Search

The abnormal immunomodulatory functions of mesenchymal stem cells (MSCs) have been implicated in the development of immune thrombocytopenia (ITP). Recent studies have suggested important effects of complement on immune cell function. However, whether complement modulates bone marrow MSCs function in ITP is poorly defined. Tacrolimus has recently been applied to the treatment of autoimmune diseases. Here, we explored whether impaired ITP-MSCs could be targeted by tacrolimus. Our results showed that the Nod-like receptor family pyrin domain containing 3 (NLRP3) inflammasome was activated in ITP MSCs with complement deposition (MSCs-C + ) and initiated caspase-1-dependent pyroptosis. Transcriptome sequencing results showed abnormal fatty acid metabolism in MSCs-C + . Enhanced fatty acid β-oxidation and reactive oxygen species production activated the NLRP3 inflammasome. Adipocytes derived from MSCs-C + secreted less adiponectin. Adiponectin promoted the differentiation of megakaryocytes and inhibited the destruction of platelets. Tacrolimus inhibited NLRP3 inflammasome activation and MSCs-C + pyroptosis in vitro and in vivo. Tacrolimus plus danazol elicited a higher sustained response than danazol monotherapy in corticosteroid-resistant patients with ITP. Our findings demonstrate that the activation of the NLRP3 inflammasome in ITP MSCs mediated by complement could be inhibited by tacrolimus, which might be a potential new therapy for ITP., (© 2022 British Society for Haematology and John Wiley & Sons Ltd.)

Impaired megakaryocyte (MK) maturation and reduced platelet production are important causes of immune thrombocytopenia (ITP). However, MK distribution and bone marrow (BM) niche alteration in ITP are unclear. To investigate the maturation and distribution of MKs in the BM niche and examine the components of BM niche regulation of MK migration, BM and peripheral blood were obtained from 30 ITP patients and 28 healthy donors. Nestin + mesenchymal stem cells (MSCs) and CD41 + MKs were sorted by fluorescence-activated cell sorting. The components of the BM niche and related signaling were analyzed via immunofluorescence, flow cytometry, enzyme-linked immunosorbent assay, reverse transcription polymerase chain reaction, and western blot analysis. The number of MKs in the BM vascular niche was reduced in ITP. Moreover, the concentrations of CXCL12 and CXCR4 + MKs in the BM were decreased in ITP. Further investigation demonstrated that nestin + MSCs and CXCL12 messenger RNA (mRNA) in nestin + MSCs were both reduced whereas the apoptosis of nestin + MSCs was significantly increased in ITP. Sympathetic nerves, Schwann cells, the proportion of β3-adrenoreceptor (β3-AR) + nestin + MSCs, and β3-AR mRNA in nestin + MSCs were all markedly reduced in ITP. Moreover, matrix metalloproteinase 9, vascular endothelial growth factor (VEGF), and VEGF receptor 1 were significantly reduced in ITP. Our data show that impaired MK distribution mediated by an abnormal CXCL12/CXCR4 axis is partially involved in reduced platelet production in ITP. Moreover, sympathetic neuropathy and nestin + MSC apoptosis may have an effect on the alterations of BM CXCL12 in ITP., (© 2019 by The American Society of Hematology.)

Immune thrombocytopenia (ITP) is an autoimmune disease. Mesenchymal stem cells (MSCs) play important roles in the physiology and homeostasis of the haematopoietic system, including supporting megakaryocytic differentiation from CD34 + haematopoietic progenitor cells. Tumour necrosis factor alpha-induced protein 3 (TNFAIP3, also termed A20) plays a key role in terminating NF-κB signalling. Human genetic studies showed that the polymorphisms of the TNFAIP3 gene may contribute to ITP susceptibility. In this study, we showed a significant decrease in TNFAIP3 and increase in NF-κB/SMAD7 in ITP-MSCs. In co-cultures with CD34 + cells, NF-κB was overexpressed in MSCs from healthy controls (HC-MSCs) after transfection with NFKBIA (IκB)-specific short hairpin (sh)RNAs, resulting in MSC deficiency and a reduction in megakaryocytic differentiation and thrombopoiesis. Knockdown of TNFAIP3 expression using TNFAIP3-specific shRNAs in HC-MSCs affected megakaryocytopoiesis. However, IKBKB knockdown corrected megakaryocytopoiesis inhibition in the ITP-MSCs by decreasing NF-κB expression. Amplified TNFAIP3 expression in ITP-MSCs by TNFAIP3 cDNA can facilitate megakaryocyte differentiation. shRNA-mediated knockdown of SMAD7 expression rescued the impaired MSC function in ITP patients. Therefore, we demonstrate that a pathological reduction in TNFAIP3 levels induced NF-κB/SMAD7 pathway activation, causing a deficiency in MSCs in ITP patients. The ability of ITP-MSCs to support megakaryocytic differentiation and thrombopoiesis of CD34 + cells was impaired., (© 2018 John Wiley & Sons Ltd.)

