Anabolic effects of IGF-1 signaling on the skeleton

Regulation of bone homeostasis: signaling pathways and therapeutic targets

As a highly dynamic tissue, bone is continuously rebuilt throughout life. Both bone formation by osteoblasts and bone resorption by osteoclasts constitute bone reconstruction homeostasis. The equilibrium of bone homeostasis is governed by many complicated signaling pathways that weave together to form an intricate network. These pathways coordinate the meticulous processes of bone formation and resorption, ensuring the structural integrity and dynamic vitality of the skeletal system. Dysregulation of the bone homeostatic regulatory signaling network contributes to the development and progression of many skeletal diseases. Significantly, imbalanced bone homeostasis further disrupts the signaling network and triggers a cascade reaction that exacerbates disease progression and engenders a deleterious cycle. Here, we summarize the influence of signaling pathways on bone homeostasis, elucidating the interplay and crosstalk among them. Additionally, we review the mechanisms underpinning bone homeostatic imbalances across diverse disease landscapes, highlighting current and prospective therapeutic targets and clinical drugs. We hope that this review will contribute to a holistic understanding of the signaling pathways and molecular mechanisms sustaining bone homeostasis, which are promising to contribute to further research on bone homeostasis and shed light on the development of targeted drugs.

Bone-organ axes: bidirectional crosstalk

In addition to its recognized role in providing structural support, bone plays a crucial role in maintaining the functionality and balance of various organs by secreting specific cytokines (also known as osteokines). This reciprocal influence extends to these organs modulating bone homeostasis and development, although this aspect has yet to be systematically reviewed. This review aims to elucidate this bidirectional crosstalk, with a particular focus on the role of osteokines. Additionally, it presents a unique compilation of evidence highlighting the critical function of extracellular vesicles (EVs) within bone-organ axes for the first time. Moreover, it explores the implications of this crosstalk for designing and implementing bone-on-chips and assembloids, underscoring the importance of comprehending these interactions for advancing physiologically relevant in vitro models. Consequently, this review establishes a robust theoretical foundation for preventing, diagnosing, and treating diseases related to the bone-organ axis from the perspective of cytokines, EVs, hormones, and metabolites.

The potential benefits and mechanisms of protein nutritional intervention on bone health improvement

Osteoporosis commonly occurs in the older people and severe patients, with the main reason of the imbalance of bone metabolism (the rate of bone resorption exceeding the rate of bone formation), resulting in a decrease in bone mineral density and destruction of bone microstructure and further leading to the increased risk of fragility fracture. Recent studies indicate that protein nutritional support is beneficial for attenuating osteoporosis and improving bone health. This review summarized the classical mechanisms of protein intervention for alleviating osteoporosis on both suppressing bone resorption and regulating bone formation related pathways (promoting osteoblasts generation and proliferation, enhancing calcium absorption, and increasing collagen and mineral deposition), as well as the potential novel mechanisms via activating autophagy of osteoblasts, altering bone related miRNA profiles, regulating muscle-bone axis, and modulating gut microbiota abundance. Protein nutritional intervention is expected to provide novel approaches for the prevention and adjuvant therapy of osteoporosis.

Interplay Between Skeletal and Hematopoietic Cells in the Bone Marrow Microenvironment in Homeostasis and Aging

PURPOSE OF THE REVIEW

In this review, we discuss the most recent scientific advances on the reciprocal regulatory interactions between the skeletal and hematopoietic stem cell niche, focusing on immunomodulation and its interplay with the cell's mitochondrial function, and how this impacts osteoimmune health during aging and disease.

RECENT FINDINGS

Osteoimmunology investigates interactions between cells that make up the skeletal stem cell niche and immune system. Much work has investigated the complexity of the bone marrow microenvironment with respect to the skeletal and hematopoietic stem cells that regulate skeletal formation and immune health respectively. It has now become clear that these cellular components cooperate to maintain homeostasis and that dysfunction in their interaction can lead to aging and disease. Having a deeper, mechanistic appreciation for osteoimmune regulation will lead to better research perspective and therapeutics with the potential to improve the aging process, skeletal and hematologic regeneration, and disease targeting.

Gut development following insulin-like growth factor-1 supplementation to preterm pigs

BACKGROUND

Reduced insulin-like growth factor-1 (IGF-1) levels may contribute to impaired organ development in preterm infants. Using preterm pigs as a model, we hypothesized that IGF-1 supplementation improves health and gut development during the first three weeks of life.

METHODS

First, clinical and organ endpoints were compared between artificially-reared, cesarean-delivered preterm pigs and vaginally-delivered, sow-reared term pigs at 5, 9 and 19 days. Next, preterm pigs were treated with recombinant human IGF-1 for 19 days (2.25 mg/kg/day, systemically).

RESULTS

Relative to term pigs, preterm pigs had lower body weight, fat, bone contents, relative weights of liver and spleen and a longer and thinner intestine at 19 days. Preterm birth reduced intestinal villi heights and peptidase activities, but only at 5 and 9 days. In preterm pigs, IGF-1 reduced mortality primarily occurring from gastrointestinal complications and with a tendency towards salvaging smaller pigs. IGF-1 supplementation also increased spleen and kidney weights, small intestine length and maltase to lactase activity, reflecting gut maturation.

CONCLUSION

Preterm birth affects body composition and gut maturation in the first 1-2 weeks, but differences are marginal thereafter. Supplemental IGF-1 may improve gut health in pigs and infants in the first few weeks after preterm birth.

IMPACT

Insulin-like growth factor 1 (IGF-1) supplementation may improve gut health and development in prematurity, but whether the effects are sustained beyond the immediate postnatal period is unclear. In preterm pigs, the prematurity effects on IGF-1 and gut health deficiencies are most pronounced during the first week of life and diminishes thereafter. In preterm pigs, IGF-1 supplementation beyond the first week of life reduced mortality. The present study provides evidence of a sustained effect of IGF-1 supplementation on the gastrointestinal tract after the immediate postnatal period.

Alteration in the gut microbiome is associated with changes in bone metabolism after laparoscopic sleeve gastrectomy

Laparoscopic sleeve gastrectomy (LSG), the most common bariatric surgical procedure, leads to durable weight loss and improves obesity-related comorbidities. However, it induces abnormalities in bone metabolism. One unexplored potential contributor is the gut microbiome, which influences bone metabolism and is altered after surgery. We characterized the relationship between the gut microbiome and skeletal health in severe obesity and after LSG. In a prospective cohort study, 23 adults with severe obesity underwent skeletal health assessment and stool collection preoperatively and 6 mo after LSG. Gut microbial diversity and composition were characterized using 16S rRNA gene sequencing, and fecal concentrations of short-chain fatty acids (SCFA) were measured with LC-MS/MS. Spearman's correlations and PERMANOVA analyses were applied to assess relationships between the gut microbiome and bone health measures including serum bone turnover markers (C-terminal telopeptide of type 1 collagen [CTx] and procollagen type 1 N-terminal propeptide [P1NP]), areal BMD, intestinal calcium absorption, and calciotropic hormones. Six months after LSG, CTx and P1NP increased (by median 188% and 61%, P < .01) and femoral neck BMD decreased (mean -3.3%, P < .01). Concurrently, there was a decrease in relative abundance of the phylum Firmicutes. Although there were no change in overall microbial diversity or fecal SCFA concentrations after LSG, those with greater within-subject change in gut community microbial composition (β-diversity) postoperatively had greater increases in P1NP level (ρ = 0.48, P = .02) and greater bone loss at the femoral neck (ρ = -0.43, P = .04). In addition, within-participant shifts in microbial richness/evenness (α-diversity) were associated with changes in IGF-1 levels (ρ = 0.56, P < .01). The lower the postoperative fecal butyrate concentration, the lower the IGF-1 level (ρ = 0.43, P = .04). Meanwhile, the larger the decrease in butyrate concentration, the higher the postoperative CTx (ρ = -0.43, P = .04). These findings suggest that LSG-induced gut microbiome alteration may influence skeletal outcomes postoperatively, and microbial influences on butyrate formation and IGF-1 are possible mechanisms.

Advances in the role and mechanism of fibroblasts in fracture healing

With the development of social population ageing, bone fracture has become a global public health problem due to its high morbidity, disability and mortality. Fracture healing is a complex phenomenon involving the coordinated participation of immigration, differentiation and proliferation of inflammatory cells, angioblasts, fibroblasts, chondroblasts and osteoblasts which synthesize and release bioactive substances of extracellular matrix components, Mortality caused by age-related bone fractures or osteoporosis is steadily increasing worldwide as the population ages. Fibroblasts play an important role in the process of fracture healing. However, it is not clear how the growth factors and extracellular matrix stiffness of the bone-regeneration microenvironment affects the function of osteoblasts and fibroblasts in healing process. Therefore, this article focuses on the role of fibroblasts in the process of fracture healing and mechanisms of research progress.

The effect of overweight or obesity on osteoporosis: A systematic review and meta-analysis

BACKGROUND

Osteoporosis and obesity are closely related, and the relationships between different types of obesity and osteoporosis are inconsistent.

OBJECTIVE

Our objective was to summarize earlier data concerning the association between osteoporosis and obesity (general and central), and to compare the impacts of these two obesity indicators on osteoporosis.

