Marta Serafini

Hematopoietic reconstitution by multipotent adult progenitor cells: precursors to long-term hematopoietic stem cells

For decades, in vitro expansion of transplantable hematopoietic stem cells (HSCs) has been an elusive goal. Here, we demonstrate that multipotent adult progenitor cells (MAPCs), isolated from green fluorescent protein (GFP)-transgenic mice and expanded in vitro for >40–80 population doublings, are capable of multilineage hematopoietic engraftment of immunodeficient mice. Among MAPC-derived GFP+CD45.2+ cells in the bone marrow of engrafted mice, HSCs were present that could radioprotect and reconstitute multilineage hematopoiesis in secondary and tertiary recipients, as well as myeloid and lymphoid hematopoietic progenitor subsets and functional GFP+ MAPC-derived lymphocytes that were functional. Although hematopoietic contribution by MAPCs was comparable to control KTLS HSCs, approximately 103-fold more MAPCs were required for efficient engraftment. Because GFP+ host-derived CD45.1+ cells were not observed, fusion is not likely to account for the generation of HSCs by MAPCs.

Characterization of CD20-Transduced T Lymphocytes as an Alternative Suicide Gene Therapy Approach for the Treatment of Graft-Versus-Host Disease

We have previously proposed the CD20 molecule as a novel suicide gene for T lymphocytes in the context of allogeneic bone marrow transplantation, because CD20 can be used both as a selection marker and as a killer gene after exposure to the anti-CD20 therapeutic antibody rituximab. We now report on preclinical studies using this novel system, in which the best transduction protocol, reproducibility, yield, feasibility, and functionality of the transduced T lymphocytes have been investigated with a large donor series. Wild-type human CD20 cDNA was transduced into human T lymphocytes, using a Moloney-derived retroviral vector. Alternative protocols were tested by employing either one or four spinoculations (in which cells are centrifuged in the presence of retroviral vector supernatant) and stimulating T cells with phytohemagglutinin (PHA) or anti-CD3/CD28. One spinoculation alone was sufficient to obtain approximately 30% CD20-positive cells within four experimental days. Four spinoculations significantly increased transduction to 60%. A small difference in transduction efficiency was observed between the two stimulation methods, with PHA being superior to anti-CD3/CD28. Transduced cells could be purified on immunoaffinity columns, with purity reaching 98% and yield being on average 50%. Finally, 86-97% of immunoselected T lymphocytes could be killed in vitro with rituximab and complement. More importantly, the CD20 transgene did not alter the functionality of T lymphocytes with respect to allogeneic recognition and cytotoxic response, anti-Epstein-Barr virus cytotoxic response, antigenic response to tetanus toxoid antigen, interleukin 2 (IL-2), IL-4, and interferon gamma production; chemotaxis in the presence of stromal cell-derived factor 1, phenotype for several activation markers including HLA-DR, CD25, CD69, and CD95, and T cell repertoire.

A human immunodeficiency virus type 1 pol gene-derived sequence (cPPT/CTS) increases the efficiency of transduction of human nondividing monocytes and T lymphocytes by lentiviral vectors

We have investigated the capacity of two human immunodeficiency virus type 1-derived lentivectors, differing in the presence of a 118-bp pol fragment containing the cPPT/CTS element, to transduce human normal primary cells of different hematopoietic lineages. Infection of resting monocytes with a high multiplicity of infection (MOI > 10) revealed that the lentivirus carrying the pol fragment (cPPT) is effective, transducing 75% of cells compared with 36% for the no-cPPT vector. Even at low MOIs (< or =1) the cPPT vector still shows a better transduction efficiency than the no-cPPT vector. Moreover, transduction does not require dendritic cell differentiation. In contrast, infection of nonactivated T lymphocytes showed that both vectors, tested at high MOIs, can transduce a small, although measurable, percentage of cells (up to 10%), which may correspond to G(1a) activated cells as detected by simultaneous staining of DNA and RNA, in our cultures in the presence of medium alone. Furthermore, we show that the sole addition of interleukin 2 or interleukin 15 represents a full proliferative signal under our conditions and permits high transduction efficiency (up to 30% with the cPPT vector and 15% with the no-cPPT vector). Still higher transduction of T lymphocytes can be achieved after stimulation with phytohemagglutinin and interleukin 2 (up to 78% with the cPPT vector vs. 42% with the no-cPPT vector). Finally, both viruses do not transduce either resting or proliferating tonsillar B lymphocytes.

