Biology subjects

Meinhardt, A.

Publications and source records attributed to Meinhardt, A..

3 recordsLinked to original sources

bioRxiv2025

Depletion of CX3CR1+ macrophages results in disrupted functionality and immune surveillance within epididymis and testis

A finely tuned immune regulation within the epididymis and testis is essential for male reproductive health. This balance is especially critical in the epididymis, where sperm mature and ascending infections frequently disrupt homeostasis, resulting in regionally different immune responses and potential long-term fertility impairments. We previously demonstrated that the epididymis harbors a region-specific immunological scaffold, with CX3CR1+ macrophages as the most prominent epithelium-associated immune cell population. Here, we established a transgenic mouse model to selectively deplete these intraepithelial CX3CR1+ macrophages within the epididymis, resulting in focal epithelial damage and impaired sperm maturation processes essential for proper sperm functionality. Additionally, a mild reduction of the testicular macrophage pool resulted in transient disruptions in spermatogenesis and steroidogenesis. Although the macrophage niche was repopulated after depletion, the newly recruited cells displayed altered phenotypes consistent with persistent sperm alterations. Following infection with uropathogenic Escherichia coli (UPEC), macrophage-depleted mice exhibited exacerbated immune responses - particularly in normally protected proximal epididymal regions - with earlier onset and more severe tissue damage. Transcriptomic analysis revealed a failure to restrain inflammatory responses, especially in genes involved in immune regulation and antibacterial defense, accompanied by elevated immune cell infiltration in infected macrophage-depleted mice. Overall, our findings confirm a crucial role for CX3CR1 macrophages in preserving epithelial integrity and modulating immune responses, supporting a stable tissue environment necessary for efficient organ function of both epididymis and testis. Significance statementMaintaining immune balance in the epididymis is essential for tissue health and protection against ascending infections. Using a transgenic mouse model that allows for selective depletion of CX3CR1 macrophages, this study examines their role in both the epididymis and testis under normal and infectious conditions. The results show that the removal of these macrophages causes localized epithelial damage, changes in immune cell make-up, and increased inflammation in the epididymis after bacterial infection, while also causing mild, reversible problems with spermatogenesis and steroid production in the testis. These findings support the idea that CX3CR1 macrophages contribute to region-specific immune regulation and epithelial stability--key features for keeping the tissue environment suitable for proper sperm development.

immunology↗

bioRxiv2023

Iron regulatory proteins 1 and 2 have opposing roles in regulating inflammation in bacterial orchitis

Acute bacterial orchitis (AO) is a prevalent cause of intra-scrotal inflammation, often resulting in sub-or infertility. A frequent cause eliciting AO is uropathogenic Escherichia coli (UPEC), a gram negative pathovar, characterized by the expression of various iron acquisition systems to survive in a low-iron environment. On the host side, iron is tightly regulated by iron regulatory proteins (IRP) 1 and 2 and these factors have been reported to play a role in testicular and immune cell function, however, their precise role remains unclear. Here, we show in a mouse model of UPEC-induced orchitis that the absence of IRP1 results in reduced immune response and testicular damage. Compared to infected wild-type (WT)-mice, testis of UPEC-infected Irp1-/- mice showed impaired ERK signalling. Conversely, IRP2 deletion led to a stronger inflammatory response. Notably, differences in immune cell infiltrations were observed among the different genotypes. In contrast to WT and Irp2-/- mice, no increase in monocytes and neutrophils was detected in testis of Irp1-/- mice upon UPEC-infection. Interestingly, in Irp1-/- UPEC-infected testis, we observed an increase in a subpopulation of macrophages (F4/80+ CD206+) associated with anti-inflammatory and wound-healing activities compared to WT. These findings suggest that IRP1 deletion may protect against UPEC-induced inflammation by modulating ERK signalling and dampening the immune response.

immunology↗

bioRxiv2022

The regional distribution of resident immune cells shapes distinct immunological environments along the murine epididymis

Summary/ AbstractThe epididymis constitutes an important transition zone for post-testicular sperm maturation and storage. As the organ consists of a single convoluted duct, inflammation-associated tissue damage has a severe impact on fertility. In order to clarify the reasons for region-specific differences in the intensity of immune responses observed in a mouse model of acute bacterial epididymitis, we investigated the heterogeneity of resident immune cell populations within the epididymis under physiological conditions by scRNASeq analysis of extravascular CD45+ cells. 12 distinct immune cell subsets were identified, displaying substantial differences in distribution along the epididymis. Several distinct subsets of macrophages constituted the majority of these cells. Crucially, the proximal and distal regions showed striking differences in their immunological landscapes. These findings indicate that resident immune cells are strategically positioned along the epididymal duct, potentially providing different immunological environments required for sperm maturations and elimination of pathogens ascending the urogenital tract.

immunology↗