Distribution and morphological variation of septoclasts during mouse cranial base development

Area of Science:

• Developmental Biology
• Cell Biology
• Craniofacial Development

Background:

• Septoclasts are mononuclear cells responsible for cartilage resorption, primarily studied in long bone growth plates.
• Their role in cranial base development, specifically in synchondroses, remains less understood.
• Pericytes are identified as the precursor cells for septoclasts.

Purpose of the Study:

• To investigate the chronological immunolocalization of septoclast and pericyte markers in the developing mouse cranial base.
• To elucidate the role of septoclasts in the morphogenesis of cranial base synchondroses.
• To characterize septoclast morphology and distribution during embryonic and neonatal development.

Main Methods:

• Immunohistochemical analysis of cell markers: epidermal fatty acid-binding protein (E-FABP, FABP5) and cathepsin B for septoclasts, platelet-derived growth factor receptor beta (PDGFRβ) for pericytes, and endomucin for vascular endothelial cells.
• Microscopic examination of the midline mouse cranial base during embryonic and neonatal periods.
• Morphological assessment of septoclasts based on cell shape and cytoplasmic processes.

Main Results:

• Septoclasts expressing FABP5, cathepsin B, and PDGFRβ were found adjacent to vascular endothelial cells (endomucin-positive).
• In neonatal mice, septoclasts were located on the spheno-occipital synchondrosis (SOS) and intersphenoidal synchondrosis (ISS), distributed along cartilage septa.
• Mature septoclasts showed features of high resorptive activity, while immature septoclasts exhibited features of low resorptive activity.

Conclusions:

• Septoclasts play a significant role in the distinct morphogenesis of the cranial base.
• These cells contribute to cartilage resorption in synchondroses and the formation of ossification centers.
• The findings highlight septoclasts as key players in cranial base skeletal development.