Phenotypic differences between red pulp capillary and sinusoidal endothelia help localizing the open splenic...

Area of Science:

• Immunohistology
• Human Anatomy
• Vascular Biology

Background:

• The splenic red pulp's microvasculature, including capillaries and sinuses, plays a crucial role in blood filtration and immune responses.
• Previous understanding of splenic vascular architecture, particularly the distinction between capillaries and sinuses, has been limited.

Purpose of the Study:

• To investigate the distribution and phenotypes of endothelial cells in human splenic vasculature.
• To differentiate between splenic red pulp capillaries and sinuses using specific endothelial markers.
• To provide a basis for understanding the "open" versus "closed" splenic circulation models.

Main Methods:

• Immunohistochemistry was performed on paraffin-embedded sections of 12 adult human spleens.
• A panel of antibodies, including anti-CD34 and anti-CD141 (thrombomodulin), was used for double staining.
• Differential expression of CD34 and CD141 on endothelial cells of capillaries, sinuses, and larger vessels was analyzed.

Main Results:

• Splenic red pulp capillary endothelia were CD34(+)CD141(-).
• Red pulp sinus endothelia exhibited a CD34(-)CD141(+) phenotype.
• Sinus endothelial cells near follicles showed co-expression of both antigens (CD34(+)CD141(+)).
• Endothelium of larger arteries and veins uniformly expressed both CD34 and CD141.
• Both antibodies also reacted with splenic stromal cells.

Conclusions:

• Splenic sinuses are distinct vascular structures, not merely a continuation of capillaries.
• The differential expression of CD34 and CD141 serves as a reliable marker to distinguish between splenic capillaries and sinuses.
• These findings support a more precise delineation of the human splenic circulation, potentially enabling 3D reconstruction for further functional studies.