Lactoferrin activates BMP7 gene expression through the mitogen-activated protein kinase ERK pathway in articular cartilage

The role of lactoferrin in bone remodeling: evaluation of its potential in targeted delivery and treatment of metabolic bone diseases and orthopedic conditions

Lactoferrin (Lf) is a multifunctional protein that is synthesized endogenously and has various biological roles including immunological regulation, antibacterial, antiviral, and anticancer properties. Recently, research has uncovered Lf's critical functions in bone remodeling, where it regulates the function of osteoblasts, chondrocytes, osteoclasts, and mesenchymal stem cells. The signaling pathways involved in Lf's signaling in osteoblasts include (low density lipoprotein receptor-related protein - 1 (LRP-1), transforming growth factor β (TGF-β), and insulin-like growth factor - 1 (IGF-1), which activate downstream pathways such as ERK, PI3K/Akt, and NF-κB. These pathways collectively stimulate osteoblast proliferation, differentiation, and mineralization while inhibiting osteoclast differentiation and activity. Additionally, Lf's inhibitory effect on nuclear factor kappa B (NF-κB) suppresses the formation and activity of osteoclasts directly. Lf also promotes chondroprogenitor proliferation and differentiation to chondrocytes by activating the mitogen-activated protein kinase/extracellular signal-regulated kinase (MAPK/ERK) and phosphoinositide 3-kinase/protein kinase B(PI3K/Akt)signaling pathways while inhibiting the expression of matrix-degrading enzymes through the suppression of the NF-κB pathway. Lf's ability to stimulate osteoblast and chondrocyte activity and inhibit osteoclast function accelerates fracture repair, as demonstrated by its effectiveness in animal models of critical-sized long bone defects. Moreover, studies have indicated that Lf can rescue dysregulated bone remodeling in osteoporotic conditions by stimulating bone formation and suppressing bone resorption. These beneficial effects of Lf on bone health have led to its exploration in nutraceutical and pharmaceutical applications. However, due to the large size of Lf, small bioactive peptides are preferred for pharmaceutical applications. These peptides have been shown to promote bone fracture repair and reverse osteoporosis in animal studies, indicating their potential as therapeutic agents for bone-related diseases. Nonetheless, the active concentration of Lf in serum may not be sufficient at the site requiring bone regeneration, necessitating the development of various delivery strategies to enhance Lf's bioavailability and target its active concentration to the site requiring bone regeneration. This review provides a critical discussion of the issues mentioned above, providing insight into the roles of Lf in bone remodeling and the potential use of Lf as a therapeutic target for bone disorders.

The mechanism underlying the remodeling effect of lactoferrin on midpalatal sutures during maxillary expansion and relapse in rats

INTRODUCTION

The remodeling effects of intragastric administration and intramaxillary injection of lactoferrin (LF) on midpalatal sutures (MPS) during maxillary expansion and relapse in rats were studied to explore the underlying bone remodeling mechanism.

METHODS

Using a rat model of maxillary expansion and relapse, rats were treated with LF by intragastric administration (1 g·kg^-1·d^-1) or intramaxillary injection (5 mg·25 μl^-1·d^-1). The effects of LF on the osteogenic and osteoclast activities of MPS were observed by microcomputed tomography, histologic staining, and immunohistochemical staining, and the expressions of key factors in the extracellular regulated protein kinase 1/2 (ERK1/2) pathway and osteoprotegerin (OPG)-receptor activator of nuclear factor-KB ligand (RANKL)-receptor activator of nuclear factor-KB (RANK) axis were detected.

RESULTS

Compared with the group with maxillary expansion alone, osteogenic activity was relatively enhanced, whereas osteoclast activity was relatively weakened in the groups administered LF, and the phosphorylated-ERK1/2: ERK1/2 and OPG: RANKL expression ratios increased significantly. The difference was more significant in the group administered LF intramaxillary.

CONCLUSIONS

Administration of LF promoted osteogenic activity at MPS and inhibited osteoclast activity during maxillary expansion and relapse in rats, which may have occurred through regulation of the ERK1/2 pathway and the OPG-RANKL-RANK axis. The efficiency of intramaxillary LF injection was greater than that of intragastric LF administration.

Effects of estrogen on root repair after orthodontically induced root resorption in ovariectomized rats

INTRODUCTION

This study aimed to investigate the effects of estrogen on root repair after orthodontically induced root resorption.

METHODS

Seventy-two 6-week-old female Wistar rats were randomly divided into 3 groups: ovariectomy only (OVX), ovariectomy plus estradiol injection (OVX + E2), and sham operation (control). E2 was administrated to all the experimental animals after the establishment of the root repair model. One-way analysis of variance with the Tukey post-hoc test was used to analyze the experimental results.

