Lactoferrin as an effector molecule in the skeleton

Exploring biological mechanisms in orthodontic tooth movement: Bridging the gap between basic research experiments and clinical applications - A comprehensive review

OBJECTIVES

The molecular mechanisms behind orthodontic tooth movements (OTM) were investigated by clarifying the role of chemical messengers released by cells.

METHODS

Using the Cochrane library, Google scholar, and PubMed databases, a literature search was conducted, and studies published from 1984 to 2024 were considered.

RESULTS

Both bone growth and remodeling may occur when a tooth is subjected to mechanical stress. These chemicals have a significant effect on the stimulation and regulation of osteoblasts, osteoclasts, and osteocytes during alveolar bone remodeling. This regulation can take place in pathological conditions, such as periodontal diseases, or during OTM alone. This comprehensive review outlines key molecular mechanisms underlying OTM and explores various clinical assumptions associated with specific molecules and their functional domains during this process. Furthermore, clinical applications of certain molecules such as relaxin, prostaglandin E (PGE), and interleukin-1β (IL-1β) in accelerating OTM have been reported. Our findings underscore the existing gap between OTM clinical applications and basic research investigations.

CONCLUSION

A comprehensive understanding of orthodontic treatment is enriched by insights into biological systems. We reported the activation of osteoblasts, osteoclast precursor cells, osteoclasts, and osteocytes in response to mechanical stress, leading to targeted cellular and molecular interventions and facilitating rapid and regulated alveolar bone remodeling during tooth movement. Despite the shortcomings of clinical studies in accelerating OTM, this review highlights the crucial role of biological agents in this process and advocates for prioritizing high-quality human studies in future research to gain further insights from clinical trials.

Protective Effects of Lactoferrin Treatment Against Sodium Arsenite Exposure-Induced Nephrotoxicity

It is said that a wide range of renal functions are at risk from arsenic exposure. We examined how lactoferrin administration may mitigate inflammation, apoptosis, redox imbalance, and fibrosis in order to counteract arsenic-induced nephrotoxicity. Accordingly, male C57BL/6 mice (6 weeks) were divided into six experimental groups with six mice in each group. The first and second groups were intragastrically administered normal saline and sodium arsenite (NaAsO2) at 5 mg/kg body weight concentrations as the negative control (NC) and NaAsO2 groups. The third, fourth, and fifth groups were intragastrically administered lactoferrin at concentrations of 100, 200, and 400 mg/kg body weight in addition to NaAsO2 at concentrations of 5 mg/kg body weight. The sixth group was intragastrically administered lactoferrin at a concentration of 200 mg/kg body weight with the experimental group set as the lactoferrin group. After daily drug administration for 4 weeks, the lactoferrin concentrations were optimized based on the results of renal index and renal function. Histopathological, biochemical, and gene expression analyses were performed to evaluate the status of renal tissue architecture, redox imbalance, inflammation, apoptosis, and fibrosis to confirm the alleviative effect of lactoferrin treatment against the NaAsO2 exposure-induced nephrotoxicity. The results confirmed that the 200 mg/kg lactoferrin treatment mitigated these arsenic effects and maintained the normal renal frameworks. Conclusively, disrupting the renal redox balance and triggering inflammation, apoptosis, along with fibrosis is a milieu that arsenic, robustly exerts its nephrotoxic effect. Lactoferrin, probably by its direct and indirect control mechanism on these said pathways, can mitigate the nephrotoxicity and preserve the normal renal health.

Nutraceutical and Health-Promoting Potential of Lactoferrin, an Iron-Binding Protein in Human and Animal: Current Knowledge

Lactoferrin is a natural cationic iron-binding glycoprotein of the transferrin family found in bovine milk and other exocrine secretions, including lacrimal fluid, saliva, and bile. Lactoferrin has been investigated for its numerous powerful influences, including anticancer, anti-inflammatory, anti-oxidant, anti-osteoporotic, antifungal, antibacterial, antiviral, immunomodulatory, hepatoprotective, and other beneficial health effects. Lactoferrin demonstrated several nutraceutical and pharmaceutical potentials and have a significant impact on improving the health of humans and animals. Lactoferrin plays a critical role in keeping the normal physiological homeostasis associated with the development of pathological disorders. The current review highlights the medicinal value, nutraceutical role, therapeutic application, and outstanding favorable health sides of lactoferrin, which would benefit from more exploration of this glycoprotein for the design of effective medicines, drugs, and pharmaceuticals for safeguarding different health issues in animals and humans.

Lactoferrin improves symptoms of dextran sulfate sodium-induced colitis in mice through modulation of cellular senescence

The multifaceted effects of lactoferrin (LF) on the digestive and immune systems make it an attractive therapeutic option in inflammatory bowel diseases. In this study, we aimed to explore the anti-inflammatory effects of LF in colitis, particularly in relation to cellular senescence. We hypothesize that LF has the potential to modulate the senescence process. The effects of LF on senescence were tested in vitro using HCT116 and SW480 cell lines, and in vivo, the dextran sulfate sodium-induced mouse model of colitis. LF (500 mg/kg) alleviated symptoms of colitis in mice with a significant decrease in colon damage (P < .0001 vs. control) and microscopic (P < .05 vs. control) scores. Cellular senescence markers p16 and p21 were significantly upregulated in the mouse colon during inflammation (both P < .01 vs. control), and LF at 500 mg/kg decreased these markers (both P < .05 vs. dextran sulfate sodium-treated mice). In vitro, LF significantly affected the expression of p16 and p21 (P < .05-P < .0001 vs. control), senescence associated secretory phenotype (P < .01-P < .0001 vs. control), and telomere-specific proteins: telomeric repeat binding factor 1 and 2 (P < .05-P < .0001 vs. control) in a concentration-dependent manner. LF modulates the expression of cellular senescence markers and shows hallmarks of senolytic and pro-senescent activity, depending on dose. Further studies are needed to fully understand the anti-inflammatory effect of LF in the context of senescence and safe utilization in patients with inflammatory bowel diseases.

Lactoferrin-Anchored Tannylated Mesoporous Silica Nanomaterials-Induced Bone Fusion in a Rat Model of Lumbar Spinal Fusion

Lactoferrin (LF) is a potent antiviral, anti-inflammatory, and antibacterial agent found in cow and human colostrum which acts as an osteogenic growth factor. This study aimed to investigate whether LF-anchored tannylated mesoporous silica nanomaterials (TA-MSN-LF) function as a bone fusion material in a rat model. In this study, we created TA-MSN-LF and measured the effects of low (1 μg) and high (100 μg) TA-MSN-LF concentrations in a spinal fusion animal model. Rats were assigned to four groups in this study: defect, MSN, TA-MSN-LF-low (1 μg/mL), and TA-MSN-LF-high (100 μg/mL). Eight weeks after surgery, a greater amount of radiological fusion was identified in the TA-MSN-LF groups than in the other groups. Hematoxylin and eosin staining showed that new bone fusion was induced in the TA-MSN-LF groups. Additionally, osteocalcin, a marker of bone formation, was detected by immunohistochemistry, and its intensity was induced in the TA-MSN-LF groups. The formation of new vessels was induced in the TA-MSN-LF-high group. We also confirmed an increase in the serum osteocalcin level and the mRNA expression of osteocalcin and osteopontin in the TA-MSN-LF groups. TA-MSN-LF showed effective bone fusion and angiogenesis in rats. We suggest that TA-MSN-LF is a potent material for spinal bone fusion.

