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Study Design: Animal laboratory study., Objective: This study investigated the effects of C. acnes and S. epidermidis on the lumbar discs of rabbits, as well as the outcomes of combined infection., Summary of Background Data: Many studies have indicated that bacterial infections are associated with lumbar disc degeneration (LDD). The most commonly cultured bacteria from disc tissues are Cutibacterium acne (C. acnes) and Staphylococcus epidermidis (S. epidermidis)., Methods: New Zealand white rabbits (n=40) were randomly divided into control, C. acnes, S. epidermidis, and C. acnes plus S. epidermidis (i.e., combined) groups. All groups except the control were injected with 25 μL of saline at L4-L5 and 25 μL of bacteria (1×107 CFU/mL) at L5-L6. All injections were performed under X-ray guidance. Weight measurements, haematological evaluations, and magnetic resonance imaging were performed after 4, 8, and 12 weeks. Histological examination and gene expression detection were performed 12 weeks after surgery., Results: Inflammatory factors in the blood and weight did not differ among the groups after 4, 8, and 12 weeks (P >0.05). However, after 4 weeks, LDD occurred in the C. acnes group, and discitis occurred in the S. epidermidis and combined groups, all of which worsened after 8 weeks. After 12 weeks, the nucleus pulposus (NP) protruded and compressed the spinal cord in the C. acnes group, and tissue staining showed decreased NP tissue and cartilaginous endplate fracture. In the S. epidermidis and combined groups, the discitis was more confined, but tissue staining revealed a significant decrease in NP tissue, and loss of the normal disc structure., Conclusions: In the early stage of infection in rabbits, C. acnes caused LDD, and S. epidermidis caused discitis. Co-infection with C. acnes and S. epidermidis caused discitis but was more limited in scope than infection with S. epidermidis alone., Competing Interests: Conflicts of interest: The authors, their immediate families, and any research foundations with which they are affiliated have not received any financial payments or other benefits from any commercial entity related to the subject of this article., (Copyright © 2024 Wolters Kluwer Health, Inc. All rights reserved.)

Mycobacterium tuberculosis infection has emerged as a global public health issue, predominantly manifesting as pulmonary tuberculosis. Bone and joint tuberculosis, with spinal tuberculosis accounting for approximately 50%, represents a significant form of extrapulmonary tuberculosis. Over the past years, there has been a rise in the incidence of spinal tuberculosis, and research concerning this area has gained significant attention. At present, animal models provide a means to investigate the pathogenesis, drug resistance, and novel treatment approaches for spinal tuberculosis. New Zealand rabbits, possessing a comparable anatomical structure to humans and capable of reproducing typical pathological features of human tuberculosis, are extensively employed in spinal tuberculosis research using animal models. This article comprehensively evaluates the strengths, considerations in strain selection, various modelling approaches, and practical applications of the rabbit model in studying spinal tuberculosis based on pertinent literature to guide fundamental research in this field by providing valuable insights into appropriate animal model selection., Competing Interests: Declaration of conflicting interestsThe author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Objective: To summarize the research progress on the calcitonin gene-related peptide (CGRP) and receptor activator of nuclear factor κB (RANK)/receptor activator of nuclear factor κB ligand (RANKL)/osteoprotegerin (OPG) system during bone reconstruction to provide theoretical basis for further research on the prevention and treatment of bone-related diseases., Methods: The relevant research results at home and abroad in recent years were analyzed and summarized., Results: CGRP and RANK/RANKL/OPG system play important regulatory roles in the bone reconstruction., Conclusion: At present, the research on the mechanism of CGRP and RANK/RANKL/OPG system in bone reconstruction is insufficient. Therefore, it is necessary to study further on the process and interrelation of CGRP and RANK/RANKL/OPG system in bone reconstruction to confirm their mechanism, which will bring new ideas and methods for the treatment of bone related diseases in clinic.

Objective: To examine the expression of neuropilin-1 (Nrp-1), semaphorin 3A (Sema3A) and vascular endothelial growth factor (VEGF) in the healing process of tibial fracture after traumatic brain injury and to explore the mechanism of Nrp-1 in the formation of pathological callus after nerve injury.
 Methods: A total of 192 Wister female rats, 8-10 weeks old and weighing 220-250 g, were randomly divided into a control group (Group C), a tibia fracture group (Group F), a traumatic brain injury group (Group TBI), a traumatic brain injury combined with the tibia fracture group (Group TBI+F) (n=48 in each group). Tissue samples were collected at 3, 5, 7, 14, 21 and 28 days, respectively (n=8 for each time point). The expression of Nrp-1 in callus tissues were examined by immunohistochemistry and Western blot, while the expression of Sema3A and VEGF were detected by Western blot.
 Results: Compared with the Group F , the expression of Nrp-1 in chondrocytes of bone formation area and cartilage area was higher in the Group TBI+F, particularly at the 7th , 14th and 21st day (P<0.05), while the expression of Nrp-1 in osteoblast cells of fresh bone trabecula region was lower in the Group TBI+F, particularly at the 14th and 21st day (both P<0.05). Western blot showed that the expression of Nrp-1, Sema 3A and VEGF had the same trends in the Group TBI+F and the Group F. However, at each time point, the expression of Nrp-1 in the Group TBI+F was significantly higher and slowly decreased, particularly at the 14th, 21st and 28th day (all P<0.05). Meanwhile, the ratio of Sema 3A/VEGF in the Group TBI+F was significantly higher than that in the Group F, with statistical difference (P<0.05).
 Conclusion: The Nrp-1 is expressed abnormally in the process of fracture healing after nerve injury. It may play a role in the formation of pathological callus after nerve injury by promoting the preliminary and proliferation of chondrocytes, and inhibiting the growth of nerve fibers in the soft callus as well as the differentiation of osteoblast cell.