A novel rat model of tibial fracture for trauma researches: a combination of different types of fractures and soft tissue injuries

Revolutionizing fracture fixation in diabetic and non-diabetic rats: High mobility group box 1-based coating for enhanced osseointegration

Chronic inflammation and hyperglycemia in diabetic patients increase the risk of implant failure and impaired fracture healing. We previously developed and characterized a titanium (Ti) coating strategy using an imidazolium-based ionic liquid (IonL) with a fully reduced, non-oxidizable High Mobility Group Box 1 (HMGB1) isoform (Ti-IonL-HMGB1) to immunomodulate tissue healing. In this study, we used an open reduction fracture fixation (ORIF) model in non-diabetic (ND) and diabetic (D) rats to further investigate the effectiveness of this Ti-IonL-HMGB1 coating on orthopedic applications. Ninety male Lewis rats (12-15 weeks) were divided into D (n = 45) and ND (n = 45) groups that were distributed into three subgroups based on the type of local treatment received: Ti (uncoated Ti), Ti-IonL, and Ti-IonL-HMGB1 implants. Fracture healing and osseointegration were evaluated using microtomographic, histological, and immunohistochemical analysis of proliferating cell nuclear antigen (PCNA), Runt-related transcription factor 2 (RUNX2), and HMGB1 markers at 2, 10, and 21 days post-ORIF. Scanning Electron Microscopy verified the coating stability after placement. Microtomographic and histological analysis demonstrated increased fracture healing and osseointegration for ND rats in all treatment groups at 10 days, with impaired healing for D rats. Immunohistochemical analysis exhibited elevated PCNA+ and RUNX2+ cells for D animals treated with Ti-IonL-HMGB1 at 21 days compared to all other groups. The immunohistochemical marker HMGB1 was elevated at all time points for D animals in comparison to ND animals, yet was lowered for D tissues near the Ti-IonL-HMGB1 treated implant. Improved osseous healing was demonstrated in D animals with Ti-IonL-HMGB1 treatment by 21 days, compared to D animals with other treatments. To the best of our knowledge, this is the first study analyzing Ti-IonL-HMGB1 implantation in an injury site through ORIF procedures in ND and D rats. This surface approach has potential for improving implanted biomaterials in diabetic environments.

High-energy open-fracture model with initial experience of fluorescence-guided bone perfusion assessment

High-energy orthopedic injuries cause severe damage to soft tissues and are prone to infection and healing complications, making them a challenge to manage. Further research is facilitated by a clinically relevant animal model with commensurate fracture severity and soft-tissue damage, allowing evaluation of novel treatment options and techniques. Here we report a reproducible, robust, and clinically relevant animal model of high-energy trauma with extensive soft-tissue damage, based on compressed air-driven membrane rupture as the blast wave source. As proof-of-principle showing the reproducibility of the injury, we evaluate changes in tissue and bone perfusion for a range of different tibia fracture severities, using dynamic contrast-enhanced fluorescence imaging and microcomputed tomography. We demonstrate that fluorescence tracer temporal profiles for skin, femoral vein, fractured bone, and paw reflect the increasing impact of more powerful blasts causing a range of Gustilo grade I-III injuries. The maximum fluorescence intensity of distal tibial bone following 0.1 mg/kg intravenous indocyanine green injection decreased by 35% (p < 0.01), 75% (p < 0.001), and 87% (p < 0.001), following grade I, II, and III injuries, respectively, compared to uninjured bone. Other kinetic parameters of bone and soft tissue perfusion extracted from series of fluorescence images for each animal also showed an association with severity of trauma. In addition, the time-intensity profile of fluorescence showed marked differences in wash-in and wash-out patterns for different injury severities and anatomical locations. This reliable and realistic high-energy trauma model opens new research avenues to better understand infection and treatment strategies. Level of evidence: Level III; Case-control.

Expression of lncRNA MALAT1 through miR-144-3p in Osteoporotic Tibial Fracture Rats and Its Effect on Osteogenic Differentiation of BMSC under Traction

Objective

To investigate the expression of lncRNA MALAT1 and miR-144-3p in osteoporotic (OP) tibial fracture rats and analyze their targeting relationship and effects on the osteogenic differentiation of bone marrow mesenchymal stem cells (BMSC) under traction.

Methods

The OP tibial fracture model was established, and the rats were divided into a sham group and a model group. The tibial tissue of these rats was taken. BMSC of cultured rats with good growth was purchased and grouped according to the presence or absence of transfection of si-MALAT1 and miR-144-3p-mimic. The expression of MALAT1 and miR-144-3p in each group was detected. The bioinformatics website and double luciferase were used to predict the targeting relationship between MALAT1 and miR-144-3p and to detect the expression of genes related to bone differentiation (collagen I, osteocalcin (OCN), osteopontin (OPN), and alkaline phosphatase (ALP)) of each component, and ALP staining and AR staining were used to detect the formation of BMSC calcium nodules.