Effects of a Functional Ice Cream Enriched with Milk Proteins on Bone Metabolism: A Feasibility Clinical Study and In Vitro Investigation

Background: Milk proteins (MPs) and their derivative whey proteins (WPs) are important components of human diet that might prevent bone loss. We aimed to investigate the effects of MP on the bones of postmenopausal women, along with the effects of WP on osteoblast cells. Methods: We conducted a feasibility controlled clinical study with 62 postmenopausal women who were asked to consume an MP-enriched ice cream. We also investigated the effect of WP on the ERK1/2 and AKT pathways, RUNX2, alkaline phosphatase, RANKL/OPG ratio, and COL1A of Saos-2. Results: After 12 weeks, we found a greater bone mineral density and bone alkaline phosphatase reduction in women who consumed the MP-enriched ice cream compared to the control group (p = 0.03 and p = 0.02, respectively). In Saos-2 cells, WP upregulated ERK1/2 and AKT pathways (p = 0.002 and p = 0.016), cell proliferation (p = 0.03), and osteoblast differentiation markers, along with downregulating RANKL/OPG (p < 0.001). Moreover, the inhibition of ERK1/2 by PD184253 reverted the effects on both the RUNX2 and ALP mRNA expression and cells proliferation (p = 0.028, p = 0.004, and p = 0.003, respectively) when treated with WP. Conclusions: WP upregulates cell proliferation, RUNX2, and alkaline phosphatase through the activation of the ERK1/2 pathways on Saos-2. These mechanisms probably contribute to preventing bone loss in postmenopausal women.

The application of lactoferrin in infant formula: The past, present and future

Human milk is universally regarded as the gold standard to fulfill nutrition needs of infants. Lactoferrin (LF) is a major multiple bioactive glycoprotein in human milk but little is presented in infant formula. LF can resist digestion in the infant gastrointestinal tract and is absorbed into the bloodstream in an intact form to perform physiological functions. Evidence suggest that LF prevents pathogen infection, promotes immune system development, intestinal development, brain development and bone health, as well as ameliorates iron deficiency anemia. However, more clinical studies of LF need to be further elucidated to determine an appropriate dosage for application in infant formula. LF is sensitive to denaturation induced by processing of infant formula such as heat treatments and spay drying. Thus, further studies should be focus on maximizing the retention of LF activity in the infant formula process. This review summarizes the structural features of LF. Then the digestion, absorption and metabolism of LF in infants are discussed, followed by the function of LF for infants. Further, we summarize LF in infant formula and effects of processing of infant formula on bioactivities of LF, as well as future perspectives of LF research.

Nanoparticular and other carriers to deliver lactoferrin for antimicrobial, antibiofilm and bone-regenerating effects: a review

Bone and joint infections are a rare but serious problem worldwide. Lactoferrin’s antimicrobial and antibiofilm activity coupled with its bone-regenerating effects may make it suitable for improving bone and joint infection treatment. However, free lactoferrin (LF) has highly variable oral bioavailability in humans due to potential for degradation in the stomach and small intestine. It also has a short half-life in blood plasma. Therefore, encapsulating LF in nanocarriers may slow degradation in the gastrointestinal tract and enhance LF absorption, stability, permeability and oral bioavailability. This review will summarize the literature on the encapsulation of LF into liposomes, solid lipid nanoparticles, nanostructured lipid carriers, polymeric micro and nanoparticles and hydroxyapatite nanocrystals. The fabrication, characterization, advantages, disadvantages and applications of each system will be discussed and compared.

The impact of SNP density on quantitative genetic analyses of body size traits in a wild population of Soay sheep

Understanding the genetic architecture underpinning quantitative traits in wild populations is pivotal to understanding the processes behind trait evolution. The 'animal model' is a popular method for estimating quantitative genetic parameters such as heritability and genetic correlation and involves fitting an estimate of relatedness between individuals in the study population. Genotypes at genome-wide markers can be used to estimate relatedness; however, relatedness estimates vary with marker density, potentially affecting results. Increasing density of markers is also expected to increase the power to detect quantitative trait loci (QTL). In order to understand how the density of genetic markers affects the results of quantitative genetic analyses, we estimated heritability and performed genome-wide association studies (GWAS) on five body size traits in an unmanaged population of Soay sheep using two different SNP densities: a dataset of 37,037 genotyped SNPs and an imputed dataset of 417,373 SNPs. Heritability estimates did not differ between the two SNP densities, but the high-density imputed SNP dataset revealed four new SNP-trait associations that were not found with the lower density dataset, as well as confirming all previously-found QTL. We also demonstrated that fitting fixed and random effects in the same step as performing GWAS is a more powerful approach than pre-correcting for covariates in a separate model.

A Low-Phenylalanine-Containing Whey Protein Hydrolysate Stimulates Osteogenic Activity through the Activation of p38/Runx2 Signaling in Osteoblast Cells

A phenylalanine (Phe)-restricted diet is indispensable for individuals suffering from phenylketonuria (PKU). Our previous study reported a low-Phe-containing whey protein hydrolysate (LPH) prepared from a selected whey protein hydrolysate (TA2H). This study aimed to investigate the osteogenic activity of LPH and TA2H in MC3T3-E1 preosteoblast cells and explore the underlying mechanism. Results showed that the treatment of TA2H and LPH (at the final concentrations of 100–1000 μg/mL) had a stimulatory effect on the proliferation, differentiation, and mineralization of MC3T3-E1 cells. The LPH of 1000 μg/mL significantly increased cell proliferation (2.15- ± 0.11-fold) and alkaline phosphatase activity (1.22- ± 0.07-fold), promoted the protein and mRNA levels of runt-related transcription factor 2 (Runx2, 2.50- ± 0.14-fold and 2.97- ± 0.23-fold, respectively), enhanced the expression of differentiation biomarkers (type-I collagen, osteocalcin, and osteopontin), increased calcium deposition (1.56- ± 0.08-fold), and upregulated the ratio of osteoprotegerin/receptor activator of nuclear factor-κB ligand. The exploration of signaling pathways indicated that the activated p38-dependent Runx2 signaling contributed to the LPH-induced osteogenesis. These results provided evidence, for the first time, that a prepared low-Phe whey protein hydrolysate positively modulated the activity of osteoblasts through the p38/Runx2 pathway, thereby providing a new osteoinductive protein substitute to make functional PKU food.

