P. Virolainen et al., GENE-EXPRESSION AT GRAFT HOST INTERFACES OF CORTICAL BONE ALLOGRAFTS AND AUTOGRAFTS, Clinical orthopaedics and related research, (297), 1993, pp. 144-149
The healing processes of autogenous and frozen allogeneic cortical bon
e grafts were compared in rats. Two unicortical defects created in the
proximal metaphysis of the tibia were autografted or allografted with
blocks of cortical bone. The biomechanical properties of the graft-ho
st junction and the time-related changes of the expression of genes co
ding for Type I, II, III, and X collagens and osteonectin were determi
ned at one, two, four, and eight weeks. The strength of the allograft
host bone union was lower than that of autografts at the early stage o
f incorporation but the difference diminished by eight weeks. Northern
analysis of graft mRNAs demonstrated a strong expression of Type I co
llagen and osteonectin genes at the beginning of autograft incorporati
on. The allografts showed a lower expression of the corresponding gene
s at one and two weeks, but the difference diminished thereafter. The
gene coding for Type III collagen showed a temporary expression at two
weeks both in allografts and autografts, probably because of the form
ation of inflammatory fibrovascular stroma provided by the host borne
at the graft-host interface. No expression of cartilage-specific Type
II and Type X collagens were observed, demonstrating that the healing
in both grafts proceeded through primary bone healing. Compared with c
ortical-cortical junctions of autografts, the graft-host interfaces of
allografts exhibited a reduced osteoinductive process and a slower in
crease of union strength.