Catalpol modulating the crosstalking between mesenchymal stromal cells and macrophages via paracrine to enhance angiogenesis and osteogenesis

Biodegradable Piezoelectric Janus Membrane Enabling Dual Antibacterial and Osteogenic Functions for Periodontitis Therapy

Guided tissue regeneration (GTR) using barrier membranes is a common clinical approach for treating periodontitis-induced alveolar bone loss. However, conventional GTR membranes lack antibacterial and osteoinductive properties, limiting their effectiveness. Piezoelectric materials, which generate electrical outputs under chewing forces, offer antibacterial and bone-regenerative potential due to their oppositely charged surfaces. Inspired by this, a piezoelectric Janus membrane was developed for dual-function GTR therapy. Biodegradable poly(l-lactide) (PLLA) and PLLA/gelatin membranes were electrospun, annealed, and polarized to create the A-P(+)/PG(-) piezoelectric Janus membrane. Notably, in this Janus membrane, the outer surface of the PLLA side (A-P(+)) carries positive charges and is positioned toward the gingival tissue to kill bacteria via charge interactions; the inner surface of the PG side (PG(-)) holds negative charges and faces the alveolar bone defect, promoting bone growth through immunomodulation and enhanced mineralization. In a mouse model of periodontitis, the Janus membrane A-P(+)/PG(-) demonstrated dual functionality, effectively reducing inflammation, inhibiting bone resorption. The bone mineral density of A-P(+)/PG(-) reached 1637 ± 37 mg/cm3 at 8 weeks after surgery, which was superior to commercial collagen membranes lacking antibacterial properties. Overall, this study introduces an innovative approach, leveraging biodegradable piezoelectric PLLA to construct a versatile Janus GTR membrane with enhanced antibacterial and osteogenic activity for periodontitis treatment.

Influences and strategies for bone regeneration based on microenvironment pH adjustment

Bone possesses remarkable endogenous regenerative capacity. Bone regeneration is typically divided into three stages: inflammation, bone formation, and bone remodeling, during which pH is a critical variable. The influence of pH on the bone regeneration process depends on three main factors: (1) the activity and differentiation of cells involved in bone regeneration are affected by pH; (2) protein activity is regulated by pH; and (3) extracellular calcium phosphate precipitates in a pH-dependent manner. The aim of this study is to review the mechanisms by which microenvironment pH affects bone regeneration and to explore specific sites and signaling pathways involved in pH regulation during the bone regeneration process. Therapeutic approaches aimed at enhancing bone regeneration via modulation of microenvironment pH are discussed, including pH adjustment via biological implant materials, pH-responsive material setting, and pH stabilization through anti-inflammatory therapy. Investigating the impact of microenvironment pH on bone regeneration is of considerable clinical importance, as it provides valuable insights for improving the success rates of bone implants and promoting bone healing. This review offers insights into regulatory mechanisms, establishes theoretical foundations, and presents new perspectives for current research on bone defect repair.

Multifaceted therapeutic potentials of catalpol, an iridoid glycoside: an updated comprehensive review

Catalpol, classified as an iridoid glucoside, is recognized for its significant role in medicine, particularly in the treatment of various conditions such as diabetes mellitus, neuronal disorders, and inflammatory diseases. This review aims to evaluate the biological implications of catalpol and the mechanisms underlying its diverse pharmacological effects. A thorough exploration of existing literature was conducted utilizing the keyword "Catalpol" across prominent public domains like Google Scholar, PubMed, and EKB. Catalpol has demonstrated a diverse array of pharmacological effects in experimental models, showcasing its anti-diabetic, cardiovascular-protective, neuroprotective, anticancer, hepatoprotective, anti-inflammatory, and antioxidant properties. In summary, catalpol manifests a spectrum of biological effects through a myriad of mechanisms, prominently featuring its anti-inflammatory and antioxidant capabilities. Its diverse pharmacological profile underscores its potential for therapeutic applications across a range of conditions. Further research is warranted to fully elucidate the clinical implications of catalpol and optimize its use in medical practice.

