Extracellular cross-striated banded structures in human connective tissue

Area of Science:

• Connective tissue biology
• Ultrastructural pathology
• Biomaterials science

Background:

• Extracellular cross-striated banded structures are infrequently observed in the connective tissues of various organs.
• These structures have been anecdotally reported in conditions including hyperplastic parathyroid, thyroid follicular adenoma, metastatic hemangiopericytoma, and sarcoidosis.
• Their presence in nerve biopsies represents a rare finding.

Purpose of the Study:

• To characterize the morphology and periodicity of extracellular cross-striated banded structures.
• To compare these structures with native and reconstituted collagen.
• To document their occurrence in specific pathological conditions and nerve biopsies.

Main Methods:

• Electron microscopy for ultrastructural morphology assessment.
• Staining techniques including phosphotungstic acid, uranyl acetate, and lead nitrate.
• Periodicity measurement of the banded structures.

Main Results:

• Observed extracellular cross-striated banded structures with variable shape, size, and periodicity (typically 1000-15000 Å).
• Identified an unusual periodicity of 270 Å in a thyroid follicular adenoma.
• Demonstrated distinct ultrastructural morphology and staining reactions compared to native and reconstituted collagen.

Conclusions:

• Extracellular cross-striated banded structures represent a distinct ultrastructural entity, differing from collagen.
• Their rare occurrence in specific pathologies warrants further investigation into their composition and function.
• The variable periodicity suggests diverse origins or formation mechanisms.