ALBERT

Description: Although many literature data are available on the role of Notch signaling in T-cell acute lymphoblastic leukemia (ALL) biology, the importance of this molecular pathway in the development of B-lineage ALL (B-ALL) cells in the BM microenvironment is unknown so far. In this study, we used anti-Notch molecules neutralizing Abs and γ-secretase inhibitor (GSI) XII to investigate the role of the Notch signaling pathway in the promotion of human B-ALL cell survival in presence of stromal cell support. The treatment with combinations of anti-Notch molecule neutralizing Abs resulted in the decrease of B-ALL cell survival, either cultured alone or cocultured in presence of stromal cells from normal donors and B-ALL patients. Interestingly, the inhibition of Notch-3 and -4 or Jagged-1/-2 and DLL-1 resulted in a dramatic increase of apoptotic B-ALL cells by 3 days, similar to what is obtained by blocking all Notch signaling with the GSI XII. Our data suggest that the stromal cell–mediated antiapoptotic effect on B- ALL cells is mediated by Notch-3 and -4 or Jagged-1/-2 and DLL-1 in a synergistic manner.

Description: Alagille syndrome (ALGS), or arteriohepatic dysplasia, is a congenital multisystem disease due to Notch signalling pathway mutations, most commonly affecting JAG1 (ALGS type 1), and more rarely NOTCH2 (ALGS type 2), leading to hepatic, lung, renal and ocular dysfunction (chronic cholestasis, peripheral pulmonary artery stenosis, dysplastic kidneys pigmentary retinopathy), and skeletal abnormalies (minor vertebral segmentation, characteristic facies, posterior embryotoxon/anterior segment defects). ALGS is an autosomal dominant disease, but it is characterized also by variable penetrance and clinical expression and somatic/germline mosaicism. A 20-year-old man with ALGS was admitted to the University Hospital of Verona because of pancytopenia. Following analyses led to the diagnosis of Philadelphia chromosome/bcr-abl-negative, CD10-positive, B-lineage acute lymphoblastic leukemia (common B-ALL). In order to identify the genetic components involved in this complex phenotype, we sequenced the exome of a bone marrow sample collected from the patient. By genome interpretation with Knome pipeline applied to the reference genome UCSC hg19, we found missense variants both in NOTCH2 (E38K) and JAG1 (P871R) genes that are mainly involved in the syndrome, although their effect on protein function was predicted not to be deleterious. However, we detected putative damaging mutations in genes such as PAX5 (R38H) and NOTCH1 (K1821N) which might be strongly related to the observed disease. In fact, PAX5 is a member of PAX protein family of transcription factors implicated into regulation of early development, that binds NOTCH2 and likely altering its functionality. On the other hand, NOTCH1 is involved in cell growth and proliferation and thus the predicted alteration of function of the corresponding protein may have an important role in neoplastic transformation. Disclosures: No relevant conflicts of interest to declare.

Description: Bone is one of the most frequently transplanted tissues, with allografts and autografts accounting for more than 80% of total grafts. Synthetic biomaterials in association with autologous or allogeneic mesenchymal stromal cells (MSCs) represent a valid alternative in orthopaedic and maxillofacial surgery. Aim of REBORNE consortium is to perform clinical trials using standardized protocols based on advanced biomaterials and MSCs. Aim of our Unit was to assess MSC immune modulatory properties in presence of a novel biomaterial consisting of hydroxyapatite and tricalcium-phosphate (HA/TCP, Biomatlante, France) as scaffold for MSC delivery. We assessed immune modulatory properties, in terms of immunophenotype, inhibitory and anti-apoptotic effects, of MSCs of different origin when associated with the HA/TCP biomaterial, including bone marrow-derived mesenchymal stromal cells (BM-MSCs), adipose-derived MSCs (ASCs) and cord blood-derived MSCs (CB-MSCs). The culture of all MSCs with HA/TCP, did not modulate the anti-apoptotic and suppressive features of all MSCs toward sorted-T, B and NK lymphocytes as compared to standard culture setting. When exposed to inflammatory cytokines, such as IFN-γ and TNF-α, all MSCs were induced to acquire the suppressive phenotype, characterized by MHC-1 and CAM molecules up-regulation, and de novo expression of HLA-DR molecules. The long-term culture of BM-MSCs with HA/TCP induced an osteoblast-like phenotype, as indicated by the up-regulation of osterix and osteocalcin transcription. The differentiation process is promoted in all MSC types, but especially in BM-MSCs, by dexamethasone and, to a higher extent, BMP-4 treatment. In view of using MSCs for advanced therapies in allogeneic setting, we evaluated the immunogenicity and immune modulatory features of pre-differentiated MSCs in association with HA/TCP towards both innate and adaptive immune cells, as well as the molecular pathways involved in MSC-mediated immune regulation. MSC-derived osteoblasts did not induce immune cell activation, as demonstrated by co-culture of unstimulated immune effector cells with pre-differentiated MSCs. We found a lower suppressive capability of pre-differentiated MSCs towards stimulated T and NK cells. However, some inhibitory effects could be exerted by BMP-4 treated-MSCs, and could be related to the presence of undifferentiated MSCs in culture, which could inhibit lymphocyte proliferation. The balance between the number of bone depositing osteocyte-like MSCs and immunosuppressive undifferentiated MSCs could be useful, in vivo, to promote bone healing and to reduce local inflammation, respectively. We then investigated in pre-differentiated MSCs the molecular mechanisms involved in the inhibition of T cell proliferation, by interfering with IDO and COX-2 activation. We found that pre-differentiated MSCs switched on their suppressive machinery by activating both IDO, which plays a central role in immune regulation, and COX-2, whose role is not significant in undifferentiated MSCs. COX-2 is produced rapidly as inflammation mediator after fracture, and recent data highlighted the role of COX-2 in improving fracture healing. In conclusion, this study increases the knowledge on MSC biology and gives pre-clinical data concerning the use of allogeneic MSC in combination with ceramic scaffolds to treat bone defects. Disclosures: No relevant conflicts of interest to declare.

