Remote-controllable bone-targeted delivery of estradiol for the treatment of ovariectomy-induced osteoporosis in rats

Estrogen and estrogen receptors mediate the mechanobiology of bone disease and repair

It is well understood that the balance of bone formation and resorption is dependent on both mechanical and biochemical factors. In addition to cell-secreted cytokines and growth factors, sex hormones like estrogen are critical to maintaining bone health. Although the direct osteoprotective function of estrogen and estrogen receptors (ERs) has been reported extensively, evidence that estrogen signaling also has a role in mediating the effects of mechanical loading on maintenance of bone mass and healing of bone injuries has more recently emerged. Recent studies have underscored the role of estrogen and ERs in many pathways of bone mechanosensation and mechanotransduction. Estrogen and ERs have been shown to augment integrin-based mechanotransduction as well as canonical Wnt/b-catenin, RhoA/ROCK, and YAP/TAZ pathways. Estrogen and ERs also influence the mechanosensitivity of not only osteocytes but also osteoblasts, osteoclasts, and marrow stromal cells. The current review will highlight these roles of estrogen and ERs in cellular mechanisms underlying bone mechanobiology and discuss their implications for management of osteoporosis and bone fractures. A greater understanding of the mechanisms behind interactions between estrogen and mechanical loading may be crucial to addressing the shortcomings of current hormonal and pharmaceutical therapies. A combined therapy approach including high-impact exercise therapy may mitigate adverse side effects and allow an effective long-term solution for the prevention, treatment, and management of bone fragility in at-risk populations. Furthermore, future implications to novel local delivery mechanisms of hormonal therapy for osteoporosis treatment, as well as the effects on bone health of applications of sex hormone therapy outside of bone disease, will be discussed.

3D-Bioprinted Gelatin Methacryloyl-Strontium-Doped Hydroxyapatite Composite Hydrogels Scaffolds for Bone Tissue Regeneration

New gelatin methacryloyl (GelMA)-strontium-doped nanosize hydroxyapatite (SrHA) composite hydrogel scaffolds were developed using UV photo-crosslinking and 3D printing for bone tissue regeneration, with the controlled delivery capacity of strontium (Sr). While Sr is an effective anti-osteoporotic agent with both anti-resorptive and anabolic properties, it has several important side effects when systemic administration is applied. Multi-layer composite scaffolds for bone tissue regeneration were developed based on the digital light processing (DLP) 3D printing technique through the photopolymerization of GelMA. The chemical, morphological, and biocompatibility properties of these scaffolds were investigated. The composite gels were shown to be suitable for 3D printing. In vitro cell culture showed that osteoblasts can adhere and proliferate on the surface of the hydrogel, indicating that the GelMA-SrHA hydrogel has good cell viability and biocompatibility. The GelMA-SrHA composites are promising 3D-printed scaffolds for bone repair.

Consumption of Phytoestrogens Affects Bone Health by Regulating Estrogen Metabolism

Osteoporosis is a significant concern in bone health, and understanding its pathomechanism is crucial for developing effective prevention and treatment strategies. This article delves into the relationship between estrogen metabolism and bone mineralization, shedding light on how phytoestrogens can influence this intricate process. Estrogen, a hormone primarily associated with reproductive health, plays a pivotal role in maintaining bone density and structure. The article explores the positive effects of estrogen on bone mineralization, highlighting its importance in preventing conditions like osteoporosis. Phytoestrogens, naturally occurring compounds found in certain plant-based foods, are the focal point of the discussion. These compounds have the remarkable ability to mimic estrogen's actions in the body. The article investigates how phytoestrogens can modulate the activity of estrogen, thereby impacting bone health. Furthermore, the article explores the direct effects of phytoestrogens on bone mineralization and structure. By regulating estrogen metabolism, phytoestrogens can contribute to enhanced bone density and reduced risk of osteoporosis. Finally, the article emphasizes the role of plant-based diets as a source of phytoestrogens. By incorporating foods rich in phytoestrogens into one's diet, individuals may potentially bolster their bone health, adding a valuable dimension to the ongoing discourse on osteoporosis prevention. In conclusion, this article offers a comprehensive overview of 137 positions of literature on the intricate interplay between phytoestrogens, estrogen metabolism, and bone health, shedding light on their potential significance in preventing osteoporosis and promoting overall well-being.

Ångstrom-scale gold particles loaded with alendronate via alpha-lipoic acid alleviate bone loss in osteoporotic mice

Osteoporosis is a highly prevalent metabolic disease characterized by low systemic bone mass and deterioration of bone microarchitecture, resulting in reduced bone strength and increased fracture risk. Current treatment options for osteoporosis are limited by factors such as efficacy, cost, availability, side effects, and acceptability to patients. Gold nanoparticles show promise as an emerging osteoporosis therapy due to their osteogenic effects and ability to allow therapeutic delivery but have inherent constraints, such as low specificity and the potential for heavy metal accumulation in the body. This study reports the synthesis of ultrasmall gold particles almost reaching the Ångstrom (Ång) dimension. The antioxidant alpha-lipoic acid (LA) is used as a dispersant and stabilizer to coat Ångstrom-scale gold particles (AuÅPs). Alendronate (AL), an amino-bisphosphonate commonly used in drug therapy for osteoporosis, is conjugated through LA to the surface of AuÅPs, allowing targeted delivery to bone and enhancing antiresorptive therapeutic effects. In this study, alendronate-loaded Ångstrom-scale gold particles (AuÅPs-AL) were used for the first time to promote osteogenesis and alleviate bone loss through regulation of the WNT signaling pathway, as shown through in vitro tests. The in vivo therapeutic effects of AuÅPs-AL were demonstrated in an established osteoporosis mouse model. The results of Micro-computed Tomography, histology, and tartrate-resistant acid phosphatase staining indicated that AuÅPs-AL significantly improved bone density and prevented bone loss, with no evidence of nanoparticle-associated toxicity. These findings suggest the possible future application of AuÅPs-AL in osteoporosis therapy and point to the potential of developing new approaches for treating metabolic bone diseases using Ångstrom-scale gold particles.

Development of bioactive and ultrasound-responsive microdroplets for preventing ovariectomy (OVX)-induced osteoporosis

As a common bone disease in the elderly population, osteoporosis-related bone loss and bone structure deterioration represent a major public health problem. Therapeutic strategies targeting excessive osteoclast formation are frequently used for osteoporosis treatment; however, potential side effects have been recorded. Here, we have developed a novel therapeutic strategy using microdroplets (MDs) encapsulated with NFATc1-siRNA and investigated the role of bioactive MDs-NFATc1 biocompatibility in RAW 264.7 macrophages and human mesenchymal stem cells (hBMSCs), respectively. Its role in regulating osteoclast differentiation and formation was also investigated in vitro. We first fabricated MDs with spherical morphology along with a well-defined core-shell structure. The ultrasound-responsive study demonstrated time-dependent responsive structural changes following ultrasound stimulation. The internalization study into unstimulated macrophages, inflammatory macrophages, and hBMSCs indicated good delivery efficiency. Furthermore, the results from the MTT assay, the live/dead assay, and the cellular morphological analysis further indicated good biocompatibility of our bioactive MDs-NFATc1. Following MDs-NFATc1 treatment, the number of osteoclasts was greatly reduced, indicating their inhibitory effect on osteoclastogenesis and osteoclast formation. Subsequently, osteoporotic rats that underwent ovariectomy (OVX) were used for the in vivo studies. The rats treated with MDs-NFATc1 exhibited significant resistance to bone loss induced by OVX. In conclusion, our results demonstrate that MDs-NFATc1 could become an important regulator in osteoclast differentiation and functions, thus having potential applications in osteoclast-related bone diseases.

Citric acid-modified pH-sensitive bone-targeted delivery of estrogen for the treatment of postmenopausal osteoporosis

Bone targeted delivery of estrogen offers great promise for the clinical application of estrogen in the treatment of postmenopausal osteoporosis (PMOP). However, the current bone-targeted drug delivery system still has several issues that need to be solved, such as the side effects of bone-targeted modifier molecules and the failure of the delivery system to release rapidly in the bone tissue. It is important to aggressively search for new bone-targeted modifier molecules and bone microenvironment-responsive delivery vehicles. Inspired by the distribution of citric acid (CA) mainly in bone tissue and the acidic bone resorption microenvironment, we constructed a CA-modified diblock copolymer poly(2-ethyl-2-oxazoline)-poly(ε-caprolactone) (CA-PEOz) drug delivery system. In our study, we found that the CA modification significantly increased the bone targeting of this drug delivery system, and the delivery system was able to achieve rapid drug release under bone acidic conditions. The delivery system significantly reduced bone loss in postmenopausal osteoporotic mice with a significant reduction in estrogenic side effects on the uterus. In summary, our study shows that CA can act as an effective bone targeting modifier molecule and provides a new option for bone targeting modifications. Our study also provides a new approach for bone-targeted delivery of estrogen for the treatment of PMOP.

Drug Delivery and Therapy Strategies for Osteoporosis Intervention

With the advent of the aging society, osteoporosis (OP) risk increases yearly. Currently, the clinical usage of anti-OP drugs is challenged by recurrent side effects and poor patient compliance, regardless of oral, intravenous, or subcutaneous administration. Properly using a drug delivery system or formulation strategy can achieve targeted drug delivery to the bone, diminish side effects, improve bioavailability, and prolong the in vivo residence time, thus effectively curing osteoporosis. This review expounds on the pathogenesis of OP and the clinical medicaments used for OP intervention, proposes the design approach for anti-OP drug delivery, emphatically discusses emerging novel anti-OP drug delivery systems, and enumerates anti-OP preparations under clinical investigation. Our findings may contribute to engineering anti-OP drug delivery and OP-targeting therapy.