The effect of lactoferrin in aging: role and potential

Aging is frequently accompanied by various types of physiological deterioration, which increases the risk of human pathologies. Global public health efforts to increase human lifespan have increasingly focused on lowering the risk of aging-related diseases, such as diabetes, neurodegenerative diseases, cardiovascular disease, and cancers. Dietary intervention is a promising approach to maintaining human health during aging. Lactoferrin (LF) is known for its physiologically pleiotropic properties. Anti-aging interventions of LF have proven to be safe and effective for various pharmacological activities, such as anti-oxidation, anti-cellular senescence, anti-inflammation, and anti-carcinogenic. Moreover, LF has a pivotal role in modulating the major signaling pathways that influence the longevity of organisms. Thus, LF is expected to be able to attenuate the process of aging and greatly ameliorate its effects.

Bovine Colostrum Supplementation Improves Bone Metabolism in an Osteoporosis-Induced Animal Model

Osteoporosis is characterized by bone loss. The present study aims to investigate the effects of bovine colostrum (BC) on bone metabolism using ovariectomized (OVX) and orchidectomized (ORX) rat models. Twenty-seven-week-old Wistar Han rats were randomly assigned as: (1) placebo control, (2) BC supplementation dose 1 (BC1: 0.5 g/day/OVX, 1 g/day/ORX), (3) BC supplementation dose 2 (BC2: 1 g/day/OVX, 1.5 g/day/ORX) and (4) BC supplementation dose 3 (BC3: 1.5 g/day/OVX, 2 g/day/ORX). Bone microarchitecture, strength, gene expression of VEGFA, FGF2, RANKL, RANK and OPG, and bone resorption/formation markers were assessed after four months of BC supplementation. Compared to the placebo, OVX rats in the BC1 group exhibited significantly higher cortical bone mineral content and trabecular bone mineral content (p < 0.01), while OVX rats in the BC3 group showed significantly higher trabecular bone mineral content (p < 0.05). ORX rats receiving BC dose 2 demonstrated significantly higher levels of trabecular bone mineral content (p < 0.05). Serum osteocalcin in the ORX was pointedly higher in all BC supplementation groups than the placebo (BC1: p < 0.05; BC2, BC3: p < 0.001). Higher doses of BC induced significantly higher relative mRNA expression of OPG, VEGFA, FGF2 and RANKL (p < 0.05). BC supplementation improves bone metabolism of OVX and ORX rats, which might be associated with the activation of the VEGFA, FGF2 and RANKL/RANK/OPG pathways.

Osteogenic effect of polymethyl methacrylate bone cement with surface modification of lactoferrin

Polymethyl methacrylate (PMMA) bone cement is a commonly used filling material in orthopedic surgery. Its good and stable performances make it the most widely used in all kinds of bone cement. With the advancement of the application and research of PMMA bone cement by surgeons, its disadvantages such as non-degradation and non-bioactivity are gradually exposed. In recent years, the biological functions of lactoferrin (LF) have been gradually explored, especially its role in promoting osteogenesis. In this study, LF was modified on the surface of solidified PMMA bone cement (LF/PMMA bone cement) by physical/chemical mixed modification and verified by cytological experiments in vitro. In vitro studies have implicated that PMMA bone cement modified with LF can improve the attachment, expansion, proliferation, extracellular matrix secretion and osteogenic differentiation of mouse preosteoblasts (MC3T3-E1) cells, indicating biocompatibility. This experiment provides a novel insight for improving the biological activity of PMMA bone cement and lays a foundation for broadening the clinical application of PMMA bone cement.

An aptamer affinity column for purification and enrichment of lactoferrin in milk

As an active glycoprotein with high nutritional value, lactoferrin is widely used in food and medical treatment. Therefore, it is very important to establish an accurate and efficient detection method for lactoferrin. At present, the detection of lactoferrin in milk faces many challenges, such as low separation degree and poor parallelism. To address this issue, we developed an aptamer affinity column (AAC) for purification and enrichment of lactoferrin in milk. The column was prepared by covalent conjugation of an amino-modified aptamer with NHS-activated Sepharose. The washing buffer type (0.01 mol/L phosphate buffer) and volume (10 mL) and the sodium chlorideconcentration (1 mol/L) in the elution buffer were optimized for the AAC method. The performance of the AAC was then evaluated in terms of the column capacity, specificity, stability, and reusability. The column capacity was 500 ± 13.7 μg and the column could be reused up to ten times with a large loss in performance. The AAC method combined with high-performance liquid chromatography gave excellent linearity over a wide range, good sensitivity with a limit of detection of 3 μg/mL, and acceptable recoveries for different concentrations of lactoferrin spiked in real raw milk samples from cattle. Finally, the AAC was successfully applied to analyze lactoferrin in milk. This method could be applied to routine analysis of samples for lactoferrin in testing laboratories and dairy factories.

Milk proteins and their derived peptides on bone health: Biological functions, mechanisms, and prospects

Bone is a dynamic organ under constant metabolism (or remodeling), where a delicate balance between bone resorption and bone formation is maintained. Disruption of this coordinated bone remodeling results in bone diseases, such as osteoporosis, the most common bone disorder characterized by decreased bone mineral density and microarchitectural deterioration. Epidemiological and clinical evidence support that consumption of dairy products is beneficial for bone health; this benefit is often attributed to the presence of calcium, the physiological contributions of milk proteins on bone metabolism, however, are underestimated. Emerging evidence highlighted that not only milk proteins (including individual milk proteins) but also their derived peptides positively regulate bone remodeling and attenuate bone loss, via the regulation of cellular markers and signaling of osteoblasts and osteoclasts. This article aims to review current knowledge about the roles of milk proteins, with an emphasis on individual milk proteins, bioactive peptides derived from milk proteins, and effect of milk processing in particular fermentation, on bone metabolism, to highlight the potential uses of milk proteins in the prevention and treatment of osteoporosis, and, to discuss the knowledge gap and to recommend future research directions.

A prospective on multiple biological activities of lactoferrin contributing to piglet welfare

Piglets, especially weaning piglets, show a lower level of immunity and higher morbidity and mortality, owing to their rapid growth, physiological immaturity, and gradual reduction of maternal antibodies, which seriously affects their growth and thus, value. It is important that piglets adapt to nutrient digestion and absorption and develop sound intestinal function and colonization with gut microbiota as soon as possible during their early life stage. Lactoferrin is a natural glycoprotein polypeptide that is part of the transferrin family. It is widely found in mucosal secretions such as saliva and tears, and most highly in milk and colostrum. As a multifunctional bioactive protein and a recommended food additive, lactoferrin is a potential alternative therapy to antibiotics and health promoting additive for piglet nutrition and development. It is expected that lactoferrin, as a natural food additive, could play an important role in maintaining pig health and development. This review examines the following known beneficial effects of lactoferrin: improves the digestion and capacity for absorption in the intestinal tract; promotes the absorption of iron and reduces the incidence of iron deficiency anemia; regulates intestinal function and helps to balance the microbial biota; and enhances the resistance to disease of the piglets via modulating and enhancing the immune system.

