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Bone formation in vivo: comparison of osteogenesis by transplanted mouse and human marrow stromal fibroblasts
P H Krebsbach1, S A Kuznetsov, K Satomura
1Laboratory of Developmental Biology and Bone Research Branch, National Institute of Dental Research, National Institutes of Health, Bethesda, Maryland 20892, USA.
Background:
Marrow stromal fibroblasts (MSFs) are known to contain bone precursor cells. However, the osteogenic potential of human MSFs has been poorly characterized. The aim of this study was to compare the osteogenic capacity of mouse and human MSFs after implantation in vivo.
Methods:
After in vitro expansion, MSFs were loaded into a number of different vehicles and transplanted subcutaneously into immunodeficient mice.
Results:
Mouse MSFs transplanted within gelatin, polyvinyl sponges, and collagen matrices all formed a capsule of cortical-like bone surrounding a cavity with active hematopoiesis. In transplants of MSFs from transgenic mice harboring type I procollagen-chloramphenicol acetyltransferase constructs, chloramphenicol acetyltransferase activity was maintained for up to 14 weeks, indicating prolonged bone formation by transplanted MSFs. New bone formation by human MSFs was more dependent on both the in vitro expansion conditions and transplantation vehicles. Within gelatin, woven bone was observed sporadically and only after culture in the presence of dexamethasone and L-ascorbic acid phosphate magnesium salt n-hydrate. Consistent bone formation by human MSFs was achieved only within vehicles containing hydroxyapatite/tricalcium phosphate ceramics (HA/TCP) in the form of blocks, powder, and HA/TCP powder-type I bovine fibrillar collagen strips, and bone was maintained for at least 19 weeks. Cells of the new bone were positive for human osteonectin showing their donor origin. HA/TCP powder, the HA/TCP powder-type I bovine fibrillar collagen strips, and HA/TCP powder held together with fibrin were easier to load and supported more extensive osteogenesis than HA/TCP blocks and thus may be more applicable for therapeutic use.
Conclusions:
In this article, we describe the differences in the requirements for mouse and human MSFs to form bone, and report the development of a methodology for the consistent in vivo generation of extensive bone from human MSFs.
Insights
Mouse marrow stromal fibroblasts (MSFs) readily form bone in vivo. Human MSFs require specific conditions and hydroxyapatite/tricalcium phosphate (HA/TCP) ceramics for consistent bone generation, offering therapeutic potential.
Area of Science:
- Biomaterials Science
- Tissue Engineering
- Regenerative Medicine
Background:
- Marrow stromal fibroblasts (MSFs) are recognized for containing bone precursor cells.
- The osteogenic potential of human MSFs remains incompletely understood.
- This study aimed to compare the bone-forming capacity of mouse and human MSFs in vivo.
Purpose of the Study:
- To compare the osteogenic capacity of mouse and human MSFs.
- To identify optimal conditions and vehicles for human MSF-mediated bone formation.
- To develop a reproducible method for generating bone from human MSFs in vivo.
Main Methods:
- In vitro expanded MSFs from mice and humans were loaded into various vehicles.
- Transplantation was performed subcutaneously into immunodeficient mice.
- Bone formation and cell origin were assessed using histological and molecular analyses.
Main Results:
- Mouse MSFs consistently formed bone and hematopoiesis in multiple matrices.
- Human MSF osteogenesis was highly dependent on in vitro expansion and vehicle composition.
- Consistent and sustained bone formation by human MSFs was achieved using hydroxyapatite/tricalcium phosphate (HA/TCP) ceramics, particularly in powder or composite forms.
Conclusions:
- Significant differences exist in the bone formation requirements between mouse and human MSFs.
- A methodology utilizing HA/TCP ceramics has been developed for consistent in vivo bone generation from human MSFs.
- These findings pave the way for therapeutic applications of human MSFs in bone regeneration.
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