Related Experiment Video
Updated: Mar 30, 2026
En Face Detection of Nitric Oxide and Superoxide in Endothelial Layer of Intact Arteries
Published on: February 25, 2016
Deficiency of inducible and endothelial nitric oxide synthase results in diminished bone formation and delayed union
D M Meesters1, S Neubert2, K A P Wijnands1
1Department of Surgery and Trauma surgery, Maastricht University Medical Center, PO Box 5800, 6202 AZ Maastricht, The Netherlands; NUTRIM School for Nutrition and Translational Research in Metabolism, PO Box 616, 6200 MD, Maastricht, The Netherlands.
Background:
Between 5% and 10% of all fractures fail to heal adequately resulting in nonunion of the fracture fragments. This can significantly decrease a patient's quality of life and create associated psychosocial and socio-economic problems. Nitric oxide (NO) and nitric oxide synthases (NOS) have been found to be involved in fracture healing, but until now it is not known if disturbances in these mechanisms play a role in nonunion and delayed union development. In this study, we explored the role of endothelial and inducible NOS deficiency in a delayed union model in mice.
Materials And Methods:
A 0.45mm femur osteotomy with periosteal cauterization followed by plate-screw osteosynthesis was performed in the left leg of 20-24week old wild type, Nos2(-/-) and Nos3(-/-) mice. Contralateral unfractured legs were used as a control. Callus volume was measured using micro-computed tomography (μCT) after 28 and 42days of fracture healing. Immuno histochemical myeloperoxidase (MPO) staining was performed on paraffin embedded sections to assess neutrophil influx in callus tissue and surrounding proximal and distal marrow cavities of the femur. After 7 and 28days of fracture healing, femurs were collected for amino acid and RNA analysis to study arginine-NO metabolism.
Results:
With μCT, delayed union was observed in wild type animals, whereas in both Nos2(-/-) and Nos3(-/-) mice nonunion development was evident. Both knock-out strains also showed a significantly increased influx of MPO when compared with wild type mice. Concentrations of amino acids and expression of enzymes related to the arginine-NO metabolism were aberrant in NOS deficient mice when compared to contralateral control femurs and wild type samples.
Discussion And Conclusion:
In the present study we show for the first time that the absence of nitric oxide synthases results in a disturbed arginine-NO metabolism and inadequate fracture healing with the transition of delayed union into a nonunion in mice after a femur osteotomy. Based on these data we suggest that the arginine-NO metabolism may play a role in the prevention of delayed unions and nonunions.
Insights
Nitric oxide synthases (NOS) deficiency impairs fracture healing, leading to nonunion in mice. The arginine-nitric oxide (NO) pathway is crucial for preventing delayed unions and nonunions.
Area of Science:
- Orthopedics
- Molecular Biology
- Biochemistry
Background:
- Fracture nonunion affects 5-10% of fractures, impacting patient quality of life.
- Nitric oxide (NO) and nitric oxide synthases (NOS) are implicated in bone healing.
- The role of NOS deficiency in delayed union and nonunion remains unclear.
Purpose of the Study:
- To investigate the role of endothelial and inducible NOS deficiency in a mouse model of delayed fracture union.
- To explore the impact of NOS deficiency on arginine-nitric oxide metabolism during fracture healing.
Main Methods:
- Femur osteotomy and internal fixation in wild type, Nos2(-/-), and Nos3(-/-) mice.
- Micro-computed tomography (μCT) for callus volume assessment.
- Immunohistochemical staining for neutrophil influx (MPO) and analysis of arginine-NO metabolism.
Main Results:
- Nos2(-/-) and Nos3(-/-) mice exhibited nonunion, unlike wild type mice with delayed union.
- Increased neutrophil influx (MPO) was observed in NOS-deficient mice.
- Aberrant arginine-NO metabolism was detected in NOS-deficient mice.
Conclusions:
- Absence of NOS leads to disturbed arginine-NO metabolism and inadequate fracture healing, progressing from delayed union to nonunion.
- The arginine-NO metabolism pathway is suggested to play a role in preventing delayed unions and nonunions.
More Related Videos
Related Concept Videos
01:28Nitric Oxide Signaling Pathway
01:29Bone Disorders
Bone deposition is also affected by the levels of sex hormones like estrogen and testosterone that promote osteoblast activity and bone matrix synthesis. When the level of these hormones decreases due to aging, it causes a reduction in bone deposition. As a result, bone resorption by osteoclasts...
01:29Bone Formation by Intramembranous Ossification
The process begins when mesenchymal cells in the embryonic skeleton gather together and differentiate into osteogenic cells, which then develop into ...
01:24Bone Formation by Endochondral Ossification
01:27Fractures: Bone Repair
Minor fractures with no bone displacement are treated by immobilizing the fractured bone using a cast or splint. However, in the case of fractures with displaced bones, the broken bones are repositioned before immobilization to ensure successful healing without deformation and loss of function. The realignment of fractured bone ends is performed through a process called reduction. If the...
01:31Bone Remodeling and Repair