Mesenchymal stromal cells (MSCs) are currently under investigation for the treatment of inflammatory disorders, including Crohn's disease. MSCs are pluripotent cells with immunosuppressive properties. Recent data suggest that resting MSCs do not have significant immunomodulatory activity, but that the immunosuppressive function of MSCs has to be elicited by interferon-γ (IFN-γ). In this article, we assessed the effects of IFN-γ prestimulation of MSCs (IMSCs) on their immunosuppressive properties in vitro and in vivo. To this end, we pretreated MSCs with IFN-γ and assessed their therapeutic effects in dextran sodium sulfate (DSS)- and trinitrobenzene sulfonate (TNBS)-induced colitis in mice. We found that mice treated with IMSCs (but not MSCs) showed a significantly attenuated development of DSS-induced colitis. Furthermore, IMSCs alleviated symptoms of TNBS-induced colitis. IMSC-treated mice displayed an increase in body weight, lower colitis scores, and better survival rates compared with untreated mice. In addition, serum amyloid A protein levels and local proinflammatory cytokine levels in colonic tissues were significantly suppressed after administration of IMSC. We also observed that IMSCs showed greater migration potential than unstimulated MSCs to sites within the inflamed intestine. In conclusion, we show that prestimulation of MSCs with IFN-γ enhances their capacity to inhibit Th1 inflammatory responses, resulting in diminished mucosal damage in experimental colitis. These data demonstrate that IFN-γ activation of MSCs increases their immunosuppresive capacities and importantly, their therapeutic efficacy in vivo.

Since human lactoferrin (hLF) binds to bacterial products through its highly positively charged N terminus, we investigated which of the two cationic domains is involved in its bactericidal activity. The results revealed that hLF lacking the first three residues (hLF ^−3N ) was less efficient than hLF in killing of antibiotic-resistant Staphylococcus aureus, Listeria monocytogenes , and Klebsiella pneumoniae . Both hLF preparations failed to kill Escherichia coli O54. In addition, hLF ^−3N was less effective than hLF in reducing the number of viable bacteria in mice infected with antibiotic-resistant S. aureus and K. pneumoniae . Studies with synthetic peptides corresponding to the first 11 N-terminal amino acids, designated hLF(1–11), and fragments thereof demonstrated that peptides lacking the first three N-terminal residues are less effective than hLF(1–11) in killing of bacteria. Furthermore, a peptide corresponding to residues 21 to 31, which comprises the second cationic domain, was less effective than hLF(1–11) in killing of bacteria in vitro and in mice having an infection with antibiotic-resistant S. aureus or K. pneumoniae . Using fluorescent probes, we found that bactericidal hLF peptides, but not nonbactericidal peptides, caused an increase of the membrane permeability. In addition, hLF killed the various bacteria, most probably by inducing intracellular changes in these bacteria without affecting the membrane permeability. Together, hLF and peptides derived from its N terminus are highly effective against infections with antibiotic-resistant S. aureus and K. pneumoniae , and the first two arginines play an essential role in this activity.