Objectives. The biomembrane (induced membrane) formed around polymethylmethacrylate (PMMA) spacers has value in clinical applications for bone defect reconstruction. Few studies have evaluated its cellular, molecular or stem cell features. Our objective was to characterise induced membrane morphology, molecular features and osteogenic stem cell characteristics. Methods. Following Institutional Review Board approval, biomembrane specimens were obtained from 12 patient surgeries for management of segmental bony defects (mean patient age 40.7 years, standard deviation 14.4). Biomembranes from nine tibias and three femurs were processed for morphologic, molecular or stem cell analyses. Gene expression was determined using the Affymetrix GeneChip Operating Software (GCOS). Molecular analyses compared biomembrane gene expression patterns with a mineralising osteoblast culture, and gene expression in specimens with longer spacer duration (> 12 weeks) with specimens with shorter durations. Statistical analyses used the unpaired student t-test (two tailed; p < 0.05 was considered significant). Results. Average PMMA spacer in vivo time was 11.9 weeks (six to 18). Trabecular bone was present in 33.3% of the biomembrane specimens; bone presence did not correlate with spacer duration. Biomembrane morphology showed high vascularity and collagen content and positive staining for the key bone forming regulators, bone morphogenetic protein 2 (BMP2) and runt-related
MicroRNAs (miRNAs ) are small non-coding RNAs
that regulate gene expression. We hypothesised that the functions
of certain miRNAs and changes to their patterns of expression may
be crucial in the pathogenesis of nonunion. Healing fractures and
atrophic nonunions produced by periosteal cauterisation were created
in the femora of 94 rats, with 1:1 group allocation. At post-fracture
days three, seven, ten, 14, 21 and 28, miRNAs were extracted from
the newly generated tissue at the fracture site. Microarray and
real-time polymerase chain reaction (PCR) analyses of day 14 samples
revealed that five miRNAs, miR-31a-3p, miR-31a-5p, miR-146a-5p,
miR-146b-5p and miR-223-3p, were highly upregulated in nonunion.
Real-time PCR analysis further revealed that, in nonunion, the expression
levels of all five of these miRNAs peaked on day 14 and declined
thereafter. Our results suggest that miR-31a-3p, miR-31a-5p, miR-146a-5p,
miR-146b-5p and miR-223-3p may play an important role in the development
of nonunion. These findings add to the understanding of the molecular mechanism
for nonunion formation and may lead to the development of novel
therapeutic strategies for its treatment. Cite this article:
