Comparative Study of DHA with Different Molecular Forms for Ameliorating Osteoporosis by Promoting Chondrocyte-to-Osteoblast Transdifferentiation in the Growth Plate of Ovariectomized Mice

ENPP1 downregulation and FGF23 upregulation in growth-related calcification of the tibial tuberosity in rats

During tibial tuberosity growth, superficial and deep portions can be observed; however, the deep portion is not observed after the growth period, as it develops into bone tissues. Calcification in vivo is known to be constitutively suppressed by ectonucleotide pyrophosphatase/phosphodiesterase-1 (ENPP1) but promoted by tissue-nonspecific alkaline phosphatase (TNAP). FGF23 promotes calcification of enthesis. Gene expression of FGF23 increased rapidly at 13W in this study. Therefore, the tibial tuberosity is speculated to develop via Enpp1 downregulation and Tnap upregulation; however, the understanding of these processes remains unclear. Hence, in the present study, we aimed to explore the age-related structural changes and underlying gene expression changes in the tibial tuberosity of rats. Male Wistar rats were divided into three groups (3-, 7-, and 13-week-old; eight each). The tibial tuberosity superficial and deep portions were clearly observed in 3- and 7-week-old rats, but the presence of the deep portion was not confirmed in 13-week-old rats. The extracellular matrix of hypertrophic chondrocytes was calcified. Furthermore, the Enpp1 expression was the highest in 3-week-old rats and decreased with growth. The TNAP expression did not differ significantly among the groups. The deep portion area was significantly lower in 3-week-old rats than in 7-week-old rats. Generally, the extracellular matrix of the immature chondrocytes is not calcified. Therefore, we speculated that the cartilaginous tibial tuberosity calcifies and ossifies with growth. The Enpp1 expression decreased with growth, whereas the Tnap expression remained unchanged. Thus, we surmise that the tibial tuberosity calcifies with growth and that this process involves Enpp1 downregulation and FGF23 upregulation. As Osgood-Schlatter disease is closely related to the calcification of the tibial tuberosity, these findings may help clarify the pathogenesis of this disease.

Metabolic bone disorders and the promise of marine osteoactive compounds

Metabolic bone disorders and associated fragility fractures are major causes of disability and mortality worldwide and place an important financial burden on the global health systems. These disorders result from an unbalance between bone anabolic and resorptive processes and are characterized by different pathophysiological mechanisms. Drugs are available to treat bone metabolic pathologies, but they are either poorly effective or associated with undesired side effects that limit their use. The molecular mechanism underlying the most common metabolic bone disorders, and the availability, efficacy, and limitations of therapeutic options currently available are discussed here. A source for the unmet need of novel drugs to treat metabolic bone disorders is marine organisms, which produce natural osteoactive compounds of high pharmaceutical potential. In this review, we have inventoried the marine osteoactive compounds (MOCs) currently identified and spotted the groups of marine organisms with potential for MOC production. Finally, we briefly examine the availability of in vivo screening and validation tools for the study of MOCs.

Attributes of Nanomaterials and Nanotopographies for Improved Bone Tissue Engineering and Regeneration

Bone tissue engineering (BTE) is a multidisciplinary area that can solve the limitation of conventional grafting methods by developing viable and biocompatible bone replacements. The three essential components of BTE, i.e., Scaffold material and Cells and Growth factors altogether, facilitate support and guide for bone formation, differentiation of the bone tissues, and enhancement in the cellular activities and bone regeneration. However, there is a scarcity of the appropriate materials that can match the mechanical property as well as functional similarity to native tissue, considering the bone as hard tissue. In such scenarios, nanotechnology can be leveraged upon to achieve the desired aspects of BTE, and that is the key point of this review article. This review article examines the significant areas of nanotechnology research that have an impact on regeneration of bone: (a) scaffold with nanomaterials helps to enhance physicochemical interactions, biocompatibility, mechanical stability, and attachment; (b) nanoparticle-based approaches for delivering bioactive chemicals, growth factors, and genetic material. The article begins with the introduction of components and healing mechanisms of bone and the factors associated with them. The focus of this article is on the various nanotopographies that are now being used in scaffold formation, by describing how they are made, and how these nanotopographies affect the immune system and potential underlying mechanisms. The advantages of 4D bioprinting in BTE by using nanoink have also been mentioned. Additionally, we have investigated the importance of an in silico approach for finding the interaction between drugs and their related receptors, which can help to formulate suitable systems for delivery. This review emphasizes the role of nanoscale approach and how it helps to increase the efficacy of parameters of scaffold as well as drug delivery system for tissue engineering and bone regeneration.