Lactoferrin-Anchored Tannylated Mesoporous Silica Nanomaterials for Enhanced Osteo-Differentiation Ability

In the present study, we created lactoferrin-anchored mesoporous silica nanomaterials with absorbed tannic acid (LF/TA-MSNs) and evaluated the effect of these LF/TA-MSNs on the in vitro osteo-differentiation ability of adipose-derived stem cells (ADSCs) by testing alkaline phosphatase (ALP) level, calcium accumulation, and expression of osteo-differentiation-specific genes, including osteocalcin (OCN) and osteopontin (OPN). Both bare MSNs and LF/TA-MSNs exhibited round nano-particle structures. The LF/TA-MSNs demonstrated prolonged LF release for up to 28 days. Treatment of ADSCs with LF (50 μg)/TA-MSNs resulted in markedly higher ALP level and calcium accumulation compared to treatment with LF (10 μg)/TA-MSNs or bare MSNs. Furthermore, LF (50 μg)/TA-MSNs remarkably increased mRNA levels of osteo-differentiation-specific genes, including OCN and OPN, compared to MSNs or LF (10 μg)/TA-MSNs. Together, these data suggest that the ability of LF/TA-MSNs to enhance osteo-differentiation of ADSCs make them a possible nanovehicle for bone healing and bone regeneration in patients with bone defect or disease.

Oral administration of bovine lactoferrin accelerates the healing of fracture in ovariectomized rats

INTRODUCTION

Lactoferrin has recently been reported for its potent bone growth effects. However, the effects of lactoferrin on the healing process of fragility fracture have not yet been studied, so the purpose of this study is to investigate whether oral administration of lactoferrin can promote the fracture healing in an OVX animal model.

MATERIALS AND METHODS

Three months after bilateral ovariectomy, all rats underwent unilateral tibial osteotomy and were then randomly divided into control group and bovine lactoferrin (bLF) group. At 4 and 8 weeks post-fracture, animals were sacrificed, and the fractured tibiae and serum samples were collected for evaluation.

RESULTS

Our results showed that bLF treatment not only accelerated the bone growth at an early stage of OPF healing but also shortened the remolding process of OPF healing. When compared to control group, bLF treatment induced a significant rise in callus BMD (by 35.0% at 4 weeks and by 39.7% at 8 weeks; both p < 0.05) consistent with enhanced biomechanical strength of the callus, with ultimate force increased by 3.39-fold at 4 weeks (p < 0.05) and 1.95-fold at 8 weeks (p < 0.05). Besides, bLF administration resulted in a substantial increase in serum levels of BALP and a significant decrease in serum levels of TRAP 5b and TNF-α. Moreover, both the RANKL/OPG mRNA ratio and the expression of TNF-α in the callus of bLF-treated group were markedly lower than those in the control group.

CONCLUSIONS

At a dose of 85mg/kg/day orally administrated bLF potently promoted the bone healing following tibial fracture in OVX rats.

Lactoferrin from Bovine Milk: A Protective Companion for Life

Lactoferrin (Lf), an iron-binding multifunctional glycoprotein belonging to the transferrin family, is present in most biological secretions and reaches particularly high concentrations in colostrum and breast milk. A key function of lactoferrin is non-immune defence and it is considered to be a mediator linking innate and adaptive immune responses. Lf from bovine milk (bLf), the main Lf used in human medicine because of its easy availability, has been designated by the United States Food and Drug Administration as a food additive that is generally recognized as safe (GRAS). Among the numerous protective activities exercised by this nutraceutical protein, the most important ones demonstrated after its oral administration are: Antianemic, anti-inflammatory, antimicrobial, immunomodulatory, antioxidant and anticancer activities. All these activities underline the significance in host defence of bLf, which represents an ideal nutraceutical product both for its economic production and for its tolerance after ingestion. The purpose of this review is to summarize the most important beneficial activities demonstrated following the oral administration of bLf, trying to identify potential perspectives on its prophylactic and therapeutic applications in the future.

Lactoferrin in Bone Tissue Regeneration

Among the multiple properties exhibited by lactoferrin (Lf), its involvement in bone regeneration processes is of great interest at the present time. A series of in vitro and in vivo studies have revealed the ability of Lf to promote survival, proliferation and differentiation of osteoblast cells and to inhibit bone resorption mediated by osteoclasts. Although the mechanism underlying the action of Lf in bone cells is still not fully elucidated, it has been shown that its mode of action leading to the survival of osteoblasts is complemented by its mitogenic effect. Activation of several signalling pathways and gene expression, in an LRPdependent or independent manner, has been identified. Unlike the effects on osteoblasts, the action on osteoclasts is different, with Lf leading to a total arrest of osteoclastogenesis. Due to the positive effect of Lf on osteoblasts, the potential use of Lf alone or in combination with different biologically active compounds in bone tissue regeneration and the treatment of bone diseases is of great interest. Since the bioavailability of Lf in vivo is poor, a nanotechnology- based strategy to improve the biological properties of Lf was developed. The investigated formulations include incorporation of Lf into collagen membranes, gelatin hydrogel, liposomes, loading onto nanofibers, porous microspheres, or coating onto silica/titan based implants. Lf has also been coupled with other biologically active compounds such as biomimetic hydroxyapatite, in order to improve the efficacy of biomaterials used in the regulation of bone homeostasis. This review aims to provide an up-to-date review of research on the involvement of Lf in bone growth and healing and on its use as a potential therapeutic factor in bone tissue regeneration.

Human Mesenchymal Stem Cell Response to Lactoferrin-based Composite Coatings

The potential of mesenchymal stem cells (MSCs) for implantology and cell-based therapy represents one of the major ongoing research subjects within the last decades. In bone regeneration applications, the various environmental factors including bioactive compounds such as growth factors, chemicals and physical characteristics of biointerfaces are the key factors in controlling and regulating osteogenic differentiation from MSCs. In our study, we have investigated the influence of Lactoferrin (Lf) and Hydroxyapatite (HA) embedded within a biodegradable PEG-PCL copolymer on the osteogenic fate of MSCs, previous studies revealing an anti-inflammatory potential of the coating and osteogenic differentiation of murine pre-osteoblast cells. The copolymer matrix was obtained by the Matrix Assisted Pulsed Laser Evaporation technique (MAPLE) and the composite layers containing the bioactive compounds (Lf, HA, and Lf-HA) were characterised by Scanning Electron Microscopy and Atomic Force Microscopy. Energy-dispersive X-ray spectroscopy contact angle and surface energy of the analysed coatings were also measured. The characteristics of the composite surfaces were correlated with the viability, proliferation, and morphology of human MSCs (hMSCs) cultured on the developed coatings. All surfaces were found not to exhibit toxicity, as confirmed by the LIVE/DEAD assay. The Lf-HA composite exhibited an increase in osteogenic differentiation of hMSCs, results supported by alkaline phosphatase and mineralisation assays. This is the first report of the capacity of biodegradable composite layers containing Lf to induce osteogenic differentiation from hMSCs, a property revealing its potential for application in bone regeneration.

