Transplant Drug Rewires Prostate Tissue in Two Distinct Phases, Rat Study Finds

A drug long used to keep transplanted organs from being rejected may also be a powerful tool for dismantling the fibrous scaffolding that helps drive prostate disease. In a new study published in Reproductive Sciences, a team of Brazilian researchers reports that mycophenolate mofetil, an immunosuppressant better known by the brand name CellCept, triggers a strikingly ordered, two-phase remodeling of the rat prostate, first dissolving the delicate reticular fibers that support the gland’s epithelium and later breaking down the thick collagen cables that give the stroma its strength. The work offers one of the most detailed timelines yet of how an antifibrotic agent reshapes a hormone-sensitive organ from the outside in, and it suggests that fibrosis and androgen signaling, long studied separately, are physically and functionally entangled.

The prostate is not just a bag of secretory cells. It is a composite tissue in which a fibromuscular stroma, packed with collagen, elastic fibers, smooth muscle, blood vessels, nerves and immune cells, wraps around and actively regulates the glandular epithelium. When that stroma stiffens with excess collagen, a process called fibrosis, the epithelial cells above it can lose their normal growth controls, a shift implicated in benign prostatic hyperplasia and in the reactive stroma that surrounds prostate tumors. Prostate cancer remains one of the most common malignancies worldwide, with roughly 1.4 million new cases recorded in 2020, making any strategy that softens or reorganizes the stromal matrix of considerable clinical interest.

Mycophenolate mofetil was developed to block lymphocyte proliferation after transplantation. Once in the body it is hydrolyzed into mycophenolic acid, a potent, selective and reversible inhibitor of inosine monophosphate dehydrogenase, an enzyme essential to the de novo synthesis of guanosine nucleotides. Lymphocytes depend heavily on this pathway, which is why the drug works as an immunosuppressant. But fibroblasts rely on the same guanosine-dependent machinery to proliferate, migrate and adhere, and mycophenolic acid also downregulates cytoskeletal proteins such as vinculin, actin and tubulin while cutting collagen output and boosting matrix metalloproteinase expression. The result, the researchers reasoned, could be a pharmacologically induced softening of fibrotic tissue, and the rat prostate offered an ideal, hormone-sensitive testing ground.

The team, led by Luiz Roberto Falleiros Junior of São Paulo State University and collaborators at the Federal University of Goiás, UNICAMP and the Faculty of Medicine of São José do Rio Preto, gave adult male Wistar rats 30 milligrams per kilogram of the drug daily by gavage for either 7 or 30 days, with a saline-treated control group for comparison. They then subjected the ventral prostate to an unusually thorough battery of analyses: stereological point counting to quantify each tissue compartment, histochemical stains for collagen I, collagen III and elastic fibers, polarization microscopy to assess collagen aggregation, and immunohistochemistry for matrix metalloproteinases 2 and 13, the inhibitor TIMP-1, the androgen receptor, both estrogen receptors, proliferation and apoptosis markers, smooth muscle actin and macrophages. Mast cells were counted with toluidine blue, and lesions were graded using standard rodent prostate pathology criteria.

The first phase of remodeling emerged within a week. After just 7 days of treatment, the area occupied by collagen III, the thin reticular fibers that form a supportive network beneath the epithelium, had dropped significantly, and elastin fibers had diminished as well. This early matrix disassembly coincided with a marked rise in matrix metalloproteinase 2, an enzyme expressed in the non-muscular stroma that not only degrades basement membrane components but also activates other, more aggressive MMPs in the stromal cascade and participates in elastolysis. Because collagen III helps anchor and polarize epithelial cells, its loss had immediate consequences upstairs: epithelial cells showed reduced androgen receptor expression, less proliferation as measured by phosphohistone H3, and more apoptosis, revealed by activated caspase-3, in both the epithelium and the stroma.

The second phase unfolded over the following weeks. By 30 days, the drug had turned its attention to collagen I, the thick, highly birefringent fiber type that organizes stromal cells and orients the smooth muscle layer. Polarization microscopy showed reduced collagen aggregation, indicating a softer extracellular matrix, and this breakdown tracked with a surge in matrix metalloproteinase 13, or collagenase 3, detected in luminal epithelial cells and in the smooth muscle layer. At the same time the muscular stroma thinned, the non-muscular stroma expanded, and blood vessel density increased, a pattern consistent with matrix softening and with MMP-13’s known association with angiogenesis. Notably, TIMP-1, the natural brake on the metalloproteinases, showed no significant change at either time point, leaving the remodeling enzymes essentially unchecked.

