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A perisinusoidal niche for extramedullary haematopoiesis in the spleen.

ABSTRACT: Haematopoietic stresses mobilize haematopoietic stem cells (HSCs) from the bone marrow to the spleen and induce extramedullary haematopoiesis (EMH). However, the cellular nature of the EMH niche is unknown. Here we assessed the sources of the key niche factors, SCF (also known as KITL) and CXCL12, in the mouse spleen after EMH induction by myeloablation, blood loss, or pregnancy. In each case, Scf was expressed by endothelial cells and Tcf21(+) stromal cells, primarily around sinusoids in the red pulp, while Cxcl12 was expressed by a subset of Tcf21(+) stromal cells. EMH induction markedly expanded the Scf-expressing endothelial cells and stromal cells by inducing proliferation. Most splenic HSCs were adjacent to Tcf21(+) stromal cells in red pulp. Conditional deletion of Scf from spleen endothelial cells, or of Scf or Cxcl12 from Tcf21+ stromal cells, severely reduced spleen EMH and reduced blood cell counts without affecting bone marrow haematopoiesis. Endothelial cells and Tcf21(+) stromal cells thus create a perisinusoidal EMH niche in the spleen, which is necessary for the physiological response to diverse haematopoietic stresses.

SUBMITTER: Inra CN

PROVIDER: S-EPMC4838203 | biostudies-literature | 2015 Nov

REPOSITORIES: biostudies-literature

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A perisinusoidal niche for extramedullary haematopoiesis in the spleen.

Inra Christopher N CN Zhou Bo O BO Acar Melih M Murphy Malea M MM Richardson James J Zhao Zhiyu Z Morrison Sean J SJ

Nature 20151116 7579

Haematopoietic stresses mobilize haematopoietic stem cells (HSCs) from the bone marrow to the spleen and induce extramedullary haematopoiesis (EMH). However, the cellular nature of the EMH niche is unknown. Here we assessed the sources of the key niche factors, SCF (also known as KITL) and CXCL12, in the mouse spleen after EMH induction by myeloablation, blood loss, or pregnancy. In each case, Scf was expressed by endothelial cells and Tcf21(+) stromal cells, primarily around sinusoids in the re ...[more]

PMID: 26570997

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Project description:IntroductionAround 5% of the world's population is expected to have some degree and type of thalassaemia. Beta thalassaemia (BT) occurs due to a deficient production of the beta-globin chain of haemoglobin. Extramedullary haematopoiesis (EMH) is one of the complications of BT, mainly observed in minor/intermedia subtypes. EMH is the production of blood cells outside the marrow as a compensatory response to longstanding hypoxia. Due to chronic transfusions, it is not expected in patients with beta-thalassaemia major (BTM). However, there are increasingly reported cases of EMH in BTM. The incidence of EMH in BTM is thought to be <1%. We aim to pool the available data and provide cumulative evidence on the occurrence of EMH in BTM patients.MethodsThis is a systematic review of case reports, series, and retrospective studies that presented data on the occurrence of EMH in BTM patients. Data were recorded and analyzed in Microsoft Excel 2016 and SPSS 26. The protocol has been registered in PROSPERO: CRD42021242943.ResultsData from 253 cases of EMH in BTM patients were extracted with a mean age of 35.3 years. Mean haemoglobin at presentation with EMH was 8.2 mg/dL. Lower limb weakness was the most common presenting feature (N = 23) (paraspinal EMH). Magnetic resonance imaging (MRI) was the most widely used diagnostic modality (226). Overall, blood transfusion was the commonest reported treatment (30), followed by radiotherapy (20), surgery (15), hydroxyurea (12), steroids (6), and exchange transfusion (2). An outcome was reported in 20% of patients, all recovered, except one who died as a result of nosocomial infection.ConclusionEMH is rare in BTM and can occur in any organ system with varied clinical features. MRI can effectively diagnose EMH, and conservative management has similar results compared to invasive treatments. Larger studies, focussing on outcomes may enhance guidelines on preventive and therapeutic strategies for managing EMH in BTM.KEY MESSAGESExtramedullary haematopoiesis is a rare complication in beta thalassaemia. Although it is more common in non-transfusion dependent thalassaemia, increasingly reported cases suggest a higher prevalence of EMH in TDT than what is known before.There are no clear guidelines on the management of EMH in TDT, with reported patients showing similar outcomes with conservative invasive treatment modalities.More extensive and preferably prospectively designed studies are required focussing on the management of EMH and its outcomes in patients with TDT to formulate evidence-based guidelines.

Dataset Information

A perisinusoidal niche for extramedullary haematopoiesis in the spleen.

Publications

A perisinusoidal niche for extramedullary haematopoiesis in the spleen.

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