METHODS

From inception to May 2021, a comprehensive search in electronic bibliographic databases was conducted, and the search was updated in December 2021, July 2022 and June 2023. The data were independently extracted and evaluated by two investigators from epidemiological studies that reported the impact of obesity on the odds of incident osteoporosis.

RESULTS

There were 24 studies included in the final analysis when it came to general obesity measured by body mass index (BMI). Individuals with overweight and obesity had decreased odds of osteoporosis (odds ratio (OR), 0.451, 95% confidence intervals (CIs): 0.366-0.557). Sensitivity analyses showed that both overweight and obesity were decreased odds of osteoporosis, with reductions of 48.6% and 70.1%, respectively (OR, 0.514, 95% CI: 0.407-0.649; OR, 0.299, 95% CI: 0.207-0.433). Conversely, individuals classified as underweight were found to have higher odds of osteoporosis (OR, 2.540, 95% CI: 1.483-4.350). In term of central obesity, the final analysis consisted of 7 studies. No significant association was observed between central obesity and osteoporosis (OR, 0.913, 95% CI: 0.761-1.096).

CONCLUSIONS

General overweight and obesity were associated with lower odds of developing osteoporosis, whereas underweight was associated with higher odds. However, central obesity did not show a significant association with osteoporosis. These findings underscore the importance of considering the impact of obesity on osteoporosis. Further research is necessary to reinforce the evidence and validate our findings.

Association of Pooled Fecal Microbiota on Height Growth in Children According to Enterotypes

OBJECTIVES

The association between fecal microbiota and height in children has yielded conflicting findings, warranting further investigation into potential differences in fecal bacterial composition between children with short stature and those of standard height based on enterotypes (ETs).

METHODS

According to the height z score for age and gender, the children were categorized into normal-stature (NS; n = 335) and short-stature (SS; n = 152) groups using a z score of -1.15 as a separator value. The human fecal bacterial FASTA/Q files (n = 487) were pooled and analyzed with the QIIME 2 platform with the National Center for Biotechnology Information alignment search tool. According to ETs, the prediction models by the machine learning algorithms were used for explaining SS, and their quality was validated.

RESULTS

The proportion of SS was 16.4% in ET Enterobacteriaceae (ET-E) and 68.1% in Prevotellaceae (ET-P). The Chao1 and Shannon indexes were significantly lower in the SS than in the NS groups only in ET-P. The fecal bacteria related to SS from the prediction models were similar regardless of ETs. However, in network analysis, the negative correlations between fecal bacteria in the NS and SS groups were much higher in the ET-P than in the ET-E. In the metagenome function, fecal bacteria showed an inverse association of biotin and secondary bile acid synthesis and downregulation of insulin/insulin-like growth factor-1-driven phosphoinositide 3-kinase Akt signaling and AMP-kinase signaling in the SS group compared with the NS group in both ETs.

CONCLUSION

The gut microbial compositions in children were associated with height. Strategies to modify and optimize the gut microbiota composition should be investigated for any potential in promoting height in children.

Stem cell-based strategies and challenges for production of cultivated meat

Cultivated meat scale-up and industrial production will require multiple stable cell lines from different species to recreate the organoleptic and nutritional properties of meat from livestock. In this Review, we explore the potential of stem cells to create the major cellular components of cultivated meat. By using developments in the fields of tissue engineering and biomedicine, we explore the advantages and disadvantages of strategies involving primary adult and pluripotent stem cells for generating cell sources that can be grown at scale. These myogenic, adipogenic or extracellular matrix-producing adult stem cells as well as embryonic or inducible pluripotent stem cells are discussed for their proliferative and differentiation capacity, necessary for cultivated meat. We examine the challenges for industrial scale-up, including differentiation and culture protocols, as well as genetic modification options for stem cell immortalization and controlled differentiation. Finally, we discuss stem cell-related safety and regulatory challenges for bringing cultivated meat to the marketplace.

Beneficial Effects of Asparagus officinalis Extract Supplementation on Muscle Mass and Strength following Resistance Training and Detraining in Healthy Males

The phytoecdysteroid 20-hydroxyecdysone (20E) is widely used for resistance training (RT). Little is known about its potential ergogenic value and detraining effects post-RT. This study aimed to examine the effects of 20E extracted from Asparagus officinalis (A. officinalis) on muscle strength and mass, as well as anabolic and catabolic hormones following RT and detraining. Twenty males, aged 20.1 ± 1.1 years, were matched and randomly assigned to consume double-blind supplements containing either a placebo (PLA) or 30 mg/day of 20E for 12 weeks of RT and detraining. Before and after RT and detraining, muscle strength and mass and anabolic and catabolic hormones were measured. This study found that 20E reduced cortisol levels significantly (p < 0.05) compared to the PLA, yet no effect was observed on muscle mass, strength, or anabolic hormones after RT. Subsequent to 6 weeks of detraining, the 20E demonstrated a lower percentage change in 1RM bench press/FFM than the PLA (p < 0.05). Compared to the PLA, detraining throughout the 12 weeks resulted in a lower percentage change in thigh (p < 0.05) and chest (p < 0.01) circumferences, as well as reduced cortisol levels (p < 0.01), with 20E. Our findings demonstrate that 20E supplementation is a promising way to maintain muscle mass and strength during detraining. Accordingly, 20E may prevent muscle mass and strength loss due to detraining by lowering catabolic hormone levels.

TMT-Based Quantitative Proteomics Analysis Reveals Differentially Expressed Proteins between Different Sources of hMSCs

Mesenchymal stem cells (MSCs) are an attractive therapeutic tool for tissue engineering and regenerative medicine owing to their regenerative and trophic properties. The best-known and most widely used are bone marrow MSCs, which are currently being harvested and developed from a wide range of adult and perinatal tissues. MSCs from different sources are believed to have different secretion potentials and production, which may influence their therapeutic effects. To confirm this, we performed a quantitative proteomic analysis based on the TMT technique of MSCs from three different sources: Wharton's jelly (WJ), dental pulp (DP), and bone marrow (BM). Our analysis focused on MSC biological properties of interest for tissue engineering. We identified a total of 611 differentially expressed human proteins. WJ-MSCs showed the greatest variation compared with the other sources. WJ produced more extracellular matrix (ECM) proteins and ECM-affiliated proteins and proteins related to the inflammatory and immune response processes. BM-MSCs expressed more proteins involved in osteogenic, adipogenic, neuronal, or muscular differentiation and proteins involved in paracrine communication. Compared to the other sources, DP-MSCs overexpressed proteins involved in the exocytosis process. The results obtained confirm the existence of differences between WJ, DP, and BM-MSCs and the need to select the MSC origin according to the therapeutic objective sought.

Case report: Transcatheter tricuspid valve-in-valve implantation using novel balloon-expandable aortic valve with 1 year follow-up

Generally, the dysfunction or failure of bioprosthetic heart valves (BHVs) is managed by replacement surgery. In the case of tricuspid valve dysfunction, re-do surgery is rarely attempted because of the critically high risk of developing pulmonary hypertension, pulmonary embolism, and intraoperative mortality. Hence, transcatheter tricuspid repair and replacement procedures are preferred. More recently, transcatheter valve-in-valve (ViV) treatments have gained importance because of their less invasiveness, especially for patients with prior surgeries. Encouraging evidence of the safety and effectiveness of a novel balloon-expandable (BE) transcatheter heart valve (THV)-the Myval THV-has been reported for ViV procedures. Here, we present a case-series of 5 patients, in whom tricuspid ViV procedure was performed using BE Myval THV, implanted supra-annularly by anchoring onto the deteriorated BHV. This case-series details the procedural steps to prevent in-hospital adverse events and early (30-day) mortality and the challenges during tricuspid ViV interventions.

Local Concentrations of TGF-β1 and IGF-1 Appear Determinant in Regulating Bone Regeneration in Human Postextraction Tooth Sockets

Healing after tooth extraction involves a series of reparative processes affecting both alveolar bone and soft tissues. The aim of the present study was to investigate whether activation of molecular signals during the healing process confers a regenerative advantage to the extraction socket soft tissue (ESsT) at 8 weeks of healing. Compared to subepithelial connective tissue graft (CTG), qRT-PCR analyses revealed a dramatic enrichment of the ESsT in osteogenic differentiation markers. However, ESsT and CTG shared characteristics of nonspecialized soft connective tissue by expressing comparable levels of genes encoding abundant extracellular matrix (ECM) proteins. Genes encoding the transforming growth factor-β1 (TGF-β1) and its receptors were strongly enriched in the CTG, whereas the transcript for the insulin-like growth factor-1 (IGF-1) showed significantly high and comparable expression in both tissues. Mechanical stimulation, by the means of cyclic strain or matrix stiffness applied to primary ESsT cells (ESsT-C) and CTG fibroblasts (CTG-F) extracted from the tissue samples, revealed that stress-induced TGF-β1 not exceeding 2.3 ng/mL, as measured by ELISA, in combination with IGF-1 up to 2.5 ng/mL was able to induce the osteogenic potential of ESsT-Cs. However, stiff matrices (50 kPa), upregulating the TGF-β1 expression up to 6.6 ng/mL, caused downregulation of osteogenic gene expression in the ESsT-Cs. In CTG-Fs, endogenous or stress-induced TGF-β1 ≥ 4.6 ng/mL was likely responsible for the complete lack of osteogenesis. Treatment of ESsT-Cs with TGF-β1 and IGF-1 proved that, at specific concentrations, the two growth factors exhibited either an inductive-synergistic or a suppressive activity, thus determining the osteogenic and mineralization potential of ESsT-Cs. Taken together, our data strongly warrant the clinical exploration of ESsT as a graft in augmentative procedures during dental implant placement surgeries.

