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MSc Inês Alvito Félix defended her dissertation in Medical microbiology and immunology entitled “Ontogeny and function of adipose tissue macrophages” at the University of Turku on 3 November 2023 at 12.00 (University of Turku, Dentalia, Arje Scheinin lecture hall, Lemminkäisenkatu 2, Turku).

Opponent: Professor Francesc Villaroya (University of Barcelona, Spain)
Custos: Docent Pia Rantakari (University of Turku)

Doctoral Dissertation at UTUPub: https://urn.fi/URN:ISBN:978-951-29-9487-8

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Summary of the Doctoral Dissertation:

Obesity is associated with the accumulation of adipose tissue and increased risk of type II diabetes and cancer, for example. This study explores the interaction between macrophages of different origins and their function in maintaining energy balance and homeostasis of adipose tissue, aiming to identify new targets for obesity prevention and treatment.

Macrophages are immune cells responsible for the clearance of pathogens and damaged cells, being central to the inflammatory process. Beyond their immune functions, they are crucial for the healthy development and homeostasis of most tissues. Tissue-resident macrophages are specialized and perform tissue-specific functions. Each adult tissue hosts a unique pool of macrophages from different origins, either from embryonic period (self-renewing within the tissue) or after birth from the bone marrow.

Adipose tissue can be white, the energy is stored as fat, or brown the fat is converted into heat. I aimed to understand the role of different origin macrophages in adipose tissue development and physiology by ing three murine fat depots: mammary gland (MG), epididymal white adipose tissue (WAT) and interscapular brown adipose tissue (BAT).

Adipose tissue macrophages modulate the functioning of both healthy and diseased adipose tissues. They regulate MG development, influx into the tissue and contribute to inflammation in WAT during obesity, and help maintain BAT‘s neuronal network. However, whether the origin of these macrophages has a significant impact on their functions within the tissue is still under study.

My research revealed that embryonic macrophages play a crucial role in the development of mammary ducts and remain the primary macrophage population in adult MG. I present a novel unified approach for the subtyping of WAT macrophages and found that embryonic-derived macrophages maintain their numbers even in obesity, suggesting a role in WAT homeostasis. In BAT, my findings suggest that embryonic macrophages are essential for neonatal thermogenesis but are rapidly replaced by bone marrow-derived macrophages during the first weeks of life.

In summary, embryonic-derived macrophages are vital for the healthy development of different adipose tissues, each exhibiting specific functions and dynamics depending on the fat pad they inhabit.