 days post-transplant. The day before transplantation, recipients received a lethal dose of radiation (4.5Gy at a time, divided into two times with an interval of 4h). In primary transplantation, 2105 bone marrow cells from the ctrl or PS group (CD45.2) mice and 2105 recipient-type (CD45.1) bone marrow cells were transplanted into recipient mice (CD45.1) mice. Cells were injected into recipients via tail vein injection. Donor chimerism was tracked using peripheral blood cells every 4 weeks for at least 16 weeks after transplantation. For secondary transplantation, donor BM cells were collected from primary transplant recipients sacrificed at 16 weeks after transplantation and transplanted at a dosage of 2106 cells into irradiated secondary recipient mice (9Gy). Analysis of donor chimerism and the cycle of transplantation in secondary transplantation were the same as in primary transplantation.

For limiting dilution assays52, 1104, 5104 and 2105 donor-derived bone marrow cells were collected from ctrl or PS mice (CD45.2) and transplanted into irradiated (9Gy) CD45.1 recipient mice with 2105 recipient-type (CD45.1) bone-marrow cells. Limiting dilution analysis was performed using ELDA software53. 16 weeks after transplantation, recipient mice with more than 1% peripheral-blood multilineage chimerism were defined as positive engraftment. On the other hand, recipient mice undergoing transplantation that had died before 16 weeks post transplantation were likewise evaluated as having failed engraftment54.

For histological analysis, small intestines were collected and fixed in 4% paraformaldehyde and embedded in paraffin, sectioned (5m thickness), and stained with H&E at ZJU Animal Histopathology Core Facility (China). We used Chius scores33,34 to evaluate the damage for each sample. The grade was as follows: 0, normal mucosa; 1, development of subepithelial Gruenhagens space at the tip of villus; 2, extension of the Gruenhagens area with moderate epithelial lifting; 3, large epithelial bulge with a few denuded villi; 4, denuded villi with lamina propria and exposed capillaries; and 5, disintegration of the lamina propria, ulceration, and hemorrhage. For TEM analysis, slices of the small intestine were fixed with 2.5% glutaraldehyde for ultra-microstructure observation of intestinal epithelial cells. The samples were postfixed for one hour at 4C with 1% osmium tetroxide and 30min with 2% uranyl acetate, followed by dehydration with a graded series of alcohol solutions (50%, 70%, 90% and 100% for 15min each) and acetone (100% twice for 20min). Subsequently, they were embedded with epon (Sigma-Aldrich, MO, US) and polymerized. Ultrathin sections (6080nm) were made, and examined using TEM (Tecnai G2 Spirit 120kV, Thermo FEI).

In the short-term and long-term mouse models for MP ingestion, mice were fasted for 4h before oral gavage of FITC-dextran (4kD, Sigma). The fluorescence intensity of FITC-dextran (50mg/100g body weight) was measured in the peripheral blood after 2h of gavage. Fluorescence was measured using a microplate reader (Molecular Devices, SpectraMax iD5) with excitation at 490nm and emission at 520 nm29.

Fecal samples (about 3050mg per sample) were collected from the ctrl, PSL and PSH mice, quickly frozen in liquid nitrogen, and stored at 80C. DNA samples for the microbial community were extracted using E.Z.N.A. Stool DNA Kit (Omega, USA), according to the manufacturers instructions. In brief, polymerase chain reaction (PCR) amplification of prokaryotic 16S rDNA gene V3V4 region was performed using the forward primer 341F (5-CCTACGGGNGGCWGCAG-3) and the reverse primer 805R (5-GACTACHVGGGTATCTAATCC-3)55. After 35 cycles of PCR, sequencing adapters and barcodes were included to facilitate amplification. The PCR products were detected by 1.5% agarose gel electrophoresis and were further purified using AMPure XT beads (Beckman Coulter Genomics, Danvers, MA, USA), while the target fragments were recovered using the AxyPrep PCR Cleanup Kit (Axygen, USA). In addition, the amplicon library was quantified with the Library Quantification Kit for Illumina (Kapa Biosciences, Woburn, MA, USA), and sequenced on the Illumina NovaSeq PE250 platform. In bioinformatics pipeline29,56, the assignment of paired-end reads to samples was determined by their unique barcode, and subsequently shortened by cutting off the barcode and primer sequence. The paired-end reads were combined by FLASH (v1.2.8). Quality filtering on the raw reads was carried out under precise parameters to obtain high-quality clean tags according to fqtrim (v0.94). The chimeric sequences were filtered by Vsearch software (v2.3.4). After the dereplication process using DADA2, we acquired a feature table and feature sequence. The bacterial sequence fragments obtained were grouped into Operational Taxonomic Units (OTUs) and compared to the Greengenes microbial gene database using QIIME2. Alpha diversity and beta diversity were generated by QIIME2, and pictures were drawn by R (v3.2.0). The species annotation sequence alignment was performed by Blast, with the SILVA and NT-16S databases as the alignment references. Additional sequencing results are provided in Supplementary Table S1. The experiment was supported by Lc-Bio Technologies.

