Hypoxia-conditioned mesenchymal stem cell secretome for anal sphincter injury: A preclinical study of tissue repair and regenerative outcomes

Abstract

Fecal incontinence may arise following anal sphincter injury, yet currently available treatments have limited capacity to restore sphincter integrity. The secretome derived from hypoxia-conditioned mesenchymal stem cells (MSCs) represents a potential cell-free regenerative therapy because of its putative immunomodulatory and tissue-remodeling properties. The aim of this study was to investigate the effects of hypoxia-conditioned human umbilical cord MSC secretome on inflammation, fibrosis, collagen deposition, and hypoxia-inducible factor-1 alpha gene (HIF-1A) expression following sphincterotomy. Male Sprague–Dawley rats were randomly assigned to receive either hypoxia-conditioned MSC secretome or 0.9% NaCl after surgical sphincterotomy. Histopathological evaluations using hematoxylin and eosin and Masson’s trichrome staining were conducted at 24 hours and 42 days, and HIF-1A was assessed using quantitative real-time polymerase chain reaction (qRT-PCR). At day 42, inflammation scores were numerically lower in the secretome group than in the control group, although the between-group difference was not statistically significant (0.00±0.00 vs 0.25±0.25; p=0.317). Fibrosis scores showed a similar numerical pattern without a significant difference (3.25±0.25 vs 3.50±0.29; p=0.495). Conversely, the secretome group exhibited numerically greater collagen area (79.93±11.11×10⁴ µm² vs 59.25±7.44×10⁴ µm²; p=0.149) and percentage collagen area (68.81±4.48% vs 56.07±3.29%; p=0.083), but neither difference reached statistical significance. HIF-1A expression was also numerically higher in the secretome group at day 42, without a statistically significant between-group difference (27.47±0.38 vs 26.44±0.54; p=0.149). Although the secretome group exhibited numerically lower inflammation and fibrosis scores and greater collagen deposition and HIF-1A expression, these differences were not statistically significant. Further adequately powered studies incorporating functional, histological, and molecular endpoints are required to clarify the regenerative potential of hypoxia-conditioned MSC secretome in anal sphincter injury.