The immune system turned out to be a scheduled participant rather than a bystander. Degranulated mast cells, which release their own matrix-degrading enzymes when they discharge their granules, rose early and remained elevated through 30 days, while intact mast cells plummeted. Macrophages, identified by the F4/80 marker, increased only at the later time point and formed clusters in the periglandular stroma of treated animals, alongside a rise in inflammatory foci. The authors interpret this sequence as successive waves of immune involvement: mast cells kick off extracellular matrix degradation, and macrophages arrive later to phagocytose the debris and clear the way for tissue reorganization. Inflammatory cells also stained positive for TIMP-1, hinting at a more complex regulatory dialogue than the simple enzyme-inhibitor balance alone.

Perhaps the most provocative finding concerns the androgen axis. Androgen receptor levels in the epithelium fell sharply at both time points, and the incidence of high-grade prostatic intraepithelial neoplasia, a precancerous lesion that depends on androgen signaling, dropped at 30 days, while simple hyperplasia increased. The authors propose a mechanistic explanation drawn from prior work: mycophenolic acid activates the aryl hydrocarbon receptor, which interferes with androgen receptor transcription, and it also impairs androgen receptor phosphorylation through the MAPK8/9 pathway, blocking the nuclear translocation the receptor needs to function. The researchers are careful to note that their two-endpoint design cannot establish causality, and that the rise in hyperplasia shows the drug did not restore normal glandular homeostasis but rather redirected the epithelium toward a proliferative pattern lacking pre-neoplastic features.

The study’s authors go further, proposing that the compartment-specific measurements they tracked, including the collagen I to III ratio, MMP2 and MMP13 immunolabeling, smooth muscle area and microvascular density, could serve as pharmacodynamic readouts of antifibrotic efficacy in future studies, much as circulating collagen turnover markers have been used to identify responders in other fibroproliferative diseases. They also raise, explicitly as an untested hypothesis, the possibility that antifibrotic interventions like mycophenolate mofetil could restrain androgen-dependent lesions in conditions such as benign prostatic hyperplasia. Validating that idea, they caution, would require established hyperplasia models, dose-response protocols, intermediate time points, paired tissue and serum measurements, long-term follow-up, and a careful weighing of the systemic immunosuppression the drug inevitably causes. Biometric data offered reassurance in the short term, with no differences in body or prostate weight between treated and control animals.

What makes the study resonate beyond urology is its demonstration that a stroma-targeted drug reached the epithelium through hormone signaling, placing fibrotic status and androgen responsiveness on connected axes of prostatic homeostasis. If the two remodeling windows the team identified hold up in larger and longer studies, clinicians may one day time antifibrotic therapy against measurable tissue benchmarks rather than trial and error, and the humble immunosuppressant in every transplant pharmacy may find a second career as a precision instrument for softening the scarred landscapes where prostate disease takes root.

Subject of Research: Antifibrotic effects of mycophenolate mofetil on stromal remodeling and collagen dynamics in the rat prostate

Article Title: Stromal Remodeling and Collagen Dynamics under Antifibrotic Conditions in the Rat Prostate

Article References: Falleiros Junior, L. R., Ruiz, T. F. R., Grigio, V., Bicalho-Silva, S., Colleta, S. J., de Souza, L. G., Ferrato, L. J., Vilamaior, P. S. L., da Silveira Antoniassi, T., Spessoto, L. C. F., Taboga, S. R., & Facio Junior, F. N. (2026). Stromal Remodeling and Collagen Dynamics under Antifibrotic Conditions in the Rat Prostate. Reproductive Sciences. https://doi.org/10.1007/s43032-026-02221-5

Image Credits: AI Generated

DOI: 10.1007/s43032-026-02221-5

Keywords: mycophenolate mofetil, prostate, fibrosis, collagen, matrix metalloproteinases, stroma, androgen receptor, mast cells, macrophages, extracellular matrix, rat model, antifibrotic therapy