Trem2/Dap12/Syk/PI3K axis contributes to the protection against cryptorchidism outcomes via modulating testicular macrophages

Published: 28 August 2024| Version 1 | DOI: 10.17632/3vkkvs26zf.1
Contributor:
Songyi Ye

Description

Reduced hormone insulin-like 3 (Insl3), exclusively secreted by Leydig cells, has been identified as a recognized mechanism of cryptorchidism. Testicular macrophages residing in the testicular interstitium were thought to play a vital role on promoting Leydig cell hormone secretion, but their exact role in cryptorchidism remained poorly understood. Here, through RNA-seq analysis of normal and human cryptorchidism testes, triggering receptor expressed on myeloid cell-2 (Trem2) could be recognized as the most significant macrophage marker gene involved in human cryptorchidism, with Trem2-/- mouse testes at embryonic day 16.5 (E16.5) showing reduced Insl3 levels, leading to approximately 60% cryptorchidism mice. In our investigation into the underlying cause, utilizing an in vitro co-culture system, we found that Trem2-silenced macrophages impaired the proliferative capacity of Testicular macrophages acquired a distinctive transcriptional profile in unique cytoplasmic cross-fingering interactions with Leydig cells, primarily mediated by the Trem2-DNAX activation protein 12 (Dap12) receptor complex, which transduces intracellular signals via the spleen tyrosine kinase (Syk) and phosphoinositide 3-kinase (PI3K). Mechanistically, we found a reduction in the level of transforming growth factor-β (TGF-β), accompanied by elevated levels of interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α) in RAW264.7 cells by ketoconazole (KET) treatment. Additionally, we found a positive correlation between Trem2 and Insl3 expression in a human ex vivo tissue culture model. In summary, our study proposes Trem2 as a novel target for maintaining normal testicular descent by regulating the testicular immune microenvironment.

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Reduced hormone insulin-like 3 (Insl3), exclusively secreted by Leydig cells, has been identified as a recognized mechanism of cryptorchidism. Testicular macrophages residing in the testicular interstitium were thought to play a vital role on promoting Leydig cell hormone secretion, but their exact role in cryptorchidism remained poorly understood. Here, through RNA-seq analysis of normal and human cryptorchidism testes, triggering receptor expressed on myeloid cell-2 (Trem2) could be recognized as the most significant macrophage marker gene involved in human cryptorchidism, with Trem2-/- mouse testes at embryonic day 16.5 (E16.5) showing reduced Insl3 levels, leading to approximately 60% cryptorchidism mice. In our investigation into the underlying cause, utilizing an in vitro co-culture system, we found that Trem2-silenced macrophages impaired the proliferative capacity of Testicular macrophages acquired a distinctive transcriptional profile in unique cytoplasmic cross-fingering interactions with Leydig cells, primarily mediated by the Trem2-DNAX activation protein 12 (Dap12) receptor complex, which transduces intracellular signals via the spleen tyrosine kinase (Syk) and phosphoinositide 3-kinase (PI3K). Mechanistically, we found a reduction in the level of transforming growth factor-β (TGF-β), accompanied by elevated levels of interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α) in RAW264.7 cells by ketoconazole (KET) treatment. Additionally, we found a positive correlation between Trem2 and Insl3 expression in a human ex vivo tissue culture model. In summary, our study proposes Trem2 as a novel target for maintaining normal testicular descent by regulating the testicular immune microenvironment.

Institutions

Affiliated Hospital of Nantong University

Categories

Microenvironment, Cryptorchidism

Funding

National Natural Science Foundation of China

82171587

Natural Science Foundation of Nantong Municipality

JC2023100

National Natural Science Foundation of China

82471631

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