Differential Hematopoietic Activity in White Adipose Tissue Depending on its Localization

Area of Science:

• Immunology
• Hematopoiesis
• Adipose tissue biology

Background:

• White adipose tissue (WAT) deposits have distinct physiopathological roles based on location (subcutaneous vs. visceral).
• Functional hematopoietic stem/progenitor cells (HSPC) previously identified in subcutaneous adipose tissue (SCAT) contribute to local immune cell renewal.
• The presence and function of HSPC in visceral adipose tissue (VAT) and potential location-specific differences in hematopoiesis remain unexplored.

Purpose of the Study:

• To investigate the presence of HSPC in VAT.
• To compare the in situ hematopoietic activity of HSPC between VAT and SCAT.
• To determine if anatomical location influences hematopoiesis and site-specific immune cell content within WAT.

Main Methods:

• Identification and characterization of HSPC in VAT.
• In vitro assays to assess hematopoietic potential of HSPC from VAT and SCAT.
• In vivo competitive repopulation experiments using sorted HSPC from VAT and SCAT.
• Analysis of the microenvironmental factors (secreted factors, extracellular matrix) influencing HSPC function in VAT.

Main Results:

• HSPC were identified for the first time in VAT.
• HSPC derived from VAT demonstrated significantly lower hematopoietic activity compared to those from SCAT.
• The reduced hematopoietic activity in VAT HSPC is attributed to their specific microenvironment, including adipose-derived stromal cells, secreted factors, and extracellular matrix components.

Conclusions:

• Hematopoietic activity within WAT is a general phenomenon but exhibits site-specific variations.
• The VAT microenvironment modulates HSPC function, leading to reduced hematopoietic capacity compared to SCAT.
• Understanding these location-specific differences in adipose tissue hematopoiesis is crucial for comprehending immune cell dynamics and potential physiopathological roles.