Mesenchymal stem cell deficiency influences megakaryocytopoiesis through the TNFAIP3/NF‐κB/SMAD pathway in patients with immune thrombocytopenia

Summary Immune thrombocytopenia ( ITP ) is an autoimmune disease. Mesenchymal stem cells ( MSC s) play important roles in the physiology and homeostasis of the haematopoietic system, including supporting megakaryocytic differentiation from CD 34 + haematopoietic progenitor cells. Tumour necrosis factor alpha‐induced protein 3 ( TNFAIP 3, also termed A20) plays a key role in terminating NF ‐κB signalling. Human genetic studies showed that the polymorphisms of the TNFAIP 3 gene may contribute to ITP susceptibility. In this study, we showed a significant decrease in TNFAIP 3 and increase in NF ‐κB/ SMAD 7 in ITP ‐ MSC s. In co‐cultures with CD 34 + cells, NF ‐κB was overexpressed in MSC s from healthy controls ( HC ‐ MSC s) after transfection with NFKBIA ( I κ B )‐specific short hairpin (sh) RNA s, resulting in MSC deficiency and a reduction in megakaryocytic differentiation and thrombopoiesis. Knockdown of TNFAIP 3 expression using TNFAIP 3 ‐specific sh RNA s in HC ‐ MSC s affected megakaryocytopoiesis. However, IKBKB knockdown corrected megakaryocytopoiesis inhibition in the ITP ‐ MSC s by decreasing NF ‐κB expression. Amplified TNFAIP 3 expression in ITP ‐ MSC s by TNFAIP 3 cDNA can facilitate megakaryocyte differentiation. sh RNA ‐mediated knockdown of SMAD 7 expression rescued the impaired MSC function in ITP patients. Therefore, we demonstrate that a pathological reduction in TNFAIP 3 levels induced NF ‐κB/ SMAD 7 pathway activation, causing a deficiency in MSC s in ITP patients. The ability of ITP ‐ MSC s to support megakaryocytic differentiation and thrombopoiesis of CD 34 + cells was impaired.