Recent advances in the multifaceted mechanisms of catalpol in treating osteoporosis

Catalpol (CAT) is a landmark active ingredient in traditional Chinese medicine Rehmannia (TCT), also known as dehydroxybenzoate catalpone, which is a kind of iridoid terpene glycoside with strong antioxidant, anti-inflammatory, antitumor and other biological activities. It can exert its anti-disease effect in a variety of ways. For some patients with chronic diseases, the application of azalea alcohol in rehmannia may bring more comprehensive and long-lasting efficacy. Studies have shown that the anti-disease effect of catalpol in osteoporosis (OP) is mainly achieved through various pathways such as Wnt/β-catenin signaling pathways to promote osteogenic differentiation, and RANKL/RANK and other signaling pathways to inhibit osteoclastic differentiation. At present, there is a slight lack of analysis of the mechanism of action of catalpa alcohol in the treatment of osteoporosis, so this study comprehensively searched the literature on the mechanism of action of catalpa alcohol in the treatment of osteoporosis in various databases, and reviewed the research progress of its role and mechanism, to provide reference and theoretical basis for the further development and application of catalpol.

Metformin enhances osteogenic differentiation of BMSC by modulating macrophage M2 polarization

Bone marrow-derived mesenchymal stem cells (BMSCs) are capable of developing into osteoblastic cell lines in vitro and regenerating bone tissue in vivo, and they are considered to be a reliable source for bone regenerative medicine. In recent years, studies have shown that the immune microenvironment is important for osteogenesis, in which macrophages are an important component of innate immunity and coordinate with stem cells. Metformin (Met), a hypoglycemic drug that exerts a powerful effect on metabolic signaling, has been shown to modulate inflammatory responses and osteogenic activity. However, whether metformin modulates macrophage polarization and subsequently affects osteogenesis remains to be elucidated. In the present study, we investigated the potential immunomodulatory capacity of metformin on macrophage inflammatory responses and phenotypic switching, and the subsequent effects on osteogenic differentiation of BMSCs. Flow cytometry and qPCR were used to study the effects of metformin on macrophage phenotypic regulation. qPCR, ALP, ARS and calcium content measurement and ALP activity assay were used to determine the effects of macrophage-secreted activators on the osteogenic differentiation of BMSCs. Our study demonstrates that metformin can improve the immune microenvironment by modulating macrophage polarization towards an anti-inflammatory phenotype, promoting an increase in a range of anti-inflammatory factors and inhibiting pro-inflammatory factors. This was characterized by increased expression of IL-10 and CD206, Arg-1 and decreased expression of IL-1β, TNF-α, IL-6 and iNOS. In addition, metformin-modulated macrophage-conditioned medium promoted osteogenic differentiation of BMSCs, increased the expression levels of genes (ALP, Runx-2, OCN, and Col-1), enhanced ALP activity, and significantly formed mineralized nodules. In conclusion, our new study elucidates that metformin can promote osteogenic differentiation of BMSCs by modulating macrophage phenotype and thereby.

Mussel inspired 3D elastomer enabled rapid calvarial bone regeneration through recruiting more osteoprogenitors from the dura mater

Currently, the successful healing of critical-sized calvarial bone defects remains a considerable challenge. The immune response plays a key role in regulating bone regeneration after material grafting. Previous studies mainly focused on the relationship between macrophages and bone marrow mesenchymal stem cells (BMSCs), while dural cells were recently found to play a vital role in the calvarial bone healing. In this study, a series of 3D elastomers with different proportions of polycaprolactone (PCL) and poly(glycerol sebacate) (PGS) were fabricated, which were further supplemented with polydopamine (PDA) coating. The physicochemical properties of the PCL/PGS and PCL/PGS/PDA grafts were measured, and then they were implanted as filling materials for 8 mm calvarial bone defects. The results showed that a matched and effective PDA interface formed on a well-proportioned elastomer, which effectively modulated the polarization of M2 macrophages and promoted the recruitment of dural cells to achieve full-thickness bone repair through both intramembranous and endochondral ossification. Single-cell RNA sequencing analysis revealed the predominance of dural cells during bone healing and their close relationship with macrophages. The findings illustrated that the crosstalk between dural cells and macrophages determined the vertical full-thickness bone repair for the first time, which may be the new target for designing bone grafts for calvarial bone healing.

