The in vivo immunogenicity of a human 3D scaffold-free tissue engineered product for bone reconstruction: a xenogenic model

December 18, 2019

Gaëtan Thirion1, Sophie Vériter1, Valérie Lebrun1, Pierre-Yves Adnet1, Céline Caty1, Marie- Ange Benoît2, Philippe Stordeur2, Ludivine Martin2, Marie Dehuy2, Cathy Mottart2, Maëlle Noelanders2, David Torres23, Denis Dufrane1
1Novadip Biosciences, Mont-Saint-Guibert, Belgium
2CER-Groupe, Département de biotechnologie, Aye, Belgium
3Institute for Medical Immunology, Université Libre de Bruxelles, Gosselies, Belgium

Introduction: Large critical size bone defect remains a real challenge for reconstructive surgery. In this context, the immunogenicity of a human 3D scaffold-free graft (derived from human adipose stem cells, ASCs) was in vivo investigated in a xenogenic model of critical-sized bone defects to study the humoral and cellular immunological responses.

Methods: A 5 mm critical-sized femoral bone-defect in Wistar rats (n=36) was firstly performed 3 weeks before-implantation. The presence of bone non-union was confirmed before implantation to avoid any spontaneous bone healing. Three groups were designed: (1) Sham, (2) Hydroxyapatite/bTCP particles as negative control and (3) the human scaffold-free 3D-graft in the bone defect. The immune response was studied, at day 1/3/7/15/30 post-implantation, in terms of immune cells populations (B/T-lymphocytes, dendritic cells, neutrophils profiles) and IgM/IgG anti-HLA-1 antibodies elicitation in the sera of recipients. The graft rejection was also studied by immunohistochemistry/histomorphometry for lymphocytes and macrophages infiltration. The osteogenicity of the graft was studied, at 1 month post-implantation (in the explant), at the molecular level for genes specifically involved in the skeletal development. The transplantation of the human 3D grafts in the bone defect of nude rats served as control.

Results: The groups 1/2 did not elicited a xenogenic response but a non-foreign body reaction (non-specific inflammation) without anti-human antibody production. In contrast, the transplantation of the human scaffold-free graft in the bone defect elicited the production of anti- HLA-1 Ab especially specific IgG at day 30 post-transplantation while specific IgM were increased at day 7 post-implantation. The transplantation of the human scaffold-free graft revealed a massive macrophages infiltration at day 15 post-implantation. Although the osteogenicity was similar (for most of osteogenic genes) at 1 month post-transplantation in nude as well as Wistar rats, the immune response directly affected specific pathways of the skeletal development.

Conclusion: The human scaffold-free 3D approach, in a xenogenic model, elicit a specific antihuman immune response but can maintain the potential of in vivo osteogenicity.