Description: Human bone marrow Mesenchymal Stromal Cells (MSC) are potent modulators of T cell activation and proliferation, mainly through the production of partially defined soluble factors, including the IFN-g-induced tryptophan-degrading enzyme IDO, a key immunosuppressive effector pathway. Actually, MSC may affect the functions of virtually all immune effector cells, including B cells. However, current literature concerning MSC immunomodulatory activity on B cells is still controversial, due to both biological peculiarities of B cells, which do not produce IFN-γ, a key MSC-triggering cytokine, and to different and poorly comparable experimental approaches. Human purified B cells, either resting or activated for 4 days with a stimulation cocktail (CD40 ligand + enhancer polyhistidine mAb MAB050 + rhIL-2 + mouse F(ab’)2 anti-human IgM/IgA/IgG + CpG oligodeoxynucleotide 2006) were co-cultured with MSC, either at resting conditions or following inflammatory priming (MSC pre-incubation with IFN-γ + TNF-α for 48 hours), or with MSC supernatants. CD27-positive (memory) and CD27-negative (naïve) B cell survival, proliferation, and intracellular activation status (through signaling network analysis by Phosphoflow) were assessed. Our results showed that MSC are normally supportive cells, not intrinsically capable of suppressing B cell proliferation, and require inflammatory priming to acquire B cell inhibitory potential. Inflammatory-primed MSC impair significantly activated B cell growth in a cell contact-independent manner, as supernatant is sufficient to provide maximal inhibition of B cell proliferation. B cell inhibition by MSC is not related to either induction of B cell apoptosis or early signaling events necessary for B cell activation. In addition, IDO pathway triggered in IFN-γ-primed MSC seems to have a role also in B cell inhibition by interfering with the tryptophan metabolism. Overall, B cell behavior following the interaction with MSC depends on the functional state of both B cells and MSC. The role of IDO in B cell regulation needs further investigation, as it may be relevant to develop new therapeutic approaches in pathological conditions related to B cell hyper-activation. Disclosures: No relevant conflicts of interest to declare.