Repurposing existing products to accelerate injury recovery (REPAIR) of military relevant musculoskeletal conditions

Musculoskeletal injuries (MSKIs) are a great hindrance to the readiness of the United States Armed Forces through lost duty time and reduced operational capabilities. While most musculoskeletal injuries result in return-to-duty/activity with no (functional) limitations, the healing process is often long. Long healing times coupled with the high frequency of musculoskeletal injuries make them a primary cause of lost/limited duty days. Thus, there exists an urgent, clinically unmet need for interventions to expedite tissue healing kinetics following musculoskeletal injuries to lessen their impact on military readiness and society as a whole. There exist several treatments with regulatory approval for other indications that have pro-regenerative/healing properties, but few have an approved indication for treating musculoskeletal injuries. With the immediate need for treatment options for musculoskeletal injuries, we propose a paradigm of Repurposing Existing Products to Accelerate Injury Recovery (REPAIR). Developing treatments via repurposing existing therapeutics for other indications has shown monumental advantages in both cost effectiveness and reduced time to bring to market compared to novel candidates. Thus, undertaking the needed research efforts to evaluate the effectiveness of promising REPAIR-themed candidates has the potential to enable near-term solutions for optimizing musculoskeletal injuries recovery, thereby addressing a top priority within the United States. Armed Forces. Herein, the REPAIR paradigm is presented, including example targets of opportunity as well as practical considerations for potential technical solutions for the translation of existing therapeutics into clinical practice for musculoskeletal injuries.

CXCR4 mediates the effects of IGF-1R signaling in rodent bone homeostasis and fracture repair

Non-union fractures have considerable clinical and economic burdens and yet the underlying pathogenesis remains largely undetermined. The fracture healing process involves cellular differentiation, callus formation and remodeling, and implies the recruitment and differentiation of mesenchymal stem cells that are not fully characterized. C-X-C chemokine receptor 4 (CXCR4) and Insulin-like growth factor 1 receptor (IGF-1R) are expressed in the fracture callus, but their interactions still remain elusive. We hypothesized that the regulation of CXCR4 by IGF-1R signaling is essential to maintain the bone homeostasis and to promote fracture repair. By using a combination of in vivo and in vitro approaches, we found that conditional ablation of IGF-1R in osteochondroprogenitors led to defects in bone formation and mineralization that associated with altered expression of CXCR4 by a discrete population of endosteal cells. These defects were corrected by AMD3100 (a CXCR4 antagonist). Furthermore, we found that the inducible ablation of IGF-1R in osteochondroprogenitors led to fracture healing failure, that associated with an altered expression of CXCR4. In vivo AMD3100 treatment improved fracture healing and normalized CXCR4 expression. Moreover, we determined that these effects were mediated through the IGF-1R/Insulin receptor substrate 1 (IRS-1) signaling pathway. Taken together, our studies identified a novel population of endosteal cells that is functionally regulated through the modulation of CXCR4 by IGF-1R signaling, and such control is essential in bone homeostasis and fracture healing. Knowledge gained from these studies has the potential to accelerate the development of novel therapeutic interventions by targeting CXCR4 signaling to treat non-unions.

Effects of 18 Months of Growth Hormone Replacement Therapy on Bone Mineral Density in Patients with Adult Growth Hormone Deficiency: A Retrospective Study

OBJECTIVE

The effect of physiological dose growth hormone (GH) replacement therapy on bone mineral density (BMD) in adults with growth hormone deficiency (GHD) is not well defined. We aimed to investigate the effects of 18 months of treatment with recombinant human growth hormone (rhGH) at physiological doses on BMD, body composition (BC), and quality of life (QoL).

METHODS

Sixty-eight patients diagnosed with adult growth hormone deficiency (AGHD) in our hospital were included in this retrospective study. All patients received individualized rhGH replacement to maintain normal serum insulin-like growth factor-1 (IGF-1) levels. BMD and BC measurements were performed by dual energy X-ray absorptiometry (DXA). Excluding those with incomplete follow-up data, we analyzed BMD in 68 patients, as well as BC and QoL in 36 of them.

RESULTS

Compared with the baseline, lumbar spine BMD decreased by 0.008 g/cm² (P=0.006) and increased by 0.011 g/cm² (P=0.045) at month 18, and total hip BMD decreased by 0.005 g/cm² (P=0.008) and did not change significantly from the baseline at month 18. The changes in BMD did not differ by sex, and the increase in BMD was more pronounced in patients with low Z-scores at the baseline (lumbar spine: P=0.005 and total hip: P=0.018). The percentage change from the baseline in BMD was greater for the lumbar spine than for the total hip (P=0.003). Lean body mass (LBM) increased significantly (P=0.012), total body fat ratio (TBF%) decreased significantly (P=0.011), visceral adipose tissue (VAT) decreased significantly (P=0.016), and QoL improved significantly (P < 0.001).

CONCLUSIONS

Within 18 months of treatment, bone resorption manifested first, BMD decreased to a nadir at month 6, and then it increased. The increase in BMD was greater in the lumbar spine than in the hip, and the increase was more pronounced in patients with low BMD. Eighteen months of rhGH replacement therapy significantly improved lumbar spine BMD and improved BC and QoL.

IGF1 deficiency integrates stunted growth and neurodegeneration in Down syndrome

Down syndrome (DS), the genetic condition caused by trisomy 21 (T21), is characterized by stunted growth, cognitive impairment, and increased risk of diverse neurological conditions. Although signs of lifelong neurodegeneration are well documented in DS, the mechanisms underlying this phenotype await elucidation. Here we report a multi-omics analysis of neurodegeneration and neuroinflammation biomarkers, plasma proteomics, and immune profiling in a diverse cohort of more than 400 research participants. We identified depletion of insulin growth factor 1 (IGF1), a master regulator of growth and brain development, as the top biosignature associated with neurodegeneration in DS. Individuals with T21 display chronic IGF1 deficiency downstream of growth hormone production, associated with a specific inflammatory profile involving elevated tumor necrosis factor alpha (TNF-α). Shorter children with DS show stronger IGF1 deficiency, elevated biomarkers of neurodegeneration, and increased prevalence of autism and other conditions. These results point to disruption of IGF1 signaling as a potential contributor to stunted growth and neurodegeneration in DS.

Osteoclasts: Other functions

Osteoclasts are the only cells that can efficiently resorb bone. They do so by sealing themselves on to bone and removing the mineral and organic components. Osteoclasts are essential for bone homeostasis and are involved in the development of diseases associated with decreased bone mass, like osteoporosis, or abnormal bone turnover, like Paget's disease of bone. In addition, compromise of their development or resorbing machinery is pathogenic in multiple types of osteopetrosis. However, osteoclasts also have functions other than bone resorption. Like cells of the innate immune system, they are derived from myeloid precursors and retain multiple immune cell properties. In addition, there is now strong evidence that osteoclasts regulate osteoblasts through a process known as coupling, which coordinates rates of bone resorption and bone formation during bone remodeling. In this article we review the non-resorbing functions of osteoclasts and highlight their importance in health and disease.

Bone loss is ameliorated by fecal microbiota transplantation through SCFA/GPR41/ IGF1 pathway in sickle cell disease mice

Bone loss is common in sickle cell disease (SCD), but the molecular mechanisms is unclear. Serum insulin-like growth factor 1 (IGF1) was low in SCD subjects and SCD mice. To determine if decreased IGF1 associated with low bone mass in SCD is due to reduced SCFA production by gut microbiota, we performed reciprocal fecal microbiota transplantation (FMT) between healthy control (Ctrl) and SCD mice. uCT and histomorphometry analysis of femur showed decreased bone volume/total volume (BV/TV), trabecular number (Tb.N), osteoblast surface/bone surface (Ob.S/BS), mineralizing surface/ bone surface (MS/BS), inter-label thickness (Ir.L.Th) in SCD mice were significantly improved after receiving Ctrl feces. Bone formation genes Alp, Col1, Runx2, and Dmp1 from SCD mice were significantly decreased and were rescued after FMT from Ctrl feces. Transplantation of Ctrl feces increased the butyrate, valerate, and propionate levels in cecal content of SCD mice. Decreased G-coupled protein receptors 41 and 43 (GPR41 and GPR43) mRNA in tibia and lower IGF1 in bone and serum of SCD mice were partially restored after FMT from Ctrl feces. These data indicate that the healthy gut microbiota of Ctrl mice is protective for SCD bone loss through regulating IGF1 in response to impaired bacterial metabolites SCFAs.

