Healthy aging can be promoted by enhanced metabolic fitness and physical capacity. Mitochondria are chief metabolic organelles with strong implications in aging that also coordinate broad physiological functions, in part, using peptides that are encoded within their independent genome. However, mitochondrial-encoded factors that actively regulate aging are unknown. Here, we report that mitochondrial-encoded MOTS-c can significantly enhance physical performance in young (2 mo.), middle-age (12 mo.), and old (22 mo.) mice. MOTS-c can regulate (i) nuclear genes, including those related to metabolism and proteostasis, (ii) skeletal muscle metabolism, and (iii) myoblast adaptation to metabolic stress. We provide evidence that late-life (23.5 mo.) initiated intermittent MOTS-c treatment (3x/week) can increase physical capacity and healthspan in mice. In humans, exercise induces endogenous MOTS-c expression in skeletal muscle and in circulation. Our data indicate that aging is regulated by genes encoded in both of our co-evolved mitochondrial and nuclear genomes.

Loss of photoreceptors is a common endpoint in degenerative retinal diseases. Human pluripotent stem cells provide a potential source for photoreceptor replacement, but, even in mouse models, the efficiency and efficacy of transplantation-based repair remains poor. In this study, we examined the degree to which immune rejection contributes to these disappointing outcomes using an immunodeficient IL2 receptor γ (IL2rγ)-null mouse model. Our results show that prevention of cell rejection in the normal and degenerating retinal environment significantly improves long-term survival and integration of hESC-derived donor retinal cells. Transplanted cells are able to differentiate into mature photoreceptors expressing various opsins and can functionally integrate into congenitally blind mice. Our work suggests that even though the retina is often considered immune-privileged, suppression of host immune-mediated cell rejection may well be a useful approach for improving long-term integration of transplanted cells with a view to successful clinical outcomes.

Mitochondrial-derived peptides (MDPs) are small bioactive peptides encoded by short open reading frames (sORF) in mitochondrial DNA that do not necessarily have traditional hallmarks of protein-coding genes. To date, eight MDPs have been identified, all of which have been shown to have various cyto- or metabolo-protective properties. The 12S ribosomal RNA (MT-RNR1) gene harbors the sequence for MOTS-c, while the other seven MDPs, [humanin and small humanin-like peptides (SHLP) 1-6] are encoded by the 16S ribosomal RNA gene. Here we review the evidence that endogenous MDPs are sensitive to changes in metabolism, showing that metabolic conditions like obesity, diabetes and aging are associated with lower circulating MDPs. Whereas, in humans, muscle MDP expression is upregulated in response to stress that perturbs the mitochondria like exercise, some mtDNA mutation-associated diseases, and healthy aging, which potentially suggests a tissue-specific response aimed at restoring cellular or mitochondrial homeostasis. Consistent with this, treatment of rodents with humanin, MOTS-c and SHLP2 can enhance insulin sensitivity and offer protection against a range of age-associated metabolic disorders. Further, assessing how mtDNA variants alter the functions of MDPs is beginning to provide evidence that MDPs are metabolic signal transducers in humans. Taken together, MDPs appear to form an important aspect of a retrograde signaling network that communicates mitochondrial status with the wider cell, and to distal tissues, to modulate adaptative responses to metabolic stress. It remains to be fully determined whether the metabolo-protective properties of MDPs can be harnessed into therapies for metabolic disease.

Retinal degeneration often results in the loss of light‐sensing photoreceptors, which leads to permanent vision loss. Generating transplantable retinal photoreceptors using human somatic cell‐derived induced pluripotent stem cells (iPSCs) holds promise to treat a variety of retinal degenerative diseases by replacing the damaged or dysfunctional native photoreceptors with healthy and functional ones. Establishment of effective methods to produce retinal cells including photoreceptors in chemically defined conditions using current Good Manufacturing Practice (cGMP)‐manufactured human iPSC lines is critical for advancing cell replacement therapy to the clinic. In this study, we used a human iPSC line (NCL‐1) derived under cGMP‐compliant conditions from CD34+ cord blood cells. The cells were differentiated into retinal cells using a small molecule‐based retinal induction protocol. We show that retinal cells including photoreceptors, retinal pigmented epithelial cells and optic cup‐like retinal organoids can be generated from the NCL‐1 iPSC line. Additionally, we show that following subretinal transplantation into immunodeficient host mouse eyes, retinal cells successfully integrated into the photoreceptor layer and developed into mature photoreceptors. This study provides strong evidence that transplantable photoreceptors can be generated from a cGMP‐manufactured human iPSC line for clinical applications. Stem Cells Translational Medicine 2018;7:210–219

Citation: Garcia TY, Gutierrez M, Reynolds J, Lamba DA. Modeling the dynamic AMD-associated chronic oxidative stress changes in human ESC and iPSC-derived RPE cells. Invest Ophthalmol Vis Sci. 2015;56:7480-7488. DOI:10.1167/iovs.15-17251 PURPOSE. Here we use human embryonic stem cells (hESCs) and human-induced pluripotent stem cell (hiPSC)-derived retinal pigment epithelium (RPE) cells to model chronic oxidative stress in vitro. This model allows us to understand the evolution of chronic stress response in RPE in vivo, as well as to monitor microRNAs changes. Finally, we use this in vitro model to identify a partial agonist of NRF2 that is protective against reactive oxygen species (ROS)-induced cytotoxicity.METHODS. The hESCs and hiPSCs were differentiated toward an RPE fate. Upon maturation, RPE cells were subjected to chronic oxidative stress using Paraquat (PQ). The cells were then analyzed using immunocytochemistry and quantitative RT-PCR to look for changes in gene expression and microRNA changes. Small molecules targeting NRF2 pathways were utilized to look for protection against oxidative stress-induced apoptosis.RESULTS. We show that 160 lM PQ can be used to generate a model of chronic oxidative stress in RPE cells derived from hESCs and hiPSCs. Using this model, we characterize the NRF2 pathway effectors during the early and late stages of chronic oxidative stress and identify microRNAs changes during oxidative stress. We find that hsa-miR144 modulates NRF2 activity during ROS stress. Lastly, we found a small molecule modulator of NRF2 that plays a protective role against oxidative stress-induced RPE apoptosis.CONCLUSIONS. In summary, pluripotent stem cell-derived retinal cells can be used to model retinal diseases in a dish. This can provide an unprecedented opportunity to understand the evolution of disease processes and allow us to identify novel therapeutics.Keywords: age-related macular degeneration, disease modeling, oxidative stress, microRNA, NRF2 A ge-related macular degeneration (AMD) is the leading cause of worldwide blindness in the elderly, affecting almost 15 million people in the United States. Retinal changes associated with AMD are present in approximately 10% of people over 65 years of age and as many as one in three people over the age of 80 years. Although the disease was first described in the 1800s, its etiology remains poorly understood, and multiple factors may be involved in the progression of the disorder, including chronic oxidative stress. A number of studies have associated oxidative stress as the key driver to AMD.1,2 The retina is one of the tissues with the greatest consumption of oxygen in the body. 3 This results in significant production of reactive oxygen species (ROS) in the retinal pigment epithelium (RPE). Increasing age results in the loss of ability to deal with this excessive ROS, which leads to oxidative damage.There are no known effective forms of treatment for the common dry form of AMD. This likely is due to the complex multifactorial etiology of AMD and...