The Immunogenicity of Mesenchymal Stem Cells
Abstract
Mesenchymal stem cells (MSCs) have been used for decades to treat a variety of conditions in humans and animals, but consistent and reproducible efficacy has yet to be demonstrated. Two possible reasons for inconsistent efficacy are 1) xenogen contamination from the methods used for MSC preparation, or 2) the use of non-cross matched allogeneic (non-self) MSCs.
Fetal bovine serum (FBS) is the most commonly used culture media supplement for the preparation of MSCs. However, proteins present in media become internalized during the culture period and foreign proteins may be recognized by the recipient immune system after MSC administration. To investigate immune recognition of FBS, we first developed an alternative method of MSC preparation that did not require FBS. We tested bone marrow supernatant (BMS) as an alternative to FBS, and found no differences in MSC preparation other than greater MSC isolation with BMS compared to FBS. In vivo, we noted an adverse clinical response after FBS-MSC administration, which did not occur after BMS-MSC administration. Importantly, we documented antibody mediated destruction of FBS-MSCs, but not BMS-MSCs.
Our laboratory transitioned to exclusively using BMS in the preparation of clinical MSCs in 2018. Retrospective analysis of BMS-MSCs for the treatment of horses with naturally occurring joint disease showed greatly improved return to function with BMS-MSCs compared to our previous clinical experience as well as to previous reports with FBS-MSCs.
To investigate the use of allogeneic MSCs, we identified four MSC donors that were homozygous for well-characterized major histocompatibility complex (MHC) haplotypes. Matched (heterozygous, carrying donor haplotype) and mismatched (dissimilar to donor haplotype) recipients received two intra-articular injections of donor MSCs isolated and expanded in BMS. In all mismatched recipients, there was marked antibody development that resulted in in vitro MSC cytotoxicity, but no sign of immune recognition in MHC-matched recipients.
Our findings definitively demonstrate that MSCs are recognized by the recipient immune system due to xenogen contamination during MSC preparation as well as to donor haplotype mismatch. This understanding will help to advance the use of MSCs clinically, and explains why there has been inconsistent efficacy demonstrated in pre-clinical and clinical trials.
Subject
mesenchymal stem cellimmunogenicity
horse
equine
bone marrow derived MSC
fetal bovine serum
fetal calf serum
allogeneic
autologous
Citation
Rowland, Aileen Long (2021). The Immunogenicity of Mesenchymal Stem Cells. Doctoral dissertation, Texas A&M University. Available electronically from https : / /hdl .handle .net /1969 .1 /195275.