Cartilaginous Callus Research Articles

Cigarette Smoke Exposure Impairs Fracture Healing in a Rat Model: Preferential Impairment of Endochondral over Membranous Healing.

Cigarette smoking affects fracture repair, leading to delayed healing or nonunion. We sought to investigate if cigarette smoke differentially affects intramembranous and endochondral ossification in healing fractures, focusing on whether endochondral ossification is particularly impaired. This study utilized a bilateral femur fracture model in Sprague Dawley rats to examine the impact of cigarette smoke exposure on healing of femur fractures, treated with either a custom-locked intramedullary nail or compression plating to induce endochondral and membranous ossification, respectively. Animals were exposed to tobacco smoke 30 days before and after surgery, with evaluations including radiographs, histomorphometry, and microCT at 10 days, 1, 3, and 6-months post-operation, and biomechanical testing at 3, 6 months. Sixty-eight animals were randomized to control or exposure groups (two died perioperatively), and 89% of the femora achieved union when harvested at 3 and 6 months. Smoke exposure delayed cartilaginous callus formation and bone maturation in nailed fractures compared to plated fractures and controls in same animals. Plated fractures in exposed animals exhibited little cartilage callus and healed like control animals. At 3 months, plated fractures were stiffer and stronger than nailed fractures in both groups, but these differences vanished by 6 months. Plated fractures healed more rapidly and more completely than nailed fractures under both control and smoke-exposed conditions. Using compression plating instead of IM nailing for closed long bone fractures may lead to better outcomes in patients who smoke compared to current results with nailing.

Hoxc10-mediated 'positional memory' regulates cartilage formation subsequent to femoral heterotopic grafting.

The Hox gene plays a crucial role in the bone development, determining their structure and morphology. Limb bone grafts expressing Hox positive genes are commonly used for free transplantation to repair Hox negative mandibular critical bone defects. However, the specific role of original Hox genes in newly formed bone during the cross-layer bone grafting healing process remains unexplored. Our findings demonstrate that femurs ectopically grafted into the mandibular environment retained a significant ability to differentiate into cartilage and form cartilaginous callus, which may be a key factor contributing to differences in bone graft healing. Hoxc10, an embryonic layer-specific genes, regulates cartilage formation during bone healing. Mechanistically, we observed Hoxc10 retention in co-cultured femoral BMSCs. Knocking out Hoxc10 narrows the bone gap and reduces cartilage formation. In summary, we reveal Hoxc10's 'positional memory' after adult cross-layer bone graft, influencing the outcomes of autologous bone graft.

Utility of ultrasound imaging in monitoring fracture healing in rat femur: Comparison with other imaging modalities

ObjectiveFractures are common injuries and various imaging modalities are employed to diagnose and monitor bone union. However, the follow-up of fracture healing using ultrasound imaging (US) remains a topic of debate. In this study, we analyzed of fracture healing process and compared US and radiological analyses with histological analyses to clarify the characteristics and limitations of each modality. MethodsAn osteotomy model was created using the femur of Wistar rats, and US, radiological (radiography and micro-computed tomography (micro-CT)), and histological analyses were performed. Radiological assessments were conducted for the evaluation of calcified tissue. The gap between the bony callus and cartilaginous callus was measured. ResultsUS effectively captured changes on the fracture surface, potentially reflecting the early healing processes. Both US and radiographic findings showed strong correlation in terms of the decrease in the bony callus gap. US was unable to distinguish cartilaginous callus from the surrounding soft tissue. During the remodeling stage, micro-CT offered a detailed assessment of the internal fracture surface, whereas US was limited to evaluating the outer bone surface and lacked accuracy in visualizing the entire fracture site. Radiography provided a general overview of the fractures. The decrease in the bony callus gap measured using US correlated with the reduction in cartilaginous callus observed histologically. ConclusionThis study demonstrated that US could be a valuable tool for evaluating fracture healing. Combining fracture management with US and radiological examinations may provide a more accurate assessment of healing progress.