RESULTS

Micro-computed tomography and hematoxylin and eosin staining showed that the total volumes of resorption lacunae were significantly smaller in the control and OVX + E2 groups than those in the OVX group. Alkaline phosphatase and tartrate-resistant acid phosphatase stainings suggested that the cementoblastic activities and the amount of new cementum formation were inhibited while the activities of osteoclasts were obvious in the OVX group. The immunohistochemistry stainings revealed that the osteoprotegerin to receptor activator of nuclear factor-кB ligand ratio and the phosphorylated extracellular signal-regulated kinases to extracellular signal-regulated kinases ratio of the control and OVX + E2 groups were significantly greater than those of the OVX group.

CONCLUSIONS

These findings demonstrated that estrogen administration might be a solution to reduce orthodontically induced root resorption through the activation of extracellular signal-regulated kinase-1/2 pathway and enhancement of cementogenesis.

Therapeutic targeting of neutrophil exocytosis

Dysregulation of neutrophil activation causes disease in humans. Neither global inhibition of neutrophil functions nor neutrophil depletion provides safe and/or effective therapeutic approaches. The role of neutrophil granule exocytosis in multiple steps leading to recruitment and cell injury led each of our laboratories to develop molecular inhibitors that interfere with specific molecular regulators of secretion. This review summarizes neutrophil granule formation and contents, the role granule cargo plays in neutrophil functional responses and neutrophil-mediated diseases, and the mechanisms of granule release that provide the rationale for development of our exocytosis inhibitors. We present evidence for the inhibition of granule exocytosis in vitro and in vivo by those inhibitors and summarize animal data indicating that inhibition of neutrophil exocytosis is a viable therapeutic strategy.

The synovial fluid proteome differentiates between septic and nonseptic articular pathologies

Articular conditions are common in horses and can result in loss of function, chronic pain and/or inability to work. Common conditions include osteoarthritis, osteochondrosis and synovial sepsis, which can be life-threatening, but despite the high clinical prevalence of these conditions, rapid and specific diagnosis, monitoring and prognostication remains a challenge for practicing veterinarians. Synovial fluid from a range of arthropathies was enriched for low abundance proteins using combinatorial peptide ligand ProteoMiner™ beads and analysed via liquid chromatography-tandem mass spectrometry. Changes in protein abundances were analysed using label-free quantification. Principle component analysis of differentially expressed proteins identified groupings associated with joint pathology. Findings were validated using ELISA. Lactotransferrin (LTF) abundance was increased in sepsis compared to all other groups and insulin-like growth factor-binding protein 6 (IGFBP6) abundance decreased in sepsis compared to other disease groups. Pathway analysis identified upregulation of the complement system in synovial joint sepsis and the downregulation of eukaryotic translation initiation factors and mTOR signalling pathways in both OA and OC compared to the healthy group. Overall, we have identified a catalogue of proteins which we propose to be involved in osteoarthritis, osteochondrosis and synovial sepsis pathogenesis. SIGNIFICANCE: Osteoarthritis, osteochondrosis and synovial sepsis, which can be life-threatening, are common articular conditions in which rapid and specific diagnosis, monitoring and prognostication remains a challenge for practicing veterinarians. This study has identified that the equine synovial fluid proteome exhibits distinctive profile changes between osteoarthritis, osteochondrosis, synovial sepsis and healthy joints. Elevated synovial abundance of lactotransferrin and decreased insulin-like growth factor-binding protein 6 were both found to distinguish synovial sepsis from all other study groups. Thus, these protein markers may have a future role in clinical practice to enable an earlier and reliable diagnosis of synovial sepsis.

RETRACTED: GZMB gene silencing confers protection against synovial tissue hyperplasia and articular cartilage tissue injury in rheumatoid arthritis through the MAPK signaling pathway

This article has been retracted: please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy). This article has been retracted at the request of the Editor-in-Chief. An Expression of Concern for this article was previously published while an investigation was conducted (see related editorial: https://doi.org/10.1016/j.biopha.2022.113812). This retraction notice supersedes the Expression of Concern published earlier. Concern was raised about the reliability of the Western blot data in Figure 7C, which appear to contain a similar phenotype to those found in other publications, as detailed here: https://pubpeer.com/publications/7DD2DDC979F8CE2B00555332B01F81; and here: https://docs.google.com/spreadsheets/d/1r0MyIYpagBc58BRF9c3luWNlCX8VUvUuPyYYXzxWvgY/edit#gid=262337249. The journal requested the corresponding author comment on these concerns and provide the associated raw data. The authors did not respond to this request and therefore the Editor-in-Chief decided to retract the article.

