Fibroblast distribution and localization in male reproductive organs: a mouse model study via lineage tracing

Background: Fibroblasts are vital for tissue structure, repair, and fibrosis in male reproductive organs, but tools for investigating their localization and distribution are limited. This study employed the collagen type I alpha 2 Cre recombinase estrogen receptor tandem dimer Tomato (Col1a2CreERtdTomato (Tom)) lineage tracing mouse model, enabling tamoxifen-inducible, fibroblast-specific labeling through Cre recombination under the Col1a2 promoter. This system labels collagen-producing fibroblasts with tdTomato, enabling lineage tracing and visualization of their organization in the penis, prostate, and testis. The study aimed to investigate fibroblast distribution and localization in these organs using this model. Methods: Male Col1a2CreERTom mice (n = 5—6) received tamoxifen (1 mg/day/mouse, intraperitoneal, for 5 consecutive days) to induce Cre recombination and label collagen-producing fibroblasts with tdTomato. Wild type (WT) control mice (n = 3) also received tamoxifen. Two days after the last injection, penis, prostate, and testis tissues were harvested, sectioned, and examined through microscopy on tdTomato epifluorescence. Fibroblasts were quantified as the percentage of tdTomato+ cells relative to total cells. Results: Quantification revealed distinct fibroblast distribution patterns among the organs. In the Col1a2CreERTom mouse, tdTomato+ fibroblasts were most abundant in the penis (75.24 ± 1.6%), followed by the prostate (26.02 ± 1.4%) and testis (13.97 ± 0.9%). Within the penis, the subtunical region had the highest density (93.42 ± 0.5%). In the prostate, fibroblasts were mainly within the fibromuscular stroma; in the testis, they were in the tunica albuginea and interstitial compartments. No tdTomato+ cells were observed in WT controls. Conclusions: The number and location of collagen-producing fibroblasts differ among the penis, prostate, and testis, and vary within penile compartments. These findings reflect the organ- and region-specific distribution of Col1a2-lineage fibroblasts, as revealed by tamoxifen-induced tdTomato lineage tracing. This study provides a useful tool for further investigation of fibroblast function in male reproductive health.