For the treatment of ununited fractures, we developed
a system of delivering magnetic labelled mesenchymal stromal cells
(MSCs) using an extracorporeal magnetic device. In this study, we
transplanted ferucarbotran-labelled and luciferase-positive bone
marrow-derived MSCs into a non-healing femoral fracture rat model
in the presence of a magnetic field. The biological fate of the
transplanted MSCs was observed using luciferase-based bioluminescence
imaging and we found that the number of MSC derived photons increased
from day one to day three and thereafter decreased over time. The
magnetic cell delivery system induced the accumulation of photons at
the fracture site, while also retaining higher photon intensity
from day three to week four. Furthermore, radiological and histological
findings suggested improved callus formation and endochondral ossification.
We therefore believe that this delivery system may be a promising
option for bone regeneration.
1. Homografts of eighteen-day-old foetal femora in pure strains of mice showed no fundamental difference in behaviour from grafts of more mature bone and cartilage. 2. Growth of bone was limited to a short period after transplantation and was abolished by previous immunisation. Cartilage growth alone was responsible for the increase in size of these transplants and did not appear to be influenced by the presence of immunity. 3. There is no reason to suppose that bone from an immature source is likely to behave more favourably than more mature bone homografts in clinical use. 4. The limited growth of cartilage and the total failure of bone survival in the heterografts indicate an immune reaction ofa different order from that which develops against the homograft. 5. The different effect of the homograft immune reaction on cartilage and bone enabled certain conclusions to be drawn concerning the part played by these two tissues in determining the form of a bone. Cartilage growth and development is shown to be regulated in large part by intrinsic factors. Bone growth and form on the other hand is shown to be dependent largely upon extrinsic influences.
