Mechanisms of mitochondrial reactive oxygen species action in bone mesenchymal cells

Area of Science:

• Bone Biology
• Mitochondrial Medicine
• Aging Research

Background:

• Aging is associated with decreased bone formation, linked to mitochondrial reactive oxygen species (ROS), reduced NAD+, and cellular senescence.
• The in vivo mechanisms by which ROS impact bone aging remain unclear.

Purpose of the Study:

• To investigate the role of mitochondrial ROS in age-related bone loss.
• To determine if senescence and NAD+ deficiency mediate ROS effects on bone formation in vivo.

Main Methods:

• Generated mice with targeted deletion of the mitochondrial antioxidant enzyme Sod2 in osteoblast lineage cells (Sod2ΔOsx1).
• Assessed bone mass, mitochondrial function, NAD+ levels, and senescence markers.
• Utilized single-cell RNA-sequencing to analyze bone mesenchymal cell responses to ROS.

Main Results:

• Sod2 deletion in osteoblastic cells resulted in low bone mass, impaired mitochondrial respiration, and reduced NAD+ levels.
• NAD+ precursor administration improved mitochondrial function in vitro but did not rescue bone mass in vivo.
• ROS did not significantly affect senescence markers but disrupted parathyroid hormone signaling, iron metabolism, and proteostasis in bone mesenchymal cells.

Conclusions:

• Mitochondrial ROS, independent of senescence, negatively impact bone formation by disrupting key cellular processes.
• Combined therapeutic strategies targeting ROS, senescent cells, and NAD+ may be effective in combating age-associated osteoporosis.