[45] Network of Thick Fibrils in Normal Fetal and Chondrodysplastic Articular Cartilage

Wei Sek Hwang. KK Women's and Children's Hospital, Singapore

Background: Articular cartilage is a highly specialized connective tissue consisting of sparse chondrocytes widely dispersed in an abundant hyaline matrix. How this complex structure is being formed and how the discrete chondrocytes communicate with each other are not well understood. An interlacunar network and thick fibrils has been described in developing hyaline cartilage, the nature of which is not well characterised. The functions of the network and fibrils remain speculative. This study attempts to further characterise the thick fibrils in fetal articular cartilage and to describe their changes in cases of type II achondrogenesis and chondrodysplasia with giant chondrocytes.
Design: Articular cartilage from normal and chondrodysplastic fetuses were obtained at autopsies and processed for light and electron microscopy. Light microscopic sections by H&E, and Victoria blue with/without hyaluronidase pre-digestion. For electron microscopy, specimens were fixed in 2.5% glutaraldehyde in 0.1M cacodylate buffer at pH 7.4 with/without addition of 0.5% tannic acid, postfixed in 1% osmium tetroxide in similar buffer with/without !.5% potassium ferrocyanide.
Results: Numerous straight or slightly curved blue fibrils were seen traversing the matrix. Some fibrils were seen attached to chondrocytes and occasionally formed connections between two cells. In Type II achondrogenesis, the thick fibrils were less distinct being blurred in a smudged background. Some fibrils appeared twisted and had a spiral appearance. A network of thick fibrils were often seen surrrounding the giant chondrocytes.
In tannic acid-glutaraldehyde fixed cartliage, the thick fibrils appeared as bundles of 10-12 nm diameter microfibrils. The microfibrils bundles were coated by a variale amount of amorphous materials. These bundles were often seen oriented in the same direction as the surrounding colllagen fibril. Some thick fibrils were seen attached to chondrocytes in apparent continuity with intracytoplasmic filaments. The cellular attachments of thick fibrils were more frequenly encountered in giant cell chondrodysplasia.
Conclusions: The thick fibrils in articular cartilage are primarily bundles of 10 nm microfibrils microfibrils coated by matrix proteins. They are directly attached to chondrocytes resulting in an interconnecting network which may play an organisational role in the formation of the articular cartilage.
Category: Bone & Soft Tissue

Tuesday, March 20, 2012 9:30 AM

Poster Session III # 10, Tuesday Morning

 

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