Mesenchymal stem cell deficiency influences megakaryocytopoiesis through the TNFAIP 3/ NF ‐κB/ SMAD pathway in patients with immune thrombocytopenia

Summary 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.