Toward clinically relevant models of complex perianal fistulas: refining preclinical evaluation for exosome-based therapies

Abstract

This letter commends Lu et al. for their innovative preclinical study demonstrating the therapeutic potential of hUCMSCs-Exo in treating complex perianal fistulas (CPF) through HIF-1α/TGF-β/Smad pathway activation, collagen synthesis, and gut microbiota modulation. While acknowledging the study's significant advances, the authors highlight three translational considerations: anatomical disparities between rodent models and humans, long-term safety concerns, and the need for comparative efficacy studies. To refine the experimental model, they propose enhancements in fistula stability and tracking, including extending wire retention to 6–8 weeks, biweekly intraluminal E. coli injections, and using contrast-enhanced MRI for longitudinal monitoring. These refinements aim to better mimic human fibrotic progression and improve clinical predictability.

1. Introduction

Complex perianal fistulas (CPF) represent a challenging clinical entity with high recurrence rates and significant morbidity. Current therapeutic options, including surgical intervention and biologic agents, often fall short, underscoring the need for innovative, minimally invasive approaches. In a recent issue of Stem Cell Research & Therapy, Lu et al. reported a groundbreaking preclinical study demonstrating the therapeutic potential of human umbilical cord mesenchymal stem cell-derived exosomes (hUCMSCs-Exo) in treating CPF. Their work elegantly delineates the molecular mechanisms involving HIF-1α/TGF-β/Smad pathway activation, enhanced collagen synthesis, and modulation of gut microbiota, providing a robust foundation for translational development.

While this study marks a significant advance, several translational considerations warrant careful attention. First, the anatomical disparities between rodent models and humans—particularly in sphincter complexity and microbiota composition—may limit the clinical predictability of the findings. Validation in large-animal models with anal physiology akin to humans, such as porcine or canine models, could enhance translational relevance. Second, although short-term safety was established, long-term risks such as unintended exosomal cargo effects or immune priming require systematic evaluation. Third, comparative efficacy studies against existing therapies, such as anti-TNF biologics or adipose-derived stem cells, would clarify the niche of hUCMSCs-Exo in clinical algorithms.