Engineering 3D-Printed Strontium-Titanium Scaffold-Integrated Highly Bioactive Serum Exosomes for Critical Bone Defects by Osteogenesis and Angiogenesis

AUTHORS

Hao Liu, Ranli Gu, Wei Li, Lijun Zeng, Yuan Zhu, Boon Chin Heng, Yunsong Liu, and Yongsheng Zhou

ABSTRACT

Currently, healing of large bone defects faces significant challenges such as a bulk of bone regeneration and revascularization on the bone defect region. Here, a “cell-free scaffold engineering” strategy that integrates strontium (Sr) and highly bioactive serum exosomes (sEXOs) inside a three-dimensional (3D)-printed titanium (Ti) scaffold (Sc) is first developed. The constructed SrTi Sc can serve as a sophisticated biomaterial platform for maintaining bone morphological characteristics of the radius during the period of critical bone defect (CBD) repair and further accelerating bone formation and fibroblastic suppression via the controlled release of Sr from the superficial layer of the scaffold. Moreover, compared with sEXO from healthy donors, the sEXO extracted from the serum of the femoral fracture rabbit model at the stage of fracture healing, named BF EXO, is robustly capable of facilitating osteogenesis and angiogenesis. In addition, the underlying therapeutic mechanism is elucidated, whereby altering miRNAs shuttled by BF EXO enables osteogenesis and angiogenesis. Further, the in vivo study revealed that the SrTi Sc + BF EXO composite dramatically accelerated bone repair via osteoconduction, osteoinduction, and revascularization in radial CBD of rabbits. This study broadens the source and biomedical potential of specifically functionalized exosomes and provides a comprehensive clinically feasible strategy for therapeutics on large bone defects.

Do bone elasticity and postmortem interval affect forensic fractographic analyses?

AUTHORS

Jessica Skinner, Natalie Langley, Malin Joseph, James Herrick, Robert Brown, Brian Waletzki, Peter Goguen Dipl, Loukham Shyamsunder, Subramaniam Rajan

ABSTRACT

Forensic fractographic features of bone reliably establish crack propagation in perimortem injuries. We investigated if similar fracture surface features characterize postmortem fractures. Experimentally induced peri- and postmortem fractures were used to assess if fractographic features vary as bone elasticity decreases during the postmortem interval (PMI). Thirty-seven unembalmed, defleshed human femoral shafts from males and females aged 33–81 years were fractured at varying PMIs with a drop test frame using a three-point bending setup and recorded with a high-speed camera. Vital statistics, cause of death, PMI length, temperature, humidity, collagen percentage, water loss, fracture energy, and fractography scores were recorded for each sample. Results showed that fractographic features associated with perimortem fractures were expressed in PMIs up to 40,600 accumulated degree hours (ADH), or 60 warm weather days. Hackle was the most consistently expressed feature, occurring in all fractures regardless of ADH. The most variable characteristics were wake features (78.4%) and arrest ridges (70.3%). Collagen percentage did not correlate strongly with ADH (r = −0.04, p = 0.81); however, there was a strong significant correlation between ADH and water loss (r = 0.74, p < 0.001). Multinomial logistic regression showed no association between fractographic feature expression and ADH or collagen percentage. In conclusion, forensic fractographic features reliably determine initiation and directionality of crack propagation in experimentally induced PMIs up to 40,600 ADH, demonstrating the utility of this method into the recent postmortem interval. This expression of reliable fractographic features throughout the early PMI intimates these characteristics may not be useful standalone features for discerning peri- versus postmortem fractures.

β-Arrestin 2 knockout prevents bone loss in response to continuous parathyroid hormone stimulation in male and female mice

AUTHORS

Gilberto Li Feng, Marc D Grynpas & Jane Mitchell

ABSTRACT

Background

β-Arrestin 2 (β-arr2) binds activated parathyroid hormone (PTH) receptors stimulating internalization. PTH stimulates both anabolic and catabolic effect on bone depending on the way it is administered. Intermittent PTH stimulation increases trabecular bone formation in mice, but this is decreased in mice lacking β-arr 2, suggesting a role for β-arr 2 in the anabolic effects of PTH. The role of β-arr 2 in the catabolic effects of continuous PTH (cPTH) treatment is not known.

Objective

To assess the effects of cPTH administration on bone in mice lacking β-arr 2 compared to wild-type (WT).

Methods

Groups of male and female WT or β-arr2 knockout (KO) mice were administered either PTH or phosphate-buffered saline by osmotic pumps for 2 weeks. Following treatment, serum calcium and phosphate levels were measured, bone structure and mineral density were measured by microcomputed tomography, and bone cells measured by static and dynamic histomorphometry.

Results

β-arr2 KO had no effects on skeletal development in mice of either sex. PTH treatment caused hypercalcemia and hypophosphatemia and decreased trabecular and cortical bone only in male WT mice. β-arr2 KO in male mice completely abrogated the effects of PTH on bone, while in female β-arr2 KO mice, PTH treatment increased trabecular bone with no effects on cortical bone.

Conclusions

These results demonstrate a profound sex effect on skeletal responses to cPTH treatment, suggesting a protective effect of estrogen on bone loss. β-arr2 plays a role in restraining the anabolic effects of PTH in both male and female mice.

