OC 20.5 - Haemophilia-mediated bleeding induces red pulp macrophage expansion

Sunday, July 10, 2022

11:45 AM – 12:00 PM

Location: ExCel Center, ICC Capital Suite Room 1

Presentation Format: In-Person

Presenting Author(s)

Heike C. Hawerkamp, PhD

Postdoctoral Researcher
School of Medicine, Trinity Biomedical Sciences Institute, Trinity College Dublin, Dublin 2, Ireland
Dublin, Dublin, Ireland

Co-Author(s)

AY

Aoife Yeow

PhD student
School of Medicine, Trinity Biomedical Sciences Institute, Trinity College Dublin, Dublin 2, Ireland
Dublin, Dublin, Ireland
CB

Ciara Byrne

Postdoctoral researcher
School of Medicine, Trinity Biomedical Sciences Institute, Trinity College Dublin, Dublin 2, Ireland
Dublin, Dublin, Ireland
AC

Anne Chevalier

Postdoctoral researcher
School of Medicine, Trinity Biomedical Sciences Institute, Trinity College Dublin, Dublin 2, Ireland
Dublin, Dublin, Ireland
LM

Laura Matarazzo

Postdoctoral researcher
School of Medicine, Trinity Biomedical Sciences Institute, Trinity College Dublin, Dublin 2, Ireland
Dublin, Dublin, Ireland
JO

Jamie M. O’Sullivan, PhD

StAR Research Lecturer
Irish Centre for Vascular Biology, School of Pharmacy and Biomolecular Sciences, Royal College of Surgeons in Ireland, Dublin, Ireland
Dublin, Dublin, Ireland
VK

Vincent P. Kelly

Professor
School of Biochemistry& Immunology, Trinity Biomedical Sciences Institute, Trinity College Dublin, Dublin 2, Ireland.
Dublin, Dublin, Ireland
BG

Bagirath Gangadharan

Professor
Baxalta Innovations GmbH, A Member of the Takeda Group of Companies, Vienna, Austria.
Vienna, Wien, Austria
BR

Birgit M. Reipert

Professor
Baxalta Innovations GmbH, A Member of the Takeda Group of Companies, Vienna, Austria.
Vienna, Wien, Austria
JO

James S. O'Donnell, MB, PhD

Professor of Haematology
Irish Centre for Vascular Biology, Royal College of Surgeons in Ireland,Dublin, Ireland
Dublin, Dublin, Ireland
Peter L. Turecek, PhD, PharmD

Professor
Baxalta Innovations GmbH, a Takeda company
Vienna, Wien, Austria
PF

Padraic G. Fallon

Professor
Trinity College Dublin
Dublin, Dublin, Ireland

Background: Haemophilia A is an X-linked bleeding disorder caused by a deficiency in the blood clotting protein, factor VIII (F8). Patients with haemophilia suffer from recurrent bleeding episodes of varying severity. The initial inflammation in joints is caused by synovial macrophages that constantly remove the accumulating iron deposits from erythrocytes entering the joints in a bleeding episode. Another cell type important in the iron recycling are splenic red pulp macrophages (RPM). Due to their unique location their main task is to scavenge damaged or aged erythrocytes.

Aims: To investigate underlying immunological mechanisms in haemophilia A, we have generated a novel factor 8 deficient (F8em1) mouse with a deletion in exon 1 using CRISPR/Cas technology. Here we aim to investigate RPMs in haemophilia, and especially their changes and adaptations during bleeding episodes in spontaneous bleeding and a model of haemophilic arthropathy.

Methods: RPMs in spleens from F8em1 and wild-type mice were analysed via flow cytometry using their characteristic low expression of the marker CD11b and high expression of macrophage marker F4/80. Changes in RPM were analysed in F8em1 mice with spontaneous bleeding and in modelled haemophilic arthropathy. We further investigated the receptor for iron uptake (transferrin receptor, CD71) during bleeding episodes via flow cytometry. Systemic iron concentrations were measured during modelled haemophilic arthropathy.

Results: While F8em1 mice without bleeds do not differ from WT animals in their RPM percentage, both spontaneous bleeding and modelled haemophilic arthropathy, significantly increased RPM. This percentage inversely correlated with hematocrit. The expansion of RPM is seen together with a strong upregulation of CD71. We further report a strong iron release before the onset of RPM expansion.

Conclusion(s): F8em1 mice respond to a bleeding with a strong expansion of RPMs, most profound at 7 days after injury. This expansion is probably facilitated by a rapid systemic iron overload.