Histopathological correlation of cartilage swelling detected by MRI in early experimental osteoarthritis

Universidad Autónoma de Madrid, Madrid, Madrid, Spain
Osteoarthritis and Cartilage (Impact Factor: 4.17). 12/2004; 12(11):878-86. DOI: 10.1016/j.joca.2004.07.007
Source: PubMed


We previously reported that an increase of cartilage thickness is the earliest measurable change by magnetic resonance imaging (MRI) in early stages of experimental osteoarthritis (OA). Our present objective was to study the microscopic translation of this finding in order to know whether the cartilage thickness increment represents the earliest structural damage or whether it alternatively constitutes a non-progressive reversible phenomenon.
OA was induced by partial medial meniscectomy in rabbits. Normal and sham-operated animals were used as controls. Gross and microscopic cartilage changes were sequentially assessed after surgery at 0, 2, 4, 6, 8, 10 and 52 weeks, and compared to MRI findings.
The swelling of cartilage detected by MRI correlated with depletion in matrix proteoglycans and cellular loss, which were closely related to the progression of OA at the earliest stages. Abnormalities of the cartilage structure appeared only in advanced OA.
Cartilage swelling detected by MRI is due to proteoglycan depletion and represents the earliest abnormality in OA. Because it is accompanied by cellular loss, it cannot be merely attributed to surgical trauma and represents true tissue damage. The biological meaning of volume variations detected by MRI should be assessed carefully taking into account the disease stage as an increase in cartilage height also reflects cartilage damage and not a reparative process.

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    • "Even though we expected a decrease in the staining intensity for glycosaminoglycans, we found that cartilage samples retained their staining properties for proteoglycans. An explanation for this observation may be derived from studies investigating cartilage tissue during early osteoarthritis, which is characterized by cartilage swelling[38],[39]. In response, chondrocytes attempt to repair damaged tissue by increasing the synthesis of collagen type II[40]–[43]and proteoglycans[42],[44],[45]; however, this is usually unsuccessful and results in degradation of the cartilage matrix. "
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    • "In the present study, the development of OA was not still advanced at eleven weeks postsurgery, although it was enough to produce detectable changes in the articular cartilage but not in the subchondral bone. Articular cartilage appears in a state of swelling -characteristic of the early stages of the disease- previous to its erosion and destruction [35]. The subchondral bone, however, had not the typical sclerosis associated with this pathology, not appearing any differences between the healthy control group and the untreated OA group in any of the microstructural parameters analysed by either histology or micro-CT. "
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    • "The observers were blinded with respect to each other's reading, and rabbit group. Assessment of cartilage histology was performed at the weight-bearing surface of the medial femoral condyle because it shows the earliest and most severe histological abnormalities [37]. "
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