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Exosomal PD-L1 induces osteogenic differentiation and promotes fracture healing by acting as an immunosuppressant.

ABSTRACT: A moderate inflammatory response at the early stages of fracture healing is necessary for callus formation. Over-active and continuous inflammation, however, impairs fracture healing and leads to excessive tissue damage. Adequate fracture healing could be promoted through suppression of local over-active immune cells in the fracture site. In the present study, we achieved an enriched concentration of PD-L1 from exosomes (Exos) of a genetically engineered Human Umbilical Vein Endothelial Cell (HUVECs), and demonstrated that exosomes overexpressing PD-L1 specifically bind to PD-1 on the T cell surface, suppressing the activation of T cells. Furthermore, exosomal PD-L1 induced Mesenchymal Stem Cells (MSCs) towards osteogenic differentiation when pre-cultured with T cells. Moreover, embedding of Exos into an injectable hydrogel allowed Exos delivery to the surrounding microenvironment in a time-released manner. Additionally, exosomal PD-L1, embedded in a hydrogel, markedly promoted callus formation and fracture healing in a murine model at the early over-active inflammation phase. Importantly, our results suggested that activation of T cells in the peripheral lymphatic tissues was inhibited after local administration of PD-L1-enriched Exos to the fracture sites, while T cells in distant immune organs such as the spleen were not affected. In summary, this study provides the first example of using PD-L1-enriched Exos for bone fracture repair, and highlights the potential of Hydrogel@Exos systems for bone fracture therapy through immune inhibitory effects.

SUBMITTER: Lin Z

PROVIDER: S-EPMC8844834 | biostudies-literature | 2022 Jul

REPOSITORIES: biostudies-literature

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Exosomal PD-L1 induces osteogenic differentiation and promotes fracture healing by acting as an immunosuppressant.

Lin Ze Z Xiong Yuan Y Meng Weilin W Hu Yiqiang Y Chen Lili L Chen Lang L Xue Hang H Panayi Adriana C AC Zhou Wu W Sun Yun Y Cao Faqi F Liu Guodong G Hu Liangcong L Yan Chenchen C Xie Xudong X Lin Chuanchuan C Cai Kaiyong K Feng Qian Q Mi Bobin B Liu Guohui G

Bioactive materials 20211103

A moderate inflammatory response at the early stages of fracture healing is necessary for callus formation. Over-active and continuous inflammation, however, impairs fracture healing and leads to excessive tissue damage. Adequate fracture healing could be promoted through suppression of local over-active immune cells in the fracture site. In the present study, we achieved an enriched concentration of PD-L1 from exosomes (Exos) of a genetically engineered Human Umbilical Vein Endothelial Cell (HU ...[more]

PMID: 35224310

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Project description:Exosomal PD-L1 (exoPD-L1) is reported to be associated with immunosuppression in various cancers. However, its clinical value in extranodal NK/T cell lymphoma (ENKTL) has not been defined yet. We retrospectively evaluated the prognostic value of pretreatment circulating soluble PD-L1 (sPD-L1) and exosomal PD-L1 (exoPD-L1) in ENKTL patients treated with VIPD-containing chemotherapy. A total of 107 ENKTL patients, including 101 early stage and 6 advanced stage patients were enrolled in our study. ExoPD-L1 and sPD-L1 in the blood were measured by single molecule array (Simoa) and enzyme-linked immunosorbent assay (ELISA), respectively. Compared with the healthy individuals (n=16), the patients with ENKTL (n=107) exhibited significantly elevated exoPD-L1 and sPD-L1 levels in the blood. High pretreatment plasma exoPD-L1 concentration was associated with higher SUVmax level and recurrence rate. Similarly, high sPD-L1 group was also associated with some adverse clinical parameters, including advanced stage, elevated LDH levels, B symptoms, high IPI score and PINK score. The 5-year progression-free survival (PFS) rate and overall survival (OS) rates were 65.2% and 85.7% for the whole cohort, respectively. Patients with a low pretreatment exoPD-L1 level (simoa signal < 1.2) had 5-year OS and PFS rates of 88.1% and 86.1%, respectively, compared with 56.0%. (P=0.012) and 35.7% (P=0.007) in patients with high exoPD-L1 level (simoa signal > 1.2). The 5-year OS and PFS rates for patients with low sPD-L1 group (< 219 pg/mL) was significantly higher than high sPD-L1 group (≥ 219 pg/mL) (OS, 91.3% vs. 55.5%, P < 0.001; PFS, 68.9% vs. 34.6%, P=0.003). However, no correlation was found between circulating exoPD-L1 and sPD-L1 levels. This is the first study to measure plasma exoPD-L1 level on the Quanterix Simoa platform. Our results proved that circulating exoPD-L1 and sPD-L1 levels were significantly elevated in ENKTL and might be potential biomarkers for predicting the survival outcomes of ENKTL patients.

Project description:BackgroundMesenchymal stem cells (MSCs) are promising targets for therapeutic use in regenerative medicine and tissue engineering. In the previous study, we have found that MSCs could be reverted to a primitive stem cell population after in vitro induction of osteogenic and de-osteogenic differentiation (de-osteogenic differentiated MSCs, De-Os-MSCs). De-Os-MSCs showed improved cell survival and osteogenic potential. However, the underlying mechanism and its potential effect on fracture healing has not been explored.MethodsMSCs were isolated from the rat bone marrow. MicroRNAs were cloned into lentiviral vectors and transduced into MSCs to observe the effects on osteogenesis. The expression levels of marker genes were evaluated by quantitative RT-PCR. Ectopic bone formation model was used to evaluate the bone regeneration ability of mir-92b transduced MSCs in vivo. An open femur fracture model was established, and MSCs or De-Os-MSCs were administrated to the fracture sites. Histological, biomechanical and microCT analysis were used to evaluate the quality of bone.ResultsIn the present study, we found that mir-92b was significantly increased in the secretions of De-Os-MSCs. And mir-92b could promote the osteogenic differentiation potential of MSCs by activating pERK and JNK signaling pathways. The ectopic bone formation assay showed that MSCs overexpressing mir-92b formed more bone like tissues in vivo. Most importantly, we found local administration of De-Os-MSCs could accelerate fracture healing using an open femur fracture model in rats. The quality of bone property was much better as shown by microCT and biomechanical testing.ConclusionTaken together, our study demonstrated that mir-92b promoted osteogenesis of MSCs, which was partially accounted for the enhanced osteogenic differentiation potential of De-Os-MSCs. And De-Os-MSCs had shown better regenerative capacity in accelerating fracture healing when they were locally given.The translational potential of this articleDe-Os-MSCs could be used to accelerate fracture healing, and reduce the occurrence of delayed unions and non-unions.

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Exosomal PD-L1 induces osteogenic differentiation and promotes fracture healing by acting as an immunosuppressant.

Publications

Exosomal PD-L1 induces osteogenic differentiation and promotes fracture healing by acting as an immunosuppressant.

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