Macrophage in vitro Response on Hybrid Coatings Obtained by Matrix Assisted Pulsed Laser Evaporation

The improvement in the research area of the implant by surface functionalization when correlated with the biological response is of major interest in the biomedical field. Based on the fact that the inflammatory response is directly involved in the ultimate response of the implant within the body, it is essential to study the macrophage-material interactions. Within this context, we have investigated the composite material-macrophage cell interactions and the inflammatory response to these composites with amorphous hydroxyapatite (HA), Lactoferrin (Lf), and polyethylene glycol-polycaprolactone (PEG-PCL) copolymer. All materials are obtained by Matrix Assisted Pulsed Laser Evaporation (MAPLE) technique and characterized by Atomic Force Microscopy and Scanning Electron Microscopy. Macrophage-differentiated THP-1 cells proliferation and metabolic activity were assessed by qualitative and quantitative methods. The secretion of tumor necrosis factor alpha (TNF-α) and interleukin 10 (IL-10) cytokine, in the presence and absence of the inflammatory stimuli (bacterial endotoxin; lipopolysaccharide (LPS)), was measured using an ELISA assay. Our results revealed that the cellular response depended on the physical-chemical characteristics of the coatings. Copolymer-HA-Lf coatings led to low level of pro-inflammatory TNF-α, the increased level of anti-inflammatory IL-10, and the polarization of THP-1 cells towards an M2 pro-reparative phenotype in the presence of LPS. These findings could have important potential for the development of composite coatings in implant applications.

Effects of lactoferrin on bone resorption of midpalatal suture during rapid expansion in rats

INTRODUCTION

The aim of this study was to investigate the effect of lactoferrin (LF) on bone resorption of rats' midpalatal sutures during rapid palatal expansion.

METHODS

Sixty male 5-week-old Wistar rats were randomly divided into 3 groups: expansion only (EO), expansion plus LF (E + LF), and sham device (control).

RESULTS

Microcomputed tomography showed that the bone volume/tissue volume ratio and the relative bone mineral density of the suture bone were significantly increased in the E + LF group compared with the EO group. Histochemical staining suggested that the activity of osteoblast-like cells and the amount of new bone formation were stimulated in the E + LF group whereas the activity of osteoclasts showed no obvious difference between groups. On the other hand, the immunohistochemical and the real-time polymerase chain reaction results showed that the expressions of receptor activator of nuclear factor kappa B ligand and osteoprotegerin had no significant difference between the EO and E + LF groups.

CONCLUSIONS

These findings demonstrated that LF could stimulate bone volume and bone density in midpalatal sutures during the suture remodeling process under tensile force. However, this enhancement effect was not caused by the reduction of bone resorption.

Erythropoietin and Nrf2: key factors in the neuroprotection provided by apo-lactoferrin

Among the properties of lactoferrin (LF) are bactericidal, antianemic, immunomodulatory, antitumour, antiphlogistic effects. Previously we demonstrated its capacity to stabilize in vivo HIF-1-alpha and HIF-2-alpha, which are redox-sensitive multiaimed transcription factors. Various tissues of animals receiving recombinant human LF (rhLF) responded by expressing the HIF-1-alpha target genes, hence such proteins as erythropoietin (EPO), ceruloplasmin, etc. were synthesized in noticeable amounts. Among organs in which EPO synthesis occurred were brain, heart, spleen, liver, kidneys and lungs. Other researchers showed that EPO can act as a protectant against severe brain injury and status epilepticus in rats. Therefore, we tried rhLF as a protector against the severe neurologic disorders developed in rats, such as the rotenone-induced model of Parkinson's disease and experimental autoimmune encephalomyelitis as a model of multiple sclerosis, and observed its capacity to mitigate the grave symptoms. Moreover, an intraperitoneal injection of rhLF into mice 1 h after occlusion of the medial cerebral artery significantly diminished the necrosis area measured on the third day in the ischaemic brain. During this period EPO was synthesized in various murine tissues. It was known that EPO induces nuclear translocation of Nrf2, which, like HIF-1-alpha, is a transcription factor. In view that under conditions of hypoxia both factors demonstrate a synergistic protective effect, we suggested that LF activates the Keap1/Nrf2 signaling pathway, an important link in proliferation and differentiation of normal and malignant cells. J774 macrophages were cultured for 3 days without or in the presence of ferric and ferrous ions (RPMI-1640 and DMEM/F12, respectively). Then cells were incubated with rhLF or Deferiprone. Confocal microscopy revealed nuclear translocation of Nrf2 (the key event in Keap1/Nrf2 signaling) induced by apo-rhLF (iron-free, RPMI-1640). The reference compound Deferiprone (iron chelator) had the similar effect. Upon iron binding (in DMEM/F12) rhLF did not activate the Keap1/Nrf2 pathway. Added to J774, apo-rhLF enhanced transcription of Nrf2-dependent genes coding for glutathione S-transferase P and heme oxygenase-1. Western blotting revealed presence of Nrf2 in mice brain after 6 days of oral administration of apo-rhLF, but not Fe-rhLF or equivalent amount of PBS. Hence, apo-LF, but not holo-LF, induces the translocation of Nrf2 from cytoplasm to the nucleus, probably due to its capacity to induce EPO synthesis.

Effects of Recombinant Human Lactoferrin on Osteoblast Growth and Bone Status in Piglets

Lactoferrin (LF), an ~80 kDa iron-binding glycoprotein, modulates many biological effects, including antimicrobial and immunomodulatory activities. Recently, it was shown that LF also regulates bone cell activity, suggesting its therapeutic effect on postmenopausal bone loss. However, a minimal amount is known regarding the effects of recombinant human LF (rhLF) supplementation on bone status in young healthy infants. We found osteoblast cell differentiation was significantly promoted in vitro. Furthermore, treatment of human osteoblast cells with rhLF rapidly induced phosphorylation of p44/p42 mitogen-activated protein kinase (p44/p42 MAPK, ERK1/2). In order to investigate the effects of rhLF on bone status in vivo, we used a piglet model, which is a useful model for human infants. Piglets were supplemented with rhLF milk for 30 days. Bone formation markers, Serum calcium concentration, bone mineral density (BMD), bone mineral content (BMC), tibia bone strength, and the overall metabolite profile analysis showed that rhLF was advantageous to the bone growth in piglets. These findings suggest that rhLF supplementation benefits neonate bone health by modulating bone formation.

