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1.  Cellular, matrix, and growth factor components of the joint capsule are modified early in the process of posttraumatic contracture formation in a rabbit model 
Acta orthopaedica  2008;79(1):116-125.
Background and purpose
A recently developed animal model of posttraumatic contractures reflects the chronic stages of the human condition. To understand the initiation of the process, we evaluated the cellular, matrix, and growth factor changes in the joint capsule in the early stages of the animal model, which would not be possible in humans.
Methods
18 skeletally mature rabbits had intraarticular cortical windows removed from the medial and lateral femoral condyles, and the knee joint was immobilized. The contralateral unoperated limb served as a control. Equal numbers of rabbits were killed 2, 4, and 6 weeks after surgery. Myofibroblast, mRNA, and protein determinations were done with immunohistochemistry, RT-PCR, and western blot, respectively.
Results
Myofibroblast numbers were statistically significantly elevated in the joint capsules of the experimental knees as compared to control knees. The mRNA and protein levels for collagen types I and III, matrix metalloproteinases 1 and 13, and transforming growth factor ╬▓1 were statistically significantly greater, and for tissue inhibitor of matrix metalloproteinases 1 significantly less, in the experimental capsules than in the control capsules.
Interpretation
The experimental joint capsule changes in the acute stages of posttraumatic contractures are similar to those in the chronic stages of the process in this model. Thus, it appears that the mechanisms that attenuate the acute stages of the response to injury are circumvented, contributing to a prolonged modulation of myofibroblast numbers, matrix molecules and growth factors, and leading to joint contractures. Thus, in clinical practice, new approaches to prevention of posttraumatic contractures should be implemented as soon as possible.
doi:10.1080/17453670710014860
PMCID: PMC2950862  PMID: 18283583 CAMSID: cams854
2.  Polymethylmethacrylate Particles Stimulate Bone Resorption of Mature Osteoclasts In Vitro 
Acta orthopaedica  2008;79(2):281-288.
Background
The interaction between wear particle debris and the cells at the implant-bone interface is an important contributing factor to periprosthetic bone loss seen in total joint arthroplasties.
Methods
To investigate this particle-induced response on different stages of osteoclast maturation, polymethylmethacrylate (PMMA) particles were added to a murine osteoclastogenic bone marrow cell culture system at either day 0, day 4, or day 8 culture time, which represented PMMA particle stimulation of precursor osteoclasts, mature osteoclasts, or end stage osteoclasts respectively. The number of TRAP-positive multinucleated cells (MNCs) and percentage of bone resorption in culture was measured.
Results
Particles added to precursor osteoclasts resulted in a significant increase in TRAP-positive MNCs that persisted for four days, but no significant increase in bone resorption. Particles added to mature osteoclasts resulted in a significant increase in TRAP-positive MNCs that persisted for eight days, and a significant increase in bone resorption. Particles added to end stage osteoclasts did not increase the number of TRAP-positive MNCs or bone resorption.
Interpretations
PMMA particles added to mature osteoclasts resulted in an increase in TRAP-positive cells which persisted over a longer time period, and a larger increase in bone resorption compared to the other stages of osteoclast development.
doi:10.1080/17453670710015166
PMCID: PMC2662348  PMID: 18484256

Results 1-2 (2)