McCune-Albright Syndrome in Infant with Growth Hormone Excess

Background: McCune-Albright is a rare syndrome, caused by mutation of the GNAS1 gene, and is characterized by an appearance of multiple endocrinopathies, most commonly premature puberty, polyostotic fibrous dysplasia and skin changes called cafe au lait macules. Case report: We present the case of a patient who is, to the best of our knowledge and after extensive review of literature, the youngest McCune-Albright syndrome patient with growth hormone excess, diagnosed at 8.9 months of age. An extensive diagnostic procedure was done upon the diagnosis. Hormonal assessment was performed and all hormone levels were within reference range, and an additional oral glucose suppression that noted the presence of growth hormone excess. Magnetic resonance imaging of the pituitary gland did not detect a tumor process. The genetic analysis of the GNAS1 gene from skin punch biopsy came back negative. Octreotide was administered as therapy for growth hormone excess at 9.8 months. After the introduction of therapy, we noted a decrease in growth rate from 29.38 to 16.6 cm/year. Conclusion: This case report emphasizes the lack of available data on treatment of growth hormone excess and follow-up in pediatric population and the need for further research.

Cationic peptide carriers enable long-term delivery of insulin-like growth factor-1 to suppress osteoarthritis-induced matrix degradation

Background

Insulin-like growth factor-1 (IGF-1) has the potential to be used for osteoarthritis (OA) treatment but has not been evaluated in clinics yet owing to toxicity concerns. It suffers from short intra-joint residence time and a lack of cartilage targeting following its intra-articular administration. Here, we synthesize an electrically charged cationic formulation of IGF-1 by using a short-length arginine-rich, hydrophilic cationic peptide carrier (CPC) with a net charge of +14, designed for rapid and high uptake and retention in both healthy and arthritic cartilage.

Methods

IGF-1 was conjugated to CPC by using a site-specific sulfhydryl reaction via a bifunctional linker. Intra-cartilage depth of penetration and retention of CPC-IGF-1 was compared with the unmodified IGF-1. The therapeutic effectiveness of a single dose of CPC-IGF-1 was compared with free IGF-1 in an IL-1α-challenged cartilage explant culture post-traumatic OA model.

Results

CPC-IGF-1 rapidly penetrated through the full thickness of cartilage creating a drug depot owing to electrostatic interactions with negatively charged aggrecan-glycosaminoglycans (GAGs). CPC-IGF-1 remained bound within the tissue while unmodified IGF-1 cleared out. Treatment with a single dose of CPC-IGF-1 effectively suppressed IL-1α-induced GAG loss and nitrite release and rescued cell metabolism and viability throughout the 16-day culture period, while free IGF at the equivalent dose was not effective.

Conclusions

CPC-mediated depot delivery of IGF-1 protected cartilage by suppressing cytokine-induced catabolism with only a single dose. CPC is a versatile cationic motif that can be used for intra-cartilage delivery of other similar-sized drugs.

Research on biochemical indexes of bone metabolism in bipolar disorder: A cross-sectional study with newly diagnosed, drug-naïve patients

BACKGROUND

In recent years, the metabolic abnormalities associated with bipolar disorder (BD) have attracted people's attention. However, clinical studies on bone metabolism in individuals with BD are unavailable. This study was designed to assess biochemical indexes of bone metabolism and related influencing factors.

METHODS

We measured bone turnover markers (BTMs), including procollagen Ⅰ N-terminal propeptide (PⅠNP), osteocalcin (OC) and C-terminal cross-linking telopeptide of type I collagen (CTX-I), and index of calcium and phosphorus metabolism in 100 drug-naïve individuals with BD (DSM-5) and 91 healthy volunteers. Besides, sociodemographic and clinical assessment were collected. Between-group comparisons and within subgroup analysis were performed.

RESULTS

The PⅠNP (t = 3.715, p < 0.001), OC (t = 2.117, p = 0.036), parathyroid hormone (PTH, t = 3.877, p < 0.001), vitamin D (t = 2.065, p = 0.041), insulin (t = 4.208, p < 0.001) and insulin resistance (t = 2.888, p = 0.004) levels in the drug-naive BD group was significantly higher than those in the healthy control (HC) group. The level of calcium (t = -2.124, p = 0.035) in the drug-naive BD group was significantly lower than that of the HC group. But OC and vitamin D loses statistical significance after Bonferroni correction. However, there was no significant difference in the CTX-I level between the two groups. There are gender differences in the level of BMTs in individuals with BD, but this phenomenon was not found in the HC subgroup. It is shown that diagnosed BD, gender, age and BMI may affect the PINP levels through multiple linear regression analysis.

CONCLUSION

The biochemical indexes of bone metabolism in drug-naive individuals with BD were more active than that of the healthy controls in a sample from the Chinese Han nationality. The finding provides new evidence for our understanding of bone metabolism in individuals with BD.

Effects of Site-Directed Mutagenesis of Cysteine on the Structure of Sip Proteins

Bacillus thuringiensis, a gram-positive bacteria, has three insecticidal proteins: Vip (vegetative insecticidal protein), Cry (crystal), and Sip (secreted insecticidal protein). Of the three, Sip proteins have insecticidal activity against larvae of Coleoptera. However, the Sip1Aa protein has little solubility in the supernatant because of inclusion bodies. This makes it more difficult to study, and thus research on Sip proteins is limited, which hinders the study of their mechanistic functions and insecticidal mechanisms. This highlights the importance of further investigation of the Sip1Aa protein. Disulfide bonds play an important role in the stability and function of proteins. Here, we successfully constructed mutant proteins with high insecticidal activity. The tertiary structure of the Sip1Aa protein was analyzed with homologous modeling and bioinformatics to predict the conserved domain of the protein. Cysteine was used to replace amino acids via site-directed mutagenesis. We successfully constructed Sip149-251, Sip153-248, Sip158-243, and Sip178-314 mutant proteins with higher solubility than Sip1Aa. Sip153-248 and Sip158-243 were the most stable compared to Sip1Aa, followed by Sip149-251 and Sip178-314. The insecticidal activity of Sip153-248 (Sip158-243) was 2.76 (2.26) times higher than that of Sip1Aa. The insecticidal activity of Sip149-251 and Sip178-314 did not differ significantly from that of Sip1Aa. Basic structural properties, physicochemical properties, and the spatial structure of the mutation site of Sip1Aa and the mutant proteins were analyzed. These results provide a molecular basis for using Sip1Aa to control Coleopteran insects and contribute to the study of the Sip1Aa insecticidal mechanism.

Lactococcus cremoris subsp. cremoris FC-fermented milk activates protein synthesis and increases skeletal muscle mass in middle-aged mice

Age-related muscle atrophy is associated with decreased protein anabolic capacity. Dietary intervention is an important strategy for the treatment of age-related muscle atrophy. This study examined the effect of Lactococcus cremoris subsp. cremoris FC-fermented milk on muscle mass and protein anabolic signaling in middle-aged mice. Male C57BL/6J mice (18-month-old) were divided into the control and Lactococcus cremoris subsp. cremoris FC-fermented milk supplementation groups. Mice were administered unfermented or fermented milk (300 μL/day) by gavage every alternate day for 8 weeks; thereafter, muscle weight, protein metabolic signaling factors, and inflammatory factors were investigated. Soleus muscle weight was higher in the fermented milk group than in the control group. Expression of insulin growth factor-1, a typical anabolic factor, and phosphorylation levels of anabolic signaling factors (mTOR and p70S6K) were higher after fermented milk supplementation. Levels of tumor necrosis factor-α, an inhibitor of protein anabolism, were lower in the fermented milk group. These data suggest that the daily intake of Lactococcus cremoris subsp. cremoris FC-fermented milk increased skeletal muscle mass as well as protein synthesis in the middle-aged mice, which may be mediated by reduction in the levels of inflammatory factors. Therefore, accelerated protein synthesis, induced by the consumption of fermented milk, has a potential role in counteracting muscle atrophy.

Tibetan Pig-Derived Probiotic Lactobacillus amylovorus SLZX20-1 Improved Intestinal Function via Producing Enzymes and Regulating Intestinal Microflora

The interaction between exogenous microorganisms and the host has received great attention, and finding new probiotics is always the way to improve the health of humans and animals. Lactobacillus amylovorus (L. amylovorus) is a kind of Lactobacillus that can efficiently utilize starch, as a food and feed additive, it has been widely used for mildew prevention and antibacterial, bacteriostasis, and enzyme production. Herein, a strain of L. amylovorus was isolated from the feces of Tibetan weaned piglets, named L. amylovorus SLZX20-1. Physiological and biochemical experiments in vitro confirmed that it had a fast growth rate and could produce a variety of enzymes, including α-galactosidase, β-galactosidase, α-glucosidase, β-glucosidase, and ferulic acid esterase. In addition, L. amylovorus SLZX20-1 exerted antibiotic effects on the growth of Salmonella typhimurium (S. typhimurium) SL1344, Citrobacter rodentium (C. rodentium) DBS100, Salmonella pullorum (S. pullorum) CVCC1791, Staphylococcus aureus (S. aureus) CVCC1882, Escherichia coli (E. coli) O157, E. coli K88, E. coli K99, and E. coli 987P, which are closely related to acid productivity, such as lactic acid and acetic acid. In vitro co-culture, L. amylovorus SLZX20-1 has shown the strong adhesion ability to intestinal porcine epithelial cells (IPEC-J2 cells) and activated IPEC-J2 cells with high expression of host defense peptides (HDPs), such as NK-Lysin, PEP2C, and PBD-1. In vivo experiment, via intragastric administration, L. amylovorus SLZX20-1 significantly improved the feed intake of mice, declined the crypt depth of jejunum and ileum, L. amylovorus SLZX20-1 changed the composition of intestinal microbes, especially at the level of colonic genus, the dominant genus was changed from Lactobacillus to S24-7, which indicated the change of intestinal carbohydrate nutrition. In conclusion, L. amylovorus SLZX20-1 showed strong probiotic characteristics, which met with the standard of probiotics and is worth further exploring its impacts on host health and its potential as a candidate strain of probiotics.

