[Calcifications in temporal arteries -- their morphogenesis in comparison to physiological osteogenesis]

Area of Science:

• Vascular biology
• Biomineralization
• Histopathology

Background:

• Vascular calcification was traditionally viewed as a degenerative process.
• Recent interpretations suggest it is a biologically regulated, bone-like phenomenon.
• Temporal arteries offer a model for studying vascular calcification due to their accessibility.

Purpose of the Study:

• To investigate the morphogenesis of calcification in temporal arteries.
• To compare this process with the development of fetal bone.
• To elucidate the cellular and molecular mechanisms underlying vascular calcification.

Main Methods:

• Analysis of formaldehyde-fixed temporal artery sections using light, transmission, and scanning electron microscopy.
• X-ray microanalysis to determine the atomic composition of calcifications.
• Comparative analysis with formaldehyde-fixed fetal bone specimens.

Main Results:

• Early vascular calcification is characterized by granular mediacalcinosis and calcospherites, sometimes showing the Liesegang phenomenon.
• Advanced calcification involves sheet-like structures containing calcospherites, with a lower magnesium content than early calcifications.
• Ultrastructural differences were observed between vascular calcospherites and those in endochondral ossification, with the latter showing apatite crystals.

Conclusions:

• Vascular calcification in temporal arteries is a calcospherite-dependent process, similar to other vascular calcifications.
• The process is biphasic: initial calcospherite formation followed by a secondary phase with bone-like apatite.
• Vascular calcification is distinct from bone formation, characterized by calcospherites and secondary apatite deposition.