MPO and colitis: While the attenuation of colitis by MSCs has been previously linked to modification of T-cell responses, studies in immunodeficient mice with dextran sodium sulfate (DSS)-induced colitis linked the therapeutic properties of MSCs with reduced MPO levels and further demonstrated a reduction in endoplasmic stress and the activation of the unfolded protein response, which is likely to contribute to oxidative stress via the generation of ROS in intestinal inflammation.37,49