Maurizio Pacifici

The Children's Hospital of Philadelphia, Filadelfia, Pennsylvania, United States

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Publications (185)828.33 Total impact

  • Maurizio Pacifici · Eileen M. Shore
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    ABSTRACT: Activin receptor-like kinase-2 (ALK2), the product of ACVR1, is a member of the type I bone morphogenetic protein (BMP) receptor family. ALK2 exerts key and non-redundant roles in numerous developmental processes, including the specification, growth and morphogenesis of endochondral skeletal elements. There is also strong evidence that BMP signaling plays important roles in determination, differentiation and function of neural cells and tissues. Here we focus on the intriguing discovery that common activating mutations in ALK2 occur in Fibrodysplasia Ossificans Progressiva (FOP) and Diffuse Intrinsic Pontine Gliomas (DIPGs), distinct pediatric disorders of significant severity that are associated with premature death. Pathogenesis and treatment remain elusive for both. We consider recent studies on the nature of the ACVR1 mutations, possible modes of action and targets, and plausible therapeutic measures. Comparisons of the diverse – but genetically interrelated – pathologies of FOP and DIPG will continue to be of major mutual benefit with broad biomedical and clinical relevance.
    No preview · Article · Dec 2015 · Cytokine & growth factor reviews
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    ABSTRACT: Heterotopic cartilage develops in certain pathologic conditions, including those affecting the human temporomandibular joint (TMJ), but the underlying molecular mechanisms remain obscure. This is in part due to the fact that a reliable animal model of such TMJ diseases is not available. Here, we show that aberrant chondrocyte differentiation and ectopic cartilage formation occur spontaneously in proteoglycan 4 (Prg4) mutant TMJ discs without further invasive procedure. By 2 mo of age, mutant disc cells displayed chondrocyte transdifferentiation, accompanied by strong expression of cartilage master gene Sox9 and matrix genes aggrecan and type II collagen. By 6 mo, heterotopic cartilage had formed in the discs and expressed cartilage hypertrophic markers Runx2 and ColX. The ectopic tissue grew in size over time and exhibited regional mineralization by 12 mo. Bone morphogenetic protein (BMP) signaling was activated with the ectopic chondrogenic cells and chondrocytes, as indicated by phosphorylated Smad 1/5/8 nuclear staining and by elevated expression of Bmp2, Bmpr1b, Bmpr2, and BMP signaling target genes. Likewise, we found that upon treatment with recombinant human BMP 2 in high-density micromass culture, mutant disc cells differentiated into chondrocytes and synthesized cartilage matrix more robustly than control cells. Importantly, a specific kinase inhibitor of BMP receptors drastically attenuated chondrogenesis in recombinant human BMP 2-treated mutant disc cultures. Unexpectedly, we found that Prg4 was expressed at joint-associated sites, including disc/muscle insertion and muscle/bone interface, and all these structures were abnormal in Prg4 mutants. Our data indicate that Prg4 is needed for TMJ disc integrity and function and that its absence leads to ectopic chondrogenesis and cartilage formation in conjunction with abnormal BMP signaling. Our findings imply that the BMP signaling pathway could be a potential therapeutic target for prevention or inhibition of ectopic cartilage formation in TMJ disease.
    No preview · Article · Nov 2015 · Journal of dental research
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    Rebekah S Decker · Eiki Koyama · Maurizio Pacifici
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    ABSTRACT: Articular cartilage has obvious and fundamental roles in joint function and body movement. Much is known about its organization, extracellular matrix, and phenotypic properties of its cells, but less is known about its developmental biology. Incipient articular cartilage in late embryos and neonates is a thin tissue with scanty matrix and small cells, while adult tissue is thick and zonal and contains large cells and abundant matrix. What remains unclear is not only how incipient articular cartilage forms, but how it then grows and matures into a functional, complex, and multifaceted structure. This review focuses on recent and exciting discoveries on the developmental biology and growth of articular cartilage, frames them within the context of classic studies, and points to lingering questions and research goals. Advances in this research area will have significant relevance to basic science, and also considerable translational value to design superior cartilage repair and regeneration strategies.