Description: Abstract 1924 Bone is among the most frequently transplanted tissue with about 1 million procedures annually in Europe. Allografts and autografts account for more than 80% of total graft volume, despite their considerable disadvantages, including the risk of disease transfer and immunologic rejection, limited supply of bone, costs and complications. Significant growth opportunities exist for synthetic bone grafts in association with mesenchymal stromal cells (MSC) from autologous or allogeneic sources as alternatives to biological bone grafts in orthopaedic and maxillofacial surgery. The objective of REBORNE is to perform clinical trials using advanced biomaterials and cells triggering bone healing in patients. To reach this goal, five phase I clinical studies with 20 patients have been planned in 12 clinical Centers spread in 8 European countries. Aim of the Immunological Unit of Reborne is to assess the MSC immunomodulatory properties in presence of the biomaterial used as scaffold for MSC delivery. All the functional experiments were performed in parallel, by comparing the effects of standard culture conditions and three-dimensional culture setting using MBCP (Biomatlante). Material and methods: Bone marrow MSC were provided from REBORNE Consortium Centers. To perform proliferation assays, different immune effector cells (T, B and NK cells) were stained with CFSE according to manufacturer's protocol. Active caspase-3 cell staining was used for survival quantification of immune effector cells after co-culture experiments. Differentiation potential was evaluated by culturing MSC with two different media containing either bone morphogenetic protein 4 (BMP4) or dexamethasone. After three weeks, osteogenic differentiation was quantified by qRT-PCR, alkaline phosphatase activity and alizarin red staining. Results: We found that primed MSC, pre-treated with the inflammatory cytokines IFNg and TNFa, displayed upregulation of HLA-ABC, CD54, CD106 and de novo expression of HLA-DR, both in standard culture conditions and in association with MBCP. Immune effector cells could be cultured and collected even in presence of MBCP and no significant differences were found between standard- (MSC + effector cells) and 3D-coculture conditions (MSC + MBCP + effector cells), in terms of immune effector cell proliferation. In both experimental conditions MSC suppressed T and NK cell proliferation (% suppression: MSC + T = 68.4; MSC + MBCP + T = 62.4; MSC + NK = 17.5; MSC + MBCP + NK = 20.2) and increased B cell proliferation (MSC + B = +13%; MSC + MBCP + B = +12.3%). In addition, immune effector cells viability was not affected by MBCP and MSC co-culture increased their survival even in presence of MBCP; in fact, in each culture condition the percentage of inhibition of T, B and NK cell apoptosis was higher than 20% in comparison to immune effector cells cultured without MSC. Dexamethasone and BMP4 were capable of inducing MSC differentiation into osteoblast-like cells, as confirmed by qRT-PCR analysis. We demonstrated that BMP4-based medium led to fully differentiated osteoblasts (Osterix+, RUNX2+, DLX5+ and alkaline-phosphatase+). Moreover, MBCP was more efficient in increasing osteoblastic differention as compared to standard culture conditions, as shown by the higher expression of Osteocalcin and Osterix. These data show that the association of MBCP and MSC does not affect MSC properties and suggest that it could be a treatment of choice of bone defects instead of allograft and autograft transplantation. Disclosures: No relevant conflicts of interest to declare.

Description: Alagille syndrome (ALGS), or arteriohepatic dysplasia, is a congenital multisystem disease due to Notch signalling pathway mutations, most commonly affecting JAGGED-1 (ALGS type 1), and more rarely NOTCH-2 (ALGS type 2), leading to hepatic, lung, renal and ocular dysfunction (chronic cholestasis, peripheral pulmonary artery stenosis, dysplastic kidneys pigmentary retinopathy), and skeletal abnormalies (minor vertebral segmentation, characteristic facies, posterior embryotoxon/anterior segment defects). ALGS is an autosomal dominant disease, but it is characterized also by variable penetrance and clinical expression and somatic/germline mosaicism. A 20-year-old man with ALGS was admitted to the University Hospital of Verona because of pancytopenia. Following analyses led to the diagnosis of Philadelphia chromosome/bcr-abl-negative, CD10-positive, B-lineage acute lymphoblastic leukemia (common B-ALL). In order to identify the genetic components involved in this complex phenotype, we sequenced the exome of a bone marrow sample collected from the patient. By genome interpretation with Knome pipeline applied to the reference genome UCSC hg19, we found missense variants both in NOTCH-2 (E38K) and JAGGED-1 (P871R) genes that are mainly involved in the syndrome, although their effect on protein function was predicted not to be deleterious. However, we detected putative damaging mutations in genes such as PAX5 (R38H) and NOTCH-1 (K1821N), which might be strongly related to the observed disease. In fact, PAX5 is a member of PAX protein family of transcription factors implicated into regulation of early development that binds NOTCH-2 and likely altering its functionality. On the other hand, NOTCH-1 is involved in cell growth and proliferation and thus the predicted alteration of function of the corresponding protein may have an important role in neoplastic transformation. Disclosures Martinelli: Novartis: Consultancy, Speakers Bureau; BMS: Consultancy, Speakers Bureau; Pfizer: Consultancy; ARIAD: Consultancy.

