Nitric Oxide Signaling in Bone Remodeling

Nitric oxide (NO) serves as a versatile paracrine and autocrine regulator in the continuous process of bone remodelling, whereby old or damaged bone is resorbed by osteoclasts and replaced by osteoblast-mediated formation. Synthesised by distinct nitric oxide synthase (NOS) isoforms, NO influences osteoblast proliferation, differentiation and survival, and restrains excessive osteoclast activity through feedback loops. Downstream activation of soluble guanylate cyclase raises intracellular cyclic guanosine monophosphate (cGMP), which in turn engages protein kinase G (PKG) to orchestrate signalling cascades such as Wnt/β-catenin and mitogen-activated protein kinase (MAPK) pathways. Mechanical stimuli, hormonal cues and inflammatory mediators each modulate NOS expression in osteocytes and endothelial cells, linking skeletal loading and vascular tone to bone metabolism. Dysregulation of NO signalling contributes to osteoporosis, impaired fracture healing and diabetic bone disease, while pharmacological modulation of the NO–cGMP–PKG axis offers promising routes to enhance bone regeneration and restore homeostasis.

Research from Nature Portfolio

Studies of bone cell crosstalk under simulated microgravity have revealed that endothelial cells subjected to unloading release factors, including interleukin-1β and lipocalin 2, which upregulate inducible NOS (NOS2) in osteoblasts. Elevated NO production promotes proliferation but suppresses differentiation of osteoblasts, an effect mediated by NF-κB activation. Inhibition of NOS2 or downstream NO signalling restores osteoblastic maturation and reduces osteoclast-stimulating RANKL expression. These findings elucidate a mechano-responsive feedback mechanism that links vascular and skeletal compartments and may underlie bone loss in disuse or microgravity conditions.

Nitric Oxide Signaling in Bone Remodeling publication trend

The graph below shows the total number of articles in nitric oxide signaling in bone remodeling across all publications each year (not limited to Nature Index journals).

Technical terms

Nitric oxide (NO): A gaseous free radical acting as a signalling molecule in bone and vascular cells.

Nitric oxide synthase (NOS): Enzymes (eNOS, iNOS, nNOS) catalysing NO production from l-arginine.

Cyclic guanosine monophosphate (cGMP): A second messenger generated by soluble guanylate cyclase upon NO binding.

Protein kinase G (PKG): A cGMP-dependent kinase that phosphorylates targets to regulate cell function.

Osteoblast: A bone-forming cell responsible for matrix synthesis and mineralisation.

Osteoclast: A multinucleated cell specialised in bone resorption.

Wnt/β-catenin signalling: A pathway promoting osteoblast differentiation and bone formation.

Mitogen-activated protein kinase (MAPK) pathway: A cascade transducing signals from growth factors and mechanical stress to regulate gene expression.

References

1. Interleukin-1β, lipocalin 2 and nitric oxide synthase 2 are mechano-responsive mediators of mouse and human endothelial cell-osteoblast crosstalk. Scientific Reports (2016).
2. Nitric oxide balances osteoblast and adipocyte lineage differentiation via the JNK/MAPK signaling pathway in periodontal ligament stem cells. Stem Cell Research & Therapy (2018).
3. Protein Kinase G1 regulates bone regeneration and rescues diabetic fracture healing. JCI Insight (2020).
4. Molecular control of nitric oxide synthesis through eNOS and caveolin-1 interaction regulates osteogenic differentiation of adipose-derived stem cells by modulation of Wnt/β-catenin signaling. Stem Cell Research & Therapy (2016).