Catalpol promotes articular cartilage repair by enhancing the recruitment of endogenous mesenchymal stem cells

Articular cartilage defect is challenged by insufficient regenerative ability of cartilage. Catalpol (CA), the primary active component of Rehmanniae Radix, could exert protective effects against various diseases. However, the impact of CA on the treatment of articular cartilage injuries is still unclear. In this study, full-thickness articular cartilage defect was induced in a mouse model via surgery. The animals were intraperitoneally injected with CA for 4 or 8 weeks. According to the results of macroscopic observation, micro-computed tomography CT (μCT), histological and immunohistochemistry staining, CA treatment could promote mouse cartilage repair, resulting in cartilage regeneration, bone structure improvement and matrix anabolism. Specifically, an increase in the expression of CD90, the marker of mesenchymal stem cells (MSCs), in the cartilage was observed. In addition, we evaluated the migratory and chondrogenic effects of CA on MSCs. Different concentration of CA was added to C3H10 T1/2 cells. The results showed that CA enhanced cell migration and chondrogenesis without affecting proliferation. Collectively, our findings indicate that CA may be effective for the treatment of cartilage defects via stimulation of endogenous MSCs.

Protective effects of catalpol on cardio-cerebrovascular diseases: A comprehensive review

Catalpol, an iridoid glucoside isolated from Rehmannia glutinosa, has gained attention due to its potential use in treating cardio-cerebrovascular diseases (CVDs). This extensive review delves into recent studies on catalpol's protective properties in relation to various CVDs, such as atherosclerosis, myocardial ischemia, infarction, cardiac hypertrophy, and heart failure. The review also explores the compound's anti-oxidant, anti-inflammatory, and anti-apoptotic characteristics, emphasizing the role of vital signaling pathways, including PGC-1α/TERT, PI3K/Akt, AMPK, Nrf2/HO-1, estrogen receptor (ER), Nox4/NF-κB, and GRP78/PERK. The article discusses emerging findings on catalpol's ability to alleviate diabetic cardiovascular complications, thrombosis, and other cardiovascular-related conditions. Although clinical studies specifically addressing catalpol's impact on CVDs are scarce, the compound's established safety and well-tolerated nature suggest that it could be a valuable treatment alternative for CVD patients. Further investigation into catalpol and related iridoid derivatives may unveil new opportunities for devising natural and efficacious CVD therapies.

Constitutive aryl hydrocarbon receptor facilitates the regenerative potential of mouse bone marrow mesenchymal stromal cells

BACKGROUND

Bone marrow mesenchymal stromal cells (BMSCs) are the commonly used seed cells in tissue engineering. Aryl hydrocarbon receptor (AhR) is a transcription factor involved in various cellular processes. However, the function of constitutive AhR in BMSCs remains unclear.

AIM

To investigate the role of AhR in the osteogenic and macrophage-modulating potential of mouse BMSCs (mBMSCs) and the underlying mechanism.

METHODS

Immunochemistry and immunofluorescent staining were used to observe the expression of AhR in mouse bone marrow tissue and mBMSCs. The overexpression or knockdown of AhR was achieved by lentivirus-mediated plasmid. The osteogenic potential was observed by alkaline phosphatase and alizarin red staining. The mRNA and protein levels of osteogenic markers were detected by quantitative polymerase chain reaction (qPCR) and western blot. After coculture with different mBMSCs, the cluster of differentiation (CD) 86 and CD206 expressions levels in RAW 264.7 cells were analyzed by flow cytometry. To explore the underlying molecular mechanism, the interaction of AhR with signal transducer and activator of transcription 3 (STAT3) was observed by co-immunoprecipitation and phosphorylation of STAT3 was detected by western blot.

RESULTS

AhR expressions in mouse bone marrow tissue and isolated mBMSCs were detected. AhR overexpression enhanced the osteogenic potential of mBMSCs while AhR knockdown suppressed it. The ratio of CD86+ RAW 264.7 cells cocultured with AhR-overexpressed mBMSCs was reduced and that of CD206+ cells was increased. AhR directly interacted with STAT3. AhR overexpression increased the phosphorylation of STAT3. After inhibition of STAT3 via stattic, the promotive effects of AhR overexpression on the osteogenic differentiation and macrophage-modulating were partially counteracted.

