IGF1 regulates RUNX1 expression via IRS1/2: Implications for antler chondrocyte differentiation

Gene proteins, growth factors/their receptors in the wall of chronic calculous cholecystitis-affected gallbladder children

BACKGROUND

Chronic calculous cholecystitis is the main cause of cholecystectomies in children, and 50.5% of patients with gallstones are asymptomatic at the time of diagnosis. However, the morphopathogenesis of chronic cholecystitis with cholelithiasis is unclear and may involve various genes, gene proteins, and growth factors.

METHODS

Tissues were obtained from four males (aged 6-18 years) and two females (aged 15 and 14 years) during planned cholecystectomies. Five healthy gallbladder tissues were obtained from the archival postmortem tissue of children. SHH, IHH, HGF, IGF1, IGF1R, and HOXB3 were detected by immunohistochemistry and evaluated semiquantitatively. Statistical analysis was used to identify statistically significant differences and correlations between the factors.

RESULTS

Decreased numbers of SHH-, IHH-, and IGF1R-positive cells, along with an increased number of HOXB3-positive cells, were observed in patients. SHH-positive epitheliocytes and connective tissue cells; IHH-positive cells in all locations; IGF1R-positive epitheliocytes, endotheliocytes, and smooth muscle cells; and HOXB3-positive smooth muscle cells were significantly different among the groups. However, the strongest negative correlation was found between HOXB3-positive smooth myocytes and SHH- and IHH-positive connective tissues, and the strongest positive correlation was detected among epithelial IHH, SHH, and IGF1R, as well as between IGF1R in the epithelium and endothelium of the blood vessels.

CONCLUSIONS

The reduced number of cells positive for the primary endodermal proteins SHH/IHH and the decreased number of IGFR1-positive cells suggest their potential roles in the development of chronic calculous cholecystitis. Additionally, the increased number of HOXB3-positive cells under these conditions likely implies stimulated growth properties, whereas HGF and IGF1 appear to have a reduced contribution to the pathogenesis of chronic calculous cholecystitis.

Double network hydrogels encapsulating genetically modified dedifferentiated chondrocytes for auricular cartilage regeneration

Microtia profoundly affects patients' appearance and psychological well-being. Tissue engineering ear cartilage scaffolds have emerged as the most promising solution for ear reconstruction. However, constructing tissue engineering ear cartilage scaffolds requires multiple passaging of chondrocytes, resulting in their dedifferentiation and loss of their special phenotypes and functions. To tackle these issues, here we employ guanidinobenzoic acid (GBA) modified generation 5 polyamidoamine (PAMAM) dendrimers (PG) as a Runx1 plasmid carrier to construct PG/pRunx1 polyplex nanoparticles. The PG/pRunx1 polyplexes are transfected into human auricular chondrocytes, significantly mitigating chondrocyte dedifferentiation and enhancing cartilage regeneration during the in vitro culture. Furthermore, we develop highly porous double-network hydrogels based on methacrylate-functionalized and oxidized chondroitin sulfate and carbohydrazide-modified gelatin and the hydrogels possessed both dynamic adaptability and mechanical support characteristics by reversible dynamic covalent crosslinking and static covalent crosslinking, serving as an ideal scaffold for tissue engineering. Consequently, chondrocytes treated with PG/pRunx1 polyplex nanoparticles are incorporated into the hydrogels to construct tissue-engineered auricular cartilage scaffolds. After subcutaneous implantation in nude mice, the scaffolds containing chondrocytes treated with PG/pRunx1 nanoparticles showed more mature cartilaginous tissue, characterized by prominent ECM deposition and enhanced chondrogenesis. Therefore, this research provides a novel strategy for the development of tissue-engineered auricular cartilage scaffolds.

Osteoporosis in polycystic ovary syndrome (PCOS) and involved mechanisms

Polycystic Ovary Syndrome (PCOS) and osteoporosis, though seemingly unrelated, exhibit intricate connections influenced by genetic and epigenetic factors. PCOS, characterized by elevated androgen levels, insulin resistance, and increased body weight, has historically been considered protective against bone fragility disorders. However, emerging research suggests that chronic inflammation, prevalent in PCOS, can adversely affect bone health. Studies have demonstrated variable bone mineral density loss in PCOS, often associated with leptin resistance and hyperinsulinemia. Key genes such as INS, IGF1, CTNNB1, AKT1, and STAT3 play pivotal roles in the complex interplay between PCOS and osteoporosis, influencing insulin signaling, oxidative stress, and inflammatory pathways. Oxidative stress, a prominent element in PCOS, can lead to osteoporosis through hormonal imbalances, chronic inflammation, insulin resistance, and lifestyle factors. The insulin signaling pathway also significantly impacts both conditions by contributing to hormonal imbalances and bone health alterations. This intricate network of genetic and epigenetic factors underscores the need for a deeper understanding of their interrelationships. Thus, this review elucidates the multifaceted genetic, epigenetic, and inflammatory connections between PCOS and osteoporosis, highlighting their implications for bone health management in individuals with PCOS.

