Zur Kenntnis der Altersveränderungen in den menschlichen Kehlkopfknorpeln, insbesondere der körnigen Entartung der Knorpelgrundsubstanz, der Vascularisations-, Resorptions- und Vérknöcherungsbefunde

Distribution, structure, and mineralization of calcified cartilage remnants in hard antlers

Antlers are paired deciduous bony cranial appendages of deer that undergo a regular cycle of growth, death and casting, and constitute the most rapidly growing bones in mammals. Antler growth occurs in an appositional mode and involves a modified form of endochondral ossification. In endochondral bones, calcified cartilage is typically a transient tissue that is eventually completely replaced by bone tissue. We studied the distribution and characteristics of calcified cartilage in hard antlers from three deer species (Capreolus capreolus, Cervus elaphus, Dama dama), i.e., in antlers from which the skin (velvet) had been shed. Remnants of calcified cartilage were regularly present as part of the trabecular framework in the late formed, distal antler portions in all three species, whereas this tissue was largely or completely missing in the more proximal antler portions. The presence of calcified cartilage remnants in the distal antler portions is attributed to the limited antler lifespan of only a few months, which is also the reason for the virtual lack of bone remodeling in antlers. The calcified cartilage matrix was more highly mineralized than the antler bone matrix. Mineralized deposits were observed in some chondrocyte lacunae and occasionally also in osteocyte lacunae, a phenomenon that has not previously been reported in antlers. Using synchrotron radiation-induced X-ray fluorescence (SR-XRF) mapping, we further demonstrated increased zinc concentrations in cement lines, along the inner borders of incompletely formed primary osteons, along the walls of partly or completely mineral-occluded chondrocyte and osteocyte lacunae, and in intralacunar mineralized deposits. The present study demonstrates that antlers are a promising model for studying the mineralization of cartilage and bone matrices and the formation of mineralized deposits in chondrocyte and osteocyte lacunae.

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Remnants of calcified cartilage are regularly present in hard antlers of deer.

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Preservation of calcified cartilage is caused by the short lifespan of antlers.

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Calcified cartilage of antlers is more highly mineralized than antler bone.

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Mineralized deposits were observed in chondrocyte and osteocyte lacunae of antlers.

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SR-XRF showed increased Zn-concentration in cement lines and intralacunar deposits.

VEGF expression in adult permanent thyroid cartilage: implications for lack of cartilage ossification

Vascular endothelial growth factor (VEGF) has been shown to play an important role during endochondral bone formation in hypertrophic cartilage remodeling, ossification, and angiogenesis, but it is not expressed in normal adult articular cartilage. Thyroid cartilage undergoes only partial ossification beginning at the age of about 20. Because it never completely ossifies, we investigated a possible role of VEGF and its receptors (VEGFRs) as well as the angiogenetic inhibitor endostatin in this permanent cartilage. In analysis of cartilage samples from all specimens evaluated, VEGF121 and VEGF165 were identified as the only VEGF splice forms expressed. In addition to VEGF, VEGFR-2 (kinase domain region/fetal liver kinase 1), but not VEGFR-1 (fms-like tyrosine kinase 1), was detectable by RT-PCR in cartilage. However, VEGFR-2 expression was only detectable up to the age of 19 years. Deposition of VEGF and VEGFR was confirmed by immunohistochemistry. VEGF concentrations measured by ELISA in thyroid cartilage increased with age in males but decreased in females. Endostatin concentrations measured by ELISA in thyroid cartilage were three times lower than in articular cartilage and showed no change with age, either in females or males. VEGF was immunostained within the intra- and pericellular matrices of some but not all chondrocytes. Thus, apart from its production in hypertrophic chondrocytes of growth plates, VEGF is also produced in single chondrocytes of thyroid cartilage. The data allow us to speculate that thyroid cartilage persists in an embryological state until it has reached its final size. After reaching its final size at the end of the second decade, VEGFR-2 is downregulated and ossification starts in the posterior part of the thyroid cartilage, proceeding ventrally. Both proteins, VEGF121 and VEGF165, should contribute to this process. VEGF concentration is high and changes in an age-related and sex-specific manner. Therefore, we postulate that VEGF is at least one of the key factors that is important for the lifelong ossification in thyroid cartilage.

Areas of asbestoid (amianthoid) fibers in human thyroid cartilage characterized by immunolocalization of collagen types I, II, IX, XI and X

The distribution of type I, II, IX, XI and X collagens in and close to areas of asbestoid (amianthoid) fibers in thyroid cartilages of various ages was investigated in this study. Asbestoid fibers were first detected in thyroid cartilage from a 3-year-old male child. Areas of asbestoid fibers functionally appear to serve as guide rails for vascularization of thyroid cartilage. Alcian blue staining in the presence of 0.3 M MgCl2 revealed a loss of glycosaminoglycans in areas of asbestoid fibers. In addition, the fibers reacted positively with antibodies against collagen types II, IX and XI, but showed no staining with antibodies to collagen types I and X. Territorial matrix of adjacent chondrocytes showed the same staining pattern. In addition to staining for type II, IX and XI collagens, asbestoid fibers showed strong immunostaining for type I collagen after puberty but not for type X collagen. However, groups of chondrocytes within areas of asbestoid fibers reacted strongly with antibodies to type X collagen, suggesting that this collagen plays an important role in matrix of highly differentiated chondrocytes. The finding that these type X collagen-positive chondrocytes also revealed immunostaining for type I collagen confirms previous studies showing that hypertrophic chondrocytes can further differentiate into cells that are characterized by the synthesis of type X and I collagens.

Bronchial cartilage alterations in lung transplantation

Changes in the hyaline cartilage of the proximal bronchial tree were investigated in a group of combined heart-lung and double-lung recipients with and without OB. Ossification, calcification and fibrovascular ingrowth into the normally avascular hyaline bronchial cartilage were observed in almost all patients and were independent of small or large airway inflammation. Alterations in the integrity of hyaline cartilage have been produced by others in animals by ligation of the blood supply. Finding similar changes in airway cartilage of all transplanted lungs argues that there is relatively poor perfusion to the proximal air-conducting passage. Such a mechanism may contribute to the development of OB, bronchiectasis and a predilection for infections following pulmonary transplantation.

A note on the histochemical and morphological characterization of the asbestoid degeneration of cartilage

Using only one histologic preparation and under the light microscope, the simple Picrosirius-polarization method permitted the histochemical characterization of the collagenous nature of amianthoid fibers in file cases of salivary gland tumors. In this regard the foregoing results agree with the electron microscopic and X-ray diffraction observations recorded in the literature. Not only did the Picrosirius-polarization method permit the precise characterization of the collagenous nature of asbestoid change but it was also useful for studying the degree of collagen polymerization in the lesion. Collagen molecules in the amianthoid fibers showed hyperpolymerization whereas the molecules in the compact areas were disoriented. Since the foregoing results demonstrate that the Picrosirius-polarization method is a simple and sensitive procedure for detecting asbestoid change in cartilage sections obtained from paraffin-embedded tissues, the usefulness of this technique for studying file cases is evident.

Amianthoid fibres in a chondrosarcoma

Amianthoid fibres up to about 1000 nm thick were found in the matrix of a chondrosarcoma. Our findings support the idea that this is a degenerative change and that these fibres are probably formed by coalescence of collagen fibrils.