Effects of local single dose administration of parathormone on the early stages of osseointegration: A pre-clinical study

The present study aimed to evaluate the effect of parathormone (PTH) administered directly to the implant's surface prior to insertion, using a large translational animal model. Sixty titanium implants were divided into four groups: (i) Collagen, control group, where implants were coated with Type-I Bovine-collagen, and three experimental groups, where implants received varying doses of PTH: (ii) 12.5, (iii) 25, and (iv) 50 μg, prior to placement. Fifteen female sheep (~2 years old, weighing ~65 kg) received four implants in an interpolated fashion in C3, C4 or C5 vertebral bodies. After 3-, 6- and 12-weeks, samples were harvested, histologically processed, qualitatively and quantitatively assessed for bone-to-implant contact (BIC) and bone area fraction occupancy (BAFO). BIC yielded lower values at 6-weeks for 50 μg relative to the control group, with no significant differences, when compared to the 12.5- and 25-μg. No significant differences were detected at 6-weeks between collagen, 12.5- and 25-μg groups. At 3- and 12-weeks, no differences were detected for BIC among PTH groups. With respect to BAFO, no significant differences were observed between the control and experimental groups independent of PTH concentration and time in vivo. Qualitative observations at 3-weeks indicated the presence of a more mature bone near the implant's surface with the application of PTH, however, no significant differences in new bone formation or healing patterns were observed at 6- and 12-weeks. Single local application of different concentrations of PTH on titanium implant's surface did not influence the osseointegration at any time-point evaluation in low-density bone.

Gut-Bone Axis: A Non-Negligible Contributor to Periodontitis

Periodontitis is a polymicrobial infectious disease characterized by alveolar bone loss. Systemic diseases or local infections, such as diabetes, postmenopausal osteoporosis, obesity, and inflammatory bowel disease, promote the development and progression of periodontitis. Accumulating evidences have revealed the pivotal effects of gut microbiota on bone health via gut-alveolar-bone axis. Gut pathogens or metabolites may translocate to distant alveolar bone via circulation and regulate bone homeostasis. In addition, gut pathogens can induce aberrant gut immune responses and subsequent homing of immunocytes to distant organs, contributing to pathological bone loss. Gut microbial translocation also enhances systemic inflammation and induces trained myelopoiesis in the bone marrow, which potentially aggravates periodontitis. Furthermore, gut microbiota possibly affects bone health via regulating the production of hormone or hormone-like substances. In this review, we discussed the links between gut microbiota and periodontitis, with a particular focus on the underlying mechanisms of gut-bone axis by which systemic diseases or local infections contribute to the pathogenesis of periodontitis.

Polypeptides IGF-1C and P24 synergistically promote osteogenic differentiation of bone marrow mesenchymal stem cells in vitro through the p38 and JNK signaling pathways

OBJECTIVES

Insulin-like growth factor-1 (IGF-1) and bone morphogenetic protein 2 (BMP-2) both promote osteogenesis of bone marrow mesenchymal stem cells (BMSCs). IGF-1C, the C domain peptide of IGF-1, and P24, a BMP-2-derived peptide, both have similar biological activities as their parent growth factors. This study aimed to investigate the effects and mechanisms of polypeptides IGF-1C and P24 on the osteogenic differentiation of BMSCs.

METHODS

The optimum concentrations of IGF-IC and P24 were explored. The effects of the two polypeptides on BMSC proliferation and osteogenic differentiation were examined using a CCK-8 assay, flow cytometry, alkaline phosphatase (ALP) staining, ALP activity assay, alizarin red S staining, qPCR, and Western blotting. In addition, specific pathway inhibitors were utilized to explore whether the p38 and JNK pathways were involved in this process.

RESULTS

The optimal concentration of both polypeptides was 50 μg/ml. IGF-1C and P24 synergistically promoted BMSC proliferation, increased ALP activity and calcified nodule formation, upregulated the mRNA and protein levels of Osx, Runx2, Ocn, Opn, and Col1a1, and improved the phosphorylation levels of p38 and JNK proteins. Inhibition of the pathways significantly reduced p38 and JNK activation and blocked Runx2 expression while inhibiting ALP activity and calcified nodule formation.

CONCLUSIONS

These findings suggest that IGF-1C and P24 synergistically promote the osteogenesis of BMSCs through activation of the p38 and JNK signaling pathways.

Reconstitution of the host holobiont in germ-free born male rats acutely increases bone growth and affects marrow cellular content

Integration of microbiota in a host begins at birth and progresses during adolescence, forming a multidirectional system of physiological interactions. Here, we present an instantaneous effect of natural, bacterial gut colonization on the acceleration of longitudinal and radial bone growth in germ-free born, 7-wk-old male rats. Changes in bone mass and structure were analyzed after 10 days following the onset of colonization through cohousing with conventional rats and revealed unprecedented acceleration of bone accrual in cortical and trabecular compartments, increased bone tissue mineral density, improved proliferation and hypertrophy of growth plate chondrocytes, bone lengthening, and preferential deposition of periosteal bone in the tibia diaphysis. In addition, the number of small in size adipocytes increased, whereas the number of megakaryocytes decreased, in the bone marrow of conventionalized germ-free rats indicating that not only bone mass but also bone marrow environment is under control of gut microbiota signaling. The changes in bone status paralleled with a positive shift in microbiota composition toward short-chain fatty acids (SCFA)-producing microbes and a considerable increase in cecal SCFA concentrations, specifically butyrate. Furthermore, reconstitution of the host holobiont increased hepatic expression of IGF-1 and its circulating levels. Elevated serum levels of 25-hydroxy vitamin D and alkaline phosphatase pointed toward an active process of bone formation. The acute stimulatory effect on bone growth occurred independently of body mass increase. Overall, the presented model of conventionalized germ-free rats could be used to study microbiota-based therapeutics for combatting dysbiosis-related bone disorders.

The Effect of Waterpipe Tobacco Smoking on Bone Healing Following Femoral Fractures in Male Rats

Background: Given the increasing use of waterpipe tobacco smoking in the world and its unknown effects on bone healing, this study investigated the repairing of femoral bone fractures in rats exposed to waterpipe tobacco smoking (WTS).

Main Methods: This study involved 40 male Wistar rats that were divided into two groups, including the femoral fracture (Fx) and the Fx + WTS groups. Each group was divided into two subgroups that were evaluated for bone healing 28 and 42 days after femoral fracture. After fixing the fractured femur, the healing process was evaluated by radiography, pathological indicators, and a measurement of the blood levels of vascular endothelial growth factor (VEGF), parathyroid hormone (PTH), Ca ++, transforming growth factor-beta (TGF-β), and insulin-like growth factor 1 (IGF-1). Additionally, the density of VEGF and CD34 in fracture tissue was investigated by immunohistochemistry.

Key Findings: Radiographic findings showed that factors related to the earlier stages of bone healing had higher scores in the Fx + WTS28 and 42 subgroups in comparison to the Fx groups. The density of VEGF and CD34 showed that the angiogenesis processes were different in the bone fracture area and callus tissue in the Fx +WTS subgroups. The serum levels of VEGF, TGF-β, and IGF-1 were significantly lower in the Fx +WTS42 group, and PTH in the Fx +WTS28 group was higher than that in the other groups.

Significance: The findings showed the disturbance and delay in the femoral fracture union in rats exposed to hookah smoke. This is partly due to the reduction of molecular stimuli of bone synthesis and the attenuation of quantitative angiogenesis.

The periosteum: a simple tissue with many faces, with special reference to the antler-lineage periostea

Periosteum is a thin membrane covering bone surfaces and consists of two layers: outer fibrous layer and inner cambium layer. Simple appearance of periosteum has belied its own complexity as a composite structure for physical bone protection, mechano-sensor for sensing mechanical loading, reservoir of biochemical molecules for initiating cascade signaling, niche of osteogenic cells for bone formation and repair, and "umbilical cord" for nourishing bone tissue. Periosteum-derived cells (PDCs) have stem cell attributes: self-renewal (no signs of senescence until 80 population doublings) and multipotency (differentiate into fibroblasts, osteoblasts, chondrocytes, adipocytes and skeletal myocytes). In this review, we summarized the currently available knowledge about periosteum and with special references to antler-lineage periostea, and demonstrated that although periosteum is a type of simple tissue in appearance, with multiple faces in functions; antler-lineage periostea add another dimension to the properties of somatic periostea: capable of initiation of ectopic organ formation upon transplantation and full mammalian organ regeneration when interacted with the covering skin. Very recently, we have translated this finding into other mammals, i.e. successfully induced partial regeneration of the amputated rat legs. We believe further refinement along this line would greatly benefit human health.