The molecular mechanisms of glycosaminoglycan biosynthesis regulating chondrogenesis and endochondral ossification

Disorders of chondrocyte differentiation and endochondral osteogenesis are major underlying factors in skeletal developmental disorders, including tibial dysplasia (TD), osteoarthritis (OA), chondrodysplasia (ACH), and multiple epiphyseal dysplasia (MED). Understanding the cellular and molecular pathogenesis of these disorders is crucial for addressing orthopedic diseases resulting from impaired glycosaminoglycan synthesis. Glycosaminoglycan is a broad term that refers to the glycan component of proteoglycan macromolecules. It is an essential component of the cartilage extracellular matrix and plays a vital role in various biological processes, including gene transcription, signal transduction, and chondrocyte differentiation. Recent studies have demonstrated that glycosaminoglycan biosynthesis plays a regulatory role in chondrocyte differentiation and endochondral osteogenesis by modulating various growth factors and signaling molecules. For instance, glycosaminoglycan is involved in mediating pathways such as Wnt, TGF-β, FGF, Ihh-PTHrP, and O-GlcNAc glycosylation, interacting with transcription factors SOX9, BMPs, TGF-β, and Runx2 to regulate chondrocyte differentiation and endochondral osteogenesis. To propose innovative approaches for addressing orthopedic diseases caused by impaired glycosaminoglycan biosynthesis, we conducted a comprehensive review of the molecular mechanisms underlying chondrocyte glycosaminoglycan biosynthesis, which regulates chondrocyte differentiation and endochondral osteogenesis. Our analysis considers the role of genes, glycoproteins, and associated signaling pathways during chondrogenesis and endochondral ossification.

Galectin-1 promotes angiogenesis and chondrogenesis during antler regeneration

BACKGROUND

Deer antlers are the only known mammalian structure that undergoes full regeneration. In addition, it is peculiar because when growing, it contains vascularized cartilage. The differentiation of antler stem cells (ASCs) into chondrocytes while inducing endochondral extension of blood vessels is necessary to form antler vascularized cartilage. Therefore, antlers provide an unparalleled opportunity to investigate chondrogenesis, angiogenesis, and regenerative medicine. A study found that Galectin-1 (GAL-1), which can be used as a marker in some tumors, is highly expressed in ASCs. This intrigued us to investigate what role GAL-1 could play in antler regeneration.

METHODS

We measured the expression level of GAL-1 in antler tissues and cells by immunohistochemistry, WB and QPCR. We constructed antlerogenic periosteal cells (APCs, one cell type of ASCs) with the GAL-1 gene knocked out (APC^GAL-1-/-) using CRISPR-CAS9 gene editing system. The effect of GAL-1 on angiogenesis was determined by stimulating human umbilical vein endothelial cells (HUVECs) using APC^GAL-1-/- conditioned medium or adding exogenous deer GAL-1 protein. The effect of APC^GAL-1-/- on chondrogenic differentiation was evaluated compared with the APCs under micro-mass culture. The gene expression pattern of APC^GAL-1-/- was analyzed by transcriptome sequencing.

RESULTS

Immunohistochemistry revealed that GAL-1 was widely expressed in the antlerogenic periosteum (AP), pedicle periosteum (PP) and antler growth center. Western blot and qRT-PCR analysis using deer cell lines further supports this result. The proliferation, migration, and tube formation assays of human umbilical vein endothelial cells (HUVECs) showed that the proangiogenic activity of APC^GAL-1-/- medium was significantly decreased (P < 0.05) compared with the APCs medium. The proangiogenic activity of deer GAL-1 protein was further confirmed by adding exogenous deer GAL-1 protein (P < 0.05). The chondrogenic differentiation ability of APC^GAL-1-/- was impeded under micro-mass culture. The terms of GO and KEGG enrichment of the differentially expressed genes (DEGs) of APC^GAL-1-/- showed that down-regulated expression of pathways associated with deer antler angiogenesis, osteogenesis and stem cell pluripotency, such as the PI3K-AKT signaling pathway, signaling pathways regulating pluripotency of stem cells and TGF-β signaling pathway.

