Xenogen-Free Stem Cell Preparation Enhances Safety and Efficacy

Introduction: Fetal bovine serum (FBS) is the conventional culture supplement for the isolation and expansion of mesenchymal stem cells (MSCs). We have previously shown the resultant intracellular contamination of FBS causes an adverse response after intra-articular injection of MSCs in horses. Our objective was to evaluate immune response after repeated intra-articular injection of autologous MSCs after culture expansion with and without FBS.

Materials and Methods: Bone marrow MSCs were cultured using conventional technique (FBS; n = 6) or with xenogen-free culture media (XENO-FREE; n = 12). MSCs from both groups were extensively washed prior to intra-articular injection. On day 0, MSCs were injected alone and on day 29, MSCs were injected along with 2.5 ng of lipopolysaccharide (LPS). Clinical reaction, antibody titer against FBS, cytotoxic response against MSCs, and synovial MSC concentration were assessed after both injections.

Results: There was no difference in lameness, but significantly more edema in the FBS-MSC group (days 1, 30 and 36). There was no change in systemic antibody titer against FBS in either group; however, cytotoxic responses against MSCs were only present in the FBS group. Synovial MSC concentration was positive for colonies more frequently and had a higher colony number in the Xeno-free group.

Discussion/Conclusion: This is further evidence for immune recognition of FBS-contaminated MSCs resulting in immune mediated rejection of autologous MSCs, despite minimal differences in visible clinical reaction.

Acknowledgment: Funding by Linda and Dennis H. Clark’68 Chair in Equine Studies and the Link Endowment for Equine Research.