    Full-text · Article · Sep 2015 · Current Osteoporosis Reports
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    ABSTRACT: Chondrogenesis subtends the development of most skeletal elements and involves mesenchymal cell condensations differentiating into growth plate chondrocytes that proliferate, undergo hypertrophy and are replaced by bone. In the pediatric disorder Hereditary Multiple Exostoses, however, chondrogenesis occurs also at ectopic sites and causes formation of benign cartilaginous tumors -exostoses- near the growth plates. No treatment is currently available to prevent or reverse exostosis formation. Here, we asked whether chondrogenesis could be stopped by targeting the hedgehog pathway, one of its major regulators. Micromass cultures of limb mesenchymal cells were treated with increasing amounts of the hedgehog inhibitor HhAntag or vehicle. The drug effectively blocked chondrogenesis and did so in a dose-dependent manner as monitored by: alcian blue-positive cartilage nodule formation; gene expression of cartilage marker genes; and reporter activity in Gli1-LacZ cell cultures. HhAntag blocked chondrogenesis even when the cultures were co-treated with bone morphogenetic protein 2 (rhBMP-2), a strong pro-chondrogenic factor. Immunoblots showed that HhAntag action included modulation of canonical (pSmad1/5/8) and non-canonical (pp38) BMP signaling. In cultures co-treated with HhAntag plus rhBMP-2, there was a surprising strong up-regulation of pp38 levels. Implantation of rhBMP-2-coated beads near metacarpal elements in cultured forelimb explants induced formation of ectopic cartilage that however, was counteracted by HhAntag co-treatment. Collectively, our data indicate that HhAntag inhibits not only hedgehog signaling, but also modulates canonical and non-canonical BMP signaling and blocks basal and rhBMP2-stimulated chondrogenesis, thus representing a potentially powerful drug-based strategy to counter ectopic cartilage growth or induce its involution. This article is protected by copyright. All rights reserved.
    No preview · Article · Sep 2015 · Journal of Cellular Physiology
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    ABSTRACT: Mucopolysaccharidosis (MPS) VII is a lysosomal storage disorder characterized by deficient β-glucuronidase activity, which leads to the accumulation of incompletely degraded glycosaminoglycans (GAGs). MPS VII patients present with severe skeletal abnormalities, which are particularly prevalent in the spine. Incomplete cartilage-to-bone conversion in MPS VII vertebrae during postnatal development is associated with progressive spinal deformity and spinal cord compression. The objectives of this study were to determine the earliest postnatal developmental stage at which vertebral bone disease manifests in MPS VII and to identify the underlying cellular basis of impaired cartilage-to-bone conversion, using the naturally-occurring canine model. Control and MPS VII dogs were euthanized at 9 and 14days-of-age, and vertebral secondary ossification centers analyzed using micro-computed tomography, histology, qPCR, and protein immunoblotting. Imaging studies and mRNA analysis of bone formation markers established that secondary ossification commences between 9 and 14days in control animals, but not in MPS VII animals. mRNA analysis of differentiation markers revealed that MPS VII epiphyseal chondrocytes are unable to successfully transition from proliferation to hypertrophy during this critical developmental window. Immunoblotting demonstrated abnormal persistence of Sox9 protein in MPS VII cells between 9 and 14days-of-age, and biochemical assays revealed abnormally high intra and extracellular GAG content in MPS VII epiphyseal cartilage at as early as 9days-of-age. In contrast, assessment of vertebral growth plates and primary ossification centers revealed no significant abnormalities at either age. The results of this study establish that failed vertebral bone formation in MPS VII can be traced to the failure of epiphyseal chondrocytes to undergo hypertrophic differentiation at the appropriate developmental stage, and suggest that aberrant processing of Sox9 protein may contribute to this cellular dysfunction. These results also highlight the importance of early diagnosis and therapeutic intervention to prevent the progression of debilitating skeletal disease in MPS patients.