Description: Aim of CASCADE is to standardize GMP-grade production and clinical use of Mesenchymal Stromal Cells (MSC). Immunological Unit is aimed at setting up and validating a standardized panel of functional assays to fully characterize the immunomodulatory properties of MSC obtained from bone marrow and adipose tissue through different GMP-grade expansion protocols (platelet lysate- vs. fetal calf serum). Immune cells were isolated using indirect immunomagnetic depletion (purity 〉96%). MSC were expanded in the same medium used for production and harvested at 70% confluence. Primed MSC (pMSC) were obtained after 48h-treatment with rh-IFNγ and rh-TNFα. MSC or pMSC were cocultured with T, B, NK cells for 4 or 6 days, and proliferation was evaluated by CFDA-SE dilution. T cells were stimulated with αCD3 + αCD28 antibodies; B cells were activated with CD40L, its enhancer, IL-2, CpG 2006, and anti-IgM/IgA/IgG; NK cells were activated with 100 U/ml rhIL-2. Cocultures were performed also with specific molecule inhibitors: L-1MT (IDO), snPP (HO-1), NS-398 (COX2), L-NMMA (iNOS) and anti-IFNγ antibody. For MSC immunogenicity assay, allogeneic T cell proliferation was evaluated at day 5 of culture; in addition, NK cells were activated for 2 days with rh-IL2, and MSC and pMSC were used as target cells. Inflammatory milieu significantly upregulated MHC class I and II, CD54, CD106, CD40, CD274, CD112, CD155 expression, and downregulated NKG2D ligands and mesenchymal markers (CD73, CD90, CD105). AT-derived MSC expressed less MHC class II, CD200 and CD106 molecules than BM-MSC. MSC coculture inhibited T and NK cell proliferation without inducing apoptosis, and this effect was greater in presence of primed MSC. Only primed MSC were capable of suppressing B cell proliferation. MSC inhibited apoptosis of resting T, B, and NK cells, while inflammatory priming increased their pro-survival activity. Activation of IDO and HO-1 was the main mechanism involved in MSC immune modulation. MSC never promoted allogeneic T cell proliferation; by contrast, IL-2-activated NK cells could efficiently recognize and kill allogenic unprimed MSC, while primed MSC became insensitive to NK cells. Some differences were observed depending on the origin and culture conditions of clinical-grade MSC. All the experimental protocols to assess MSC inhibitory effects on immune effector cells have been standardized and will be applied for the release of GMP-grade MSC produced inside the CASCADE Consortium. Disclosures: No relevant conflicts of interest to declare.

Description: Developing a therapeutic strategy for lung regeneration still remains complex. Stem cell-based therapeutical approaches have been suggested as a potential tool; among them, human mesenchymal stromal cells (MSC) possess some promising features to this aim. MSC are stem cells residing in many tissue, i.e. bone marrow (BM), adipose tissue, cord blood, lung, etc., and they are capable of differentiating into different cell types of mesodermal origin, such as fat, bone and cartilage. To assess MSC epithelial differentiation potential, through a partially known process called Mesenchymal to Epithelial Transition (MET), MSC were collected from bone (BM) aspirates and lung biopsies after informed consent. MSC were characterized by immunophenotyping and clonogenicity assay. MSC mesodermal differentiation potential was assessed by testing their ability to differentiate into adipocytes, osteoblasts and chondrocytes. MSCs at different culture passages were induced to acquire the epithelial phenotype by culturing in presence of retinoic acid. The epithelial differentiation was checked by quantitative RT-PCR, immunofluorescence and a functional assay based on the Trans Epithelial Electrical Resistance Measurement (TEER). In presence of retinoic acid, MSC from BM and, mostly, lung upregulated a panel of general epithelial genes (cytokeratin 18, occludin, tight junction protein and claudin) and downregulated some specific mesenchymal markers (smooth muscle actin, snail2, vimentin, THY1), as detected by quantitative RT-PCR. Immunofluorescence confirmed the presence of E-cadherin4, occludin and cytokeratin 18 in a small number of cells (about 0,2 %). Trans Epithelial Electrical Resistance (TEER) measurement confirmed that MSC can acquire in vitro partial epithelial polarization after retinoic acid treatment. These data show that MSC can be induced to differentate into cells resembling some morphological, phenotypical and functional properties of epithelial cells. BM-MSC are less prone to acquire an epithelial phenotype as compared to hLung-MSC. Additional in vivo studies on mouse model with lung damage are in progress. Disclosures: No relevant conflicts of interest to declare.

Description: Allogeneic stem cell-based therapy is a promising tool for the treatment of a range of human degenerative and inflammatory diseases. Many reports highlighted the immune modulatory properties of some stem cell (SC) types, such as mesenchymal stromal cells (MSCs), but a comparative study with SCs of different origin, to assess whether immune regulation is a general SC property, is still lacking. To this aim, we applied highly standardized methods employed for MSC characterization to compare the immunological properties of bone marrow-MSCs, olfactory ecto-mesenchymal stem cells, leptomeningeal stem cells, and three different c-Kit-positive SC types, i.e. amniotic fluid SCs, cardiac SCs, and lung SCs. We found that all the analyzed human SCs share a common pattern of immunological features, in terms of expression of activation markers, modulatory activity towards immune effector cells, immunogenicity and molecular inhibitory pathways, with some SC type-related peculiarities. In addition, we found that the inhibitory behaviour is not a constitutive property of SCs, but is acquired as a consequence of immune effector cell activation, as previously described for MSCs. Thus, immune regulation is a general property of stem cells and the characterization of this phenomenon may be useful for a proper therapeutical use of SCs. Disclosures: No relevant conflicts of interest to declare.