Lactoferrin from Milk: Nutraceutical and Pharmacological Properties

Lactoferrin is an iron-binding protein present in large quantities in colostrum and in breast milk, in external secretions and in polymorphonuclear leukocytes. Lactoferrin's main function is non-immune protection. Among several protective activities shown by lactoferrin, those displayed by orally administered lactoferrin are: (i) antimicrobial activity, which has been presumed due to iron deprivation, but more recently attributed also to a specific interaction with the bacterial cell wall and extended to viruses and parasites; (ii) immunomodulatory activity, with a direct effect on the development of the immune system in the newborn, together with a specific antinflammatory effects; (iii) a more recently discovered anticancer activity. It is worth noting that most of the protective activities of lactoferrin have been found, sometimes to a greater extent, also in peptides derived from limited proteolysis of lactoferrin that could be generated after lactoferrin ingestion. Lactoferrin could therefore be considered an ideal nutraceutic product because of its relatively cheap production from bovine milk and of its widely recognized tolerance after ingestion, along with its well demonstrated protective activities. The most important protective activities shown by orally administered bovine lactoferrin are reviewed in this article.

Acute phase proteins as promising biomarkers: Perspectives and limitations for human and veterinary medicine

Acute phase proteins (APPs) are highly conserved plasma proteins that are increasingly secreted by the liver in response to a variety of injuries, independently of their location and cause. APPs favor the systemic regulation of defense, coagulation, proteolysis, and tissue repair. Various APPs have been applied as general diagnostic parameters for a long time. Through proteomic techniques, more and more APPs have been discovered to be differentially altered. Since they are not consistently explainable by a stereotypic hepatic expression of sets of APPs, most of these results have unfortunately been neglected or attributed to the nonspecificity of the acute phase reaction. Moreover, it appears that various extrahepatic tissues are also able to express APPs. These extrahepatic APPs show focally specific roles in tissue homeostasis and repair and are released primarily into interstitial and distal fluids. Since these focal proteins might leak into the circulatory system, mixtures of hepatic and extrahepatic APP species can be expected in blood. Hence, a selective alteration of parts of APPs might be expected. There are several hints on multiple molecular forms and fragments of tissue-derived APPs. These differences offer the chance for multiple selective determinations. Thus, specific proteoforms might indeed serve as tissue-specific disease indicators.

Coupling Hydroxyapatite Nanocrystals with Lactoferrin as a Promising Strategy to Fine Regulate Bone Homeostasis

Lactoferrin (LF) is an interesting glycoprotein in the field of bone biology for its regulatory effect on cells involved in bone remodeling, that results compromised in several pathological conditions, as osteoporosis. In a previous study we observed that the coupling of LF and biomimetic hydroxyapatite nanocrystals (HA), a material well-known for its bioactivity and osteoconductive properties, leads to a combined effect in the induction of osteogenic differentiation of mesenchymal stem cells. On the basis of this evidence, the present study is an extension of our previous work aiming to investigate the synergistic effect of the coupling of HA and LF on bone homeostasis. Biomimetic HA nanocrystals were synthesized and functionalized with LF (HA-LF) and then pre-osteoblasts (MC3T3-E1) and monocyte/macrophage cells lines (RAW 264.7), using as osteoclastogenesis in vitro model, were cultured separately or in co-culture in presence of HA-LF. The results clearly revealed that HA and LF act in synergism in the regulation of the bone homeostasis, working as anabolic factor for osteoblasts differentiation and bone matrix deposition, and as inhibitor of the osteoclast formation and activity.

Fe-bLf nanoformulation targets survivin to kill colon cancer stem cells and maintains absorption of iron, calcium and zinc

Aim: To validate the anticancer efficacy of alginate-enclosed, chitosan-conjugated, calcium phosphate, iron-saturated bovine lactoferrin (Fe-bLf) nanocarriers/nanocapsules (NCs) with improved sustained release and ability to induce apoptosis by downregulating survivin, as well as cancer stem cells. Materials & methods: The stability, nanotoxicity of the modified nanoformulation was evaluated and their anticancer efficacy was re-examined. Their mechanism of internalization was studied and we identified the role of various miRNAs in absorption of these NCs/iron in various body parts of mice. We determined the effect of these NCs on survivin, stem cell markers, red blood cell count, iron, calcium and zinc concentration in mice, determined the antiangiogenic properties of these NCs and studied their effect on cancer stem-like cells. Results: Spherical NCs (396.1 ± 27.2 nm) exceedingly reduced viability of Caco-2 cells (32 ± 2.83%). The NCs also showed effective internalization and reduction of cancer stem cell markers in triple-positive CD133, survivin and CD44 cancer stem-like cells. Mice treated with the NCs showed no nanotoxicity and did not develop any tumors in xenograft colon cancer models. We found that the serum iron, zinc and calcium absorption were increased. DMT1, LRP, transferrin and lactoferrin receptors were responsible for internalization of the NCs. Different miRNAs were responsible for iron regulation in different organs. Interestingly, NCs inhibited survivin and its different isoforms. Conclusion: Our results confirmed that NCs internalized and changed the expression of selected miRNAs that further enhanced their uptake. The NCs activated both extrinsic, as well as intrinsic apoptotic pathways to induce apoptosis by targeting survivin in cancer cells and cancer stem cells, without inducing any nonspecific nanotoxicity. Apart from inhibiting angiogenesis and stem cell markers, NCs also maintained iron and calcium levels.

Original submitted 4 May 2014; Revised submitted 25 June 2014

Lactoferrin Induces Osteoblast Growth through IGF-1R

Objectives. To investigate the role of the IGF-1R by which lactoferrin induces osteoblast growth. Methods. Osteoblast received 5 d lactoferrin intervention at a concentration of 0.1, 1, 10, 100, and 1000 μg/mL, and the IGF-1 and IGF-1R were detected using RT-PCR and western blot. The osteoblast into the control, 100 μg/mL lactoferrin, Neo-scramble (NS, empty vector), NS + 100 μg/mL lactoferrin, shIGF-1R and shIGF-1R + 100 μg/mL lactoferrin group. We test the apoptosis and proliferation and the level of PI3K and RAS in osteoblasts after 5 d intervention. Results. (1) 1, 10, 100, and 1000 μg/mL lactoferrin induced the expression of IGF-1 mRNA and protein. 10 μg/mL and 100 μg/mL lactoferrin induced the expression of IGF-1R mRNA and protein. (2) Lactoferrin (100 μg/mL) induced osteoblast proliferation while inhibiting apoptosis. Osteoblasts with silenced IGF-1R exhibited decreased proliferation but increased apoptosis. MMT staining and flow cytometry both indicated that there was no significant difference between the shIGF-1R group and the shIGF-1R + 100 μg/mL lactoferrin group. (3) Lactoferrin (100 μg/mL) induced PI3K and RAS phosphorylation and silence of IGF-1R resulted in decreased p-PI3K and p-RAS expression. Lactoferrin-treated shIGF-1R cells showed significantly higher level of p-PI3K and p-RAS when compared with shIGF-1R. Conclusion. Lactoferrin induced IGF-1/IGF-1R in a concentration-dependent manner. Lactoferrin promoted osteoblast proliferation while inhibiting apoptosis through IGF-1R. Lactoferrin activated PI3K and RAS phosphorylation via an IGF-1R independent pathway.

