Longitudinal intravital imaging of transplanted mesenchymal stem cells elucidates their functional integration and therapeutic potency in an animal model of interstitial cystitis/bladder pain syndrome

Abstract

<b>Rationale:</b> Mesenchymal stem cell (MSC) therapy may be a novel approach to improve interstitial cystitis/bladder pain syndrome (IC/BPS), an intractable disease characterized by severe pelvic pain and urinary frequency. Unfortunately, the properties of transplanted stem cells have not been directly analyzed <i>in vivo</i>, which hampers elucidation of the therapeutic mechanisms of these cells and optimization of transplantation protocols. Here, we monitored the behaviors of multipotent stem cells (M-MSCs) derived from human embryonic stem cells (hESCs) in real time using a novel combination of <i>in vivo</i> confocal endoscopic and microscopic imaging and demonstrated their improved therapeutic potency in a chronic IC/BPS animal model. <b>Methods:</b> Ten-week-old female Sprague-Dawley rats were instilled with 10 mg of protamine sulfate followed by 750 μg of lipopolysaccharide weekly for 5 weeks. The sham group was instilled with phosphate-buffered saline (PBS). Thereafter, the indicated dose (0.1, 0.25, 0.5, and 1×10⁶ cells) of M-MSCs or PBS was injected once into the outer layer of the bladder. The distribution, perivascular integration, and therapeutic effects of M-MSCs were monitored by <i>in vivo</i> endoscopic and confocal microscopic imaging, awake cystometry, and histological and gene expression analyses. <b>Results:</b> A novel combination of longitudinal intravital confocal fluorescence imaging and microcystoscopy in living animals, together with immunofluorescence analysis of bladder tissues, demonstrated that transplanted M-MSCs engrafted following differentiation into multiple cell types and gradually integrated into a perivascular-like structure until 30 days after transplantation. The beneficial effects of transplanted M-MSCs on bladder voiding function and the pathological characteristics of the bladder were efficient and long-lasting due to the stable engraftment of these cells. <b>Conclusion:</b> This longitudinal bioimaging study of transplanted hESC-derived M-MSCs in living animals reveals their long-term functional integration, which underlies the improved therapeutic effects of these cells on IC/BPS.