Leukemia inhibitory factor: Role in human mesenchymal stem cells mediated immunosuppression
Introduction
Mesenchymal stem cells (MSCs)1 are multipotent progenitor cells with high capacity for proliferation, self-renewal and differentiation into various mesenchymal tissues [1]. They have immunomodulatory properties. They inhibit immune response to allo-antigen in vitro[2], [3], [4], [5], [6], [7], and could be infused to experimental animal models without immediate or late adverse side effects [8]. The infusion of MSCs did prolong graft survival in primate and murine models [8], [9].
Clinically, systemic infusion of haploidentical MSCs suppressed severe graft versus host disease (GVHD) [10], [11]. We need to identify the underlying molecular mechanisms responsible for these immunosuppressive effects in order to anticipate possible harmful results.
Previous studies described a potential role of indoleamine 2,3-dioxygenase (IDO) [7], [12], prostaglandin E2 (PGE2) [2], transforming growth factor (TGF-β), hepatocyte growth factor (HGF) [13], interleukin-10 (IL-10) [14] and human leukocyte antigen-G (HLA-G) [15] as partial mediators of human MSC (hMSC) inhibitory effect in vitro. In addition, MSCs secrete other cytokines, the levels of which increase upon peripheral blood mononuclear cells (PBMC) co-culture with MSC in MSC/MLR, such as interleukin-6 (IL-6), interleukin-8 (IL-8) and vascular epidermal growth factor (VEGF) [2], without confirming their implication in the MSC-mediated inhibitory effect. MSCs suppressed differentiation and function of monocyte-derived dendritic cells [16] and contributed to the expansion of Foxp3+ regulatory T cells [17]. The inhibitory effect of MSC seems to be very complex and involves multiple soluble factors.
Pregnancy represents a fantastic model of immunotolerance. Mothers could tolerate an allogeneic fetus by naturally acting factors without using immunosuppressive treatment. Several mediators are implicated in this phenomenon, including HLA-G and leukemia inhibitory factor (LIF) [18], [19]. We explored the possible involvement of these molecules in ‘MSCs’ inhibitory effect’. Previously, we demonstrated the involvement of HLA-G [15]. In this work we analyzed implication of LIF in MSCs’ inhibitory effect.
LIF is a functional glycoprotein cytokine [20], named according to its ability to inhibit the proliferation of a myeloid leukemic cell line. It coordinates the humoral and cellular immune response cytokines and exhibits intrinsic antiviral activity that represents the first line of defense against pathogens [21]. LIF plays an essential role in establishing pregnancy, enabling an allogeneic fetus to avoid rejection by the mother [19], [22], prolongs allogeneic skin graft survival in mouse and is linked to transplantation tolerance [23], [24], [25]. LIF induces in vivo expansion of bone marrow progenitor cells that accelerate hematopoietic reconstitution [26] enabling the maintenance of highly enriched competitive repopulating stem cells and supporting hematopoiesis [27], [28].
Production of LIF protein by adult MSC/MLR had never been demonstrated. Based on these facts we investigated whether MSCs secrete LIF protein constitutively and in MSC/MLR, and whether it contributes to MSC-mediated inhibition in vitro.
Mechanistically, we report here that MSCs produced an elevated level of LIF protein in MSC/MLR, and that use of LIF-neutralizing antibody can partially counterbalance MSC-mediated immunosuppression. In addition, LIF was a contributory factor in expression of Foxp3+ regulatory cells.
Section snippets
Isolation and culture of human bone marrow mesenchymal stem cells (hMSC)
Bone marrow (BM) aspirates were drawn from patients undergoing total hip replacement surgery after informed consent and were used in accordance with the procedures approved by the human experimentation and ethic committees of St. Antoine hospital (Paris/France). The BM aspirate (10–20 ml) was combined with Iscove’s Medium (Biochrom, Berlin, Germany) and centrifuged at 200g for 10 min at 20 °C. The cells were then re-suspended and plated at 50,000 cells/cm2 in α-MEM (Invitrogen, Gergy, France)
Characteristics of human MSC
At the end of passage P2, the cells were negative for hematopoietic antigens CD45 and CD34 and exhibited an immunophenotype characteristic for hMSC: CD73, CD90 and CD105. MSCs were able to differentiate into osteogenic, chondrogenic and adipogenic cells as shown in Fig. 1.
Previous results have demonstrated that hMSCs are able to suppress an ongoing immune response by inhibiting the T-cell proliferation stimulated in a MLR or by mitogens. Therefore, we first examined the hMSC-mediated
Discussion
Previous studies showed that TGF-β, HGF, IL-10, PGE2, IDO and HLA-G are produced by MSCs during inhibition of allogeneic lymphocytes [27], [12]. MSCs express cytokines and growth factor genes that support hematopoiesis. One of these factors is LIF [33]. LIF has been claimed to promote the survival [33], [34] and the ex vivo expansion of hematopoietic stem cells (HSC) in combination with the stromal cell line [35]. Additionally LIF enhances the formation of megakaryocytic colonies [36], [37],
References (56)
- et al.
Human mesenchymal stem cells modulate allogeneic immune cell responses
Blood
(2005) - et al.
Mesenchymal stem cells inhibit lymphocyte proliferation by mitogens and alloantigens by different mechanisms
Exp. Cell Res.
(2005) - et al.
Human bone marrow stromal cells inhibit allogeneic T-cell responses by indoleamine 2,3-dioxygenase-mediated tryptophan degradation
Blood
(2004) - et al.
Mesenchymal stem cells suppress lymphocyte proliferation in vitro and prolong skin graft survival in vivo
Exp. Hematol.
(2002) - et al.
Treatment of severe acute graft-versus-host disease with third party haploidentical mesenchymal stem cells
Lancet
(2004) - et al.
Human bone marrow stromal cells suppress T-lymphocyte proliferation induced by cellular or nonspecific mitogenic stimuli
Blood
(2002) - et al.
Human mesenchymal stem cells alter antigen-presenting cell maturation and induce T-cell unresponsiveness
Blood
(2005) - et al.
Human mesenchymal stem cells inhibit differentiation and function of monocyte-derived dendritic cells
Blood
(2005) - et al.
HLA-G in transplantation: a relevant molecule for inhibition of graft rejection?
Am. J. Transplant.
(2003) - et al.
M-CSF and Th2-type cytokines by T cells at fetomaternal interface is associated with pregnancy loss
J. Reprod. Immunol.
(2001)