Calcium carbonate-enriched pumpkin affects calcium status in ovariectomized rats

Calcium carbonate (CaCO₃)-enriched pumpkin may serve as a good source of calcium for patients diagnosed with osteoporosis. In this study, we aimed to determine the effect of CaCO₃-enriched pumpkin on Ca status in ovariectomized rats. The study included 40 female Wistar rats divided into five groups (n = 8). One group was fed with a standard diet (control group), while the other four groups were ovariectomized and received a standard diet (control ovariectomized group), or a diet containing CaCO₃-enriched pumpkin, alendronate, or both. The nutritional intervention lasted 12 weeks, and then the rats were euthanized. Tissue and blood samples were collected and assessed for the levels of total Ca, estradiol, parathyroid hormone, and procollagen type I N propeptide. In addition, a histological analysis was performed on femurs. The results of the study suggest that CaCO₃-enriched pumpkin can increase Ca content in femurs and improve bone recovery in ovariectomized rats. Furthermore, enriched pumpkin contributes to Ca accumulation in the kidneys, and this effect is more pronounced in combination with alendronate.

Targeting Agents in Biomaterial-Mediated Bone Regeneration

Bone diseases are a global public concern that affect millions of people. Even though current treatments present high efficacy, they also show several side effects. In this sense, the development of biocompatible nanoparticles and macroscopic scaffolds has been shown to improve bone regeneration while diminishing side effects. In this review, we present a new trend in these materials, reporting several examples of materials that specifically recognize several agents of the bone microenvironment. Briefly, we provide a subtle introduction to the bone microenvironment. Then, the different targeting agents are exposed. Afterward, several examples of nanoparticles and scaffolds modified with these agents are shown. Finally, we provide some future perspectives and conclusions. Overall, this topic presents high potential to create promising translational strategies for the treatment of bone-related diseases. We expect this review to provide a comprehensive description of the incipient state-of-the-art of bone-targeting agents in bone regeneration.

Dual Targeting Anti-Osteoporotic Therapy through Potential Nanotherapeutic Approaches

Osteoporosis is characterised by a major public health burden, particularly taking into account the ageing global population. Therapeutic modalities for osteoporosis are categorised on the basis of their effect on bone remodeling: antiresorptive agents and anabolic agents. Anabolic drugs are favoured as they promote the formation of new bone, whereas antiresorptive drugs terminate the further deterioration of bone. Non-specific delivery of anabolic agents results in prolonged kidney exposure causing malignant hypercalcemia, whereas antiresorptive agents and bisphosphonates may produce osteonecrosis of the jaw. Several clinical trials have been reported for combinational therapy of anabolic agents and antiresorptive agents for osteoporosis. However, none of them have proven their cumulative effectiveness in the treatment of disease. The present work emphasizes on dual-targeting drug delivery approach comprising of bone anabolic and antiresorptive agents that would deliver the therapeutic agents to both the zones of bone simultaneously. The anticipated pioneering delivery approach will intensify the explicit interaction between the therapeutic agent and bone surfaces separately without developing severe adverse effects and improve the osteoporotic therapy effectively compared to non-targeted drug delivery.

Hope for bone regeneration: The versatility of iron oxide nanoparticles

Although bone tissue has the ability to heal itself, beyond a certain point, bone defects cannot rebuild themselves, and the challenge is how to promote bone tissue regeneration. Iron oxide nanoparticles (IONPs) are a magnetic material because of their excellent properties, which enable them to play an active role in bone regeneration. This paper reviews the application of IONPs in bone tissue regeneration in recent years, and outlines the mechanisms of IONPs in bone tissue regeneration in detail based on the physicochemical properties, structural characteristics and safety of IONPs. In addition, a bibliometric approach has been used to analyze the hot spots and trends in the field in order to identify future directions. The results demonstrate that IONPs are increasingly being investigated in bone regeneration, from the initial use as magnetic resonance imaging (MRI) contrast agents to later drug delivery vehicles, cell labeling, and now in combination with stem cells (SCs) composite scaffolds. In conclusion, based on the current research and development trends, it is more inclined to be used in bone tissue engineering, scaffolds, and composite scaffolds.

Biomaterials and advanced technologies for the evaluation and treatment of ovarian aging

Ovarian aging is characterized by a progressive decline in ovarian function. With the increase in life expectancy worldwide, ovarian aging has gradually become a key health problem among women. Over the years, various strategies have been developed to preserve fertility in women, while there are currently no clinical treatments to delay ovarian aging. Recently, advances in biomaterials and technologies, such as three-dimensional (3D) printing and microfluidics for the encapsulation of follicles and nanoparticles as delivery systems for drugs, have shown potential to be translational strategies for ovarian aging. This review introduces the research progress on the mechanisms underlying ovarian aging, and summarizes the current state of biomaterials in the evaluation and treatment of ovarian aging, including safety, potential applications, future directions and difficulties in translation.