HMGB1 promotes bone fracture healing through activation of ERK signaling pathway in a rat tibial fracture model

This work was to investigate potential roles of HMGB1-mediated ERK pathway in the healing process of bone fracture. Rat tibial fracture models were established and divided into control (rats with normal saline), HMGB1 (rats with HMGB1), and HMGB1+ PD98059 groups (rats with HMGB1 and 1 mg/kg of ERK1/2 inhibitor PD98059) with 30 rats per each. The healing of rats' fracture was observed by X-ray films, the morphological changes of bone fractures by HE staining, the callus formation by micro-CT and biomechanical test, and the expression of osteogenesis-related genes, HMGB1 and ERK-related proteins by qRT-PCR and Western blot. Rats in the HMGB1 group was increased in X-ray scores, peak torque, torsional stiffness, and the bone volume fraction (bone volume/total volume, BV/TV); meanwhile, those rats presented elevations in osteogenesis-related genes and HMGB1 expressions, as well as p-ERK/ERK ratio. However, rats in the HMGB1+ PD98059 group was significantly reduced in X-ray score, peak torque, torsional stiffness, and BV/TV, as well as the expression of osteogenesis-related genes and the ratio of p-ERK/ERK, as compared to those from HMGB1 group. HMGB1 could promote the expressions of osteogenesis-related genes and accelerate the healing process of fracture via activation of the ERK signaling pathway.

A retrospective study of 63 hallux valgus corrections using the osteodesis procedure

Osteotomy procedures have been the most popular approach to hallux valgus deformity correction. Soft tissue approaches have, in general, been regarded as ineffective for moderate and severe hallux valgus deformities. Osteodesis is a soft tissue technique that has been shown to be effective in the past but is still seldom practiced. In the present report, we describe a retrospective study of 63 hallux valgus feet in 36 patients who had undergone the osteodesis procedure. Their mean age was 46 ± 12 years, and the mean follow-up period was 25.4 ± 9.6 months. The surgical technique consisted of metatarsus primus varus deformity correction by intermetatarsal cerclage sutures and hallux valgus deformity correction by rebalancing the ligaments. The first metatarsophalangeal angle improved from a mean of 32.5° ± 7.6° preoperatively to 18.4° ± 7° postoperatively, the first intermetatarsal angle improved from 14.6° ± 2.6° to 6.8° ± 1.8°, and the American Orthopaedic Foot and Ankle Society score improved from 59 ± 14 to 93 ± 8 points. The rate of patient satisfaction after surgery was 92% (33 of 36 patients, 59 of 63 feet). The complications included a second metatarsal stress fracture in 3 feet (5%), metatarsophalangeal joint medial subluxation in 3 feet (5%), and metatarsophalangeal joint stiffness in 5 feet (8%). This soft tissue, nonosteotomy procedure was a safe technique that effectively corrected hallux valgus and metatarsus primus varus deformities of various severities without osteotomy or fusion.

A quantitative and non-invasive vibrational method to assess bone fracture healing: a clinical case study

Orthopaedics needs a robust diagnostic tool that can help or even replace traditional radiography in bone healing assessment, thus reducing patient exposure to ionizing radiation. We used a vibrational method to assess the healing of a complex fracture treated with external fixation, exploiting a quantitative and non-invasive procedure. Callus stiffening was monitored from the time of surgery until the fixator was removed. Our approach overcomes previous limitations and involves a longer period of healing monitoring (about 9 months), very frequent tests (bi-weekly), and the analysis of a single test configuration. The healing process was monitored by analysing the percentage increments of the squared resonant frequencies (SFIs), related to the stiffness variation and the changes in the frequency response functions. The results were validated by X-rays images, and revealed that the most sensitive parameter to quantify the healing was the SFI of the first resonant frequency which increased by about 20% per month during the formation of the woven callus and up to about 50% at the end of healing completion. This study confirms the potential of the vibrational method as an alternative to radiography in fracture healing assessment.

Refeeding partially reverses impaired fracture callus in undernourished rats

Background

Adequate nutritional intake plays a crucial role in maximizing skeletal acquisition. The specific effects of a general food restriction and refeeding on fracture healing are yet to be fully understood. The aim of this study was to assess the impact of general food restriction and refeeding on fracture repair.

Methods

Fifty-four male Wistar Hannover rats were randomly assigned into three groups: (1) Sham: Sham rats with femoral fracture; (2) FRes: Food-restricted rats with fracture, (3) Fres+Ref: Fres rats with refeeding. Following weaning, the FRes and Fres+Ref groups received 50% of the food amount provided to the Shams. In the sixth week of the experiment, all animals underwent a mid-right femur bone fracture, which was subsequently surgically stabilized. Following the fracture, the Fres+Ref group was refed, while the other groups maintained their pre-fracture diet. Bone calluses were analyzed on the fifth-day post-fracture by gene expression and on the sixth-week post-fracture using dual-energy X-ray absorptiometry, morphometry, histomorphometry, immunohistochemistry, computed microtomography, and torsion mechanical testing. Statistical significance was determined at a probability level of less than 0.05, and comparisons were made using the ANOVA test.