The methods for the analysis of feces from HSCT donors were slightly different from those used for mice. All samples were stored in the GUHE Flora Storage buffer (GUHE Laboratories, China). The bacterial genomic DNA was extracted with the GHFDE100 DNA isolation kit (GUHE Laboratories, China) and quantified using a NanoDrop ND-1000 spectrophotometer (Thermo Fisher Scientific, USA). The V4 region of the bacterial 16S rDNA genes was amplified by PCR, with the forward primer 515F (5-GTGCCAGCMGCCGCGGTAA-3) and the reverse primer 806R (5-GGACTACHVGGGTWTCTAAT-3). PCR amplicons were purified with Agencourt AMPure XP Beads (Beckman Coulter, IN) and quantified by the PicoGreen dsDNA Assay Kit (Invitrogen, USA). Following the previously reported steps57, the paired-end 2150bp sequencing was performed on the Illumina NovaSeq6000 platform. The details of bacterial OTUs are summarized in Supplementary Table S5. Sequence data analyses were performed using QIIME2 and R packages (v3.2.0).

For metabolite evaluation, samples from mice feces were prepared and detected as previously described55,58,59. In a nutshell, metabolites were extracted from feces through precooled 50% methanol buffer and stored at 80C before the LCMS analysis. All chromatographic separations were conducted using an ultra-performance liquid chromatography (UPLC) system (SCIEX, UK). A reversed phase separation was performed using an ACQUITY UPLC T3 column (100mm * 2.1mm, 1.8m, Waters, UK). The temperature of the column oven was maintained at 35C and the flow rate was 0.4mL/min. Both positive (the ionspray voltage floating set at 5000V) and negative ion modes (4500V) were analyzed using a TripleTOF 5600 Plus high-resolution tandem mass spectrometer (SCIEX, UK). The mass spectrometry data were obtained in Interactive Disassembler Professional (IDA) mode, with a time-of-flight (TOF) mass range of 60 to 1200Da. The survey scans were acquired in 150 milliseconds and product ion scans with a charge state of 1+ and 100 counts per second (counts/s) were recorded up to 12. Cycle duration was 0.56s. Stringent quality assurance (QA) and quality control (QC) procedures were applied, as the mass accuracy was calibrated every 20 samples and a QC sample was obtained every 10 samples. LCMS raw data files underwent processing in XCMS (Scripps, La Jolla, CA) to perform peak picking, peak alignment, gap filling, and sample normalization. Online KEGG was adopted to annotate metabolites through the matching between the precise molecular mass data (m/z) of samples and those from the database. PCA and volcano plot were utilized to identify ion characteristics that exhibit significant differences between the groups. The details of metabolomes can be found in Supplementary Table S2. The experiment was supported by Lc-Bio Technologies.

Before FMT, SPF mice received a 200L antibiotic treatment (1g/L ampicillin, 0.5g/L neomycin, 0.5g/L vancomycin and 1g/L metronidazole) for three consecutive days by oral gavage. Fresh feces were collected from ctrl or PS mice and resuspended in reduced PBS (0.5g/L cysteine and 0.2g/L Na2S in PBS) at a ratio of about 120mg feces/mL reduced PBS. Feces were then centrifuged at 500g for 1min to remove insolubilize particles25. Recipients (C57BL/6J mice) were administered 100mL of the supernatant from different groups by oral gavage twice every week for 4 weeks. 2 days after the last FMT, recipients were euthanized to analyze the changes in the hematopoietic system.

The Rikenellaceae strain (ATCC BAA-1961), purchased from ATCC, was cultured in an anaerobic chamber using BD Difco Dehydrated Culture Media: Reinforced Clostridial Medium at a temperature of 37C with a gas mixture of 80% N2 and 20% CO2. The final concentration of Rikenellaceae was 2108 viable c.f.u. per 100L and hypoxanthine (200mg/kg, Sigma, Germany) was dissolved in double distilled water29. Mice first received antibiotic treatment (same as FMT) and were then treated by oral gavage with 100L of either Rikenellaceae or hypoxanthine suspension three times a week for 4 weeks. Reinforced Clostridial Medium or double distilled water was used as a vehicle control, respectively. 2 days after the last administration, recipients were euthanized to analyze the changes in the hematopoietic system. To examine the impact of hypoxanthine on HSCs, we exposed bone marrow cells to direct co-culture with hypoxanthine at a concentration of 100pg/mL for a period of 3 days.

Mouse bone marrow cells were harvested by flushing the mices tibia and femur in phosphate buffered saline (PBS) with 2% fetal bovine serum (GIBCO). Harvested cells were grown into 96-well u-bottom plates containing freshly made HSC culture medium (StemSpanTM SFEM, Stemcell Tec.) with SCF (50ng/mL; PeproTech) and TPO (50ng/mL; PeproTech), at 37C with 5% CO2. For HSC culture, the medium was changed every 3 days by manually removing half of the conditioned medium and replacing it with fresh medium60. To assess the effects of WNT10A, IL-17, TNF and NF-kappa B on hematopoiesis, we cultured HSCs in a basic medium and supplemented them with related proteins (10ng/mL; Cosmo Bio, USA) or PBS as a control for two days, followed by flow cytometry analysis. Different concentrations of PS were added to the medium and tested using CCK-8 and FACS to detect the effect of MPs on cultured HSCs.

