A new study maps how aging cells contribute to bone loss and degeneration, offering fresh insights into treating skeletal diseases

Life expectancy is increasing globally, and along with it, skeletal diseases like osteoporosis, osteoarthritis, and spinal disc degeneration are becoming major causes of disability and poor quality of life. These conditions affect millions and lead to chronic pain, falls, fractures, immobility, and dependence. In older adults, even a minor fracture can result in hospitalization or permanent loss of independence. These disorders were long thought to be the result of “wear and tear”—gradual breakdown due to physical stress or bone loss over time. But growing research suggests that the true cause lies deeper.

Hidden within bone, cartilage, and connective tissue are aging cells that quietly lose function, disrupt the surrounding environments, and weaken the entire skeletal system from inside out. Despite this emerging understanding, there hasn’t been a clear explanation of how aging at the cellular level contributes to skeletal decline. Existing studies often focused on specific diseases or isolated cell types, leaving gaps in the bigger picture.

A new literature review, published online in the journal Bone Research on July 07, 2025, addresses this by bringing together findings from across cell biology, immunology, and aging science. The study was led by Dr. Hao Chen, Dr. Sihan Hu, and Dr. Ke Li from the Institute of Translational Medicine, Medical College, Yangzhou University, China. Together, the team outlines how cellular changes—especially senescence, inflammation, and stem cell exhaustion—can alter the balance of bone renewal and repair, driving disease across the skeleton.

Among the key cellular changes discussed in the review, cellular senescence—a state in which damaged cells stop dividing but don’t die—stands out as a major driver of skeletal decline. These cells remain in the body and release a harmful mix of molecules known as the senescence-associated secretory phenotype (SASP), which can trigger inflammation, break down nearby tissues, and even spread aging signals to neighboring healthy cells. “Our bones are maintained through a constant process of breaking down and rebuilding,” explains Dr. Chen. “Senescent cells interrupt this cycle, leading to imbalances that cause bones to weaken or joints to break down.”

In the bone marrow, mesenchymal stem cells, which normally give rise to bone-forming cells, begin to favor fat production as they age. This reduces the availability of new bone cells and weakens the overall structure. Osteoblasts (bone forming cells) and osteoclasts (breaks bone tissue) also become less efficient and poorly coordinated, resulting in fragile, porous bones, prone to fractures. Senescence also affects the cartilage cells, or chondrocytes, which begin producing enzymes that degrade the supportive tissues in joints. This breakdown, combined with chronic inflammation from SASP factors, contributes to osteoarthritis—a major cause of pain and reduced mobility in aging adults. In the spine, cells in intervertebral discs lose their ability to handle pressure and regenerate, leading to disc degeneration and spinal problems.

“Senescent cells don’t just affect their own tissues,” says Dr. Chen. “They send signals that alter the behavior of nearby immune cells, blood vessels, and bone stem cells—changing how the whole environment functions.”

This review also connects cellular aging to conditions like rheumatoid arthritis and bone tumors, where senescence-related changes may either trigger abnormal immune responses or support tumor growth in the aged tissues. While the role of senescence sounds alarming, the findings open promising new paths for treatment.

This study also highlights the efforts to develop senolytics—drugs that selectively remove senescent cells—and compounds that suppress their harmful secretions. In animal studies, these approaches have led to improved bone strength and joint health. The researchers also explore other emerging strategies, including cell therapy to restore aged stem cells, genetic interventions to reverse or slow aging-related damage, and even vaccine-based approaches designed to help the immune system clear senescent cells. Though many of these are still experimental, they represent a growing shift toward treating the root causes of skeletal aging—not just its symptoms.

“This review helps clarify the link between cellular aging and skeletal disease,” says Dr. Chen. “By targeting these root causes, we may be able to go beyond symptom relief and actually prevent or delay the onset of bone disorders.”

The researchers emphasize that more research is needed, especially on how different cell types communicate during aging and how systemic factors—like immune changes or blood supply—interact with local skeletal cells.

Overall, this study offers a valuable framework for understanding how aging at the cellular level contributes to bone loss and degeneration. By bringing together findings across different cell types and skeletal conditions, it sheds light on the common cellular changes that drive these disorders. As research advances, these insights could guide the development of therapies aimed at preserving bone health and promoting healthier aging in the years to come.

Reference
Title of original paper: Cellular senescence and other age-related mechanisms in skeletal diseases
Journal: Bone Research
DOI: 10.1038/s41413-025-00448-7