Deconstructing cellular senescence in bone and beyond.

Area of Science:

• Gerontology
• Skeletal Biology
• Cellular Senescence

Background:

• Osteocytes, specialized bone cells, regulate skeletal remodeling.
• Senescent osteocytes, marked by p16Ink4a activation, contribute to bone loss disorders.
• Senolysis, the removal of senescent cells, is a potential therapeutic strategy.

Purpose of the Study:

• To investigate the impact of systemic and cell-specific senolysis on age-related bone loss.
• To explore the role of osteocyte senescence in bone loss.
• To examine the effects of senescent cell transplantation on host osteocytes.

Main Methods:

• Systemic senolysis was administered to aged mice.
• Cell-specific senolysis targeted osteocytes.
• Senescent fibroblasts were transplanted into young mice to induce osteocyte senescence.
• Bone mineral density, bone marrow adiposity, osteoblast, and osteoclast activity were assessed.

Main Results:

• Systemic senolysis prevented bone loss in the spine and femur and reduced bone marrow adiposity.
• Senolysis primarily affected osteoblasts and osteoclasts, indirectly impacting osteocytes.
• Targeting senescent osteocytes specifically yielded only partial protection against bone loss.
• Transplantation of senescent fibroblasts induced osteocyte senescence and bone loss in young mice.

Conclusions:

• Systemic senolysis is effective in combating age-related bone loss and associated adiposity.
• Osteocyte senescence can be influenced by senescent cells distant from bone.
• Targeting senescent cells broadly, rather than osteocytes specifically, may be a more effective senolytic strategy for bone aging.