Docosahexaenoic Acid-Enriched Phosphatidylcholine Exerted Superior Effects to Triglyceride in Ameliorating Obesity-Induced Osteoporosis through Up-Regulating the Wnt/β-Catenin Pathway

A growing number of studies reported that obesity is one of the major inducements for osteoporosis by promoting excessive adipogenic differentiation of bone marrow mesenchymal stem cells (BMSCs). Marine-derived DHA-enriched phosphatidylcholine (DHA-PC) exhibited activities to improve ovariectomized-induced osteoporosis and kidney damage. However, the potential effect of DHA-PC and efficacy differences between DHA-PC and traditional DHA (DHA-triglyceride, DHA-TG) on BMSCs differentiation in obesity-induced osteoporosis were not clear. In the present study, obesity-induced osteoporotic mice were supplemented with DHA-TG and DHA-PC for 120 days. Results showed that supplementing with DHA-PC improved the bone mineral density and biomechanical properties, increased the new bone formation rate by 55.2%, and reduced the amount of bone marrow fat to a greater extent than DHA-TG. Further in vitro results showed that DHA-PC significantly promoted the osteogenic differentiation and inhibited the adipogenic differentiation of BMSCs. Mechanistically, DHA-PC supplement up-regulated Wnt/β-catenin pathway in BMSCs and up-regulated the expression of osteogenic transcription factors, thereby promoting osteogenic differentiation. In summary, DHA-PC exerted a superior effect to DHA-TG in improving obesity-induced osteoporosis. The results provided new evidence for the application of different molecular forms of DHA in treatment of osteoporosis.

Novel Peptides Derived from Sea Cucumber Intestine Promotes Osteogenesis by Upregulating Integrin-Mediated Transdifferentiation of Growth Plate Chondrocytes to Osteoblasts

The sea cucumber intestine is a major by-product of sea cucumber processing and contains high levels of protein. In this study, we isolated and identified 28 novel osteogenic peptides from sea cucumber intestinal hydrolysis by the activity-tracking method for the first time. In vitro experimental results showed that compared with high molecular weight, the peptides from sea cucumber intestine (SCIP) with molecular weight <3 kDa more significantly promoted the proliferation and mineralized nodules of MC3T3-E1 cell and exhibited potential integrin binding capacity. In vivo experimental results showed that the SCIP supplement significantly increased the longitudinal bone length and elevated the height of the growth plate (especially the hypertrophic zone, 37.2%, p < 0.01) in adolescent mice. Further, immunofluorescence labeling results indicated that the SCIP supplement increased chondrocyte transdifferentiate to osteoblast in the growth plate close to the diaphysis. Mechanistically, transcriptome analysis revealed that the SCIP supplement induced the dedifferentiation of chondrocyte to osteoprogenitor cell via integrin-mediated histone acetylation and then redifferentiated to osteoblast via integrin-mediated Wnt/β-catenin signaling. These results reported for the first time that sea cucumber intestine had the potential to develop into a dietary supplement for promoting osteogenic, and provide new evidence for the mechanism of dietary promotes chondrocyte to osteoblast transdifferentiation.

Comparative Study of Docosahexaenoic Acid with Different Molecular Forms for Promoting Apoptosis of the 95D Non-Small-Cell Lung Cancer Cells in a PPARγ-Dependent Manner

Cancer is a leading cause of death in worldwide. Growing evidence has shown that docosahexaenoic acid (DHA) has ameliorative effects on cancer. However, the effects of DHA-enriched phosphatidylcholine (DHA-PC) and efficacy differences between DHA-PC, DHA-triglyceride (DHA-TG), and DHA- ethyl esters (DHA-EE) on cancer cells had not been studied. In this study, 95D lung cancer cells in vitro were used to determine the effects and underlying mechanisms of DHA with different molecular forms. The results showed that DHA-PC and DHA-TG treatment significantly inhibited the growth of 95D cells by 53.7% and 33.8%, whereas DHA-EE had no significantly effect. Morphological analysis showed that DHA-PC and DHA-TG prompted promoted cell contraction, increased concentration of cell heterochromatin, vacuolization of cytoplasm, and edema of endoplasmic reticulum and mitochondria. TUNEL and AO/EB staining indicated that both DHA-PC and DHA-TG promoted cell apoptosis, in which DHA-PC performed better than DHA-TG. Mechanistically, DHA-PC and DHA-TG treatment up-regulated the PPARγ and RXRα signal, inhibited the expression of NF-κB and Bcl-2, and enhanced the expression of Bax and caspase-3, thereby promoting cell apoptosis. In conclusion, DHA-PC exerted superior effects to DHA-TG and DHA-EE in promoting apoptosis in 95D non-small-cell lung cancer cells. These data provide new evidence for the application of DHA in treatment of cancer.