    No preview · Article · Sep 2015 · Molecular Genetics and Metabolism
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    Full-text · Dataset · Aug 2015
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    Full-text · Dataset · Aug 2015
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    Full-text · Dataset · Aug 2015
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    ABSTRACT: To determine whether and how transcription factor Erg participates in the genesis, establishment and maintenance of articular cartilage. Floxed Erg mice were mated with Gdf5-Cre mice to create conditional mutants lacking Erg in their joints. Mutant and control joints were subjected to morphological and molecular characterization and also experimental osteoarthritis (OA) surgery. Gene expression, promoter reporter assays and gain- and loss-of-function in vitro tests were used to characterize molecular mechanisms of Erg action. Conditional Erg ablation did not elicit obvious changes in limb joint development and overall phenotype in juvenile mice. Over aging, however, mutant joints became spontaneously deranged and exhibited clear OA-like phenotypic defects. Mutant joints in juvenile mice were more sensitive to surgically induced OA and became defective sooner than operated control joints. Global gene expression data and other studies identified PTHrP and lubricin as possible downstream effectors and mediators of Erg action in articular chondrocytes. Reporter assays using control and mutated promoter/enhancer constructs did indicate that Erg acted on ets DNA binding sites to stimulate PTHrP expression. ERG was up-regulated in severely affected areas in human OA articular cartilage, but remained barely appreciable in less affected cartilage areas. The study shows for the first time that Erg is a critical molecular regulator of articular cartilage's endurance over postnatal life and ability to mitigate spontaneous and experimental OA. Erg appears to do so through its regulation of PTHrP and lubricin expression, factors known for their protective roles in joints. This article is protected by copyright. All rights reserved. © 2015, American College of Rheumatology.
    Full-text · Article · Jun 2015 · Arthritis and Rheumatology
  • Paul C Billings · Maurizio Pacifici
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    ABSTRACT: Heparan sulfate (HS) is a component of cell surface and matrix-associated proteoglycans (HSPGs) that collectively, play crucial roles in many physiologic processes including cell differentiation, organ morphogenesis and cancer. A key function of HS is to bind and interact with signaling proteins, growth factors, plasma proteins, immune-modulators and other factors. In so doing, the HS chains and HSPGs are able to regulate protein distribution, bio-availability and action on target cells and can also serve as cell surface co-receptors, facilitating ligand-receptor interactions. These proteins contain an HS/heparin-binding domain (HBD) that mediates their association and contacts with HS. HBDs are highly diverse in sequence and predicted structure, contain clusters of basic amino acids (Lys, Arg) and possess an overall net positive charge, most often within a consensus Cardin-Weintraub (CW) motif. Interestingly, other domains and residues are now known to influence protein-HS interactions, as well as interactions with other glycosaminoglycans, such as chondroitin sulfate. In this review we provide a description and analysis of HBDs in proteins including amphiregulin, fibroblast growth factor family members, heparanase, sclerostin and hedgehog protein family members. We discuss HBD structural and functional features and important roles carried out by other protein domains, and also provide novel conformational insights into the diversity of CW motifs present in Sonic, Indian and Desert hedgehogs. Finally, we review progress in understanding the pathogenesis of a rare pediatric skeletal disorder, Hereditary Multiple Exostoses (HME), characterized by HS deficiency and cartilage tumor formation. Advances in understanding protein-HS interactions will have broad implications for basic biology and translational medicine as well as for the development of HS-based therapeutics.
    No preview · Article · Jun 2015 · Connective tissue research
  • Rong Han · Maurizio Pacifici · Masahiro Iwamoto · Maria Trojanowska
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    ABSTRACT: Members of the ETS family of transcription factors are involved in several developmental processes including endothelial cell specification and blood vessel formation, but their exact roles remain unclear. The family member Erg is highly expressed in endothelial cells as compared to other developing cell types including chondrocytes, hematopoietic cells and mesodermal cells. To study the specific roles ERG plays in endothelial cell specification and function during early embryogenesis, we conditionally ablated it by mating Erg(loxP/loxP) and Tie2-Cre mice. We found that mutant embryos died by mid-gestation and that angiogenesis and vascular integrity were highly compromised. Our study reveals that ERG has essential and cell autonomous roles in endothelial cell development and blood vessel maintenance.