1104 HSCs were obtained in triplicate from mouse bone marrow cells from the ctrl or PSH group by flow cytometry sorting and RNA was extracted with RNAiso Plus (Takara, Japan) according to the manufacturers protocol. The concentration and integrity of RNA were examined by Qubit 2.0 and Agilent 2100 (Novogene, China), respectively. Oligo (dT)-coated magnetic beads (Novogene, China) were used to enrich eukaryotic mRNA. After cDNA synthesis and PCR amplification, the PCR product was purified using AMPure XP beads (Novogene, China) to obtain the final library. The Illumina high-throughput sequencing platform NovaSeq 6000 was used for sequencing. Analysis of gene expression was calculated by R or the DESeq2 package61. Detailed information regarding RNA-seq is listed in Supplementary Table S3.

For RNA expression analysis, total RNA from bone marrow cells was extracted using Trizol (Invitrogen, US) and resuspended in nuclease-free water. Reverse transcription was performed using the QuantiTect Reverse Transcription kit (Qiagen NV). qPCR was conducted using cDNA, primers and SYBR-green (Takara, Japan) in 20L using the ABI 7500 Q-PCR system62. Results were calculated using the RQ value (RQ=2Ct). Mouse Actin was chosen as the normalization control. Gene-specific primer sequences are shown in Supplementary Table S7.

Bone marrow and Rikenellaceae supernatant in different groups were obtained by centrifugation. Fecal supernatant was obtained from human samples. Hypoxanthine (LANSO, China) and WNT10A (EIAab, China) were measured by ELISA with respective kits according to the manufacturers protocols.

Human feces and peripheral blood samples were obtained from 14 subjects who provided grafts for HSCT patients. They were divided into graft success group and graft failure (GS)/poor graft function (GF/PGF) group, with 7 participants in each group. Research involving humans was approved by the Clinical Research Ethics Committee of the First Affiliated Hospital, College of Medicine, Zhejiang University (IIT20230067B). All participants read and signed the informed consent. Detailed information on patients was listed in Supplementary Table S4.

The Agilent 8700 Laser Direct Infrared Imaging system was utilized for fast and automated analysis of MPs in feces received from donors. An excessive nitric acid concentration (68%) was added to the sample and heated to dissolve the protein. Large particles were first intercepted with a large aperture filter and then filtered by vacuum extraction. After rinsing with ultra-pure water and ethanol several times, the materials, including MPs, were dispersed in the ethanol solution. The LDIR test was carried out when the ethanol was completely volatilized63. The sample of MPs was positioned on the standard sample stage. The stage was then put into the sample stage, and the Agilent Clarity was initiated to advance the sample stage into the sample chamber. The software rapidly scanned the chosen test area using a constant wave number of 1800cm1, and accurately detected and pinpointed the particles within the selected area. The unoccupied area devoid of particles was automatically designated as the background. The background spectrum was gathered and readjusted, followed by the visualization of detected particles and the collection of the whole infrared spectrum. After obtaining the particle spectrum, the spectrum library was utilized to carry out qualitative analysis automatically, including the inclusion picture, size, and area of each particle. The test was supported by Shanghai WEIPU Testing Technology Group.

MPs in peripheral blood from donors were tested by Py-GC/MS. Nitric acid was added to samples for digestion at 110C for 12h, and then used deionized water to make the solution weakly acidic. After concentration, the solution was dribbled into the sampling crucible of Py-GCMS and tested when the solvent in the crucible was completely volatilized17. Various standards of MPs were prepared and analyzed using Py-GCMS in order to construct the quantitative curve. PY-3030D Frontier was employed for lysis, with a lysis temperature set at 550 C. The chromatographic column dimensions were 30m in length, 0.25mm inner diameter, and 0.25m film thickness. The sample was subjected to a heat preservation period of 2min at 40C, followed by a gradual increase in temperature at a rate of around 20C per minute until it reached 320C. The sample was maintained at this temperature for 14min and the entire process takes a total of 30min. The carrier gas utilized was helium, with the ion source temperature of 230C. The split ratio employed was 5:1, and the m/z scan range spanned from 40 to 60064. The experiment was supported by Shanghai WEIPU Testing Technology Group.

Each animal experiment was tested using at least 56 replicates and each in vitro experiment was at least three replicates. Specific replication details are provided in relevant figure captions. Statistical significance was ascertained through unpaired two-tailed t-tests by GraphPad Prism when the P value was less than 0.05. Error bars in all figures indicate the standard deviation (SD).

Link:
Microplastics dampen the self-renewal of hematopoietic stem cells by disrupting the gut microbiota-hypoxanthine-Wnt ... - Nature.com

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