Table 1.

Previously Published Research on Neurogenesis in Enteric Nerves After Postnatal Day 21

Mouse strain/genetic background	Age at DNA replication label application	Anatomic region analyzed	Method	No. of ganglia/neurons counted, no. of mice used	ENS neurogenesis/replication after P21	Reference
CD-1	E8-E18, P1-P5, P7, P9, P14, and P21	Duodenum and jejunum	[3H] thymidine; 4 injections in 12 or 24 h, analysis at P30	142 ± 5 myenteric ganglia, 341 ± 42 submucosal ganglia per 1 cm, no. of mice not specified	No	Pham et al, 1991
SvEv129	At least 6 weeks	Small intestine (not specified) and colon	Alzet pump (BrdU ∼30 mg, kg−1, d−1) 7 days, then 2-wk chase	No. of ganglia/neurons not specified, no. of mice not specified	No	Liu et al, 2009
Not specified	E7.5, E8.5, E12.5, P0, P7, P30, P84	Small intestine (not specified)	Lineage tracing (Sox10::iCreERT2;R26eYFP) analysis at P84, P140	More than 3000 neurons, no. of mice = 4	P30 = 1.6% ± 1.1%, P84 = 0.6% ± 0.2%	Laranjeira et al, 2011
C57BL/6J	P120	Stomach, duodenum, distal ileum, cecum, and colon	6-wk pulse, 6-wk chase (intraperitoneal injection of BrdU 50 μg/g body weight, followed by BrdU in the drinking water (0.5 mg/mL) for 6 weeks	More than 1000 neurons per mouse, no. of mice = 3	No	Joseph et al, 2011
C57BL/6J	4 months	Distal colon	EdU (intraperitoneal 50 mg/kg) every 48 hours for 7 days, then every 12 hours for the next 48 hours, and 1 and 2 hours before death	No. of ganglia/neurons not specified, no. of mice = 4	No	Belkind-Gerson et al, 2015
C57BL/6J	2–4 months	Distal colon	Lineage tracing (Sox2CreER:YFP) and EdU (intraperitoneal 50 mg/kg) every 24 hours (total 7 injections)	More than 10,000 neurons to analyze EdU+ neurons, no. of mice = 4	2 mo = 3.5% ± 2.2% YFP+/HuD+ 4 mo = 0.7% ± 1.1% YFP+/HuD+, no EdU+/HuD+	Belkind-Gerson et al, 2017
C57BL/6J	8–24 weeks	Ileum	IdU (1 mg/mL) for 7 days in the drinking water or IdU (1 mg/mL) for 7 days and then exchanged to CldU (1 mg/mL) for 7 days in the drinking water	No. of ganglia/neurons not specified, no. of mice = 3	Yes, ∼70% after 1 week, 88% 2 weeks	Kulkarni et al, 2017
C57BL/6J	8–12 weeks	Ileum and colon	EdU (intraperitoneal 1 mg) for 7 days	Not specified	No	Vicentini et al, 2021

NOTE. Pham et al⁴ analyzed the ENS at P30 after injecting tritiated thymidine 4 times within 24 hours on days P1-P5, P7, P9, P14, and P21, but they reported no enteric neurons in the duodenum and jejunum that had retained the label after P21. Liu et al⁵ did not observe new enteric neurons in the adult mouse gut after continuous application of BrdU for 7 days, followed by a 2-week chase without BrdU. Laranjeira et al⁶ did not find convincing evidence of neurogenesis in the adult small intestine after 1–3 months of age in fate-mapping experiments using Sox10::iCreER^T2;R26ReYFP mice, which were analyzed for YFP expression at P84 and P130. Joseph et al⁷ did not observe label retention of BrdU in the ENS throughout the GI tract in 4-month-old mice with 6 weeks of BrdU labelling in the drinking water, followed by a 6-week chase without BrdU. Belkind-Gerson et al^8,9 used EdU labelling to analyze the distal colon and found no evidence of neuronal replication in adult mice. Similarly, Vicentini et al¹⁰ found no evidence of neuronal replication after EdU labelling. Kulkarni et al¹¹ observed ∼70% turnover rate of enteric neurons after 1 week and 88% turnover rate after 2 weeks using IdU and CldU labelling in the ileum.