Role of SDHAF1 in Aging Hematopoietic Stem Cells: Enhancing Metabolic Resilience through Mitochondrial ATP Production
Research Background and Objective
As individuals age, hematopoietic stem cells (HSCs) progressively accumulate in the bone marrow, exhibiting metabolic resilience under various stress conditions. This metabolic resilience provides an aging advantage for HSCs, enabling them to maintain cell viability even under low metabolic conditions. Although aging typically results in a decline in HSC function, some studies indicate that elderly HSCs can survive under conditions of low growth factor concentration within the bone marrow microenvironment under homeostasis. For HSCs during aging, energy metabolism, metabolic pathway adaptability, and intracellular oxidative stress resistance are key scientific questions under investigation.
This study, led by Shintaro Watanuki and Hiroshi Kobayashi among others, was published in “Cell Stem Cell” and aims to elucidate the effects of aging on the metabolic characteristics of hematopoietic stem cells. The research team is primarily from institutions such as Tohoku University and Keio University in Japan. The study explores changes in the metabolic network of aging HSCs under steady-state conditions and their adaptive mechanisms to oxidative stress through real-time ATP analysis and metabolic pathway tracking analysis, providing molecular-level insights into the metabolic resilience of aging HSCs.
Research Process
Research Subjects and Methods
The research team first conducted metabolic pathway tracing analysis on young and aged mouse HSCs, employing 13C-labeled glucose tracing in combination with 13C metabolic flux analysis (13C-MFA), to systematically analyze the metabolic characteristics of HSCs at different ages. Additionally, the study designed in vitro culture experiments under low growth factor concentrations and applied high-resolution real-time ATP analysis technology to assess ATP generation in HSCs under different metabolic pressures.
The experimental design encompassed several phases. Initially, the research team employed real-time ATP analysis and quantitative metabolomics detection to analyze how aging HSCs enhance mitochondrial ATP production under low metabolic conditions. Subsequently, the adaptation of aging HSCs to exogenous oxidative stress and changes in their intracellular ROS levels were analyzed. The study also explored the expression and functional role of the key protein SDHAF1 in mitochondrial complex II in HSCs, and further verified the impact of SDHAF1 on the metabolic resilience of HSCs through overexpression and knockout experiments.
Application of Special Technologies and Algorithms
The real-time ATP detection technology and 13C metabolic flux analysis in this study are highlights. The real-time ATP detection technology provided high-resolution data on ATP production rates, while 13C metabolic flux analysis enabled researchers to trace glucose metabolic flux in HSCs. Additionally, the study employed growth factor concentration gradient culture and ROS quantitative analysis, with these techniques combined to help reveal the adaptation mechanisms of HSCs under homeostasis and metabolic pressure.
Research Results
1. Enhanced Metabolic Adaptability of Aged HSCs
Experiments indicated that aging HSCs exhibit higher cell survival rates and differentiation advantages than young HSCs under low concentrations of growth factors (such as stem cell factor SCF and thrombopoietin TPO). This phenomenon is due to the increased metabolic adaptability of aging HSCs, including the activation of the pentose phosphate pathway (PPP) and reduced dependence on glycolysis. The experiments revealed that aging HSCs show reduced proliferation but maintain an undifferentiated stem cell phenotype under low growth factor conditions, aiding in energy conservation and survival capability, closely related to intrinsic metabolic pathway restructuring in aged HSCs.
2. Upregulation of SDHAF1 Protein in Aged HSCs
SDHAF1 (succinate dehydrogenase assembly factor 1) is a key protein in mitochondrial complex II. The experiment found a significant upregulation of SDHAF1 expression in aging HSCs, consistent with enhanced ATP generation capability under low metabolic conditions. In vitro, through overexpression of SDHAF1 in young HSCs, the research team observed significantly improved ATP generation capacity in low glucose environments. Conversely, in SDHAF1-knockout aged HSCs, both cell survival capacity and metabolic resilience were significantly reduced. These results indicate that SDHAF1 expression in HSCs is crucial for enhanced metabolic resilience.
3. Increased Resistance to Oxidative Stress in Aging HSCs
The study further analyzed ROS levels in HSCs under oxidative stress, finding significantly lower reactive oxygen species (ROS) levels in aging HSCs compared to young HSCs. Under high oxygen conditions, aging HSCs showcased higher ROS clearance ability, primarily supported by NADPH from the PPP. Moreover, inhibiting the key enzyme G6PD in the PPP resulted in a significant increase in HSC ROS levels, further confirming that PPP activation offers protective action against oxidative stress in aging HSCs.
4. Accumulation of SDHAF1 Through Chronic TPO Stimulation
The research also demonstrated that chronic stimulation with physiological concentrations of TPO (thrombopoietin) leads to SDHAF1 accumulation in aged HSCs. By regulating key signaling molecules (such as JAK2 and STAT3) in the TPO pathway, the experiment further validated SDHAF1’s role in HSC metabolic adaptation, providing direct evidence of SDHAF1’s importance in age-related HSC metabolic changes.
Research Conclusion
This research reveals the metabolic adaptability characteristics of aging HSCs, particularly their superior performance under low metabolic and oxidative stress conditions. Aging HSCs not only have stronger survival capabilities in low growth factor environments but also adapt better to metabolic pressure through metabolic pathway restructuring. Increased expression of SDHAF1 is one of the key mechanisms for enhanced metabolic adaptation in aging HSCs, facilitated by chronic TPO stimulation. The study shows that SDHAF1 not only plays a role in maintaining intracellular homeostasis but also provides robust metabolic resilience for HSCs under metabolic stress.
Through the metabolic adaptation of cells, aging HSCs can functionally compensate for proliferative and differentiation defects associated with aging, offering potential intervention targets for combating age-related hematopoietic dysfunctions.
Research Significance
This research first unveils the core role of SDHAF1 in the metabolic resilience of aging HSCs and proposes a new theory that the metabolic adaptability of elderly HSCs can be enhanced through activation of mitochondrial complex II. This discovery not only offers a new perspective for understanding the aging process of hematopoietic stem cells but also provides a foundation for future development of intervention strategies targeting age-related hematopoietic system diseases.