CONCLUSION

AhR plays a beneficial role in the regenerative potential of mBMSCs partially by increasing phosphorylation of STAT3.

Targeting different phenotypes of macrophages: A potential strategy for natural products to treat inflammatory bone and joint diseases

BACKGROUND

Macrophages, a key class of immune cells, have a dual role in inflammatory responses, switching between anti-inflammatory M2 and pro-inflammatory M1 subtypes depending on the specific environment. Greater numbers of M1 macrophages correlate with increased production of inflammatory chemicals, decreased osteogenic potential, and eventually bone and joint disorders. Therefore, reversing M1 macrophages polarization is advantageous for lowering inflammatory factors. To better treat inflammatory bone disorders in the future, it may be helpful to gain insight into the specific mechanisms and natural products that modulate macrophage polarization.

OBJECTIVE

This review examines the impact of programmed cell death and different cells in the bone microenvironment on macrophage polarization, as well as the effects of natural products on the various phenotypes of macrophages, in order to suggest some possibilities for the treatment of inflammatory osteoarthritic disorders.

METHODS

Using 'macrophage polarization,' 'M1 macrophage' 'M2 macrophage' 'osteoporosis,' 'osteonecrosis of femoral head,' 'osteolysis,' 'gouty arthritis,' 'collagen-induced arthritis,' 'freund's adjuvant-induced arthritis,' 'adjuvant arthritis,' and 'rheumatoid arthritis' as search terms, the relevant literature was searched using the PubMed, the Cochrane Library and Web of Science databases.

RESULTS

Targeting macrophages through different signaling pathways has become a key mechanism for the treatment of inflammatory bone and joint diseases, including HIF-1α, NF-κB, AKT/mTOR, JAK1/2-STAT1, NF-κB, JNK, ERK, p-38α/β, p38/MAPK, PI3K/AKT, AMPK, AMPK/Sirt1, STAT TLR4/NF-κB, TLR4/NLRP3, NAMPT pathway, as well as the programmed cell death autophagy, pyroptosis and ERS.

CONCLUSION

As a result of a search of databases, we have summarized the available experimental and clinical evidence supporting herbal products as potential treatment agents for inflammatory osteoarthropathy. In this paper, we outline the various modulatory effects of natural substances targeting macrophages in various diseases, which may provide insight into drug options and directions for future clinical trials. In spite of this, more mechanistic studies on natural substances, as well as pharmacological, toxicological, and clinical studies are required.

A biomimetic piezoelectric scaffold with sustained Mg2+ release promotes neurogenic and angiogenic differentiation for enhanced bone regeneration

Natural bone is a composite tissue made of organic and inorganic components, showing piezoelectricity. Whitlockite (WH), which is a natural magnesium-containing calcium phosphate, has attracted great attention in bone formation recently due to its unique piezoelectric property after sintering treatment and sustained release of magnesium ion (Mg²⁺). Herein, a composite scaffold (denoted as PWH scaffold) composed of piezoelectric WH (PWH) and poly(ε-caprolactone) (PCL) was 3D printed to meet the physiological demands for the regeneration of neuro-vascularized bone tissue, namely, providing endogenous electric field at the defect site. The sustained release of Mg²⁺ from the PWH scaffold, displaying multiple biological activities, and thus exhibits a strong synergistic effect with the piezoelectricity on inhibiting osteoclast activation, promoting the neurogenic, angiogenic, and osteogenic differentiation of bone marrow mesenchymal stromal cells (BMSCs) in vitro. In a rat calvarial defect model, this PWH scaffold is remarkably conducive to efficient neo-bone formation with rich neurogenic and angiogenic expressions. Overall, this study presents the first example of biomimetic piezoelectric scaffold with sustained Mg²⁺ release for promoting the regeneration of neuro-vascularized bone tissue in vivo, which offers new insights for regenerative medicine.