Establishment of bone marrow and hematopoietic niches in vivo by reversion of chondrocyte differentiation of human bone marrow stromal cells

Human bone marrow stromal cells (BMSCs, also known as bone marrow-derived mesenchymal stem cells) can establish the hematopoietic microenvironment within heterotopic ossicles generated by transplantation at non-skeletal sites. Here we show that non-mineralized cartilage pellets formed by hBMSCs ex vivo generate complete ossicles upon heterotopic transplantation in the absence of exogenous scaffolds. These ossicles display a remarkable degree of architectural fidelity, showing that an exogenous conductive scaffold is not an absolute requirement for bone formation by transplanted BMSCs. Marrow cavities within the ossicles include erythroid, myeloid and granulopoietic lineages, clonogenic hematopoietic progenitors and phenotypic HSCs, indicating that complete stem cell niches and hematopoiesis are established. hBMSCs (CD146(+) adventitial reticular cells) are established in the heterotopic chimeric bone marrow through a unique process of endochondral bone marrow formation, distinct from physiological endochondral bone formation. In this process, chondrocytes remain viable and proliferate within the pellet, are released from cartilage, and convert into bone marrow stromal cells. Once explanted in secondary culture, these cells retain phenotype and properties of skeletal stem cells (MSCs), including the ability to form secondary cartilage pellets and secondary ossicles upon serial transplantation. Ex vivo, hBMSCs initially induced to form cartilage pellets can be reestablished in adherent culture and can modulate gene expression between cartilage and stromal cell phenotypes. These data show that so-called cartilage differentiation of BMSCs in vitro is a reversible phenomenon, which is actually reverted, in vivo, to the effect of generating stromal cells supporting the homing of hematopoietic stem cells and progenitors.

Neonatal bone marrow transplantation prevents bone pathology in a mouse model of mucopolysaccharidosis type I

Neonatal bone marrow transplantation (BMT) could offer a novel therapeutic opportunity for genetic disorders by providing sustainable levels of the missing protein at birth, thus preventing tissue damage. We tested this concept in mucopolysaccharidosis type I (MPS IH; Hurler syndrome), a lysosomal storage disorder caused by deficiency of α-l-iduronidase. MPS IH is characterized by a broad spectrum of clinical manifestations, including severe progressive skeletal abnormalities. Although BMT increases the life span of patients with MPS IH, musculoskeletal manifestations are only minimally responsive if the timing of BMT delays, suggesting already irreversible bone damage. In this study, we tested the hypothesis that transplanting normal BM into newborn MPS I mice soon after birth can prevent skeletal dysplasia. We observed that neonatal BMT was effective at restoring α-l-iduronidase activity and clearing elevated glycosaminoglycans in blood and multiple organs. At 37 weeks of age, we observed an almost complete normalization of all bone tissue parameters, using radiographic, microcomputed tomography, biochemical, and histological analyses. Overall, the magnitude of improvements correlated with the extent of hematopoietic engraftment. We conclude that BMT at a very early stage in life markedly reduces signs and symptoms of MPS I before they appear.

Hurler disease bone marrow stromal cells exhibit altered ability to support osteoclast formation

Mucopolysaccharidosis type I (MPS IH; Hurler syndrome) is a rare genetic disorder that is caused by mutations in the α-L-iduronidase (IDUA) gene, resulting in the deficiency of IDUA enzyme activity and intra-cellular accumulation of glycosaminoglycans. A characteristic skeletal phenotype is one of the many clinical manifestations in Hurler disease. Since the mechanism(s) underlying these skeletal defects are not completely understood, and bone and cartilage are mesenchymal lineages, we focused on the characterization of mesenchymal cells isolated from the bone marrow (BM) of 5 Hurler patients. IDUA-mutated BM stromal cells (BMSC) derived from MPS IH patients exhibited decreased IDUA activity, consistent with the disease genotype. The expansion rate, phenotype, telomerase activity, and differentiation capacity toward adipocytes, osteoblasts, chondrocytes, and smooth muscle cells in vitro of the MPS I BMSC lines were similar to those of BMSC from age-matched normal control donors. MPS I BMSC also had a similar in vivo osteogenic capacity as normal BMSC. However, MPS I BMSC displayed an increased capacity to support osteoclastogenesis, which may correlate with the up-regulation of the RANKL/RANK/OPG molecular pathway in MPS I BMSC compared with normal BMSC.

mTORC1 hyperactivation arrests bone growth in lysosomal storage disorders by suppressing autophagy

