Nerve Growth Factor-Preconditioned Mesenchymal Stem Cell-Derived Exosome-Functionalized 3D-Printed Hierarchical Porous Scaffolds with Neuro-Promotive Properties for Enhancing Innervated Bone Regeneration.

The essential role of the neural network in enhancing bone regeneration has often been overlooked in biomaterial design, leading to delayed or compromised bone healing. Engineered mesenchymal stem cells (MSCs)-derived exosomes are becoming increasingly recognized as potent cell-free agents for manipulating cellular behavior and improving therapeutic effectiveness. Herein, MSCs are stimulated with nerve growth factor (NGF) to regulate exosomal cargoes to improve neuro-promotive potential and facilitate innervated bone regeneration. In vitro cell experiments showed that the NGF-stimulated MSCs-derived exosomes (N-Exos) obviously improved the cellular function and neurotrophic effects of the neural cells, and consequently, the osteogenic potential of the osteo-reparative cells. Bioinformatic analysis by miRNA sequencing and pathway enrichment revealed that the beneficial effects of N-Exos may partly be ascribed to the NGF-elicited multicomponent exosomal miRNAs and the subsequent regulation and activation of the MAPK and PI3K-Akt signaling pathways. On this basis, N-Exos were delivered on the micropores of the 3D-printed hierarchical porous scaffold to accomplish the sustained release profile and extended bioavailability. In a rat model with a distal femoral defect, the N-Exos-functionalized hierarchical porous scaffold significantly induced neurovascular structure formation and innervated bone regeneration. This study provided a feasible strategy to modulate the functional cargoes of MSCs-derived exosomes to acquire desirable neuro-promotive and osteogenic potential. Furthermore, the developed N-Exos-functionalized hierarchical porous scaffold may represent a promising neurovascular-promotive bone reparative scaffold for clinical translation.

1,25(OH)2D3 inhibits osteogenic differentiation through activating ß­catenin signaling via downregulating bone morphogenetic protein 2.

The present study explored whether bone morphogenetic proteins (BMPs) and Wnt/ß­catenin signaling pathways were involved in the 1,25(OH)2D3­induced inhibition of osteogenic differentiation in bone marrow­derived mesenchymal stem cells (BMSCs). To evaluate the osteogenic differentiation of BMSCs, the expression levels of ossification markers, including BMP2, Runt­related transcription factor 2 (Runx2), Msh homeobox 2 (Msx2), osteopontin (OPN) and osteocalcin (OCN), and the activity of alkaline phosphatase (ALP), as well as the calcified area observed by Alizarin red­S staining, were investigated. Chromatin immunoprecipitation (ChIP) assay was used to detect the effect of 1,25(OH)2D3 on the DNA methylation and histone modification of BMP2, while an immunoprecipitation (IP) assay was performed to assess the crosstalk between Smad1 and disheveled­1 (Dvl­1) proteins. It was observed that 1,25(OH)2D3 significantly decreased the expression levels of BMP2, Runx2, Msx2, OPN and OCN, and reduced ALP activity and the calcified area in BMSCs, whereas these effects were rescued by BMP2 overexpression. ChIP assay revealed that BMSCs treated with 1,25(OH)2D3 exhibited a significant increase in H3K9me2 level and a decrease in the acetylation of histone H3 at the same BMP2 promoter region. In addition, 1,25(OH)2D3 treatment promoted the nuclear accumulation of ß­catenin by downregulating BMP2. Furthermore, the ß­catenin signaling inhibitor XAV­939 weakened the inhibitory effect of 1,25(OH)2D3 on osteogenic differentiation. Additionally, knockdown of ß­catenin rescued the attenuation in Dvl­1 and Smad1 interaction caused by 1,25(OH)2D3. Overexpression of Smad1 also reversed the inhibitory effect of 1,25(OH)2D3 on osteogenic differentiation. Taken together, the current study demonstrated that 1,25(OH)2D3 inhibited the differentiation of BMSCs into osteoblast­like cells by inactivating BMP2 and activating Wnt/ß­catenin signaling.

Anatomic study of coracoclavicular ligaments for reconstruction of acromioclavicular joint dislocations.

BACKGROUND: There has been a trend to reconstruct the coracoclavicular (CC) ligaments anatomically for management of acromioclavicular (AC) joint dislocations. PURPOSE: The aim of this study was to determine the location and orientation of the CC ligaments for anatomic reconstruction of the AC joint. METHODS: The subjects were a total of 40 shoulders from 20 Chinese cadavers. Two K-wires were drilled through the insertion center of the conoid and trapezoid ligaments respectively. The distance from the center of the CC ligaments to the bone landmarks of the clavicle and the oblique angle of the two K-wires was measured respectively. RESULTS: The distance from the center of the trapezoid ligament to the lateral end and the anterior border of the clavicle was 21.7 ± 1.1 mm and 6.4 ± 0.5 mm, respectively. The valgus angle and retroversion angle of the trapezoid ligament was 39.3°±0.9° and 6.0°±0.6°, respectively. The distance from the center of the conoid ligament to the lateral end and the posterior border of the clavicle was 36.6 ± 0.9 mm and 5.5 ± 0.4 mm, respectively. The valgus angle and retroversion angle of the conoid ligament was 6.6°±0.7° and 11.0°±0.9°, respectively. CONCLUSIONS: These findings are important for the anatomic reconstruction of the AC joint dislocations, by predicting the location and orientation of the conoid and trapezoid ligaments accurately.

The relevance of the anatomical basis of fracture for the subsequent treatment of the anterior humeral circumflex artery and the axillary nerve.

PURPOSE: The purpose of this study was to determine the location of the anterior humeral circumflex artery and axillary nerve based on bony landmarks, and to provide anatomical information that enables a safe approach when treating a proximal humeral fractures. METHODS: Thirty cadavers were included. The distances of both the anterior humeral circumflex artery and the axillary nerve from body landmarks were measured using Vernier calipers. RESULTS: The mean distance between the inferior border of the medial acromion and the superior border of the anterior humeral circumflex artery was 5.1 ± 0.2 cm (range, 4.6-5.5 cm); the mean distance between the prominence of the lesser tuberosity and the superior border of the anterior humeral circumflex artery was 2.5 ± 0.2 cm (range, 2.0-3.0 cm); the mean distance between the anterior-inferior border of the acromion and the superior border of the axillary nerve was 6.3 ± 0.5 cm (range, 5.2-7.0 cm). CONCLUSIONS: The artery is located approximately 5.1 cm below the inferior border of the medial acromion and 2.5 cm below the prominence of the lesser tuberosity, and the nerve was located approximately 6.3 cm below the anterio-inferior border of the acromion and 3.5 cm below the prominence of the greater tuberosity. The reduction manoeuvres should be conducted with extreme care in this region.

[Biomechanical analysis of stability of internal fixator for proximal humeral fractures].

OBJECTIVE: To review the biomechanics of internal fixators for proximal humeral fractures, and to compare the mechanical stability of various internal fixators. METHODS: The literature concerning the biomechanics of internal fixators for proximal humeral fractures was extensively analyzed. RESULTS: The most important things for best shoulder functional results are optimal anatomical reduction and stable fixation. At present, there are a lot of methods to treat proximal humeral fractures. Locking-plate exhibits significant mechanical stability and has many advantages over other internal fixators by biomechanical comparison. CONCLUSION: Locking-plate has better fixation stability than other internal fixators and is the first choice to treat proximal humeral fractures.