Effects of lactoferrin on intestinal epithelial cell growth and differentiation: an in vivo and in vitro study

This study was designed to analyse the effects of human (h) and bovine lactoferrin (bLF) on the growth and differentiation of intestinal cells using the mice model supplemented with Lactoferrin (LF) and the enterocyte-like model of Caco-2 cells which spontaneously differentiate after confluency. In mice, bLF supplementation increased jejunal villus height and the expression of several intestinal brush border membrane enzymes activities. Addition of bLF or hLF to undifferentiated Caco-2 cells was able to increase cell proliferation with confluency being reached more rapidly. Moreover, when Caco-2 cells were grown in the presence of LF for 3 weeks, brush-border membrane-associated enzyme activities i.e. sucrase, alkaline phosphatase and neutral aminopeptidase, as well as the L-glutamate transporter expression were all increased indicating an increased Caco-2 cell differentiation. Accordingly, cDNA Atlas array and Western blot analysis of cell cycle proteins shown a decreased expression of Cdck2 and an increased TAF1 expression; these proteins being implicated in the regulation of numerous genes related to cellular proliferation and differentiation. These modifications were associated with an inhibition of Caco-2 cell spontaneous apoptosis. Altogether, our results indicate that LF increase in vivo and in vitro enterocyte differentiation. In addition, LF was found to increase in vitro enterocyte proliferation resulting in higher cell density in cell flasks, an effect that was likely partly due to a reduction of the cellular apoptosis. The different stimulation patterns observed for the different parameters associated with cell differentiation in relationship with specific gene regulation is discussed.

Enzymatically cross-linked bovine lactoferrin as injectable hydrogel for cell delivery

Lactoferrin (LF), a 78 kDa glycoprotein, has recently been recognized as an effector molecule in the skeleton due to its ability to decrease osteoclastogenesis and increase osteoblast proliferation, survival, and differentiation. The objective of the study is to investigate the feasibility of developing an injectable hydrogel from bovine lactoferrin (bLF) as a cell delivery vehicle. The study demonstrated the feasibility of cross-linking tyramine substituted bLF in the presence of horse radish peroxidase and hydrogen peroxide (H2O2). The gel presented a mild environment to maintain mouse bone marrow-derived stromal cell (mBMSC) viability and proliferation. Stromal cells derived from multiple gene reporter transgenic mouse (Ibsp-Topaz/Dmp1-mCherry) line showed the ability of the cells to undergo osteogenic differentiation in the hydrogel when cultured in mineralization media. The cross-linked gel supported protein phosphorylation/de-phosphorylation in the encapsulated MC3T3-E1 cells. bLF and bLF gel also showed the ability to modulate growth factor production in mBMSCs.

Lactoferrin inhibits apoptosis through insulin-like growth factor I in primary rat osteoblasts

AIM

Excessive apoptosis of osteoblasts is the major cause of low bone mass, and bovine lactoferrin (bLF), an iron-binding glycoprotein, might protect osteoblastic cells from apoptosis induced by serum withdrawal. The aim of this study was to elucidate the mechanisms underlying the anti-apoptotic action of bLF in rat osteoblasts in vitro.

METHODS

Primary rat osteoblasts were incubated in the presence of varying concentrations of bLF for 24 h. The expression of insulin-like growth factor I (IGF-I) and IGF-I receptor (IGF-IR) was measured uisng RT-PCR and Western blotting. Cell apoptosis was examined with flow cytometry. siRNAs targeting IGF-I was used in this study.

RESULTS

Treatment of bLF (0.1-1000 μg/mL) dose-dependently increased the expression of IGF-I and IGF-IR in the osteoblasts. Treatment with bLF (10, 100 μg/mL) markedly inhibited the osteoblast apoptosis (with the rate of total apoptosis of 70% at 10 μg/mL), but the high concentration of bLF (1000 μg/mL) significantly promoted the osteoblast apoptosis. Knockdown of the IGF-I gene in osteoblasts with siRNA markedly increased the osteoblast apoptosis.

CONCLUSION

Lactoferrin (10 and 100 μg/mL) effectively inhibits apoptosis of primary rat osteoblasts by upregulating IGF-I expression.

Lactoferrin inhibits dexamethasone-induced chondrocyte impairment from osteoarthritic cartilage through up-regulation of extracellular signal-regulated kinase 1/2 and suppression of FASL, FAS, and Caspase 3

Dexamethasone (Dex) is commonly used for osteoarthritis (OA) with excellent anti-inflammatory and analgesic effect. However, Dex also has many side effects following repeated use over prolonged periods mainly through increasing apoptosis and inhibiting proliferation. Lactoferrin (LF) exerts significantly anabolic effect on many cells and little is known about its effect on OA chondrocytes. Therefore, the aim of this study is to investigate whether LF can inhibit Dex-induced OA chondrocytes apoptosis and explore its possible molecular mechanism involved in. MTT assay was used to determine the optimal concentration of Dex and recombinant human LF (rhLF) on chondrocytes at different time and dose points. Chondrocytes were then stimulated with Dex in the absence or presence of optimal concentration of rhLF. Cell proliferation and viability were evaluated using MTT and LIVE/DEAD assay, respectively. Cell apoptosis was evaluated by multi-parameter apoptosis assay kit using both confocal microscopy and flow cytometry, respectively. The expression of extracellular signal-regulated kinase (ERK), FAS, FASL, and Caspase-3 (CASP3) at the mRNA and protein levels were examined by real-time polymerase chain reaction (PCR) and immunocytochemistry, respectively. The optimal concentration of Dex (25 μg/ml) and rhLF (200 μg/ml) were chosen for the following experiments. rhLF significantly reversed the detrimental effect of Dex on chondrocytes proliferation, viability, and apoptosis. In addition, rhLF significantly prevented Dex-induced down-regulation of ERK and up-regulation of FAS, FASL, and CASP3. These findings demonstrated that rhLF acts as an anabolic effect on chondrocytes through significantly reversing Dex-induced chondrocytes apoptosis. This study may contribute to further investigating the clinical application of LF on OA.

Immunoexpression of lactoferrin in bone metastases and corresponding primary carcinomas

Although the immunohistochemical presence of lactoferrin (LF) in pathological neoplastic bone and cartilage samples has previously been studied, no data concerning the distribution of LF in bone metastases of cancers that have originated from different organs are available at present. Consequently, using a monoclonal antibody, we have investigated the immunohistochemical LF pattern in 50 formalin-fixed and paraffin-embedded samples of human bone metastases and their corresponding primary carcinoma tumours (breast, 8; prostate, 4; kidney, 4; lung, 3; colon-rectum, 2 and uterus, 4). Quantification of LF immunoreactivity was performed using an intensity distribution (ID) score. LF immuno staining with a variable ID score was encountered in 11/25 (44%) metastatic lesions. In particular, the LF immunoreactivity was identified with a percentage ranging from 50 to 75% of bone metastases due to prostatic, renal, uterine and colorectal carcinomas; the positivity decreased in breast carcinomas (37.5%) and was completely absent in lung cancers. No differences in the LF-ID score were observed between primary and metastatic neoplastic localisations. Additionally, no correlations were identified between LF immunoexpression and the other parameters tested, including the age and gender of patients. Regardless of the mechanism of action of LF in human malignant tumours, we identified LF immunohistochemical reproducibility at primary and metastatic sites. Therefore, we hypothesise that the presence of LF in native neoplastic carcinomatous clones is maintained in secondary bone metastatic deposits.