Dnmt3b ablation affects fracture repair process by regulating apoptosis

PurposePrevious studies have shown that DNA methyltransferase 3b (Dnmt3b) is the only Dnmt responsive to fracture repair and Dnmt3b ablation in Prx1-positive stem cells and chondrocyte cells both delayed fracture repair. Our study aims to explore the influence of Dnmt3b ablation in Gli1-positive stem cells in fracture healing mice and the underlying mechanism.MethodsWe generated Gli1-CreERT2; Dnmt3bflox/flox (Dnmt3bGli1ER) mice to operated tibia fracture. Fracture callus tissues of Dnmt3bGli1ER mice and control mice were collected and analyzed by X-ray, micro-CT, biomechanical testing, histopathology and TUNEL assay.ResultsThe cartilaginous callus significantly decrease in ablation of Dnmt3b in Gli1-positive stem cells during fracture repair. The chondrogenic and osteogenic indicators (Sox9 and Runx2) in the fracture healing tissues in Dnmt3bGli1ER mice much less than control mice. Dnmt3bGli1ER mice led to delayed bone callus remodeling and decreased biomechanical properties of the newly formed bone during fracture repair. Both the expressions of Caspase-3 and Caspase-8 were upregulated in Dnmt3bGli1ER mice as well as the expressions of BCL-2.ConclusionsOur study provides an evidence that Dnmt3b ablation Gli1-positive stem cells can affect fracture healing and lead to poor fracture healing by regulating apoptosis to decrease chondrocyte hypertrophic maturation.

Endochondral Repair of Jawbone Defects Using Periosteal Cell Spheroids

Recapitulation of the natural healing process is receiving increasing recognition as a strategy to induce robust tissue regeneration. Endochondral ossification has been recognized as an essential reparative approach in natural jawbone defect healing. However, such an approach has been overlooked in the recent development of cell-based therapeutics for jawbone repair. Therefore, this study aimed to explore a bioinspired stem cell–based strategy for jawbone repair by mimicking the mesenchymal condensation of progenitor cells during the early endochondral ossification process. For this purpose, passage 3 of jawbone periosteum-derived cells (jb-PDCs) was cultured in our previously reported nonadherent microwells (200 µm in diameter, 148 µm in depth, and 100 µm space in between) and self-assembled into spheroids with a diameter of 96.4 ± 5.8 µm after 48 h. Compared to monolayer culture, the jb-PDC spheroids showed a significant reduction of stemness marker expression evidenced by flow cytometry. Furthermore, a significant upregulation of chondrogenic transcription factor SOX9 in both gene and protein levels was observed in the jb-PDC spheroids after 48 h of chondrogenic induction. RNA sequencing and Western blotting analysis further suggested that the enhanced SOX9-mediated chondrogenic differentiation in jb-PDC spheroids was attributed to the activation of the p38 MAPK pathway. Impressively, inhibition of p38 kinase activity significantly attenuated chondrogenic differentiation jb-PDC spheroids, evidenced by a significant decline of SOX9 in both gene and protein levels. Strikingly, the jb-PDC spheroids implanted in 6- to 8-wk-old male C57BL/6 mice with critical-size jawbone defects (1.8 mm in diameter) showed an evident contribution to cartilaginous callus formation after 1 wk, evidenced by histological analysis. Furthermore, micro–computed tomography analysis showed that the jb-PDC spheroids significantly accelerated bone healing after 2 wk in the absence of exogenous growth factors. In sum, the presented findings represent the successful development of cell-based therapeutics to reengineer the endochondral bone repair process and illustrate the potential application to improve bone repair and regeneration in the craniofacial skeleton.

Reverse Dynamization Accelerates Regenerate Bone Formation and Remodeling in a Goat Distraction Osteogenesis Model.

This article was updated on December 20, 2023, because of previous errors, which were discovered after the preliminary version of the article was posted online. Figure 4 has been replaced with a figure that presents different p values. Also, on page 1943, the text that had read: "Quantitative microCT confirmed that the total volume of the regenerate in the RD group was much smaller compared with the SF (p = 0.06) and DF (p = 0.007) groups, although it was significantly smaller only compared with the DF group (Fig. 4-A). The total volume of the intact bone (contralateral tibia) was significantly smaller in the RD group compared with the other groups, but the RD group had values closest to those for the intact tibia. Similarly, the RD group had less bone volume compared with the SF and DF groups, and this value was significantly different from the DF group (p = 0.034; Fig. 4-B). Of the 3 groups, the RD group had vBMD that was the closest to that of intact bone. It also had significantly higher vBMD compared with the SF and DF groups (p < 0.0001 for both; Fig. 4-C).The results of torsional testing (Fig. 4-D) confirmed that the regenerate bone formed under conditions of RD was significantly stronger than that formed under SF or DF (p < 0.001 versus SF group, and p = 0.0493 versus DF group)."now reads: "Quantitative microCT confirmed that the total volume of the regenerate in the RD group was significantly smaller compared with the SF and DF groups (p < 0.01 for both groups; Fig. 4-A). The total volume of the intact bone (contralateral tibia) was significantly smaller compared with the SF and DF groups (p < 0.0001 for both). The RD group had values closest to those for the intact tibia, and this difference was not significant (Fig. 4-A). Similarly, the RD group had less bone volume compared with the SF and DF groups, and this value was significantly different from the DF group (p < 0.01; Fig. 4-B). Of the 3 groups, the RD group had vBMD that was the closest to that of intact bone, but the intact bone was significantly different compared with all of the other groups (p < 0.0001 for all groups). The RD group had significantly higher vBMD compared with the SF and DF groups (p = 0.042 and p = 0.046, respectively; Fig. 4-C).The results of torsional testing (Fig. 4-D) confirmed that the regenerate bone formed under conditions of RD was significantly stronger than that formed under SF or DF (p < 0.0001 versus SF group, and p = 0.0493 versus DF group). The intact group was significantly different compared with the SF group (p < 0.0001)."

Bone Regeneration in a Large Animal Model Featuring a Modular Off-the-Shelf Soft Callus Mimetic.

Implantation of engineered cartilage with soft callus features triggers remodeling to bone tissue via endochondral bone regeneration (EBR). Thus far, EBR has not progressed to the level of large animals on the axis of clinical translation. Herein, the feasibility of EBR is aimed for a critical-sized defect in a large animal model. Chondrogenesis is first induced in goat-derived multipotent mesenchymal stromal cells (MSCs) by fine-tuning the cellular differentiation process. Through a unique devitalization process, two off-the-shelf constructs aimed to recapitulate the different stages of the transient cartilaginous soft callus template in EBR are generated. To evaluate bone regeneration, the materials are implanted in an adapted bilateral iliac crest defect model in goats, featuring a novel titanium star-shaped spacer. After 3 months, the group at the more advanced differentiation stage shows remarkable regenerative capacity, with comparable amounts of bone regeneration as the autograft group. In contrast, while the biomaterial mimicking the earlier stages of chondrogenesis shows improved regeneration compared to the negative controls, this is subpar compared to the more advanced material. Concluding, EBR is attainable in large animals with a soft callus mimetic material that leads to fast conversion into centimeter-scale bone, which prospects successful implementation in the human clinics.

3D Biomimetic Calcified Cartilaginous Callus that Induces Type H Vessels Formation and Osteoclastogenesis (Adv. Sci. 16/2023)

3D Biomimetic Calcified Cartilaginous Callus Based on the natural bone repair process, a 3D biomimetic calcified cartilaginous callus (PHS) is prepared using calcium ion chelation and 3D printing technology to promote the regeneration of large-segment bone defects. PHS can promote both type H vessels formation and osteoclast formation and promote bone regeneration by facilitating the expression of osteogenesis-promoting coupling factors. More details can be found in article number 2207089 by Jin Qi, Wenguo Cui, Lianfu Deng, and co-workers.

T cells heal bone fractures with help from the gut microbiome.

Immune cells play an important functional role in bone fracture healing. Fracture repair is a well-choreographed process that takes approximately 21 days in healthy mice. While the process is complex, conceptually it can be divided into four overlapping stages: inflammation, cartilaginous callus formation, bony callus formation, and remodeling. T cells play a key role in both the cartilaginous and bony callus phases by producing IL-17A. In this issue of the JCI, Dar et al. showed that T cells were recruited from the gut, where the gut microbiota determined the pool of T cells that expressed IL-17A. Treatment with antibiotics and dysbiosis reduced the expansion of IL-17-expressing CD4+ T cells (Th17) and impaired callus formation. These findings demonstrate crosstalk among the gut microbiota, the adaptive immune system, and bone that has clinical implications for fracture healing.

IMPACT OF BMP-1 MODULATION IN EARLY FRACTURE REPAIR

BMP-1 is the major procollagen-C-peptidase activating, besides fibrillar collagen types I-III, several enzymes and growth factors involved in the generation of extracellular matrix. This study investigated the effect of adding and inhibiting BMP-1 directly post fracture.Standardised femoral fractures were stabilized by an intramedullary nail in 12 week-old female C57Bl/6J mice. We injected either 20 µL recombinant active BMP-1, activity buffer or the BMP-1 specific inhibitor “sizzled”. After 7, 14 and 28 days, mice were sacrificed. Femurs were dissected and paraffin slides were prepared. Callus composition was divided into soft tissue, mineralized and cartilaginous callus. Murine MC3T3 pre-osteoblastic cells were kept in culture adding BMP-1 and sizzled during osteoblastic differentiation. Putative cytotoxicity was determined using MTT-vitality assay. Cell calcification, collagen deposition, and BMP-2 and myostatin protein quantity were characterized.Adding BMP-1 displayed a weak positive effect on the outcome. After 7 days, more mineralised callus was present, meanwhile the cartilaginous callus was apparently remodelled at higher rate. In the case of BMP-1 inhibition, we observed more cartilaginous callus, which may indicate reduced stability. In cell culture, we could observe a high interference with mineralisation capabilities depending on the stage of osteoblastic development when adding BMP-1 or inhibiting it. Addition and inhibition impaired myostatin (anti-osteogen) and BMP-2 (pro-osteogen) expression.Interfering with BMP-1 homeostasis in this early stage of fracture repair seems to have rather negative effects. Inhibition apparently yields lower callus quality while the addition of BMP-1 does not significantly accelerate the healing outcome. Cell culture experiments show that BMP-1 application after 7 days of healing leads to higher collagen output but has no effect on mineralisation. This may suggest that BMP-1 application at a later time-point may lead to more pronounced beneficial effects on fracture repair.

INTEGRIN A2B1 DEFICIENCY REVEALS FASTER REGENERATION THROUGH BMP PATHWAY ACTIVATION IN A MURINE FRACTURE HEALING MODEL

Integrin α2β1 is one of the major transmembrane receptors for fibrillary collagen. In native bone we could show that the absence of this protein led to a protective effect against age-related osteoporosis. The objective of this study was to elucidate the effects of integrin α2β1 deficiency on fracture repair and its underlying mechanisms.Standardised femoral fractures were stabilised by an intramedullary nail in 12 week old female C57Bl/6J mice (wild type and integrin α2-/-). After 7, 14 and 28 days mice were sacrificed. Dissected femura were subjected to µCT and histological analyses. To evaluate the biomechanical properties, 28-day-healed femura were tested in a torsional testing device. Masson goldner staining, Alizarin blue, IHC and IF staining were performed on paraffin slices. Blood serum of the animals were measured by ELISA for BMP-2. Primary osteoblasts were analysed by in/on-cell western technology and qRT-PCR.Integrin α2β1 deficient animals showed earlier transition from cartilaginous callus to mineralized callus during fracture repair. The shift from chondrocytes over hypertrophic chondrocytes to bone-forming osteoblasts was accelerated. Collagen production was increased in mutant fracture callus. Serum levels of BMP-2 were increased in healing KO mice. Isolated integrin deficient osteoblast presented an earlier expression and production of active BMP-2 during the differentiation, which led to earlier mineralisation. Biomechanical testing showed no differences between wild-type and mutant bones.Knockout of integrin α2β1 leads to a beneficial outcome for fracture repair. Callus maturation is accelerated, leading to faster recovery, accompanied by an increased generation of extra-cellular matrix material. Biomechanical properties are not diminished by this accelerated healing. The underlying mechanism is driven by an earlier availability of BMP-2, one main effectors for bone development. Local inhibition of integrin α2β1 is therefore a promising target to accelerate fracture repair, especially in patients with retarded healing.

3D Biomimetic Calcified Cartilaginous Callus that Induces Type H Vessels Formation and Osteoclastogenesis.

The formation of a calcified cartilaginous callus (CACC) is crucial during bone repair. CACC can stimulate the invasion of type H vessels into the callus to couple angiogenesis and osteogenesis, induce osteoclastogenesis to resorb the calcified matrix, and promote osteoclast secretion of factors to enhance osteogenesis, ultimately achieving the replacement of cartilage with bone. In this study, a porous polycaprolactone/hydroxyapatite-iminodiacetic acid-deferoxamine (PCL/HA-SF-DFO) 3D biomimetic CACC is developed using 3D printing. The porous structure can mimic the pores formed by the matrix metalloproteinase degradation of the cartilaginous matrix, HA-containing PCL can mimic the calcified cartilaginous matrix, and SF anchors DFO onto HA for the slow release of DFO. The in vitro results show that the scaffoldsignificantly enhances angiogenesis, promotes osteoclastogenesis and resorption by osteoclasts, and enhances the osteogenic differentiation of bone marrow stromal stem cells by promoting collagen triple helix repeat-containing 1 expression by osteoclasts. The in vivo results show that the scaffold significantly promotes type H vessels formation and the expression of coupling factors to promote osteogenesis, ultimately enhancing the regeneration of large-segment bone defects in rats and preventing dislodging of the internal fixation screw. In conclusion, the scaffold inspired by biological bone repair processes effectively promotes bone regeneration.

Development of numerical model-based machine learning algorithms for different healing stages of distal radius fracture healing

Background and objectivesEarly therapeutic exercises are vital for the healing of distal radius fractures (DRFs) treated with the volar locking plate. However, current development of rehabilitation plans using computational simulation is normally time-consuming and requires high computational power. Thus, there is a clear need for developing machine learning (ML) based algorithms that are easy for end-users to implement in daily clinical practice. The purpose of the present study is to develop optimal ML algorithms for designing effective DRF physiotherapy programs at different stages of healing. MethodFirst, a three-dimensional computational model for the healing of DRF was developed by integrating mechano-regulated cell differentiation, tissue formation and angiogenesis. The model is capable of predicting time-dependant healing outcomes based on different physiologically relevant loading conditions, fracture geometries, gap sizes, and healing time. After being validated using available clinical data, the developed computational model was implemented to generate a total of 3600 clinical data for training the ML models. Finally, the optimal ML algorithm for each healing stage was identified. ResultsThe selection of the optimal ML algorithm depends on the healing stage. The results from this study show that cubic support vector machine (SVM) has the best performance in predicting the healing outcomes at the early stage of healing, while trilayered ANN outperforms other ML algorithms in the late stage of healing. The outcomes from the developed optimal ML algorithms indicate that Smith fractures with medium gap sizes could enhance the healing of DRF by inducing larger cartilaginous callus, while Colles fractures with large gap sizes may lead to delayed healing by bringing excessive fibrous tissues. ConclusionsML represents a promising approach for developing efficient and effective patient-specific rehabilitation strategies. However, ML algorithms at different healing stages need to be carefully chosen before being implemented in clinical applications.

Irisin Modulates Inflammatory, Angiogenic, and Osteogenic Factors during Fracture Healing.

Bone fractures are a widespread clinical event due to accidental falls and trauma or bone fragility; they also occur in association with various diseases and are common with aging. In the search for new therapeutic strategies, a crucial link between irisin and bone fractures has recently emerged. To explore this issue, we subjected 8-week-old C57BL/6 male mice to tibial fracture, and then we treated them with intra-peritoneal injection of r-Irisin (100 µg/kg/weekly) or vehicle as control. At day 10 post fracture, histological analysis showed a significant reduced expression of inflammatory cytokines as tumor necrosis factor-alpha (TNFα) (p = 0.004) and macrophage inflammatory protein-alpha (MIP-1α) (p = 0.015) in the cartilaginous callus of irisin-treated mice compared to controls, supporting irisin's anti-inflammatory role. We also found increased expressions of the pro-angiogenic molecule vascular endothelial growth factor (VEGF) (p = 0.002) and the metalloproteinase MMP-13 (p = 0.0006) in the irisin-treated mice compared to the vehicle ones, suggesting a myokine involvement in angiogenesis and cartilage matrix degradation processes. Moreover, the bone morphogenetic protein (BMP2) expression was also upregulated (p = 0.002). Taken together, our findings suggest that irisin can contribute to fracture repair by reducing inflammation and promoting vessel invasion, matrix degradation, and bone formation, supporting its possible role as a novel molecule for fracture treatment.

Establishing a Diaphyseal Femur Fracture Model in Mice.

Bones have a significant regenerative capacity. However, fracture healing is a complex process, and depending on the severity of the lesions and the age and overall health status of the patient, failures can occur, leading to delayed union or nonunion. Due to the increasing number of fractures resulting from high-energy trauma and aging, the development of innovative therapeutic strategies to improve bone repair based on the combination of skeletal/mesenchymal stem/stromal cells and biomimetic biomaterials is urgently needed. To this end, the use of reliable animal models is fundamental to better understanding the key cellular and molecular mechanisms that determine the healing outcomes. Of all the models, the mouse is the preferred research model because it offers a wide variety of transgenic strains and reagents for experimental analysis. However, the establishment of fractures in mice may be technically challenging due to their small size. Therefore, this article aims to demonstrate the procedures for the surgical establishment of a diaphyseal femur fracture in mice, which is stabilized with an intramedullary wire and resembles the most common bone repair process, through cartilaginous callus formation.

Radioelectronic wireless systems for non-invasive diagnostics of tubular bone fractures during body osteosynthesis

During the rehabilitation of the patient, accidental and shock loads are the main cause of aseptic loosening and damage to the elements of the fixing structure (FC). The lack of control over the formation of cartilaginous callus in the fracture zone causes an increase in the period of incapacity for work and an increase in material costs associated with the patient's stay in the hospital.The partial load on the bone is simulated, which is 25% of the calculated value and is equal to the average body weight of the patient. On the basis of the obtained data, a new method and device were developed for non-invasive detection of the initial moment of weakening or fracture of the fixing structure, detection of improper fracture fusion, diagnosis of the formation and control of cartilage callus growth, detection of the appearance of the initial moment of the inflammatory process in the patient's body and diagnosis of the causes of this process. The requirements for a possible method of non-invasive diagnosis of the condition of a tubular bone fracture are formulated. Criterion dependencies of the controlled parameters were established. The effect of random loads, which are the cause of failures of the fixing structure, has been proven. Wireless transmission of electricity and information made it possible to develop a method of non-invasive control and diagnosis of fracture of tubular bones and to establish criterion dependencies between controlled parameters. For a comprehensive diagnosis of the patient's recovery, it is sufficient to monitor the pressure at three points, the bending moment at the site of the bone fracture, the temperature of the periosteum and the temperature of any other point of the body.

The role of hypertrophic chondrocytes in regulation of the cartilage-to-bone transition in fracture healing

Endochondral bone formation is an important pathway in fracture healing, involving the formation of a cartilaginous soft callus and the process of cartilage-to-bone transition. Failure or delay in the cartilage-to-bone transition causes an impaired bony union such as nonunion or delayed union. During the healing process, multiple types of cells including chondrocytes, osteoprogenitors, osteoblasts, and endothelial cells coexist in the callus, and inevitably crosstalk with each other. Hypertrophic chondrocytes located between soft cartilaginous callus and bony hard callus mediate the crosstalk regulating cell-matrix degradation, vascularization, osteoclast recruitment, and osteoblast differentiation in autocrine and paracrine manners. Furthermore, hypertrophic chondrocytes can become osteoprogenitors and osteoblasts, and directly contribute to woven bone formation. In this review, we focus on the roles of hypertrophic chondrocytes in fracture healing and dissect the intermingled crosstalk in fracture callus during the cartilage-to-bone transition.

X-ray macromorphological and biochemical assessment of consolidation of fractures of long tubular bones under conditions of osteoreplacement with calcium-phosphate ceramics doped with germanium for osteoporosis in rab-bits

Among several factors that can cause a violation of the course of reparative osteogenesis, previous diseases associated with a change in the structural and functional state of bone tissue and primarily osteoporosis are considered significant. Osteoporotic fractures are difficult to treat. Along with systemic therapy, locally applied bone substitute materials, particularly unalloyed and alloyed calcium phosphate ceramics with pronounced osteoconductive, osteoinductive, and osteointegration properties. The work aims to evaluate the effect of calcium-phosphate ceramics doped with germanium on post-traumatic bone regeneration in conditions of secondary osteoporosis in rabbits. Experimental osteoporosis in rabbits was induced by administration of 0.4 % dexamethasone solution (KRKA, Slovenia) for 21 days at a dose of 1.2 mg/kg of body weight. Experimental (n = 9) and control (n = 9) groups of animals were formed. Animals of the experimental group had defects replaced with granules of hydroxyapatite ceramics, synthesized based on hydroxyapatite and β-tricalcium phosphate, doped with germanium. In rabbits of the control group, bone defects healed under a blood clot. Blood samples to determine the level of total calcium (Ca) and inorganic phosphorus (P) were taken before surgery and on 7-,14th, 30th, and 60th day of the study. X-ray studies were performed on the RUM-20 X-ray machine on the 14th, 30th, and 60th day of reparative osteogenesis. Radiologically and macromorphologically, it was established that reparative osteogenesis in the experimental animals proceeds more dynamically compared to the control group and is characterized by a high density of bone tissue at the site of the defect already on the 14th day after the injury, a moderate periosteal and early appearance of the endosteal reaction. The content of total calcium in the animals of the experimental group on the 14th day after the injury was 1.3 times (P &lt; 0.001) higher than that of the control and animals before the operation, and on the 30th day, it was 1.2 times (P &lt; 0.001) in accordance. The concentration of inorganic phosphorus (P) on the 14th and 30th days of reparative osteogenesis in animals of the experimental group was 1.1 times (P &lt; 0.05) lower than in control animals, and on the 60th day in 1.4 times (P &lt; 0.01), respectively. Systemic osteoporosis in experimental animals causes a violation of reparative osteogenesis due to the prolongation of the inflammatory-resorptive stage and cartilaginous callus and complicated mineralization of bone regeneration. Calcium-phosphate ceramics is a promising material for replacing bone defects in animals with systemic secondary osteoporosis.

Micro-Vibration Environment Promotes Bone Marrow Mesenchymal Stem Cells (BMSCs) Healing of Fracture Ends and Matrix Metalloproteinase-9 (MMP-9) Expression

When the muscle is stimulated by micro-vibration environment, it will produce a mechanical effect on skeletal muscle, thereby promoting growth of skeletal muscle cells. Bone marrow mesenchymal stem cells (BMSCs), as mechanically sensitive cells, have ability to multipolarize and multiple tropisms. This experiment explores the effect of BMSC cells on fracture end healing in fracture rats in a micro-vibration environment, and further explores whether it promotes the healing of fracture end to provide biological treatment ideas for the clinical repair of fracture patients. After modeling, SD rats were assigned into blank group, control group, and experimental group (treated with BMSCs) followed by analysis of bone volume fraction and bone trabecular thickness and number by Micro-CT, callus growth by H&amp;E staining, and expression of p38 and MMP-9 by immunohistochemical staining. The BV/TV value of experimental group was (0.41±0.06), Tb.Th value (0.08±0.01), Tb.N value (3.96±0.48) and was higher than other two groups (P &lt; 0.05). The growth of capillaries, trabecular bone, fibrous callus and cartilaginous callus in experimental group showed increased growth and the calcification was observed at the edge of cartilage callus. In addition, experimental group showed increased distribution area of MMP-9 and elevated expression of MMP-9 and p38MAPK. In conclusion, the micro-vibration environment can effectively promote the chemotaxis of BMSC cells to the fracture site to activate ossification, thereby promoting the proliferation and ossification and differentiation of BMSC, and further promoting the repair of fracture ends.

Collagen X Longitudinal Fracture Biomarker Suggests Staged Fixation in Tibial Plateau Fractures Delays Rate of Endochondral Repair.

To use a novel, validated bioassay to monitor serum concentrations of a breakdown product of collagen X in a prospective longitudinal study of patients sustaining isolated tibial plateau fractures. Collagen X is the hallmark extracellular matrix protein present during conversion of soft, cartilaginous callus to bone during endochondral repair. Previous preclinical and clinical studies demonstrated a distinct peak in collagen X biomarker (CXM) bioassay levels after long bone fractures. Level 1 academic trauma facility. Thirty-six patients; isolated tibial plateau fractures. (3) Closed treatment, ex-fix (temporizing/definitive), and open reduction internal fixation. Collagen X serum biomarker levels (CXM bioassay). Twenty-two men and 14 women (average age: 46.3 y; 22.6-73.4, SD 13.3) enrolled (16 unicondylar and 20 bicondylar fractures). Twenty-five patients (72.2%) were treated operatively, including 12 (33.3%) provisionally or definitively treated by ex-fix. No difference was found in peak CXM values between sexes or age. Patients demonstrated peak expression near 1000 pg/mL (average: male-986.5 pg/mL, SD 369; female-953.2 pg/mL, SD 576). There was no difference in peak CXM by treatment protocol, external fixator use, or fracture severity (Schatzker). Patients treated with external fixation (P = 0.05) or staged open reduction internal fixation (P = 0.046) critically demonstrated delayed peaks. Pilot analysis demonstrates a strong CXM peak after fractures commensurate with previous preclinical and clinical studies, which was delayed with staged fixation. This may represent the consequence of delayed construct loading. Further validation requires larger cohorts and long-term follow-up. Collagen X may provide an opportunity to support prospective interventional studies testing novel orthobiologics or fixation techniques. Level II, prospective clinical observational study.