Senescent Mesenchymal Stem Cells Present at the Early Post Allogeneic Hematopoietic Stem Cell Transplantation Period Are Associated with an Increased Incidence of Acute Graft-Versus Host Disease and Increased Plasma Levels of Fas Ligand
Authors: Rivera Daniel , Osugui Lika , Muntion Sandra , Alcoceba Miguel , Rodriguez Concepcion , Ortega Rebeca , Espinosa Natalia , Gomez de la Torre Ana , Rico Ana , López-Parra Miriam , Redondo Alba , Villarón Eva , López Cadenas Félix , Preciado Silvia , Díez-Campelo Maria , Corral Lucía López , González Marcos , Caballero Dolores , Sanchez-Guijo Fermin 
Published: October 2019

Abstract
Introduction
Mesenchymal stem cells (MSC) are a key component of the hematopoietic niche. In the allogeneic hematopoietic stem cell transplantation (allo-HSCT) setting, the bone marrow stroma, and thus, their MSC remain of host origin. In a preliminary study we observed that, some patients at the early post allo-HSCT period, presented senescent bone marrow (BM) MSC, a finding that has not been previously described nor studied.
The aims of our current study were: a) To multiparametrically characterize BM MSC at the early post allo-HSCT period (day +21). b) To confirm senescence of MSC and correlate with clinical and biological parameters (including biomarkers). c) To compare these cells with those from healthy donors.
Methods
We obtained BM samples on the day +21 post allo-HSCT from 136 patients. MSC were isolated, ex-vivo expanded and characterized, according to the criteria of the International Society for Cellular Therapy. We also obtained samples from peripheral blood at same day +21, for the study of biomarkers, which were analyzed by Luminex technique. The data were correlated with information from complete blood counts (CBC), and the morphological study of the bone marrow the same day. MSC from healthy donors were used as control.
Results
Patient baseline and transplant related characteristics are detailed in table 1. MSC were expanded ex-vivo showing normal growth, which were cryopreserved in passage 3 in the 33% (n=45/136) of the patients (Group-MSC-N). On the other hand, the remaining 67% (n=91/136), MSC showed premature signs of senescence, thus, not reaching to passage 1 (Group-MSC-S). Full BM chimerism on day+21 was seen in both groups (p=0.03). Concerning acute graft versus-host disease (aGVHD), in the Group-MSC-S, the incidence was 73% compared to 44% in the Group-MSC-N (p=0.001). The median time of the onset of aGVHD was 43 and 37 days respectively (p=0.04). The majority of cases presented with grades I-II in both groups. Plasma levels of biomarkers showed increased levels of Fas Ligand in the Group-MSC-S (p=0.009). There were no statistically significant differences regarding mortality nor relapse rates.
Conclusions
Bone marrow Mesenchymal stem cells may be severely damaged in some allo-HSCT recipients early after transplantation (day+21). This fact strongly correlates with the risk of development of acute GVHD.

Disclosures
Díez-Campelo: Novartis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Celgene: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau.