1/11 www.jpnim.com Open Access eISSN: 2281-0692 Journal of Pediatric and Neonatal Individualized Medicine 2020;9(1):e090118 doi: 10.7363/090118 Received: 2019 Feb 21; revised: 2019 Jul 10; accepted: 2019 Jul 11; published online: 2020 Feb 10 Multiple specialized stem cell niches characterize hematopoiesis in the human fetal liver Daniela Fanni 1 , Francesco Angotzi 1 , Clara Gerosa 1 , Doris Barcellona 2 , Giancarlo Senes 1 , Federica Lai 1 , Giovanni Martino 3 , Stefano Ascani 4 , Vassilios Fanos 5 , Gavino Faa 1 1 Department of Pathology, University of Cagliari, “S. Giovanni di Dio” University Hospital, Cagliari, Italy 2 Department of Medical Sciences and Public Health, University of Cagliari, Cagliari, Italy 3 Hematology and Clinical Immunology, University of Perugia, Perugia, Italy 4 Institute of Pathology, Azienda Ospedaliera S. Maria Terni, University of Perugia, Perugia, Italy 5 Neonatal Intensive Care Unit, University of Cagliari, Cagliari, Italy Abstract Before birth, different organs retain hematopoiesis. The liver is involved in the 6 th -8 th week of gestation. The hepatic hematopoietic stem cell (HSC) niche begins when HSCs colonize the liver and make contact with sinusoidal endothelial cells. The aim of this study is to characterize the development of each hematopoietic cell lineage in 9 human liver specimens between 10 and 29 weeks of gestation with immunohistochemistry. Hematopoietic activity was coherent with gestational age. Erythropoiesis was the greatest fraction of fetal liver hematopoiesis: myeloid/erythroid ratio was inverted compared to the adult bone marrow. Myelopoiesis was compartmentalized in the periportal zone. Factor-VIII-positive cells were small, with a megakaryoblast-like morphology. Lymphoid precursors were absent. A small quantity of T and B lymphocytes was found. CD34-reactive hematopoietic stem and progenitor cells were found in a minority of cells. The understanding of the hematopoietic process during gestation could in the future contribute to better understand child and adult hematologic conditions. Keywords Liver, stem cell niches, hepatic hematopoiesis, human, erythropoiesis, myelopoiesis. Corresponding author Francesco Angotzi, Department of Pathology, University of Cagliari, “S. Giovanni di Dio” University Hospital, Cagliari, Italy; email: frangotzi@gmail.com. Original article