    No preview · Article · Jun 2015 · Organogenesis
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    ABSTRACT: Hereditary multiple exostoses is a pediatric skeletal disorder characterized by benign cartilaginous tumors called exostoses that form next to growing skeletal elements. Hereditary multiple exostoses patients carry heterozygous mutations in the heparan sulfate (HS)-synthesizing enzymes EXT1 or EXT2, but studies suggest that EXT haploinsufficiency and ensuing partial HS deficiency are insufficient for exostosis formation. Searching for additional players, we analyzed presence and distribution of heparanase in human exostoses. Heparanase was readily detectable in most chondrocytes, particularly in cell clusters. In control growth plates from unaffected persons, however, heparanase was detectable only in hypertrophic zone. Treatment of mouse embryo limb mesenchymal micromass cultures with exogenous heparanase greatly stimulated chondrogenesis and bone morphogenetic protein signaling as revealed by Smad1/5/8 phosphorylation. It also stimulated cell migration and proliferation. Interfering with HS function both with the chemical antagonist Surfen or treatment with bacterial heparitinase up-regulated endogenous heparanase gene expression, suggesting a counterintuitive feedback mechanism that would result in further HS reduction and increased signaling. Thus, we tested a potent heparanase inhibitor (SST0001), which strongly inhibited chondrogenesis. Our data clearly indicate that heparanase is able to stimulate chondrogenesis, bone morphogenetic protein signaling, cell migration, and cell proliferation in chondrogenic cells. These properties may allow heparanase to play a role in exostosis genesis and pathogenesis, thus making it a conceivable therapeutic target in hereditary multiple exostoses. Copyright © 2015 American Society for Investigative Pathology. Published by Elsevier Inc. All rights reserved.
    No preview · Article · Apr 2015 · American Journal Of Pathology

  • No preview · Article · Feb 2015 · Molecular Genetics and Metabolism
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    ABSTRACT: Hereditary Multiple Exostoses (HME) is an autosomal-dominant disorder characterized by benign cartilage tumors (exostoses) forming near the growth plates, leading to severe health problems. EXT1 and EXT2 are the two genes known to harbor heterozygous loss-of-function mutations that account for the vast majority of the primary genetic component of HME. However, patients present with wide clinical heterogeneity, suggesting that modifier genes play a role in determining severity. Our previous work has pointed to an imbalance of β-catenin signaling being involved in the pathogenesis of osteochondroma formation. TCF7L2 is one of the key 'gate-keeper' TCF family members for Wnt/β-catenin signaling pathway, and TCF7L2 and EXT2 are among the earliest associated loci reported in genome wide appraisals of type 2 diabetes (T2D). Thus we investigated if the key T allele of single nucleotide polymorphism (SNP) rs7903146 within the TCF7L2 locus, which is strongly over-represented among T2D cases, was also associated with HME. We leveraged genotype data available from ongoing GWAS efforts from genomics and orthopedic centers in the US, Canada and Italy. Collectively 213 cases and 1890 controls were analyzed and, surprisingly, the T allele was in fact significantly under-represented in the HME patient group [P=0.009; odds ratio=0.737 (95% C.I. 0.587-0.926)]; in addition, the direction of effect was consistent within each individual cohort. Immunohistochemical analyses revealed that TCF7L2 is differentially expressed and distributed in normal human growth plate zones, and exhibits substantial variability in human exostoses in terms of staining intensity and distribution. In summary, the data indicate that there is a putative genetic connection between TCF7L2 and EXT in the context of HME. Given this observation, we suggest that these loci could possibly modulate shared pathways, in particular with respect to β-catenin, and their respective variants interplay to influence HME pathogenesis as well as T2D. Copyright © 2014 Elsevier Inc. All rights reserved.