Immune thrombocytopenia (ITP) is an autoimmune disease in which dendritic cells (DCs) play a crucial role in the breakdown of self-tolerance. Studies have identified the function of mesenchymal stem cells (MSCs) in promoting the development of regulatory DCs (regDCs). Our previous work revealed that MSCs in ITP exerted senescence, apoptosis, and impaired immunosuppressive effects on T and B cells. However, it is unclear whether the effects of MSCs on regDC induction are altered in ITP. Our data demonstrated that MSCs in ITP were impaired in inhibiting CD1a + DC and CD14 + DC differentiation from CD34 + hematopoietic progenitor cells (CD34 + HPCs). DCs differentiated with MSCs in ITP exhibited an increased expression of costimulatory molecules CD80/CD86 and secretion of proinflammatory interleukin-12 (IL-12). Accordingly, the tolerogenic characteristics were deficient in DCs induced by MSCs in ITP. DCs differentiated with MSCs in ITP exhibited an impaired ability to inhibit CD3 + T cell proliferation, to suppress T helper (Th)1 cell differentiation, and to induce anergic and regulatory T cells (Tregs). The expression of Notch signaling components was measured in MSCs in ITP. Reduced expression of the ligand Jagged-1, the receptor Notch-1 intracellular domain (NICD-1), and the target gene Hes-1 was identified in MSCs in ITP. The addition of biologically active Jagged-1 to CD34 + HPCs was observed to promote regDC differentiation. When cultured on Jagged-1-coated plates, MSCs in ITP showed an enhancement of the Notch-1 pathway activation, Jagged-1 expression, and the function in inducing regDCs. Pretreatment with all-trans retinoic acid (ATRA) was found to partially restore the capacity of MSCs in both ITP patients and healthy controls in inducing CD34 + -derived regDCs. Our data elucidated that MSCs in ITP were impaired in inducing CD34 + -regDCs, associated with the Notch-1/Jagged-1 signaling pathway. ATRA could partially correct the impairment of MSCs, suggesting that ATRA could serve as a potential therapeutic alternative for ITP.

: Immune thrombocytopenia (ITP) is characterized by platelet destruction and megakaryocyte dysfunction. Mesenchymal stem cells (MSCs) from ITP patients (MSC-ITP) do not exhibit conventional proliferative abilities and thus exhibit defects in immunoregulation, suggesting that MSC impairment might be a mechanism involved in ITP. Platelet-derived growth factor (PDGF) improves growth and survival in various cell types. Moreover, PDGF promotes MSC proliferation. The aim of the present study was to analyze the effects of PDGF-BB on MSC-ITP. We showed that MSC-ITP expanded more slowly and appeared flattened and larger. MSC-ITP exhibited increased apoptosis and senescence compared with controls. Both the intrinsic and extrinsic pathways account for the enhanced apoptosis. P53 and p21 expression were upregulated in MSC-ITP, but inhibition of p53 with pifithrin-α markedly inhibited apoptosis and senescence. Furthermore, MSCs from ITP patients showed a lower capacity for inhibiting the proliferation of activated T cells inducing regulatory T cells (Tregs) and suppressing the synthesis of anti-glycoprotein (GP)IIb-IIIa antibodies. PDGF-BB treatment significantly decreased the expression of p53 and p21 and increased survivin expression in MSC-ITP. In addition, the apoptotic rate and number of senescent cells in ITP MSCs were reduced. Their impaired ability for inhibiting activated T cells, inducing Tregs, and suppressing the synthesis of anti-GPIIb-IIIa antibodies was restored after PDGF-BB treatment. In conclusion, we have demonstrated that PDGF-BB protects MSCs derived from ITP patients against apoptosis, senescence, and immunomodulatory defects. This protective effect of PDGF-BB is likely mediated via the p53/p21 pathway, thus potentially providing a new therapeutic approach for ITP., Significance: Immune thrombocytopenia (ITP) is characterized by platelet destruction and megakaryocyte dysfunction. Platelet-derived growth factor (PDGF) improves growth and survival in various cell types and promotes mesenchymal stem cell (MSC) proliferation. PDGF-BB protects MSCs derived from ITP patients against apoptosis, senescence, and immunomodulatory defects. This protective effect of PDGF-BB is likely mediated via the p53/p21 pathway, thus potentially providing a new therapeutic approach for ITP., (©AlphaMed Press.)

Recent findings have shown that the level of interleukin‐35 (IL‐35) is abnormal in several autoimmune diseases. Nonetheless, whether IL‐35 participates in the pathogenesis of immune thrombocytopenia (ITP) remains unclear. The current study investigates whether IL‐35 modulates megakaryopoiesis. The results show that IL‐35 receptors are progressively expressed on bone marrow megakaryocytes during the in vitro differentiation of CD34+ progenitors. IL‐35 increases the number of megakaryocyte colony‐forming units through the Akt pathway. The level of bone marrow IL‐35 is reduced in ITP patients, and the decreased level of IL‐35 may inhibit megakaryopoiesis. Then, the potential causes of decreased IL‐35 in ITP patients are explored. The primary type of cell that secretes IL‐35, known as IL‐35‐producing regulatory T cells (iTr35), is reduced in ITP patients. Bone marrow mesenchymal stem cells (MSCs) from ITP patients exhibit an impaired capability of inducing iTr35 due to enhanced apoptosis, which may contribute to the reduced level of bone marrow IL‐35 in ITP patients. Iguratimod promotes megakaryocyte development and differentiation by elevating the expression of IL‐35 receptors on megakaryocytes. Iguratimod improves response rates and reduces bleeding symptoms in corticosteroid‐resistant ITP patients. [ABSTRACT FROM AUTHOR]