Evaluation of the bioactivity of recombinant human lactoferrins toward murine osteoblast-like cells for bone tissue engineering

Lactoferrin (LF), which belongs to the iron-binding transferrin family, is an important regulator of the levels of free iron in the body fluids. LF has raised significant interest as a bioactive protein due to its wide array of physiological effects on many different cell types, including osteoblasts and osteoclasts. The glycoprotein's degree of iron saturation has a pivotal influence on its physical structure. The objective of this study is to investigate the biological effects of apo (low iron saturation), pis (partially iron saturated), and holo (high iron saturation) recombinant human LF (rhLF) on MC3T3-E1 cells to identify the suitable candidate for bone tissue engineering application. Our studies demonstrated a dose-dependent mitogenic response of MC3T3 to rhLF treatment irrespective of the iron concentration. Furthermore, rhLF induced the cells to produce transcription factors, chemokines, and cytokines as determined by β-catenin activation, phosphorylation of Akt, vascular endothelial growth factor, and interleukin (IL-6) expression. The iron saturation of rhLF did not have any significant effect on these biological activities of MC3T3 cells. In addition, the overall pattern of gene regulation in MC3T3-E1 cells upon rhLF treatment was followed by a global microarray analysis. Among the 45,200 genes tested, only 251 genes were found to be regulated by rhLFs of different iron concentrations. Of these, the transferrin receptor (Tfrc) was the only gene differentially regulated by the iron saturated and iron depleted (apo) rhLFs. In conclusion, the study demonstrated that rhLF is a bioactive protein and that the iron saturation of rhLF may not play a significant role in modulating osteoblast functions.

An energetic orphan in an endocrine tissue: a revised perspective of the function of estrogen receptor-related receptor alpha in bone and cartilage

Estrogen receptor-related receptor alpha (ERRα) is an orphan nuclear receptor with sequence homology to the estrogen receptors, ERα/β, but it does not bind estrogen. ERRα not only plays a functional role in osteoblasts but also in osteoclasts and chondrocytes. In addition, the ERRs, including ERRα, can be activated by coactivators such as peroxisome proliferator-activated receptor-gamma coactivator-1 (PGC1α and β) and are implicated in adipogenesis, fatty acid oxidation, and oxidative stress defense, suggesting that ERRα-through its activity in bone resorption and adipogenesis--may regulate the insulin and leptin pathways and contribute to aging-related changes in bone and cartilage. In this review, we discuss data on ERRα and its cellular and molecular modes of action, which have broad implications for considering the potential role of this orphan receptor in cartilage and bone endocrine function, on whole-organism physiology, and in the bone aging process.

Molecular mechanisms involved in the mitogenic effect of lactoferrin in osteoblasts

Lactoferrin, an iron-binding glycoprotein present in milk and other exocrine secretions in mammals, is anabolic to bone at physiological concentrations. Lactoferrin stimulates the proliferation, differentiation and survival of osteoblasts, as well as potently inhibiting osteoclastogenesis in bone marrow cultures. In the current study we further investigated the mechanism of action of lactoferrin in osteoblasts. We used low-density arrays to measure the level of expression of 45 genes in MC3T3-E1 osteoblast-like cells treated with lactoferrin, and identified transient, dose-dependent increases in the transcription levels of interleukin-6, of the pro-inflammatory factor prostaglandin-endoperoxide synthase 2 (Ptgs2), and of the transcription factor nuclear factor of activated T cells (Nfatc1). We demonstrated similar changes in primary osteoblast cultures from human and rat. Levels of prostaglandin E2 were increased in conditioned media collected from osteoblasts treated with lactoferrin, indicating that the activity of the enzyme cyclooxygenase 2 (COX2), which is encoded by Ptgs2, was also up-regulated. Using a luciferase reporter construct we showed that lactoferrin induced transcription from the NFAT consensus sequence. We found that inhibiting either COX2 or NFATc1 activity blocked the mitogenic effect of lactoferrin in osteoblasts and that inhibition of NFATc1 activity partially blocked the transcriptional activation of Ptgs2. Our study has provided the first evidence that COX2 and NFATc1 activities are increased by lactoferrin, and demonstrated a role for each of these molecules as mediators of the mitogenic effects of lactoferrin in osteoblasts.

Lactoferrin in human tumours: immunohistochemical investigations during more than 25 years

Lactoferrin (LF) is an iron-binding glycoprotein of the transferrin family, today known to have multifunctional physiological activities. In humans, under normal conditions, LF has been found in blood, mucosal secretions, gastrointestinal fluids, urine and mostly in milk and colostrum. The first pioneering immunohistochemical report about LF distribution in human tissues dated in 1978; successively, many studies have been performed to analyze the LF immunohistochemical pattern in different normal and neoplastic tissues. In this review, we present data from literature concerning the evidence of LF in tumors together with those by us obtained during more than 25 years; the immunohistochemical applications to human neoplastic tissues have been done to investigate the LF pathogenetic role as well as its activity in cancer. After a systematic analysis of LF immunoreactivity in different human districts, a possible explanation for its presence and function has been modulated for each site or tissue, according to experimental evidences obtained either by in vivo as well as by in vitro studies.

Immunohistochemical evidence of lactoferrin in human embryo-fetal bone and cartilage tissues

Lf (lactoferrin) is an 80-kDa iron-binding protein, which has been suggested to promote bone growth in murine models. In view of this, we aimed to analyse the immunohistochemical distribution of Lf in human embryonal and fetal bone and cartilaginous tissues at different gestational weeks in order to evaluate whether a role for this protein might be proposed also in human osteogenesis. Bone and cartilaginous specimens were taken at autopsy from 25 fetuses (8-34 weeks of gestation). Ten samples of human adult bone and cartilage were also submitted to the immunohistochemical procedures. Sections, 4-microm thick, were cut from formalin-fixed paraffin-embedded tissue blocks and stained with a monoclonal antibody against human Lf, following antigen retrieval procedures. Lf immunoreactivity was mainly localized in the mesenchymal cells forming the periosteum as well as in chondroblasts at the eighth gestational week; a strong Lf immunoexpression in immature osteocytes and osteoblasts was noted up to the 18th gestation week, with a considerable decrease by the 24th week. No Lf expression was found in any bone area after the 30th and up to the 34th week of gestation. Our data seem to suggest an important role for Lf as a bone growth regulator in the early phases of the human endochondral ossification, with an anabolic action similar to that previously reported in cell culture lines and in animal models.