No abstract

Bone marrow transplantation (BMT) to treat severe hematologic malignancies often leads to potentially fatal acute graft-versus-host disease (GVHD), despite attempts at better donor-recipient matching and/or use of immunosuppressive agents. We report that embryo-derived PreImplantation Factor (PIF) plays a determining role in developing maternal/host tolerance toward the semiallogeneic or total allogeneic embryo and in regulating systemic immune response. Synthetic PIF treatment has proven effective in preventing immune attacks in nonpregnant models of autoimmunity. In this study, we tested the capability of PIF to prevent the development of acute GVHD in semiallogeneic or totally allogeneic murine BMT models. We examined the regulatory effect of PIF both in vivo and in vitro to control deleterious GVHD while maintaining its ability to preserve the beneficial graft-versus-leukemia (GVL) effect. Bone marrow and spleen cells from C57BL/6 donors were transplanted in semiallogeneic (C57BL/6xBALB/c) F1 or allogeneic (BALB/c) mice, which were then treated with PIF 1 mg/kg/day for 2 weeks. Short-term PIF administration reduced acute GVHD in both models and increased survival for up to 4 months after semiallogeneic or totally allogeneic BMT. This effect was coupled with decreased skin inflammation (semiallogeneic model) and decreased liver inflammation (both models), as well as reduced colon ulceration (allogeneic model). GVHD-associated cytokine and chemokine gene expression were decreased in the liver. PIF further lowered circulating IL-17 levels, but not IFN-γ levels. Both in vivo and in vitro, PIF treatment was demonstrated to lead to decreased inducible nitric oxide synthase expression and decreased lipopolysaccharide-activated macrophages to lower nitric oxide secretion. Significantly, PIF did not diminish the beneficial GVL effect in the B cell leukemia model. PIF acts primarily by inducing the regulatory phenotype on monocytes/antigen-presenting cells, which controls T cell proliferation. Overall, our data demonstrate that PIF protects against semiallogeneic and allogeneic GVHD long term by reducing both target organ and systemic inflammation and by decreasing oxidative stress, while preserving the beneficial GVL effect.

Acute Radiation Syndrome (ARS) may lead to cancer and death and has few effective countermeasures. Efficacy of synthetic PIF treatment was demonstrated in preclinical autoimmune and transplantation models. PIF protected against inflammation and mortality following lethal irradiation in allogeneic bone marrow transplant (BMT) model. Herein, we demonstrate that PIF imparts comprehensive local and systemic protection against lethal and sub-lethal ARS in murine models. PIF treatment 2 h after lethal irradiation led to 100% survival and global hematopoietic recovery at 2 weeks after therapy. At 24 h after irradiation PIF restored hematopoiesis in a semi-allogeneic BMT model. PIF-preconditioning provided improved long-term engraftment. The direct effect of PIF on bone marrow cells was also demonstrated in vitro: PIF promoted pre-B cell differentiation and increased immunoregulatory properties of BM-derived mesenchymal stromal cells. PIF treatment also improved hematopoietic recovery and reduced systemic inflammatory cytokine production after sub-lethal radiation exposure. Here, PIF also prevented colonic crypt and basal membrane damage coupled with reduced nitric oxide synthetase (iNOS) and increased (B7h1) expression. Global upper GI gene pathway analysis revealed PIF's involvement in protein-RNA interactions, mitochondrial oxidative pathways, and responses to cellular stress. Some effects may be attributed to PIF's influence on macrophage differentiation and function. PIF demonstrated a regulatory effect on irradiated macrophages and on classically activated M1 macrophages, reducing inflammatory gene expression (iNOS, Cox2), promoting protective (Arg1) gene expression and inducing pro-tolerance cytokine secretion. Notably, synthetic PIF is stable for long-term field use. Overall, clinical investigation of PIF for comprehensive ARS protection is warranted.

Over the past decade there has been a growing interest in using mesenchymal stem cells (MSCs) as an immune-regulatory agent for prevention and treatment of various immune disorders including graft-versus-host disease (GVHD), transplanted organ rejection, and autoimmune diseases. However, the high diversity in the results from clinical trials using MSCs for such disorders emphasizes the need for MSCs to be "professionalized" ex vivo to a more defined regulatory phenotype before administering to patients. To this aim, we have established an ex vivo immunomodulatory triple combination treatment (TCT) for MSCs, using IFNc, TGFb, and kynurenine. We show that pretreated MSCs acquire an immunomodulatory phenotype, have improved regulatory functions, and upregulate the expression of inducible nitric oxide synthase, indoleamine 2,3-dioxygenase, cyclooxygenase-2 (COX2), heme oxygenase 1, leukemia inhibitory factor (LIF), and programmed death ligand 1. We define the pathway of kynurenine induced aryl hydrocarbon receptor activation in MSCs and how it contributes to the upregulation of COX2 expression and IL-6 downregulation. The combination of reduced IL-6 secretion with enhanced LIF expression leads to the inhibition of Th17 differentiation in coculture of TCT MSCs and lymphocytes. To test the immunomodulatory function of TCT MSCs in vivo, we used the cells as GVHD prophylaxis in a GVHD mouse model. TCT MSCs administration significantly decreased GVHD score and improved mouse survival. Importantly, single administration could attenuate disease symptoms for more than 3 weeks. Based on these results, we suggest considering TCT MSCs as an improved cell therapy for systemic diseases with an underlying inflammatory and immunologic etiology.

Small leucine rich proteoglycans (SLRPs), including Biglycan, have key roles in many organ and tissue systems. The goal of this article is to review the function of Biglycan and other related SLRPs in mineralizing tissues of the skeleton. The review is divided into sections that include Biglycan’s role in structural biology, signaling, craniofacial and long bone homeostasis, remodeled skeletal tissues, and in human genetics. While many cell types in the skeleton are now known to be affected by Biglycan, there are still unanswered questions about its mechanism of action(s).