Neural Stem Cell Transplantation in the Stomach Rescues Gastric Function in Neuronal Nitric Oxide Synthase–Deficient Mice

Background & Aims: Nitric oxide is a major inhibitory neurotransmitter in the enteric nervous system. Loss or dysfunction of nitrinergic neurons is associated with serious disruptions of motility, intractable symptoms, and long-term suffering. The aim of this study was to evaluate the effect of intrapyloric transplantation of neural stem cells (NSCs) on gastric emptying and pyloric function in nNOS^−/− mice, a well-established genetic model of gastroparesis. Methods: NSCs were isolated from embryonic mice transgenically engineered to express green fluorescent protein and transplanted into the pylorus of nNOS^−/− mice. Grafted cells were visualized in pyloric sections and further characterized by immunofluorescence staining. One week posttransplantation, gastric emptying to a non-nutrient meal was measured using the phenol red method and pyloric function was assessed by measuring the relaxation of pyloric strips in an organ bath in response to electrical field stimulation (EFS) under nonadrenergic, noncholinergic conditions. Results: One week following implantation, grafted NSCs differentiated into neurons and expressed neuronal nitric oxide synthase. Gastric emptying was significantly increased in mice that received NSCs as compared with vehicle-injected controls (49.67% vs 35.09%; P < .01 by Student t test). EFS-induced relaxation of pyloric strips was also significantly increased (P < .01 by 2-way analysis of variance). The nitric oxide synthase inhibitor N^G-nitro-l-arginine methyl ester and the neuronal blocker tetrodotoxin blocked the EFS-induced relaxation, indicating that the observed effect is NO mediated and neuronally derived. Conclusions: Our results support the potential of NSC transplantation as a viable therapeutic option for neuroenteric disorders.

Abbreviations used in this paper:  CNS, central nervous system , EFS, electrical field stimulation , GFAP, glial fibrillary acidic protein , GFP, green fluorescent protein , l-NAME, N^G-nitro-l-arginine methyl ester , NANC, nonadrenergicnoncholinergic , nNOS, neuronal nitric oxide synthase , NSC, neural stem cell , PGP9.5, protein gene product 9.5 , TTX, tetrodotoxin , VIP, vasoactive intestinal polypeptide