Undenatured Type II Collagen Relieves Bone Impairment through Improving Inflammation and Oxidative Stress in Ageing db/db Mice

Ageing-related bone impairment due to exposure to hyperglycemic environment is scarcely researched. The aim was to confirm the improvement effects of undenatured type II collagen (UC II) on bone impairment in ageing db/db mice, and the ageing model was established by normal feeding for 48-week-old. Then, the ageing db/db mice were randomly assigned to UC II intervention, the ageing model, and the chondroitin sulfate + glucosamine hydrochloride control groups. After 12 weeks of treatment, femoral microarchitecture and biomechanical parameters were observed, biomarkers including bone metabolism, inflammatory cytokines, and oxidative stress were measured, and the gastrocnemius function and expressions of interleukin (IL) 1β, receptor activator of nuclear factor (NF)-κB ligand (RANKL), and tartrate-resistant acid phosphatase (TRAP) were analyzed. The results showed that the mice in the UC II intervention group showed significantly superior bone and gastrocnemius properties than those in the ageing model group, including bone mineral density (287.65 ± 72.77 vs. 186.97 ± 32.2 mg/cm³), gastrocnemius index (0.46 ± 0.07 vs. 0.18 ± 0.01%), muscle fiber diameter (0.0415 ± 0.005 vs. 0.0330 ± 0.002 mm), and cross-sectional area (0.0011 ± 0.00007 vs. 0.00038 ± 0.00004 mm²). The UC II intervention elevated bone mineralization and formation and decreased bone resorption, inflammatory cytokines, and the oxidative stress. In addition, lower protein expression of IL-1β, RANKL, and TRAP in the UC II intervention group was observed. These findings suggested that UC II improved bones impaired by T2DM during ageing, and the likely mechanism was partly due to inhibition of inflammation and oxidative stress.

Metabolic Hormone Profiles in Breast Milk From Mothers of Moderate-Late Preterm Infants Are Associated With Growth From Birth to 4 Months in a Sex-Specific Manner

Background: Differing environmental conditions experienced by mother-infant dyads may influence composition of the milk received by the infant. As a consequence, diverse milk compositional profiles may contribute to different postnatal outcomes, especially in infants facing adverse perinatal environments. We investigated whether variability in milk concentrations of key metabolic hormones is associated with different growth outcomes in infants born preterm, a perinatal complication known to impact on infant growth. Methods: Human milk samples were collected from 169 mothers of 191 infants enrolled in the DIAMOND trial, a randomized trial of nutrition for moderate-late preterm infants, at 5 and 10 days postpartum and again at 4 months' corrected age and analyzed for leptin, adiponectin and insulin-like growth factor (IGF)-1. Infant weight and body composition were measured at birth, discharge and 4 months' corrected age. Multiple linear regression models were used to examine correlations between milk hormone concentrations, weight z-scores and body composition at discharge and 4 months' corrected age, and weight gain from birth to 4 months' corrected age. Sex-specific interactions were examined. Results: Higher milk IGF-1 concentrations on day 5 after birth were associated with greater infant fat-free mass at 4 months' corrected age. Milk IGF-1 concentrations at 4 months were positively associated with fat mass and fat-free mass at 4 months in boys but not girls. Milk leptin concentrations on day 5 after birth were positively associated with fat mass at discharge from hospital, but negatively associated with fat mass at 4 months' corrected age. No significant association was found for milk adiponectin concentrations. Conclusion: Milk IGF-1 and leptin concentrations in mothers of moderate-late preterm babies are associated with different growth and body composition through to 4 months' corrected age and these associations are often different in boys and girls. The sex-specific effects of nutrient and hormone exposure during early life in preterm infants warrants further investigation to optimize the nutritional care these infants receive, particularly in hospital, where the same nutrition is provided to boys and girls.

Persistent fontanelles in Chihuahuas. Part II: Association with craniocervical junction abnormalities, syringomyelia, and ventricular volume

Background

Persistent fontanelles (PFs) are, in Chihuahuas, almost ubiquitous. Furthermore, Chihuahuas are predisposed to other craniomorphological abnormalities, including syringomyelia (SM), ventriculomegaly, and craniocervical junction (CCJ) overcrowding resulting in neural tissue deviation. It is, however, undetermined if PFs are more common in dogs with these structural abnormalities, and their etiology is unknown.

Hypothesis/Objectives

Persistent fontanelles are more numerous and larger in Chihuahuas with low body weight, older age, SM, dilated fourth ventricle, ventriculomegaly, and CCJ overcrowding.

Animals

Fifty client‐owned Chihuahuas.

Methods

Cross‐sectional study evaluating the association of both the number of cranial sutures affected by PFs (NAS) and total fontanelle area (TFA), based on computed tomography with SM, fourth ventricle dilatation, lateral ventricle volume, and extent of neural tissue compression at the CCJ based on magnetic resonance images.

Results

The NASs was higher and TFA larger in dogs with low body weight (NAS: P = .007; 95% confidence interval [CI] = 0.384‐0.861; TFA: P = .002; 95% CI = −1.91 to −0.478), larger lateral ventricles (NAS: P ≤ .001; 95% CI = 1.04‐1.15; TFA: P ≤ .001; 95% CI = 0.099‐0.363), and more severe neural tissue compression at the CCJ (NAS: P ≤ .001; 95% CI = 1.26‐2.06; TFA: P = .03; 95% CI = 0.066‐1.13). Similarly, dogs with SM (NAS: P = .004; 95% CI = 1.26‐3.32; TFA: mean ± SD, 130 ± 217 mm²; P = .05) had higher NAS and larger TFA than did dogs without SM (43.7 ± 61.0 mm²). Age was not associated with NAS (P = .81; 95% CI = 0.989‐1.01) or TFA (P = .33; 95% CI = −0.269 to 0.092).

Conclusions and Clinical Importance

Persistent fontanelles are associated with small size, SM, ventriculomegaly, and CCJ overcrowding.

Mechanical stress determines the configuration of TGFβ activation in articular cartilage

Our incomplete understanding of osteoarthritis (OA) pathogenesis has significantly hindered the development of disease-modifying therapy. The functional relationship between subchondral bone (SB) and articular cartilage (AC) is unclear. Here, we found that the changes of SB architecture altered the distribution of mechanical stress on AC. Importantly, the latter is well aligned with the pattern of transforming growth factor beta (TGFβ) activity in AC, which is essential in the regulation of AC homeostasis. Specifically, TGFβ activity is concentrated in the areas of AC with high mechanical stress. A high level of TGFβ disrupts the cartilage homeostasis and impairs the metabolic activity of chondrocytes. Mechanical stress stimulates talin-centered cytoskeletal reorganization and the consequent increase of cell contractile forces and cell stiffness of chondrocytes, which triggers αV integrin–mediated TGFβ activation. Knockout of αV integrin in chondrocytes reversed the alteration of TGFβ activation and subsequent metabolic abnormalities in AC and attenuated cartilage degeneration in an OA mouse model. Thus, SB structure determines the patterns of mechanical stress and the configuration of TGFβ activation in AC, which subsequently regulates chondrocyte metabolism and AC homeostasis.

The functional relationship between subchondral bone and articular cartilage is unclear. Here, the authors show that transforming growth factor-beta propagates the mechanical impact of subchondral bone on articular cartilage through αV integrin–talin mechanical transduction system in chondrocytes.

Analysis of the bone fracture targeting properties of osteotropic ligands

PURPOSE

Although more than 18,000,000 fractures occur each year in the US, methods to promote fracture healing still rely primarily on fracture stabilization, with use of bone anabolic agents to accelerate fracture repair limited to rare occasions when the agent can be applied to the fracture surface. Because management of broken bones could be improved if bone anabolic agents could be continuously applied to a fracture over the entire course of the healing process, we undertook to identify strategies that would allow selective concentration of bone anabolic agents on a fracture surface following systemic administration. Moreover, because hydroxyapatite is uniquely exposed on a broken bone, we searched for molecules that would bind with high affinity and specificity for hydroxyapatite. We envisioned that by conjugating such osteotropic ligands to a bone anabolic agent, we could acquire the ability to continuously stimulate fracture healing.

RESULTS

Although bisphosphonates and tetracyclines were capable of localizing small amounts of peptidic payloads to fracture surfaces 2-fold over healthy bone, their specificities and capacities for drug delivery were significantly inferior to subsequent other ligands, and were therefore considered no further. In contrast, short oligopeptides of acidic amino acids were found to localize a peptide payload to a bone fracture 91.9 times more than the control untargeted peptide payload. Furthermore acidic oligopeptides were observed to be capable of targeting all classes of peptides, including hydrophobic, neutral, cationic, anionic, short oligopeptides, and long polypeptides. We further found that highly specific bone fracture targeting of multiple peptidic cargoes can be achieved by subcutaneous injection of the construct.

CONCLUSIONS

Using similar constructs, we anticipate that healing of bone fractures in humans that have relied on immobilization alone can be greately enhanced by continuous stimulation of bone growth using systemic administration of fracture-targeted bone anabolic agents.

