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VEGF and Sema3A signaling for vascularized bone grafts

English title VEGF and Sema3A signaling for vascularized bone grafts
Applicant Di Maggio Nunzia
Number 158312
Funding scheme Marie Heim-Voegtlin grants
Research institution Departement Biomedizin Universität Basel
Institution of higher education University of Basel - BS
Main discipline Cellular Biology, Cytology
Start/End 01.02.2015 - 31.01.2017
Approved amount 235'984.00
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Keywords (5)

Semaphorin 3A; Bone; Vascularization; Mesenchymal progenitors; Vascular Endothelial Growth Factor

Lay Summary (Italian)

Lead
L’obiettivo di questo studio è di delucidare lo scambio di segnali tra il processo di formazione di vasi sanguigni (angiogenesi) e la formazione di tessuto osseo per generare sostituti ossei in vitro che possano essere rapidamente vascolarizzati dopo l’impianto in vivo. Qui proponiamo di investigare la regolazione dei segnali del VEGF e della Sema3A e come queste due molecole possano essere combinate per ottenere sia efficiente crescita di vasi sanguigni sia robusta formazione di osso in costrutti di dimensioni clinicamente rilevanti. I risultati ottenuti saranno utili per disegnare nuove strategie terapeutiche per migliorare il trattamento di molti pazienti per i quali le terapie chirurgiche attuali non sono efficaci.
Lay summary

Il “bone tissue engineering” ha come obiettivo quello di sviluppare sostituti per la perdita di tessuto osseo dovuta a traumi, tumori o altre malattie. L’osso ottenuto dal paziente stesso è al momento lo stato dell’arte ma presenta diverse limitazioni, come il dolore cronico e la limitata quantità di tessuto disponibile. Tuttavia, gli approcci d’ingegneria dei tessuti non sono ancora efficaci per la routine nella pratica clinica. Una delle principali limitazioni è che i vasi crescono troppo lentamente per assicurare la sopravvivenza delle cellule al centro dello scaffold. Questo progetto propone di risolvere questo problema per ottenere un’efficiente formazione di vasi sanguigni e una robusta formazione di tessuto osseo. Qui proponiamo di investigare: 1) il cross-talk molecolare tra il Vascular endothelial growth factor (VEGF), che è il regolatore principale dell’angiogenesi, e la Semaphorin 3A (Sema3A), anch’essa regolatrice della formazione di vasi, ma anche molecola osteoprotettiva; 2) il potenziale terapeutico di VEGF e di Sema3A per migliorare la vascolarizzazione dei sostituti ossei. Utilizzeremo un sistema che consente il rilascio controllato di fattori contenuti all’interno di un gel di fibrina. La fibrina è un prodotto naturale della coagulazione del sangue ed è matrice ideale per la presentazione di segnali angiogenici. Il gel di fibrina sarà combinato con granuli di idrossiapatite per identificare la concentrazione ottimale di VEGF e Sema3A per una rapida vascolarizzazione e un’efficiente formazione di osso.

Questo progetto fornirà le basi per nuove strategie terapeutiche atte a generare sostituti ossei di dimensioni clinicamente rilevanti. Inoltre, il sistema di rilascio basato sulla fibrina è  una strategia prontamente applicabile in clinica. Offre, infatti, diversi vantaggi dal punto di vista regolatorio, come quello di essere un prodotto “pronto all’uso”, privo di modificazioni genetiche e con una durata controllata del rilascio dei fattori.
Direct link to Lay Summary Last update: 06.01.2015

Responsible applicant and co-applicants

Employees

Collaboration

Group / person Country
Types of collaboration
Jeffrey Hubbel- EPFL Switzerland (Europe)
- in-depth/constructive exchanges on approaches, methods or results

