Raw264

Mouse macrophages cell line (Raw 264.7) and human umbilical vein endothelial cells (HUVECs) were purchased from the Procell Life Science&Technology Company (Wuhan, China). Raw 246.7 cells and HUVECs were cultured with DMEM high-glucose. All medium supplemented with 10% FBS and 1% penicillin/streptomycin (P/S, Beyotime). Moreover, all cells were cultured in a humid incubator at 37 °C and a CO₂ level of 5%.

Mouse cardiac myocytes line of HL-1 was purchased from Shanghai Zhongqiao Xinzhou Biotech (ZQ0920; Shanghai, China) and mouse bone marrow derived macrophages line of RAW 264.7 was purchased from Procell (CP-M141, China). HL-1 cells and RAW 264.7 cells were cultured in DMEM culture medium contained 10% FBS and 1% penicillin/streptomycin (P/S; E607011, Sangon, China) at 37 °C in an atmosphere of 95% air and 5% CO₂.
To explore the effect of ferroptosis on exosome derived from cardiac myocytes, HL-1 cells were maintained at hypoxic conditions with 7% O₂ and treated with 50 µM ferrostatin-1 (Fer-1), a ferroptosis inhibitor, for 16 h. HL-1 cells treated with PBS as control. Later, culture supernatants were harvested for exosome isolation.
To explore the role of Wnt/β-catenin in exosome-mediated macrophage polarization, RAW 264.7 cells were treated with 10  µM IWR-1 (681669, Sigma-Aldrich), a Wnt/β-catenin signaling pathway inhibitor, for 48 h. Later, Wnt expression was detected by RT-qPCR and western blot.

Four MM cell lines (MM.1S, RPMI8226, KMS11, and U266) and monocytic osteoclast progenitor cell line (RAW264.7) were purchased from Procell (Wuhan, China). MM cell lines and RAW264.7 cells were incubated in RPMI-1640 or DMEM medium (Meilunbio, China), which contained 10% FBS (ExCell, China), penicillin and streptomycin. 5% CO₂ at 37 °C was used to culture all cells. From September 2019 to January 2021, paraffin sections of bone marrow samples of 24 MM patients and 7 iron deficiency anemia (IDA) patients were obtained from the First Affiliated Hospital of Fujian Medical University. And the percentage of CD138 + cells in the bone marrow of MM patients was obtained from the pathology report. Primary plasma cells were isolated from bone marrow specimens of patients with MM and healthy donors using anti-CD138 MicroBeads (Miltenyi, Germany) and immediately frozen in − 80 °C until the subsequent extraction of RNA. The Ethics Committee of the First Affiliated Hospital of Fujian Medical University approved this study. According to the Declaration of Helsinki, informed consent was obtained.

The mouse macrophage line Raw 264.7, mouse preosteoblast cell line MC3T3-E1, and BMSCs were obtained from Procell Life Science & Technology (Wuhan, China). MC3T3-E1 cells were cultured in α-MEM supplemented with 10% FBS, 100 IU/mL penicillin and 100 µg/mL streptomycin. RAW264.7 cells were cultured in DMEM supplemented with 10% FBS, 100 IU/mL penicillin and 100 µg/mL streptomycin. Mouse BMSCs were cultured in mouse MSC Medium (Cyagen) according to the manufacturer’s protocol (Nuwacell, Hefei, China). The cell cultures were maintained in an incubator at 37 °C in a humidified atmosphere with 5% CO2.
C57BL/6J female mice of specific pathogen-free (SPF) quality were purchased from the Model Animal Research Center of Tongji Medical College of Huazhong University of Science and Technology (HUST, Wuhan, China). All mice were housed under controlled conditions, which included room temperature of 25 °C, humidity maintained at 60 ± 10%, and a natural light–dark cycle throughout the study. All animals were treated according to the regulations of Chinese law and the local Ethics Committee. All animal experiments were reviewed and approved by the IACUC of HUST (IACUC Number: 3469).

MC38 and B16F10 were brought from American Type Culture Collection and were cultured in a complete RPMI-1640 medium. B16F10 cells transfected with Control Double Nickase Plasmid (Scramble B16F10), and B16F10 cells transfected with PD-L1 Double Nickase Plasmids (B16F10^{PD-L1 KO} cells) were established in our previous work^{19 (link)} (a kind gift from Prof. Zhirong Zhang, West China School of Pharmacy, Sichuan University, Chengdu, China), and they were cultured in complete RPMI-1640 medium. CTLL2 (catalog number CL-0331) was purchased from Procell Life Science & Tech-nology.Co.,Ltd, and it was cultured in a complete RPMI-1640 medium with IL-2 (100 U mL⁻¹). A375 (catalog number CL-0014) and LLC (catalog number CL-0140) were brought from Procell Life Science & Tech-nology.Co.,Ltd, and they were cultured in complete DMEM medium. RAW264.7 (catalog number CL-0190) was brought from Procell Life Science & Tech-nology.Co.,Ltd, and it was cultured in complete RPMI-1640 medium. CTLL2-PD1 cell was established by Shanghai Genechem in China, and it was cultured in a complete RPMI-1640 medium with IL-2 (100 U mL⁻¹). All cells were maintained in a humidified atmosphere incubator containing 5% CO₂ at 37 °C.