Advanced protein adsorption properties of a novel silicate-based bioceramic: A proteomic analysis

Silicate bioceramics have been shown to possess excellent cytocompatibility and osteogenic activity, but the exact mechanism is still unclear. Protein adsorption is the first event taking place at the biomaterial-tissue interface, which is vital to the subsequent cellular behavior and further influence the biomaterial-tissue interaction. In this work, the protein adsorption behavior of a novel CPS bioceramic was evaluated using the proteomics technology. The results showed that CPS adsorbed more amount and types of serum proteins than HA. FN1 and IGF1 proteins selected from proteomics results were validated by Western-blot experiment. Pathway analysis also revealed mechanistic insights how these absorbed proteins by CPS help mediate cell adhesion and promotes osteogenic activity. Firstly, the dramatically enhanced adsorption of FN1 could greatly promote cell adhesion and growth. Secondly, IGF1 was uniquely adsorbed on CPS bioceramic and IGF1 could activate Rap1 signaling pathway to promote cell adhesion. Thirdly, the increased adsorption of FN1, IGF1 and COL1A2 proteins on CPS explains its better ability on bone regeneration than HA. Fourthly, the increased adsorption of IGF1, CHAD, COL2A1 and THBS4 proteins on CPS explains its ability on cartilage formation. Lastly, the increased adsorption of immunological related proteins on CPS may also play a positive role in bone regeneration. In addition, CPS had a much better cell adhesion ability than HA, proving that more adsorbed proteins really had a positive effect on cell behavior. The more adsorbed proteins on CPS than HA might indicated a better bone regeneration rate at early stage of implantation.

The Hyperglycemia and Hyperketonemia Impaired Bone Microstructures: A Pilot Study in Rats

Though diabetes mellitus (DM) is one of the known causes of osteoporosis, it is also realized that ketogenic diet (KD), an effective regimen for epilepsy, impairs bone microstructures. However, the similarities and differences of effects between these two factors are still unknown. The purpose of this study is to identify different effects between hyperglycemia and hyperketonemia, which are manifestations of DM and KD, on bone in rats. Thirty male Sprague-Dawley rats were randomly divided into three groups: the sham, DM, and KD groups. Hyperglycemia was achieved by intravenous injection of streptozotocin in DM group, while hyperketonemia was induced by application of ketogenic diet (carbohydrates-to-fat as 1:3) in KD group. The body weight, blood ketone body, and blood glucose were recorded, and the bone turnover markers, bone length, bone microstructures, bone biomechanics and histomorphology were measured after 12 weeks intervention. Compared with the control and KD groups, a significant body weight loss was found in the DM group, and the bone lengths of tibia and femur of the group were shortened. The blood glucose and blood ketone were noticeably increased in the DM and KD rats, respectively. Microstructures and properties of cancellous bone were significantly deteriorated in both the DM and KD groups compared with the sham group, as the bone volumes were decreased and the bone trabecula structures were disturbed. Meanwhile, the thickness and strength of cortical bone was reduced more in the DM group than those in the sham and KD groups. The HE staining showed that bone trabecula was significantly decreased in both the DM and KD groups, and more adipose tissue was observed in the KD rats. The activity of osteoblasts was decreased more in both the KD and DM groups than that in the sham group, while the activity of osteoclasts of the two groups was remarkably increased. The present study indicates that both hyperglycemia and hyperketonemia have adverse effects on bone. Therefore, it is worth paying more attention to the bone status of patients with hyperglycemia and hyperketonemia in clinic.

Role of Alternatively Spliced Messenger RNA (mRNA) Isoforms of the Insulin-Like Growth Factor 1 (IGF1) in Selected Human Tumors

Insulin-like growth factor 1 (IGF1) is a key regulator of tissue growth and development that is also implicated in the initiation and progression of various cancers. The human IGF1 gene contains six exons and five long introns, the transcription of which is controlled by two promoters (P1 and P2). Alternate promoter usage, as well as alternative splicing (AS) of IGF1, results in the expression of six various variants (isoforms) of mRNA, i.e., IA, IB, IC, IIA, IIB, and IIC. A mature 70-kDa IGF1 protein is coded only by exons 3 and 4, while exons 5 and 6 are alternatively spliced code for the three C-terminal E peptides: Ea (exon 6), Eb (exon 5), and Ec (fragments of exons 5 and 6). The most abundant of those transcripts is IGF1Ea, followed by IGF1Eb and IGF1Ec (also known as mechano-growth factor, MGF). The presence of different IGF1 transcripts suggests tissue-specific auto- and/or paracrine action, as well as separate regulation of both of these gene promoters. In physiology, the role of different IGF1 mRNA isoforms and pro-peptides is best recognized in skeletal muscle tissue. Their functions include the development and regeneration of muscles, as well as maintenance of proper muscle mass. In turn, in nervous tissue, a neuroprotective function of short peptides, produced as a result of IGF1 expression and characterized by significant blood-brain barrier penetrance, has been described and could be a potential therapeutic target. When it comes to the regulation of carcinogenesis, the potential biological role of different var iants of IGF1 mRNAs and pro-peptides is also intensively studied. This review highlights the role of IGF1 isoform expression (mRNAs, proteins) in physiology and different types of human tumors (e.g., breast cancer, cervical cancer, colorectal cancer, osteosarcoma, prostate and thyroid cancers), as well as mechanisms of IGF1 spliced variants involvement in tumor biology.

Fermented Oyster Extract Promotes Insulin-Like Growth Factor-1-Mediated Osteogenesis and Growth Rate

Fermented oyster (Crassostrea gigas) extract (FO) prevents ovariectomy-induced osteoporosis by inhibiting osteoclastogenesis and activating osteogenesis. However, the molecular mechanisms underlying FO-mediated bone formation and growth rate are unclear. In the current study, we found that FO significantly upregulated the expression of growth-promoting genes in zebrafish larvae including insulin-like growth factor 1 (zigf-1), insulin-like growth factor binding protein 3 (zigfbp-3), growth hormone-1 (zgh-1), growth hormone receptor-1 (zghr-1), growth hormone receptor alpha (zghra), glucokinase (zgck), and cholecystokinin (zccka). In addition, zebrafish larvae treated with 100 μg/mL FO increased in total body length (3.89 ± 0.13 mm) at 12 days post fertilization (dpf) compared to untreated larvae (3.69 ± 0.02 mm); this effect was comparable to that of the β-glycerophosphate-treated zebrafish larvae (4.00 ± 0.02 mm). Furthermore, FO time- and dose-dependently increased the extracellular release of IGF-1 from preosteoblast MC3T3-E1 cells, which was accompanied by high expression of IGF-1. Pharmacological inhibition of IGF-1 receptor (IGF-1R) using picropodophyllin (PPP) significantly reduced FO-mediated vertebrae formation (from 9.19 ± 0.31 to 5.53 ± 0.35) and growth performance (from 3.91 ± 0.02 to 3.69 ± 0.01 mm) in zebrafish larvae at 9 dpf. Similarly, PPP significantly decreased FO-induced calcium deposition in MC3T3-E1 cells by inhibiting GSK-3β phosphorylation at Ser9. Additionally, DOI hydrochloride, a potent stabilizer of GSK-3β, reduced FO-induced nuclear translocation of RUNX2. Transient knockdown of IGF-1Rα/β using specific silencing RNA also resulted in a significant decrease in calcium deposition and reduction in GSK-3β phosphorylation at Ser9 in MC3T3-E1 cells. Altogether, these results indicate that FO increased phosphorylated GSK-3β at Ser9 by activating the autocrine IGF-1-mediated IGF-1R signaling pathway, thereby promoting osteogenesis and growth performance. Therefore, FO is a potential nutritional supplement for bone formation and growth.

Glucocorticoid-insulin-like growth factor 1 (GC-IGF1) axis programming mediated hepatic lipid-metabolic in offspring caused by prenatal ethanol exposure

Prenatal ethanol exposure (PEE) could increase offspring's susceptibility to adult liver lipid-metabolism diseases. This study aimed to confirm intrauterine programming mechanism of glucocorticoid-insulin-like growth factor 1 (GC-IGF1) axis for liver dysfunction in offspring rats induced by PEE. The results showed that levels of hepatic IGF1, lipid metabolism-related enzymes (e.g. FASN and HMGCR) and serum phenotype (TG, TCH, HDL-C, and LDL-C) were low in fetal rats of PEE but high in adult offspring except for HDL-C, meanwhile, hepatic H3K9ac and expression levels of IGF1 were low in fetal rats but high in adult offspring. Furthermore, levels of serum corticosterone and hepatic glucocorticoid-activation system (mainly including expression of 11β-HSD1, GR, and C/EBPα as well as 11β-HSD1/11β-HSD2 ratio) were high in fetal rats of PEE but low or unchanged in adult offspring. The adult F2 generation of PEE maintained the same GC-IGF1 axis programming alteration as the F1 generation despite gender differences. In vitro, cortisol was proved to activate hepatocyte glucocorticoid-activation system and decrease H3K9ac and expression levels of IGF1 by GR. Therefore, PEE has a long-term effect on the offspring's liver functional development, which may be mainly related to the epigenetic programming alteration of the GC-IGF1 axis mediated by the glucocorticoid-activation system.

The Actions of IGF-1 in the Growth Plate and Its Role in Postnatal Bone Elongation

PURPOSE OF REVIEW

Bone elongation is a complex process driven by multiple intrinsic (hormones, growth factors) and extrinsic (nutrition, environment) variables. Bones grow in length by endochondral ossification in cartilaginous growth plates at ends of developing long bones. This review provides an updated overview of the important factors that influence this process.

RECENT FINDINGS

Insulin-like growth factor-1 (IGF-1) is the major hormone required for growth and a drug for treating pediatric skeletal disorders. Temperature is an underrecognized environmental variable that also impacts linear growth. This paper reviews the current state of knowledge regarding the interaction of IGF-1 and environmental factors on bone elongation. Understanding how internal and external variables regulate bone lengthening is essential for developing and improving treatments for an array of bone elongation disorders. Future studies may benefit from understanding how these unique relationships could offer realistic new approaches for increasing bone length in different growth-limiting conditions.

