No abstract

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.