The mammalian target of rapamycin complex 1 (mTORC1) kinase promotes cell growth by activating biosynthetic pathways and suppressing catabolic pathways, particularly that of macroautophagy. A prerequisite for mTORC1 activation is its translocation to the lysosomal surface. Deregulation of mTORC1 has been associated with the pathogenesis of several diseases, but its role in skeletal disorders is largely unknown. Here, we show that enhanced mTORC1 signaling arrests bone growth in lysosomal storage disorders (LSDs). We found that lysosomal dysfunction induces a constitutive lysosomal association and consequent activation of mTORC1 in chondrocytes, the cells devoted to bone elongation. mTORC1 hyperphosphorylates the protein UV radiation resistance-associated gene (UVRAG), reducing the activity of the associated Beclin 1-Vps34 complex and thereby inhibiting phosphoinositide production. Limiting phosphoinositide production leads to a blockage of the autophagy flux in LSD chondrocytes. As a consequence, LSD chondrocytes fail to properly secrete collagens, the main components of the cartilage extracellular matrix. In mouse models of LSD, normalization of mTORC1 signaling or stimulation of the Beclin 1-Vps34-UVRAG complex rescued the autophagy flux, restored collagen levels in cartilage, and ameliorated the bone phenotype. Taken together, these data unveil a role for mTORC1 and autophagy in the pathogenesis of skeletal disorders and suggest potential therapeutic approaches for the treatment of LSDs.

Description and molecular modeling of two novel HLA alleles: HLA-A*0343 and A*0345

We report the identification of two novel human leucocyte antigen (HLA) in two Caucasian individuals. HLA-A*0343 differs from A*03010101 by four changes at nucleotides 411-414 (CCGG-->TGAA) and by a point mutation at position 418 (G-->C). These differences lead to two amino acid substitutions at codon 114, where arginine has changed into negatively charged glutamic acid, and at codon 116, where aspartic acid has changed into positively charged histidine. Molecular modeling showed that these changes have a profound influence on the overall charge of the F pocket of the groove, resulting in potentially important changes in the peptide repertoire. HLA-A*0345 was found in a hematological female patient candidate to bone marrow transplantation. This new variant differs from HLA-A*03010101 at position 845 (C-->A) encoding an amino acid change of threonine to asparagine at codon 258 located in the alpha3 domain. Molecular modeling does not suggest a substantial role of this substitutions on the interaction with beta2-microglobulin or CD8.

The impact of immunogenetics and clinical factors on the outcome of unrelated cord blood transplantation: The Milano Cord Blood Bank data

In this article we examined the role of HLA incompatibility, of KIR C1 and C2 ligands and of other clinical factors on 99 cord blood transplants performed using single units from Milano Cord Blood Bank (MICB). We analyzed the occurrence of rejection, overall patient survival (OS) and occurrence of acute GvHD >or= 2 grade (severe aGvHD). No correlation was found between the end points and the number of HLA-A,-B, -DRB1 and -DQB1 mismatches. Only HLA-C disparities are associated with the occurrence of rejection (P=0.03). Our results showed that the presence of the C1 ligand in the donor decreased the occurrence of aGvHD (grade >or= 2) in the recipient while recipients of donors expressing the C2 KIR ligand experienced more frequently aGvHD (P=0.03). The HLA-C1 ligand, therefore, proved to have a protective effect towards severe aGvHD. The probability of rejection increased in KIR epitope-mismatched recipient/donor pairs (P=0.01). Finally the stage of disease at transplantation and cell dose were important for patient survival (P=0.003, P=0.048 respectively).

Thrombosis after liver transplantation for hepatocellular carcinoma

The influence of thrombosis on the prognosis of patients with hepatocellular carcinoma (HCC) after liver transplantation (LT) and the role of the commonest inherited thrombophilia abnormalities factor V Leiden and prothrombin G20210A in the development of thrombosis are unknown. We investigated a cohort of patients who underwent LT for HCC with the aim to estimate the incidence rate (IR) of thrombosis, its influence on mortality and re-transplantation rates and, in the frame of a nested case-control study, the role of thrombophilia in donors and recipients for the development of thrombosis. Four-hundred and thirty patients underwent LT and were followed for a median of 7.2 years. Twenty-six recipients (6%) developed thrombosis (IR 1.06 [95%CI: 0.71–1.53] per 100 pts-yr). Mortality rate after LT was 3.95 (95%CI: 3.22–4.79) per 100 pts-yr and was not influenced by thrombosis. Re-transplantation was planned for 33 patients and was more common in patients with thrombosis than in those without (HR 2.50 [95%CI: 0.87–7.17]). The risk of thrombosis was 4 times higher in recipients with thrombophilia than in those without (OR 4.23 [95%CI: 0.99–18.04]) and 6 times higher when the analysis was restricted to venous thrombosis (OR 6.26 [95%CI: 1.19–32.85]). The presence of inherited thrombophilia in the donors did not increase the risk of thrombosis of the recipient. In conclusion, thrombosis is a complication of 6% of patients transplanted for HCC and increases the risk of re-transplantation but not of mortality. The risk of thrombosis, particularly venous, is increased in the presence of thrombophilia abnormalities in the recipients.