Osteoclast-derived IGF1 is required for pagetic lesion formation in vivo

We report that transgenic mice expressing measles virus nucleocapsid protein (MVNP) in osteoclasts (OCLs) (MVNP mice) are Paget's disease (PD) models and that OCLs from patients with PD and MVNP mice express high levels of OCL-derived IGF1 (OCL-IGF1). To determine OCL-IGF1's role in PD and normal bone remodeling, we generated WT and MVNP mice with targeted deletion of Igf1 in OCLs (Igf1-cKO) and MVNP/Igf1-cKO mice, and we assessed OCL-IGF1's effects on bone mass, bone formation rate, EphB2/EphB4 expression on OCLs and osteoblasts (OBs), and pagetic bone lesions (PDLs). A total of 40% of MVNP mice, but no MVNP/Igf1-cKO mice, had PDLs. Bone volume/tissue volume (BV/TV) was decreased by 60% in lumbar vertebrae and femurs of MVNP/Igf1-cKO versus MVNP mice with PDLs and by 45% versus all MVNP mice tested. Bone formation rates were decreased 50% in Igf1-cKO and MVNP/Igf1-cKO mice versus WT and MVNP mice. MVNP mice had increased EphB2 and EphB4 levels in OCLs/OBs versus WT and MVNP/Igf1-cKO, with none detectable in OCLs/OBs of Igf1-cKO mice. Mechanistically, IL-6 induced the increased OCL-IGF1 in MVNP mice. These results suggest that high OCL-IGF1 levels increase bone formation and PDLs in PD by enhancing EphB2/EphB4 expression in vivo and suggest OCL-IGF1 may contribute to normal bone remodeling.

Serpina3c Regulates Adipogenesis by Modulating Insulin Growth Factor 1 and Integrin Signaling

Preadipocyte differentiation can be induced upon a hormonal treatment, and various factors secreted by the cells may contribute to adipogenesis. In this study, RNA-seq revealed Serpina3c as a critical factor regulating the signaling network during adipogenesis. Serpina3c is a secretory protein and is highly expressed in fat tissues. Knockdown of Serpina3c decreased adipogenesis by attenuating the mitotic clonal expansion of 3T3-L1 cells. These cells exhibited decreases in integrin α5, which abolished the phosphorylation of integrin β3. We found that Serpina3c inhibits a serine protease that regulates integrin α5 degradation. Knockdown of Serpina3c disrupted integrin-mediated insulin growth factor 1 (IGF-1) signaling and ERK activation. Serpina3c-mediated regulation of integrin-IGF-1 signaling is also associated with AKT activation, which affects the nuclear translocation of GSK3β. Altogether, our results indicate that Serpina3c secreted from differentiating adipocytes inhibits serine proteases to modulate integrin/IGF-1-mediated ERK and AKT signaling and thus is a critical factor contributing to adipogenesis.

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RNA-seq revealed Serpina3c as a critical factor regulating adipogenesis

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Knockdown of Serpina3c attenuated the mitotic clonal expansion of 3T3-L1 cells

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Knockdown of Serpina3c leads to the degradation of integrin α5

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Serpina3c regulates integrin-mediated IGF-1 signaling and ERK/AKT activation

Oral delivery of novel human IGF-1 bioencapsulated in lettuce cells promotes musculoskeletal cell proliferation, differentiation and diabetic fracture healing

Human insulin-like growth factor-1 (IGF-1) plays important roles in development and regeneration of skeletal muscles and bones but requires daily injections or surgical implantation. Current clinical IGF-1 lacks e-peptide and is glycosylated, reducing functional efficacy. In this study, codon-optimized Pro-IGF-1 with e-peptide (fused to GM1 receptor binding protein CTB or cell penetrating peptide PTD) was expressed in lettuce chloroplasts to facilitate oral delivery. Pro-IGF-1 was expressed at high levels in the absence of the antibiotic resistance gene in lettuce chloroplasts and was maintained in subsequent generations. In lyophilized plant cells, Pro-IGF-1 maintained folding, assembly, stability and functionality up to 31 months, when stored at ambient temperature. CTB-Pro-IGF-1 stimulated proliferation of human oral keratinocytes, gingiva-derived mesenchymal stromal cells and mouse osteoblasts in a dose-dependent manner and promoted osteoblast differentiation through upregulation of ALP, OSX and RUNX2 genes. Mice orally gavaged with the lyophilized plant cells significantly increased IGF-1 levels in sera, skeletal muscles and was stable for several hours. When bioencapsulated CTB-Pro-IGF-1 was gavaged to femoral fractured diabetic mice, bone regeneration was significantly promoted with increase in bone volume, density and area. This novel delivery system should increase affordability and patient compliance, especially for treatment of musculoskeletal diseases.

Links Between Testosterone, Oestrogen, and the Growth Hormone/Insulin-Like Growth Factor Axis and Resistance Exercise Muscle Adaptations

Maintenance of skeletal muscle mass throughout the life course is key for the regulation of health, with physical activity a critical component of this, in part, due to its influence upon key hormones such as testosterone, estrogen, growth hormone (GH), and insulin-like growth factor (IGF). Despite the importance of these hormones for the regulation of skeletal muscle mass in response to different types of exercise, their interaction with the processes controlling muscle mass remain unclear. This review presents evidence on the importance of these hormones in the regulation of skeletal muscle mass and their responses, and involvement in muscle adaptation to resistance exercise. Highlighting the key role testosterone plays as a primary anabolic hormone in muscle adaptation following exercise training, through its interaction with anabolic signaling pathways and other hormones via the androgen receptor (AR), this review also describes the potential importance of fluctuations in other hormones such as GH and IGF-1 in concert with dietary amino acid availability; and the role of estrogen, under the influence of the menstrual cycle and menopause, being especially important in adaptive exercise responses in women. Finally, the downstream mechanisms by which these hormones impact regulation of muscle protein turnover (synthesis and breakdown), and thus muscle mass are discussed. Advances in our understanding of hormones that impact protein turnover throughout life offers great relevance, not just for athletes, but also for the general and clinical populations alike.

Insulin-like growth factor 1 signaling in tenocytes is required for adult tendon growth

Tenocytes serve to synthesize and maintain collagen fibrils and other extracellular matrix proteins in tendon. Despite the high prevalence of tendon injury, the underlying biologic mechanisms of postnatal tendon growth and repair are not well understood. IGF1 plays an important role in the growth and remodeling of numerous tissues but less is known about IGF1 in tendon. We hypothesized that IGF1 signaling is required for proper tendon growth in response to mechanical loading through regulation of collagen synthesis and cell proliferation. To test this hypothesis, we conditionally deleted the IGF1 receptor (IGF1R) in scleraxis (Scx)-expressing tenocytes using a tamoxifen-inducible Cre-recombinase system and caused tendon growth in adult mice via mechanical overload of the plantaris tendon. Compared with control Scx-expressing IGF1R-positive (Scx:IGF1R⁺) mice, in which IGF1R is present in tenocytes, mice that lacked IGF1R in their tenocytes [Scx-expressing IGF1R-negative (Scx:IGF1R^Δ) mice] demonstrated reduced cell proliferation and smaller tendons in response to mechanical loading. Additionally, we identified that both the PI3K/protein kinase B and ERK pathways are activated downstream of IGF1 and interact in a coordinated manner to regulate cell proliferation and protein synthesis. These studies indicate that IGF1 signaling is required for proper postnatal tendon growth and support the potential use of IGF1 in the treatment of tendon disorders.-Disser, N. P., Sugg, K. B., Talarek, J. R., Sarver, D. C., Rourke, B. J., Mendias, C. L. Insulin-like growth factor 1 signaling in tenocytes is required for adult tendon growth.

Dysfunctional stem and progenitor cells impair fracture healing with age

Successful fracture healing requires the simultaneous regeneration of both the bone and vasculature; mesenchymal stem cells (MSCs) are directed to replace the bone tissue, while endothelial progenitor cells (EPCs) form the new vasculature that supplies blood to the fracture site. In the elderly, the healing process is slowed, partly due to decreased regenerative function of these stem and progenitor cells. MSCs from older individuals are impaired with regard to cell number, proliferative capacity, ability to migrate, and osteochondrogenic differentiation potential. The proliferation, migration and function of EPCs are also compromised with advanced age. Although the reasons for cellular dysfunction with age are complex and multidimensional, reduced expression of growth factors, accumulation of oxidative damage from reactive oxygen species, and altered signaling of the Sirtuin-1 pathway are contributing factors to aging at the cellular level of both MSCs and EPCs. Because of these geriatric-specific issues, effective treatment for fracture repair may require new therapeutic techniques to restore cellular function. Some suggested directions for potential treatments include cellular therapies, pharmacological agents, treatments targeting age-related molecular mechanisms, and physical therapeutics. Advanced age is the primary risk factor for a fracture, due to the low bone mass and inferior bone quality associated with aging; a better understanding of the dysfunctional behavior of the aging cell will provide a foundation for new treatments to decrease healing time and reduce the development of complications during the extended recovery from fracture healing in the elderly.