Microfibrils in glomerulopathies of children: an ultrastructural study

Area of Science:

• Nephrology
• Pathology
• Electron Microscopy

Background:

• Renal biopsies are crucial for diagnosing pediatric nephropathies.
• The ultrastructural composition of the kidney's extracellular matrix is not fully understood.
• Microfibrils have been implicated in various connective tissue disorders.

Purpose of the Study:

• To investigate the presence and characteristics of extracellular microfibrils in pediatric renal biopsies.
• To determine the association of microfibrils with different nephropathies.
• To explore the potential origin of these microfibrils.

Main Methods:

• Analysis of 360 pediatric renal biopsies using electron microscopy.
• Morphological characterization of identified extracellular microfibrils.
• Comparison with known extracellular matrix components like fibrin and collagen.

Main Results:

• Extracellular microfibrils were detected in 47% of the biopsies.
• Microfibrils measured 17-35 nm in diameter, with some showing ~10 nm cross-striations.
• They were located within the mesangial matrix and basal lamina.
• Microfibrils differed morphologically from fibrin and interstitial collagen.
• A close association with thinner filaments was observed, suggesting a common origin.

Conclusions:

• Extracellular microfibrils are a notable ultrastructural finding in a significant proportion of pediatric renal biopsies.
• Their presence in the mesangial matrix and basal lamina may indicate a role in the pathogenesis of various nephropathies.
• The observed association with thinner filaments suggests these microfibrils may originate from mesangial or basal lamina components.