Results

The levels of ALP and TRAP in the model group were higher than that in the sham group (P < 0.05). qRT-PCR results showed that the relative expression level of MALAT1 in the model group was higher than that in the sham group, and the relative expression level of miR-144-3p was lower than that in the sham group (P < 0.05). MALAT1 has a targeting relationship with miR-144-3p. qRT-PCR results showed that the relative expression level of MALAT1 in the tension-MSC group was higher than the MSC group, and the relative expression level of miR-144-3p was lower than the MSC group (P < 0.05). The expressions of collagen I, OCN, OPN, and ALP proteins in the si-MALAT1 group were higher than those of the si-NC group (P < 0.05). The results of ALP staining showed that BMSCs of the si-MALAT1 group had stronger osteogenic differentiation capacity and higher ALP activity than those of the si-NC group. The results of AR staining showed that compared with the si-NC group, the mineralization degree of cells in the si-MALAT1 group was higher, the number of calcium nodules was more, and the cells were more deeply stained. The expressions of collagen I, OCN, OPN, and ALP proteins in the miR-144-3p-mimic group were higher than the mimic-NC group (P < 0.05). ALP staining results showed that BMSCs in the miR-144-3p-mimic group had strong osteogenic differentiation capacity and high ALP activity compared with the mimic-NC group. The results of AR staining showed that, compared with the mimic-NC group, the mineralization degree of cells in the miR-144-3p-mimic group was higher, the number of calcium nodules was more and the cells were more deeply stained.

Conclusion

In the OP rat model with the tibial fracture, the expression of MALAT1 is upregulated and that of miR-144-3p is downregulated. MALAT1 has a targeting relationship with miR-144-3p, and downregulation of MALAT1 and upregulation of miR-144-3p can promote the osteogenic differentiation of BMSC under traction.

Review of immunological plasma markers for longitudinal analysis of inflammation and infection in rat models

Disease or trauma of orthopedic tissues, including osteomyelitis, osteoporosis, arthritis, and fracture, results in a complex immune response, leading to a change in the concentration and milieu of immunological cells and proteins in the blood. While C-reactive protein levels and white blood cell counts are used to track inflammation and infection clinically, controlled longitudinal studies of disease/injury progression are limited. Thus, the use of clinically-relevant animal models can enable a more in-depth understanding of disease/injury progression and treatment efficacy. Though longitudinal tracking of immunological markers has been performed in rat models of various inflammatory and infectious diseases, currently there is no consensus on which markers are sensitive and reliable for tracking levels of inflammation and/or infection. Here, we discuss the blood markers that are most consistent with other outcome measures of the immune response in the rat, by reviewing their utility for longitudinal tracking of infection and/or inflammation in the following types of models: localized inflammation/arthritis, injury, infection, and injury + infection. While cytokines and acute phase proteins such as haptoglobin, fibrinogen, and α₂ -macroglobulin demonstrate utility for tracking immunological response in many inflammation and infection models, there is likely not a singular superior marker for all rat models. Instead, longitudinal characterization of these models may benefit from evaluation of a collection of cytokines and/or acute phase proteins. Identification of immunological plasma markers indicative of the progression of a pathology will allow for the refinement of animal models for understanding, diagnosing, and treating inflammatory and infectious diseases of orthopedic tissues.

LncRNA HAGLR absorbing miR-214-3p promotes BMP2 expression and improves tibial fractures

OBJECTIVE

To determine whether long-chain non-coding RNA (lncRNA) HAGLR can regulate BMP2 by absorbing microRNA-214-3p (miR-214-3p), and to explore its role and mechanism in tibial fracture (TF) healing.

METHODS

The HAGLR, miR-214-3p, and BMP2 expression levels in TF and in adjacent normal tissues were measured using quantitative real-time polymerase chain reaction (qRT-PCR). MC3T3-E1 osteoblasts were used to construct the in vitro model. HAGLR was localized subcellularly through RNA-fluorescence in situ hybridization (FISH). A dual-luciferase report experiment confirmed that miR-214-3p has a targeted relationship with HAGLR and BMP2. It was then divided into a HAGLR over-expression group, an miR-214-3p mimic group, a HAGLR+miR-214-3p mimic group, an sh-HAGLR group, a BMP over-expression group, an sh-HAGLR+over-expression BMP2 group, and a negative control group. The proliferation and apoptosis of the MC3T3-E1 osteoblasts were examined using MTT assays and flow cytometry. A TF model was established in male C57BL/6J mice. The serum alkaline phosphatase (ALP) and osteoprotegerin (OPG) levels in the sham group, the TF group, and the TF group that were injected with HAGLR were compared using ELISA. Hematoxylin-eosin (HE) staining was used to confirm the fracture healing in the mouse model.

RESULTS

Compared with the adjacent normal tissues in the TF patients, the HAGLR and BMP2 expressions decreased but the miR-214-3p expressions increased in the TF tissues (P<0.05). HAGLR, an endogenous sponge, absorbed the miR-214-3p, and the BMP2 expression was directly regulated by miR-214-3p. HAGLR increased the proliferative activity of the osteoblasts and decreased the apoptosis rate. The over-expression of miR-214-3p partly reversed the effect of HAGLR on the cells, decreased the proliferative activity, and increased the apoptosis rate (all P<0.05). The sh-HAGLR decreased the proliferative activity and increased the apoptosis rate. But after the over-expression of BMP2, the proliferative activity of the cells was higher, and the apoptosis rate was lower than it was in the sh-HAGLR group (all P<0.05). The over-expression of HAGLR can up-regulate the ALP and OPG levels in mouse models (P<0.05).

CONCLUSION

lncRNA HAGLR can regulate BMP2 to play a protective role in TF by absorbing miR-214-3p, and it is related to promoting the osteoblast proliferation, inhibiting apoptosis, and up-regulating the serum ALP and OPG levels to accelerate bone healing.