Composition of the Extracellular Matrix of Lymphatic Novel Threadlike Structures : Is It Keratin?

Abstract EN

Background.

The lumen of novel threadlike structures (NTSs) is enclosed by a single layer of endothelial cells surrounded by extracellular matrix (ECM).

We hypothesized that collagen may be a component of the ECM associated with lymphatic NTSs.

Methods.

Six female New Zealand white rabbits were anesthetized, and the NTS structures within lymphatic vessels were identified by contrast-enhanced stereomicroscopy or alcian blue staining.

Isolated NTS specimens were stained with acridine orange, YOYO-1, and 1,1′-dioctadecyl-3,3,3′,3′-tetramethylindocarbocyanine perchlorate (DiI).

The structural and molecular composition of the ECM was investigated using transmission electron microscopy (TEM), electrospray ionization-mass spectrometry, and proteomic analysis.

Results.

The lymph vessel wall was stained red by DiI, and rod-shaped nuclei were stained green by YOYO-1.

The area surrounding the NTS was also stained red and contained green rod-shaped nuclei.

TEM images showed that the NTS consisted of many ECM fibers and the ECM fibers appeared to be ~100 nm in diameter and had narrowly spaced striated bands.

Proteomic analysis of the lymphatic NTS-associated ECM identified 4 proteins: keratin 10, cytokeratin 3, cytokeratin 12, and soluble adenylyl cyclase.

Conclusion.

The TEM study suggested that the lymphatic NTS-associated ECM did not contain collagen.

This was confirmed by proteomic analysis, which showed that keratin was the major component of the ECM.