Results

Food restriction resulted in significant phenotypic changes in bone calluses when compared to sham rats characterized by deterioration in microstructure (i.e., BV, BV/TV, Tb.N, and Conn.D) reduced collagen deposition, bone mineral density, and mechanical strength (i.e., torque at failure, energy, and stiffness). Moreover, a higher rate of immature bone indicated a decrease in bone callus quality. Refeeding stimulated bone callus collagen formation, reduced local resorption, and effectively restored the microstructural (i.e., SMI, BCa.BV/TV, Tb.Sp, Tb.N, and Conn.D) and mechanical changes (i.e., torque at failure, energy, and angular displacement at failure) caused by food restriction. Despite these positive effects, the density of the bone callus, collagen deposition, and OPG expression remained lower when compared to the shams. Gene expression analysis didn't evidence any significant differences among the groups.

Conclusions

Food restriction had detrimental effects on osseous healing, which was partially improved by refeeding. Based on these findings, new research can be developed to create targeted nutritional strategies to treat and improve fracture healing.

Investigation into the effect of epidermal growth factor and hyaluronic acid on fracture healing in a rat femoral fracture model

OBJECTIVE

This study aimed to investigate the role of an exogenous Epidermal Growth Factor and a hyaluronic acid-based scaffold on fracture healing in a rat femoral fracture model Methods: Forty-eight male Wistar-Albino rats, each weighing a mean 392 grams (range= 350-450 grams) and aged 8.2 months (6-9 months), were used for this experimental study. All surgical procedures were performed on the left femur by a single surgeon. An open femoral fracture was created in all rats. The animals were randomly divided into one of the four groups: Control (12), EGF (12), HA (12) and Combined (12). In the 4th and sixth weeks, samples were processed and analyzed using biomechanical and histological methods.

RESULTS

Fracture healing was significantly improved in the Combined group compared to the control one, EGF and HA groups in all parameters at both experimental time points. At the fourth and sixth weeks after surgery, fracture healing in the EGF and HA groups was significantly increased at histological evaluation compared to controls. In addition, compared with EGF, HA and Control groups, a significant difference in callus tissue was detected in the Combined group at 4 and 6-week time points in biomechanical features.

CONCLUSION

This study has shown that combining local EGF and HA scaffold accelerates bone healing and strengthens the bony callus histologically and biomechanically. Using EGF-HA combined scaffolds may represent a possible future strategy in trauma surgery.

LEVEL OF EVIDENCE

N/A.

A Comparative Study of the Pharmacokinetics of Bis- and Pentaphosphonic Acids Labeled with Gallium-68 in Rats with Experimental Model of Bone Callus

We analyzed biodistribution of ⁶⁸Ga-labeled hydroxyethylidenediphosphonic acid (⁶⁸Ga-HEDP) and diethylenetriaminepentakis(methylenephosphonic acid) (⁶⁸Ga-DTPMP) in Wistar rats with experimental model of bone callus. It was shown that the content of ⁶⁸Ga-DTPMP and ⁶⁸Ga-HEDP in bone callus was ~1.5-fold higher than in intact femur. ⁶⁸Ga-DTPMP was characterized by higher stability in vivo, higher uptake in the bone tissue, and lower uptake in others visceral organs in comparison with ⁶⁸Ga-HEDP. Thus, ⁶⁸Ga-DTPMP had more suitable pharmacokinetic properties than ⁶⁸Ga-HEDP.

Distinct Morphologies of Bone Apatite Clusters in Endochondral and Intramembranous Ossification

Bone apatite crystals grow in clusters, but the microstructure of these clusters is unknown. This study compares the structural and compositional differences between bone apatite clusters formed in intramembranous (IO) and endochondral ossification (EO). Calvaria (IO) and femurs (EO) are isolated from mice at embryonic days (E) 14.5 to 15.5 and post-natal days (P) 6 to 7, respectively. Results show that the initially formed bone apatite clusters in EO (≅1.2 µm² ) are >10 times larger than those in IO (≅0.1 µm² ), without significant changes in ion composition. In IO (E14.5 calvarium), early minerals are formed inside matrix vesicles (MVs). In contrast, in EO (P6 femur epiphysis), no MVs are observed, and chondrocyte-derived plasma membrane nanofragments (PMNFs) are the nucleation site for mineralization. Apatite cluster size difference is linked with the different nucleation sites. Moreover, an alkaline pH and slow P supply into a Ca-rich microenvironment are suggested to facilitate apatite cluster growth, as demonstrated in a biomimetic mineralization system. Together, the results reveal for the first time the distinct and exquisite microstructures of bone apatite clusters in IO and EO, and provide insightful inspirations for the design of more efficient materials for bone tissue engineering and repair.