Magnesium phosphate ceramics incorporating a novel indene compound promote osteoblast differentiation in vitro and bone regeneration in vivo

Incorporating bioactive molecules into synthetic ceramic scaffolds is challenging. In this study, to enhance bone regeneration, a magnesium phosphate (MgP) ceramic scaffold was incorporated with a novel indene compound, KR-34893. KR-34893 induced the deposition of minerals and expression of osteoblast marker genes in primary human bone marrow mesenchymal stem cells (BMSCs) and a mouse osteoblastic MC3T3-E1 cell line. Analysis of the mode of action showed that KR-34893 induced the phosphorylation of MAPK/extracellular signal-regulated kinase and extracellular signal-regulated kinase, and subsequently the expression of bone morphogenetic protein 7, accompanied by SMAD1/5/8 phosphorylation. Accordingly, KR-34893 was incorporated into an MgP scaffold prepared by 3D printing at room temperature, followed by cement reaction. KR-34893-incorporated MgP (KR-MgP) induced the expression of osteoblast differentiation marker genes in vitro. In a rat calvaria defect model, KR-MgP scaffolds enhanced bone regeneration and increased bone volume compared with MgP scaffolds, as assessed by micro-computed tomography and histological analyses. In conclusion, we developed a method for producing osteoinductive MgP scaffolds incorporating a bioactive organic compound, without high temperature sintering. The KR-MgP scaffolds enhanced osteoblast activation in vitro and bone regeneration in vivo.

Matrigel scaffold combined with Ad-hBMP7-transfected chondrocytes improves the repair of rabbit cartilage defect

The aim of this study was to explore an effective method for the repair of cartilage defects using chitosan/glycerophosphate (C/GP) gel- and Matrigel-engineered human bone morphogenetic protein 7 (hBMP7)-expressing chondrocytes. Rabbit chondrocytes were obtained, cultured in vitro and transfected with an adenovirus containing hBMP7 and green fluorescent protein (Ad-hBMP7-GFP). The expression of hBMP7 in the transfected cells was tested by reverse transcription-polymerase chain reaction (RT-PCR) and western blotting. The phenotype of the transfected cells was evaluated by detecting the yields of collagen II and hyaluronic acid using RT-PCR and enzyme-linked immunosorbent assay (ELISA). The growth of chondrocytes in the C/GP gel and Matrigel was accessed by measuring the cell growth rate, hematoxylin and eosin (H&E) staining and observation under a scanning microscope. Twelve adult male New Zealand white rabbits were randomly divided into three groups. Two cartilage defects were created in the rabbits' knees by aseptic surgery. Group A (n=4) did not receive any treatment, group B (n=4) were treated with C/GP gel and Matrigel-engineered Ad-mock-GFP-transfected chondrocytes, and group C (n=4) were treated with C/GP gel and Matrigel-engineered Ad-hBMP7-GFP-transfected chondrocytes. Rabbits were sacrificed at 4 weeks after transplantation, and the repair effect was measured by the Wakitani scoring method. On the basis of the RT-PCR and western blot results, hBMP7 was efficiently overexpressed in the Ad-hBMP7-GFP-transfected chondrocytes. The ELISA results showed that the yields of collagen II and hyaluronic acid in Ad-hBMP7-GFP-transfected chondrocytes were significantly higher than those in Ad-mock-GFP-transfected chondrocytes. Chondrocytes have a better morphology and arrangement in a Matrigel scaffold than in C/GP, as assessed by H&E staining and scanning microscopy. According to the Wakitani score, Matrigel combined with Ad-hBMP7-GFP-transfected chondrocytes successfully promoted the repair of cartilage defects in rabbit knees.

Lactoferrin and the newborn: current perspectives

Neonatal sepsis and necrotizing enterocolitis (NEC) are associated with significant mortality and morbidity. Inflammation secondary to sepsis and NEC increases morbidity, especially those related to the lung, brain and eye. Therapeutic strategies that target inflammation and decrease the emergence of antibiotic resistance are urgently needed. Lactoferrin (Lf) is a multifunctional protein that modulates inflammation, cell growth and differentiation and has broad antimicrobial activity. Studies evaluating the efficacy and safety of Lf in the prevention of neonatal sepsis and NEC are currently in progress, and one completed study shows significant promise. In this article, the functions of this multifunctional molecule and current clinical evidence for its use in the newborn are reviewed. Lf prophylaxis and therapy may have a significant impact in improving clinical outcomes of vulnerable preterm neonates.