The pain-related behavior changes correlate with the bone damage in a rat model of rheumatoid arthritis

In view of the extensive bone damage in rheumatoid arthritis, we used a commonly utilized animal model to detect behavioral changes in pain-related and the bone damage during the early disease, and to explore the correlation between bone damage and pain-related behavioral changes. Methods： Arthritis were induced in Sprague-Dawley （SD） male rats by injecting complete Freund＇s adjuvant （CFA） into the tails. Pain-related behavior changes were studied using the Hargreaves, VonFrey, and acetone tests on the 0, 7, 14, day and 28 day after CFA injection. The rats were sacrificed according the same schedule. The bone damage of the right proximal tibia was studied by microCT scan and bone histological slices. Results： Animals developed soft tissue inflammation and polyarthritis on 7 days after CFA injection, and arthritic score proved obvious arthritis were established within the study period. Mechanical hyperalgesia and cold allodynia were present in the affected hind paw from the 7 day through the 28 day, but the heat hyperalgesia and the mechanical allodynia lasted a short time after CFA injection. Trabecular bone number （Tb.N）, Tissue Mineral Content （TMC） and Bone Volume to Tissue Volume （BV/TV） in the proximal tibia by microCT scan were also reduced after induction, especial 14 days after CFA injection. The bone histologicalslices showed the trabecular bone and proteoglycan diminished, the bone damage severity scores became more severely on the 7 day after CFA injection. Using analysis of covariance, these changes had statistical significance compared with baseline. By linear regression analysis demonstrated mechanical hyperalgesia and cold allodynia correlated well with arthritic score, bone damage parameters and bone damage severity scores. Conclusion： Adjuvant-induced arthritis （AA） were observed after CFA injection and lasted within the later experimental period. Pain-related behavioral changes were observed in the early time of AA. Bone damage was also occurred with arthritis development. Pain-related behavioral change correlated well with arthritic score and bone damage parameters

Interplay between mesenchymal stem cells and macrophages:Promoting bone tissue repair

The repair of bone tissue damage is a complex process that is well-orchestrated in time and space,a focus and difficulty in orthopedic treatment.In recent years,the success of mesenchymal stem cells(MSCs)-mediated bone repair in clinical trials of large-area bone defects and bone necrosis has made it a candidate in bone tissue repair engineering and regenerative medicine.MSCs are closely related to macrophages.On one hand,MSCs regulate the immune regulatory function by influencing macrophages proliferation,infiltration,and phenotype polarization,while also affecting the osteoclasts differentiation of macrophages.On the other hand,macrophages activate MSCs and mediate the multilineage differentiation of MSCs by regulating the immune microenvironment.The cross-talk between MSCs and macrophages plays a crucial role in regulating the immune system and in promoting tissue regeneration.Making full use of the relationship between MSCs and macrophages will enhance the efficacy of MSCs therapy in bone tissue repair,and will also provide a reference for further application of MSCs in other diseases.

Drilling Force and Temperature of Bone under Dry and Physiological Drilling Conditions

Many researches on drilling force and temperature have been done with the aim to reduce the labour intensiveness of surgery, avoid unnecessary damage and improve drilling quality. However, there has not been a systematic study of mid- and high-speed drilling under dry and physiological conditions（injection of saline）. Furthermore, there is no consensus on optimal drilling parameters. To study these parameters under dry and physiological drilling conditions, pig humerus bones are drilled with medical twist drills operated using a wide range of drilling speeds and feed rates. Drilling force and temperature are measured using a YDZ-II01W dynamometer and a NEC TVS-500EX thermal infrared imager, respectively, to evaluate internal bone damage. To evaluate drilling quality, bone debris and hole morphology are observed by SEM（scanning electron microscopy）. Changes in drilling force and temperature give similar results during drilling such that the value of each parameter peaks just before the drill penetrates through the osteon of the compact bone into the trabeculae of the spongy bone. Drilling temperatures under physiological conditions are much lower than those observed under dry conditions, while a larger drilling force occurs under physiological conditions than dry conditions. Drilling speed and feed rate have a significant influence on drilling force, temperature, bone debris and hole morphology. The investigation of the effect of drilling force and temperature on internal bone damage reveals that a drilling speed of 4500 r/min and a feed rate of 50 mm/min are recommended for bone drilling under physiological conditions. Drilling quality peaks under these optimal parameter conditions. This paper proposes the optimal drilling parameters under mid- and high-speed surgical drilling, considering internal bone damage and drilling quality, which can be looked as a reference for surgeons performing orthopedic operations.