Cellular direct conversion by cell penetrable OCT4-30Kc19 protein and BMP4 growth factor

Background

The number of patients suffering from osteoporosis is increasing as the elderly population increases. The demand for investigating bone regeneration strategies naturally arises. One of the approaches to induce bone regeneration is somatic cell transdifferentiation. Among the transcriptional regulators for transdifferentiation, octamer-binding transcription factor 4 (OCT4) is famous for its role in the regulation of pluripotency of stem cells. Bone morphogenetic protein 4 (BMP4) is another factor that is known to have a significant role in osteogenic differentiation. Previous studies have achieved transdifferentiation of cells into osteoblasts using viral and plasmid deliveries of these factors. Although these methods are efficient, viral and plasmid transfection have safety issues such as permanent gene incorporations and bacterial DNA insertions. Herein, we developed a cell penetrating protein-based strategy to induce transdifferentiation of endothelial cells into osteoblasts via nuclear delivery of OCT4 recombinant protein combined with the BMP4 treatment. For the nuclear delivery of OCT4 protein, we fused the protein with 30Kc19, a cell-penetrating and protein stabilizing protein derived from a silkworm hemolymph of Bombyx mori with low cytotoxic properties. This study proposes a promising cell-based therapy without any safety issues that existing transdifferentiation approaches had.

Methods

OCT4-30Kc19 protein with high penetrating activities and stability was synthesized for a protein-based osteogenic transdifferentiation system. Cells were treated with OCT4-30Kc19 and BMP4 to evaluate their cellular penetrating activity, cytotoxicity, osteogenic and angiogenic potentials in vitro. The osteogenic potential of 3D cell spheroids was also analyzed. In addition, in vivo cell delivery into subcutaneous tissue and cranial defect model was performed.

Results

OCT4-30Kc19 protein was produced in a soluble and stable form. OCT4-30Kc19 efficiently penetrated cells and were localized in intracellular compartments and the nucleus. Cells delivered with OCT4-30Kc19 protein combined with BMP4 showed increased osteogenesis, both in 2D and 3D culture, and showed increased angiogenesis capacity in vitro. Results from in vivo subcutaneous tissue delivery of cell-seeded scaffolds confirmed enhanced osteogenic properties of transdifferentiated HUVECs via treatment with both OCT4-30Kc19 and BMP4. In addition, in vivo mouse cranial defect experiment demonstrated successful bone regeneration of HUVECs pretreated with both OCT4-30Kc19 and BMP4.

Conclusions

Using a protein-based transdifferentiation method allows an alternative approach without utilizing any genetic modification strategies, thus providing a possibility for safer use of cell-based therapies in clinical applications.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40824-022-00280-8.

Comparative study of holothurin A and echinoside A on inhibiting the high bone turnover via downregulating PI3K/AKT/β-catenin and OPG/RANKL/NF-κB signaling in ovariectomized mice

Holothurin A (HA) and Echinoside A (EA) are the most abundant monomers in sea cucumber saponins, exhibiting different structures only in the side chain at position 20. However, although sea cucumber saponins have been proved to have osteogenic activity, the effect and structure-activity relationship of sea cucumber saponins to improve osteoporosis remain unknown. In the current study, mice with ovariectomization-induced osteoporosis were orally administered with HA and EA for 90 days. The result showed that both HA and EA reduced the levels of serum osteogenesis markers ALP, collagen I, and OCN and bone resorption markers MMP-9, Cath-K and TRAP, and thus inhibited the high bone turnover induced by ovariectomy. Furthermore, we found that HA and EA increased the bone mineral density and apposition rate, reversed the loss of trabecular bone and bone marrow stroma, in which EA exhibited more effective effects. CB1 and MKP-1 are the targets of the glucocorticoid-like effect of saponins. PCR and western blot results indicated that HA and EA alleviated overactive osteogenesis via stimulating CB1 and MKP-1, downregulating the PI3K/AKT/β-catenin signal pathway. The OPG/RANKL/NF-κB pathway was identified as a critical regulator of bone resorption. Further investigation revealed that HA and EA significantly downregulate the expression of IKK, NF-κB and phosphorylated NF-κB p65, suppressing the expression of osteoclastogenesis transcription factors c-fos and NFATC1. To the best of our knowledge, this is the first report showing that both HA and EA improved osteoporosis, and these activities depend on the structure of saponins. These findings would provide guidance for the application of saponins in the management of osteoporosis.

Mesenchymal Stem Cell-Derived Extracellular Vesicle: A Promising Alternative Therapy for Osteoporosis

Osteoporosis is the chronic metabolic bone disease caused by the disturbance of bone remodeling due to the imbalance of osteogenesis and osteoclastogenesis. A large population suffers from osteoporosis, and most of them are postmenopausal women or older people. To date, bisphosphonates are the main therapeutic agents in the treatment of osteoporosis. However, limited therapeutic effects with diverse side effects caused by bisphosphonates hindered the therapeutic applications and decreased the quality of life. Therefore, an alternative therapy for osteoporosis is still needed. Stem cells, especially mesenchymal stem cells, have been shown as a promising medication for numerous human diseases including many refractory diseases. Recently, researchers found that the extracellular vesicles derived from these stem cells possessed the similar therapeutic potential to that of parental cells. To date, a number of studies demonstrated the therapeutic applications of exogenous MSC-EVs for the treatment of osteoporosis. In this article, we reviewed the basic back ground of EVs, the cargo and therapeutic potential of MSC-EVs, and strategies of engineering of MSC-EVs for osteoporosis treatment.