Introduction :

At the cardiac level, the intrinsic cardiac nervous system (ICNS) functions as a local integration center for autonomic afferent signals. As such, it plays a critical role in the physiological regulation of cardiac function, and its pathophysiological remodeling has become a subject of growing research interest. Recent evidence suggests that neurogenesis can occur in the adult peripheral nervous system through the differentiation of progenitor cells. This raises questions about the potential presence of such progenitor cells within the ICNS and their involvement in its pathological remodeling.

Objectives :

Given that ICNS can be influenced by cardiac pathologies and clinical interventions such as atrial fibrillation ablation, we investigated the presence of progenitor cells in the adult ICNS and their capacity to exhibit key stem cell properties in vitro.

Materials and Methods :

Cardiac ganglia were isolated from adult mice, dissociated, and cultured in neural stem cell medium to facilitate sphere formation. Progenitor cells were identified based on the expression of stem cell markers SOX2 and nestin. Self-renewal and proliferative capacities were assessed by the formation of secondary spheres upon replating and by the expression of the proliferation marker Ki-67. In vitro differentiation was evaluated through beta III tubulin expression following culture in differentiation medium; in some cultures, BrdU was added to determine the fate of cells born in vitro. Additionally, a rat model of monocrotaline-induced right heart disease was used to investigate the impact on progenitor cell proliferation in situ via immunohistochemistry.

Results :

Our study demonstrated the presence of the stem cell marker SOX2 in the cardiac ganglia of adult mice. In vitro, these proliferate to from primary spheres that, express the proliferation marker Ki-67, along with the progenitor markers SOX2 and nestin. To assess self-renewal, the primary spheres were dissociated into individual cells and replated on new dishes. Secondary spheres expressing the same markers were then obtained, confirming the self-renewing properties of SOX2 positive cells. Besides, these neural stem-like cells undergo differentiation in culture toward a neuronal fate, as demonstrated by the expression of tubulin beta 3, the neuron specific protease PGP9.5 and PSA-NCAM, when cultured with differentiation factors. Finally, numerous proliferative cells expressing Ki-67 can be observed in ganglia of the monocrotaline rat model compared to control, including SOX2 positive cells.

Conclusion :

Our study unveils for the first time the existence of neurogenesis in adult rodent ICNS through the identification of SOX2 positive cells that display properties of neuronal progenitor in vitro.