The open microcirculation in human spleens: a three-dimensional approach

Area of Science:

• Hematology
• Anatomy
• Physiology

Background:

• The microcirculation of the human spleen's red pulp has been debated, with uncertainty regarding whether it's an open or closed system.
• Understanding spleen microcirculation is crucial for comprehending its role in blood filtration and immune responses.

Purpose of the Study:

• To definitively determine the nature of the microcirculation within the human splenic red pulp.
• To investigate the connections between arterial microvessels and venous sinuses in the spleen.

Main Methods:

• Differential immunohistology using CD34 and CD141 reagents to stain endothelium of arterial microvessels and venous sinuses.
• Three-dimensional reconstruction of splenic red pulp microvasculature from serial paraffin sections.
• Analysis of 142 arterial microvascular ends in specimens from three individuals to trace their connections.

Main Results:

• No arterial microvascular ends in the splenic red pulp were found to connect directly to venous sinuses.
• The study provides strong evidence for an entirely open circulatory system within the human splenic red pulp.
• This suggests the spleen is unique among human organs for having blood flow through spaces not fully lined by endothelial cells.

Conclusions:

• The human splenic red pulp operates as an entirely open circulatory system.
• This finding resolves the long-standing debate regarding spleen microcirculation.
• The spleen's unique circulatory arrangement has implications for its function in blood processing and immune surveillance.