Vitamin A retinoic acid contributes to muscle stem cell and mitochondrial function loss in old age
Paula M. Fraczek, Pamela Duran, Benjamin A. Yang, Valeria Ferre, Leanne Alawieh, Jesus A. Castor-Macias, Vivian T. Wong, Steve D. Guzman, Celeste Piotto, Klimentini Itsani, Jacqueline A. Larouche, Carlos A. Aguilar
Paula M. Fraczek, Pamela Duran, Benjamin A. Yang, Valeria Ferre, Leanne Alawieh, Jesus A. Castor-Macias, Vivian T. Wong, Steve D. Guzman, Celeste Piotto, Klimentini Itsani, Jacqueline A. Larouche, Carlos A. Aguilar
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Research Article Aging Muscle biology Stem cells

Vitamin A retinoic acid contributes to muscle stem cell and mitochondrial function loss in old age

Abstract

Adult stem cells decline in number and function in old age, and identifying factors that can delay or revert age-associated adult stem cell dysfunction are vital for maintaining a healthy lifespan. Here we show that vitamin A, a micronutrient that is derived from diet and metabolized into retinoic acid, acts as an antioxidant and transcriptional regulator in muscle stem cells. We first show that obstruction of dietary vitamin A in young animals drives mitochondrial and cell cycle dysfunction in muscle stem cells that mimics old age. Next, we pharmacologically targeted retinoic acid signaling in myoblasts and aged muscle stem cells ex vivo and in vivo and observed reductions in oxidative damage, enhanced mitochondrial function, and improved maintenance of quiescence through fatty acid oxidation. We next detected that the receptor for vitamin A–derived retinol, stimulated by retinoic acid 6 or Stra6, was diminished with muscle stem cell activation and in old age. To understand the relevance of Stra6 loss, we knocked down Stra6 and observed an accumulation of mitochondrial reactive oxygen species, as well as changes in mitochondrial morphology and respiration. These results demonstrate that vitamin A regulates mitochondria and metabolism in muscle stem cells and highlight a unique mechanism connecting stem cell function with vitamin intake.

Authors

Paula M. Fraczek, Pamela Duran, Benjamin A. Yang, Valeria Ferre, Leanne Alawieh, Jesus A. Castor-Macias, Vivian T. Wong, Steve D. Guzman, Celeste Piotto, Klimentini Itsani, Jacqueline A. Larouche, Carlos A. Aguilar

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Figure 1

Dietary depletion of vitamin A induces premature activation and oxidative damage in muscle stem cells.

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Dietary depletion of vitamin A induces premature activation and oxidativ...
(A) Experiment schematic whereby young mice were fed either a vitamin A–deficient or control diet for a total of 8 weeks, after which muscle stem cells were isolated and profiled. (B) Representative images of Pax7-nGFP and MyoD fluorescence of freshly isolated and fixed MuSCs from CTRL diet (top row) and VA-deficient diet (bottom row). DAPI, blue; Pax7, green; MyoD, red. Scale bar: 20 μm. (C and D) Quantification of mean fluorescence intensity of Pax7-nGFP and MyoD, respectively. Comparisons made via t test with n = 3–4 wells per diet. (E and F) Quantification of Ki67 and MitoTracker Deep Red, respectively, in MuSCs fixed immediately after isolation from mice receiving CTRL diet (red) or VA-free diet (blue). Comparisons made via t test with n = 3–4 wells per diet. (G) Proportion of colony-forming single MuSCs isolated from mice receiving CTRL diet (red) or VA-free diet (blue) after 5 days in growth conditions. Comparisons made via t test with n = 4 mice (60 wells per mouse) for the control diet, and n = 3 mice (95 wells per mouse) for VA-free diet. (H) Representative images of 8-OHdG fluorescence of freshly isolated and fixed MuSCs from CTRL diet (top row) and VA-free diet (bottom row). DAPI, blue; 8-OHdG, red. Scale bar: 20 μm. (I) Quantification of mean fluorescence intensity of 8-OHdG in MuSCs fixed immediately after isolation from mice receiving CTRL diet (red) or VA-free diet (blue). n = 6 image fields (across 2 mice) per diet. Data are shown as mean ± SEM (*P < 0.05, **P < 0.01, ***P < 0.001, ****P < 0.0001 for all comparisons).