OTUB1 promotes osteoblastic bone formation through stabilizing FGFR2

AUTHORS

Qiong Zhu, Yesheng Fu, Chun-Ping Cui, Yi Ding, Zhikang Deng, Chao Ning, Fan Hu, Chen Qiu, Biyue Yu, Xuemei Zhou, Guan Yang, Jiang Peng, Weiguo Zou, Cui Hua Liu & Lingqiang Zhang

ABSTRACT

Bone homeostasis is maintained by the balance between osteoblastic bone formation and osteoclastic bone resorption. Dysregulation of this process leads to multiple diseases, including osteoporosis. However, the underlying molecular mechanisms are not fully understood. Here, we show that the global and conditional osteoblast knockout of a deubiquitinase Otub1 result in low bone mass and poor bone strength due to defects in osteogenic differentiation and mineralization. Mechanistically, the stability of FGFR2, a crucial regulator of osteogenesis, is maintained by OTUB1. OTUB1 attenuates the E3 ligase SMURF1-mediated FGFR2 ubiquitination by inhibiting SMURF1’s E2 binding. In the absence of OTUB1, FGFR2 is ubiquitinated excessively by SMURF1, followed by lysosomal degradation. Consistently, adeno-associated virus serotype 9 (AAV9)-delivered FGFR2 in knee joints rescued the bone mass loss in osteoblast-specific Otub1-deleted mice. Moreover, Otub1 mRNA level was significantly downregulated in bones from osteoporotic mice, and restoring OTUB1 levels through an AAV9-delivered system in ovariectomy-induced osteoporotic mice attenuated osteopenia. Taken together, our results suggest that OTUB1 positively regulates osteogenic differentiation and mineralization in bone homeostasis by controlling FGFR2 stability, which provides an optical therapeutic strategy to alleviate osteoporosis.

Isosinensetin alleviates estrogen deficiency-induced osteoporosis via suppressing ROS-mediated NF-κB/MAPK signaling pathways

AUTHORS

Yiwu Qin, Dezhi Song, Shijie Liao, Junchun Chen, Minglian Xu, Yuangang Su, Haoyu Lian, Hui Peng, Linhua Wei, Kai Chen, Jiake Xu, Jinmin Zhao, Qian Liu

ABSTRACT

The formation of osteoclasts and their hyperactive bone resorption are related to the aggregation of intracellular reactive oxygen species (ROS). Flavonoids, derived from plant active ingredients, can alleviate the symptoms of osteoporosis (OP). Isosinensetin (Iss) is a flavonoid with antioxidant effects obtained mainly from citrus fruits, and its effect on osteoclastogenesis has not been reported. In this study, we investigated the antioxidant activity of Iss on osteoclast differentiation and function, as well as the therapeutic impact of Iss on OP. We found that Iss inhibited osteoclastogenesis and suppressed the bone resorption function of osteoclasts. Additionally, Iss reduced receptor activator of nuclear factor-κB ligand (RANKL)-induced intracellular ROS. Using quantitative real-time polymerase chain reaction and western blot, we further found that Iss inhibited osteoclast-specific genes and related proteins, while promoting the expression of antioxidant enzyme-related genes and proteins. Mechanistically, Iss reduces intracellular ROS by activating nuclear factor-erythroid 2-related factor 2 (Nrf2) and its related antioxidant enzymes and inhibits the downstream nuclear factor-κB (NF-κB) and mitogen-activated protein kinase (MAPK) signaling pathways of ROS, which in turn inhibits nuclear factor of activated T cells 1 (NFATc1), and ultimately inhibits osteoclastogenesis. In vivo, by micro-computed tomography (Micro-CT) assay and histological analyses, we found that Iss could reduce bone loss in ovariectomized (OVX) mice. Therefore, Iss has the potential as an OP preventative and therapeutic drug option.

Cedrol, a Ginger-derived sesquiterpineol, suppresses estrogen-deficient osteoporosis by intervening NFATc1 and reactive oxygen species

AUTHORS

Cong Xu, Shu-Qing Jin, Chen Jin, Zi-Han Dai, Yu-Hao Wu, Gao-Lu He, Hai-Wei Ma, Chao-Yi Xu, Wen-Lai Fang

ABSTRACT

Osteoporosis is a prevalent bone metabolic disease in menopause, and long-term medication is accompanied by serious side effects. Ginger, a food spice and traditional medicine with ancient history, exhibits the potential to alleviate osteoporosis in preclinical experiments, whereas its complex composition leads to ambiguous pharmacological mechanisms. The purpose of this study was to investigate the effect and mechanism of Ced in estrogen-deficient osteoporosis, a sesquiterpene alcohol recently discovered from Ginger with multiple pharmacological properties. RANKL was stimulated BMM (bone marrow macrophages) differentiation into osteoclasts in vitro. And the osteoclast activity and number were assessed by TRAcP and SEM. We found that Ced mitigated RANKL-induced osteoclastogenesis by descending the ROS content and obstructing NFATc1, NF-κB, and MAPK signaling. Also, Ced-mediated anti-osteolytic property was found in ovariectomized mice by Micro-CT scanning and histological staining. Summarily, our works demonstrated the anti-osteoporotic potential of Cedrol in Ginger for the first time, which also offered more pharmacological evidence for Ginger as food or medicine used for bone metabolic disease.