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Emerging research in human studies suggests an association among vitamin B6, sarcopenia, and muscle strength. However, very little is known regarding its potential role at the cellular level, especially in muscle satellite cells. Therefore, to determine whether vitamin B6 affects the satellite cells, we isolated single myofibers from muscles of vitamin B6-deficient and vitamin B6-supplemented mice. Subsequently, we subjected them to single myofiber culture and observed the number and function of the satellite cells, which remained in their niche on the myofibers. Prior to culture, the vitamin B6-deficient myofibers exhibited a significantly lower number of quiescent satellite cells, as compared to that in the vitamin B6-supplemented myofibers, thereby suggesting that vitamin B6 deficiency induces a decline in the quiescent satellite cell pool in mouse muscles. After 48 and 72 h of culture, the number of proliferating satellite cells per cluster was similar between the vitamin B6-deficient and -supplemented myofibers, but their numbers decreased significantly after culturing the myofibers in vitamin B6-free medium. After 72 h of culture, the number of self-renewing satellite cells per cluster was significantly lower in the vitamin B6-deficient myofibers, and the vitamin B6-free medium further decreased this number. In conclusion, vitamin B6 deficiency appears to reduce the number of quiescent satellite cells and suppress the proliferation and self-renewal of satellite cells during myogenesis.

Objectives So far, there is scarce information on potential roles of vitamin B6 (B6) in muscle regeneration. Thus, we examined if B6 has any effects on satellite cells (SCs), the muscle stem cells crucial for muscle regeneration. Methods Male ICR mice were divided into two groups receiving a B6 deficient level diet (1 mg pyridoxine (PN) HCl/kg diet) or a B6 supplement level diet (35 mg PN HCl) for 6 weeks (n = 6/group). Single fibers were isolated from EDL muscles and cultured in plating medium at 37°C, for 0 or 48 hr. Then, fixed fibers were co-immunostained for Pax7 and MyoD. Without culturing (0 hr), SCs are in quiescent state and stained positive with Pax7 +. Following 48 hr of culture, SCs will be activated and enter cell cycle for proliferation (stained positive with MyoD + Pax7+), commitment to differentiation (stained positive with MyoD+), or self-renew (stained positive with Pax7+). Results Without culturing (0 hr), the number of SCs on single fibers isolated from the muscles of the B6-deficient mice was lower than that in the B6-supplement mice (4.0 vs. 7.2 Pax7 + nuclei/fiber, P < 0.01), suggesting that B6 deficiency possibly induced a decline in the quiescent population of SCs. At 48 hr of culture, as compared to the B6-supplement mice, the B6-deficient mice showed the lower number of MyoD + Pax7 + clusters (3.7 vs. 8.1 clusters/fiber, P < 0.01) and the lower number of Pax7 + nuclei (P < 0.01), but no effects on the number of MyoD + nuclei. This suggested that B6 deficiency might affect the self-renewal function of SCs, while had less effects on proliferation and differentiation. Next, we hypothesized that the adverse effects of B6 deficiency on SCs is reversible, since the plating medium contained normal levels of B6. To test this hypothesis, single fibers isolated from the muscles of the B6-deficient mice were cultured in the medium contained with or without B6. As a result, the number of MyoD + Pax7 + clusters on single fibers in the culture without B6 was lower than that with B6 (2.6 vs. 3.7 clusters/fiber, P < 0.05), indicating that SCs cultured without B6 barely proliferated and possibly underwent apoptosis. Conclusions B6 may play a role in proliferation and apoptosis prevention of SCs. This study is the first to show the effects of B6 on SC function and will pave the way for new research on the role of B6 in muscle regeneration in the future. Funding Sources None.