Periosteal progenitor cell fate in segmental cortical bone graft transplantations: implications for functional tissue engineering.
A murine segmental femoral bone graft model was used to show the essential role of donor periosteal progenitor cells in bone graft healing. Transplantation of live bone graft harvested from Rosa 26A mice showed that approximately 70% of osteogenesis on the graft was attributed to the expansion and differentiation of donor periosteal progenitor cells. Furthermore, engraftment of BMP-2-producing bone marrow stromal cells on nonvital allografts showed marked increases in cortical graft incorporation and neovascularization, suggesting that gene-enhanced, tissue engineered functional periosteum may improve allograft incorporation and repair.


BACKGROUND
The loss of cellular activity in a structural bone allograft markedly reduces its healing potential compared with a live autograft. To further understand the cellular mechanisms for structural bone graft healing and repair and to devise a therapeutic strategy aimed at enhancing the performance of allograft, we established a segmental femoral structural bone graft model in mice that permits qualitative and quantitative analyses of graft healing and neovascularization.


METHODS
Using this segmental femoral bone graft model, we transplanted live isografts harvested from Rosa 26A mice that constitutively express beta-galactosidase into their wildtype control mice. In an attempt to emulate the osteogenic and angiogenic properties of periosteum, we applied a cell-based, adenovirus-mediated gene therapy approach to engraft BMP-2-producing bone marrow stromal cells onto devitalized allografts.


RESULTS
X-gal staining for donor cells allowed monitoring the progression of periosteal progenitor cell fate and showed that 70% of osteogenesis was attributed to cellular proliferation and differentiation of donor progenitor cells on the surface of the live bone graft. Quantitative muCT analyses showed a 3-fold increase in new bone callus formation and a 6.8-fold increase in neovascularization for BMP-2/stromal cell-treated allograft compared with control acellular allografts. Histologic analyses showed the key features of autograft healing in the BMP-2/stromal cell-treated allografts, including the formation of a mineralized bone callus completely bridging the segmental defects, abundant neovascularization, and extensive resorption of bone graft.


CONCLUSIONS
The marked improvement of healing in these cellularized allografts suggests a clinical strategy for engineering a functional periosteum to improve the osteogenic and angiogenic properties of processed allografts.
Zhang
Xinping
X
Department of Orthopaedics, University of Rochester Medical Center, New York, USA. Xinping_Zhang@URMC.rochester.edu
Xie
Chao
C
Lin
Angela S P
AS
Ito
Hiromu
H
Awad
Hani
H
Lieberman
Jay R
JR
Rubery
Paul T
PT
Schwarz
Edward M
EM
O'Keefe
Regis J
RJ
Guldberg
Robert E
RE
D000135:Acid Phosphatase / Q000378:metabolism; D000469:Alkaline Phosphatase / Q000378:metabolism; D000818:Animals; D016026:Bone Marrow Transplantation; D055396:Bone Morphogenetic Protein 2; D019485:Bone Morphogenetic Proteins / Q000235:genetics / Q000378:metabolism; D001861:Bone Regeneration / Q000502:physiology*; D016723:Bone Remodeling / Q000502:physiology; D016025:Bone Transplantation; D001842:Bone and Bones / Q000098:blood supply / Q000166:cytology / Q000378:metabolism; D002356:Cartilage / Q000166:cytology / Q000254:growth & development; D002454:Cell Differentiation / Q000502:physiology; D049109:Cell Proliferation; D015316:Genetic Therapy / Q000379:methods; D006801:Humans; D007527:Isoenzymes / Q000378:metabolism; D059630:Mesenchymal Stem Cells / Q000166:cytology* / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D018919:Neovascularization, Physiologic / Q000502:physiology; D010012:Osteogenesis / Q000502:physiology; D010521:Periosteum / Q000098:blood supply / Q000166:cytology* / Q000601:surgery; D017154:Stromal Cells / Q000378:metabolism / Q000637:transplantation; D000071681:Tartrate-Resistant Acid Phosphatase; D023822:Tissue Engineering / Q000379:methods*; D014162:Transfection; D016212:Transforming Growth Factor beta / Q000235:genetics / Q000378:metabolism
C525718:BMP2 protein, human; C525719:Bmp2 protein, mouse; D055396:Bone Morphogenetic Protein 2; D019485:Bone Morphogenetic Proteins; D007527:Isoenzymes; D016212:Transforming Growth Factor beta; D000469:Alkaline Phosphatase; D000135:Acid Phosphatase; D000071681:Tartrate-Resistant Acid Phosphatase