Scientific events

Active participation

Title Type of contribution Title of article or contribution Date Place Persons involved
2016 eCM XVII: Stem cells, Bone Fixation, Repair & Regeneration Talk given at a conference Short-Term Delivery of VEGF Protein for Vascularized Engineered Bone 20.06.2016 Davos, Switzerland Di Maggio Nunzia;
Bone and Teeth Gordon Research Conference Talk given at a conference Short-Term Delivery of VEGF Protein for Vascularized Engineered Bone 13.02.2016 Galveston, Texas, United States of America Di Maggio Nunzia;


Awards

Title Year
Best poster prize 2015

Associated projects

Number Title Start Funding scheme
170809 Super Resolution and Endoscopic Two Photon Microscopy - Imaging of Cell Migration in Inflammation, Metastasis and Regeneration 01.01.2017 R'EQUIP

Abstract

Background: Reconstruction of large bone defects is a major challenge in tissue engineering. Stimulation of rapid graft vascularization in vivo is required for cell survival and efficient bone formation and represents a critical issue for the generation of clinical-size constructs. Vascular endothelial growth factor (VEGF) is the master regulator of angiogenesis. However, it was previously found that, while sustained over-expression of VEGF by genetically modified human BMSC was effective to improve vascularization of tissue-engineered bone grafts, it also caused an undesired increase in osteoclast recruitment with excessive bone resorption. Several lines of evidence show that the regulation of angiogenesis and osteogenesis are intimately connected, but their relation is complex and not yet fully clarified. Therefore, a better understanding of the molecular crosstalk between angiogenesis and bone formation is clearly needed to design rational strategies to generate vascularized osteogenic grafts.Semaphorin3A (Sema3A) is a regulator of angiogenesis and has recently been found to also have an osteoprotective function. Interestingly, preliminary data indicate that VEGF can directly and dose-dependently inhibit Sema3A expression both in skeletal muscle and in osteogenic grafts. Here I propose to investigate: 1) whether Sema3A down-regulation by VEGF is responsible for unbalancing bone homeostasis towards resorption, and 2) the therapeutic potential of Sema3A and VEGF co-delivery to stimulate both effective angiogenesis and osteogenesis.Working hypotheses: 1) Uncontrolled VEGF impairs bone formation by inhibiting Sema3A expression in osteogenic grafts; 2) Sema3A treatment can improve bone formation efficiency without impairing VEGF-induced vascularization; 3) short-term co-delivery of VEGF and Sema3A improves both vascularization and bone formation in a preclinical model.Specific aims: Aim1 will investigate the role of Sema3A in bone impairment by VEGF over-expression. We will generate osteogenic constructs taking advantage of a state-of-the-art fibrin-based platform, which allows controlled delivery of covalently bound recombinant factors, in combination with human bone marrow-derived mesenchymal progenitors seeded on hydroxyapatite granules. Non-critical-size constructs will be implanted subcutaneously in nude mice. With this highly tunable platform we will first rigorously investigate the relationship between VEGF dose and expression of endogenous Sema3A in osteogenic grafts, and its impact on bone formation and osteoclast recruitment. In order to determine whether Sema3A loss is the mechanism of VEGF-induced bone impairment, we will inhibit Sema3A binding to its receptor Neuropilin-1 with the specific antibody anti-NP-1A YW64.3 (loss-of-function). Conversely, in order to investigate the therapeutic potential of Sema3A to prevent VEGF-induced impairment of bone homeostasis, we will perform gain-of-function experiments, in which both VEGF and Sema3A will be incorporated in the fibrin gel. In Aim2, we will test whether the results obtained in Aim1 could be translated in a preclinical model, applying short-term co-delivery of VEGF and Sema3A to functionally improve both vascularization and bone formation in a rat model of critical-size calvarial defect.Expected value of the proposed project: The proposed experiments will help elucidating the molecular crosstalk between angiogenesis and bone formation and provide rational bases for novel therapeutic strategies to generate large-size vascularized bone grafts. Moreover, the fibrin-based delivery platform represents an attractive and clinically applicable strategy to ensure both effective angiogenesis and bone formation. Remarkably, it also offers several clinical and regulatory advantages, such as providing an “off-the-shelf” product, avoidance of genetic modification of implanted cells and controlled duration of factor delivery.
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