    No preview · Article · Dec 2014 · Bone
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    Maurizio Pacifici

    Preview · Article · Oct 2014 · Matrix Biology
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    ABSTRACT: Limb development requires the coordinated growth of several tissues and structures including long bones, joints and tendons, but the underlying mechanisms are not wholly clear. Recently, we identified a small drug-like molecule -we named Kartogenin (KGN)- that greatly stimulates chondrogenesis in marrow-derived mesenchymal stem cells (MSCs) and enhances cartilage repair in mouse osteoarthritis (OA) models. To determine whether limb developmental processes are regulated by KGN, we tested its activity on committed preskeletal mesenchymal cells from mouse embryo limb buds and whole limb explants. KGN did stimulate cartilage nodule formation and more strikingly, boosted digit cartilaginous anlaga elongation, synovial joint formation and interzone compaction, tendon maturation as monitored by ScxGFP, and interdigit invagination. To identify mechanisms, we carried out gene expression analyses and found that several genes, including those encoding key signaling proteins, were up-regulated by KGN. Amongst highly up-regulated genes were those encoding hedgehog and TGFβ superfamily members, particularly TFGβ1. The former response was verified by increases in Gli1-LacZ activity and Gli1 mRNA expression. Exogenous TGFβ1 stimulated cartilage nodule formation to levels similar to KGN, and KGN and TGFβ1 both greatly enhanced expression of lubricin/Prg4 in articular superficial zone cells. KGN also strongly increased the cellular levels of phospho-Smads that mediate canonical TGFβ and BMP signaling. Thus, limb development is potently and harmoniously stimulated by KGN. The growth effects of KGN appear to result from its ability to boost several key signaling pathways and in particular TGFβ signaling, working in addition to and/or in concert with the filamin A/CBFβ/RUNX1 pathway we identified previously to orchestrate overall limb development. KGN may thus represent a very powerful tool not only for OA therapy, but also limb regeneration and tissue repair strategies.
    Full-text · Article · Sep 2014 · Developmental Biology
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    Rebekah S Decker · Eiki Koyama · Maurizio Pacifici
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    ABSTRACT: Limb synovial joints are intricate structures composed of articular cartilage, synovial membranes, ligaments and capsule. Each joint has a unique shape, organization and biomechanical function, and articular cartilage itself is rather complex and organized in distinct zones, including the superficial zone that produces lubricans and contains stem/progenitor cells. There has been a great of interest for many years to decipher the mechanisms by which the joints form and come to acquire such unique structural features and diversity. Decades ago, classic embryologists discovered that the first overt sign of joint formation at each prescribed limb site is the appearance of a dense and compact population of mesenchymal cells collectively called the interzone. Work carried out since by several groups has provided evidence that the interzone cells do actively participate in joint tissue formation over developmental time. This minireview provides a succinct but comprehensive description of the many and important recent advances in this field of research. These includes: studies using various conditional reporter mice to genetically trace and track the origin, fate and possible function of joint progenitor cells; studies on the involvement and roles in signaling pathways and transcription factors in joint cell determination and functioning; and studies using advanced methods of gene expression analyses to uncover novel genetic determinants of joint formation and diversity. The overall advances are impressive, and the findings are not only of obvious interest and importance, but have major implications to conceive future translational medicine tools to repair and regenerate defective, overused or aging joints.
    Full-text · Article · Aug 2014 · Matrix biology: journal of the International Society for Matrix Biology
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    E Koyama · C Saunders · I Salhab · R S Decker · I Chen · H Um · M Pacifici · H D Nah
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    ABSTRACT: The Proteoglycan 4 (Prg4) product lubricin plays essential roles in boundary lubrication and movement in limb synovial joints, but its roles in temporomandibular joint (TMJ) are unclear. Thus, we characterized the TMJ phenotype in wild-type and Prg4(-/-) mouse littermates over age. As early as 2 weeks of age, mutant mice exhibited hyperplasia in the glenoid fossa articular cartilage, articular disc, and synovial membrane. By 1 month of age, there were fewer condylar superficial tenascin-C/Col1-positive cells and more numerous apoptotic condylar apical cells, while chondroprogenitors displayed higher mitotic activity, and Sox9-, Col2-, and ColX-expressing chondrocyte zones were significantly expanded. Mutant subchondral bone contained numerous Catepsin K- expressing osteoclasts at the chondro-osseous junction, increased invasive marrow cavities, and suboptimal subchondral bone. Mutant glenoid fossa, disc, synovial cells, and condyles displayed higher Hyaluronan synthase 2 expression. Mutant discs also lost their characteristic concave shape, exhibited ectopic chondrocyte differentiation, and occasionally adhered to condylar surfaces. A fibrinoid substance of unclear origin often covered the condylar surface. By 6 months of age, mutant condyles displayed osteoarthritic degradation with apical/mid-zone separation. In sum, lubricin exerts multiple essential direct and indirect roles to preserve TMJ structural and cellular integrity over post-natal life.
    Full-text · Article · May 2014 · Journal of Dental Research
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    ABSTRACT: Slow proliferation is one of the characteristics of stem cells. We examined the presence, distribution, and regulation of slow-cycling cells in the developing and growing skeleton using a pulse-chase method with a new nucleoside derivative, 5-ethynyl-2'-deoxyuridine (EdU). C57BL/6 mice received daily intraperitoneal injections of EdU from postnatal day 4 to day 7. One day after the last EdU injection, a large population of cells in articular cartilage and growth plate was labeled. Six weeks after the last injection, the number of EdU-labeled cells dramatically decreased, but a small number of them were dominantly present in the articular surface, and the labeling index was significantly higher in the surface than that in the rest of articular cartilage. In the growth plate, most EdU-positive cells were found in the top layer that lies immediately below the secondary ossification center. Interestingly, postnatal conditional ablation of β-catenin in cartilage caused a complete loss of the EdU-labeled cells in growth plate that displayed disorganization and dysfunction. Together, our data demonstrate that slow-cycling cells do reside in specific locations and numbers in both articular cartilage and growth plate. The β-catenin signaling pathway appears to play a previously unsuspected role in maintenance of the slow-cycling cells. © 2014 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res.
    Preview · Article · May 2014 · Journal of Orthopaedic Research
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    R.S. Decker · P. Maye · M. Kronenberg · D. Rowe · M. Pacifici

    Full-text · Article · Apr 2014 · Osteoarthritis and Cartilage

Publication Stats

6k Citations
828.33 Total Impact Points

Institutions

  • 2011-2015
    • The Children's Hospital of Philadelphia
      • Department of Orthopaedic Surgery
      Filadelfia, Pennsylvania, United States
    • Tokyo Dental College
      • Department of Periodontology
      Tiba, Chiba, Japan
  • 2003-2011
    • Thomas Jefferson University
      • Department of Orthopaedic Surgery
      Philadelphia, Pennsylvania, United States
  • 1976-2009
    • University of Pennsylvania
      • • School of Dental Medicine
      • • Department of Anatomy & Cell Biology
      • • Department of Biochemistry
      • • Department of Medicine
      Philadelphia, Pennsylvania, United States
  • 2007-2008
    • Thomas Jefferson University Hospitals
      • Department of Dermatology and Cutaneous Biology
      Philadelphia, Pennsylvania, United States
  • 1998
    • William Penn University
      Filadelfia, Pennsylvania, United States
  • 1993
    • Harvard Medical School
      Boston, Massachusetts, United States
  • 1982
    • University of Rome Tor Vergata
      Roma, Latium, Italy
    • Wistar Institute
      Philadelphia, Pennsylvania, United States
  • 1980
    • Università Degli Studi Roma Tre
      Roma, Latium, Italy