Currently, there is no animal model in which
to evaluate the underlying physiological processes leading to the heterotopic
ossification (HO) which forms in most combat-related and blast wounds.
We sought to reproduce the ossification that forms under these circumstances
in a rat by emulating patterns of injury seen in patients with severe
injuries resulting from blasts. We investigated whether exposure
to blast overpressure increased the prevalence of HO after transfemoral
amputation performed within the zone of injury. We exposed rats
to a blast overpressure alone (BOP-CTL), crush injury and femoral
fracture followed by amputation through the zone of injury (AMP-CTL)
or a combination of these (BOP-AMP). The presence of HO was evaluated
using radiographs, micro-CT and histology. HO developed in none
of nine BOP-CTL, six of nine AMP-CTL, and in all 20 BOP-AMP rats.
Exposure to blast overpressure increased the prevalence of HO. This model may thus be used to elucidate cellular and molecular
pathways of HO, the effect of varying intensities of blast overpressure,
and to evaluate new means of prophylaxis and treatment of heterotopic
ossification. Cite this article:
We attempted to characterise the biological quality
and regenerative potential of chondrocytes in osteochondritis dissecans
(OCD). Dissected fragments from ten patients with OCD of the knee
(mean age 27.8 years (16 to 49)) were harvested at arthroscopy.
A sample of cartilage from the intercondylar notch was taken from
the same joint and from the notch of ten patients with a traumatic
cartilage defect (mean age 31.6 years (19 to 52)). Chondrocytes
were extracted and subsequently cultured. Collagen types 1, 2, and
10 mRNA were quantified by polymerase chain reaction. Compared with
the notch chondrocytes, cells from the dissecate expressed similar
levels of collagen types 1 and 2 mRNA. The level of collagen type
10 message was 50 times lower after cell culture, indicating a loss
of hypertrophic cells or genes. The high viability, retained capacity
to differentiate and metabolic activity of the extracted cells suggests
preservation of the intrinsic repair capability of these dissecates.
Molecular analysis indicated a phenotypic modulation of the expanded
dissecate chondrocytes towards a normal phenotype. Our findings
suggest that cartilage taken from the dissecate can be reasonably
used as a cell source for chondrocyte implantation procedures.
The mammalian growth plate is a complex structure which is essential for the elongation of long bones. However, an understanding of how the growth plate functions at the cellular level is lacking. This review, summarises the factors involved in growth-plate regulation, its failure and the consequence of injury. We also describe some of the cellular mechanisms which underpin the increase in volume of the growth-plate chondrocyte which is the major determinant of the rate and extent of bone lengthening. We show how living in situ chondrocytes can be imaged using 2-photon laser scanning microscopy to provide a quantitative analysis of their volume. This approach should give better understanding of the cellular control of bone growth in both healthy and failed growth plates.