CONCLUSIONS

Deer GAL-1, has strong angiogenic activity, is widely and highly expressed in deer antler. The APCs can induce angiogenesis by secreting GAL-1. The knockout of GAL-1 gene of APCs damaged its ability to induce angiogenesis and differentiate into chondrocytes. This ability is crucial to the formation of deer antler vascularized cartilage. Moreover, Deer antlers offer a unique model to explore explore how angiogenesis at high levels of GAL-1 expression can be elegantly regulated without becoming cancerous.

Comparison of genome-wide DNA methylation patterns between antler precartilage and cartilage

Deer antlers are the only mammalian organs that can fully regenerate after being lost and provide a valuable model for cartilage development. As one of the best-studied epigenetic mechanisms, DNA methylation is known to engage in organ and tissue development. This study aimed to investigate the role of DNA methylation in antler chondrogenesis by comparing whole-genome DNA methylation between precartilage and cartilage. Quantitative reverse transcription PCR (RT-qPCR) showed significant differences in the expression levels of DNA methyltransferase genes (DNMT1, DNMT3A, and DNMT3B) between precartilage and cartilage. Subsequently, we obtained DNA methylation profiles of antler precartilage and cartilage tissues by whole-genome bisulfite sequencing. Although sequencing data indicated that overall methylation levels at CpG and non-CpG sites were similar between precartilage and cartilage, 140,784 differentially methylated regions (DMRs, P < 0.05) and 3,941 DMR-related genes were identified. Gene ontology (GO) analysis of DMR-related genes demonstrated some significantly enriched GO terms (P < 0.05) related to chondrogenesis, including insulin receptor binding, collage trimer, integrin binding, and extracellular matrix structural constituent. Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis of DMR-related genes uncovered that the PI3K/AKT, cortisol synthesis and secretion, glycosaminoglycan biosynthesis-keratan sulfate, Hippo, and NF-κB signaling pathways might play a pivotal role in the transition of precartilage to cartilage. Moreover, we found that 25 DMR-related genes, including CD44, IGF1, ITGAV, ITGB1, RUNX1, COL2A1, COMP, and TAGLN, were most likely involved in antler chondrogenesis. In conclusion, this study revealed the genome-wide DNA methylation patterns of antler precartilage and cartilage, which may contribute to understanding the epigenetic regulation of antler chondrogenesis.

Igf1 Regulates Fibrocartilage Stem Cells, Cartilage Growth, and Homeostasis in the Temporomandibular Joint of Mice

Temporomandibular joint (TMJ) growth requires orchestrated interactions between various cell types. Recent studies revealed that fibrocartilage stem cells (FCSCs) in the TMJ cartilage play critical roles as cell resources for joint development and repair. However, the detailed molecular network that influences FCSC fate during TMJ cartilage development remains to be elucidated. Here, we investigate the functional role of Igf1 in FCSCs for TMJ cartilage growth and homeostasis by lineage tracing using Gli1-CreER⁺ ; Tm^flfl mice and conditional Igf1 deletion using Gli1-/Col2-CreER⁺ ; Igf1^fl/fl mice. In Gli1-CreER⁺ ; Tm^flfl mice, red fluorescence⁺ (RFP⁺ ) FCSCs show a favorable proliferative capacity. Igf1 deletion in Gli1⁺ /Col2⁺ cell lineages leads to distinct pathological changes in TMJ cartilage. More serious cartilage thickness and cell density reductions are found in the superficial layers in Gli1-CreER⁺ ; Igf1^fl/fl mice. After long-term Igf1 deletion, a severe disordered cell arrangement is found in both groups. When Igf1 is conditionally deleted in vivo, the red fluorescent protein-labeled Gli1⁺ FCSC shows a significant disruption of chondrogenic differentiation, cell proliferation, and apoptosis leading to TMJ cartilage disarrangement and subchondral bone loss. Immunostaining shows that pAkt signaling is blocked in all cartilage layers after the Gli1⁺ -specific deletion of Igf1. In vitro, Igf1 deletion disrupts FCSC capacities, including proliferation and chondrogenesis. Moreover, the deletion of Igf1 in FCSCs significantly aggravates the joint osteoarthritis phenotype in the unilateral anterior crossbite mouse model, characterized by decreased cartilage thickness and cell numbers as well as a loss of extracellular matrix secretions. These findings uncover Igf1 as a regulator of TMJ cartilage growth and repair. The deletion of Igf1 disrupts the progenitor capacity of FCSCs, leading to a disordered cell distribution and exaggerating TMJ cartilage dysfunction. © 2023 American Society for Bone and Mineral Research (ASBMR).

The roles of Runx1 in skeletal development and osteoarthritis: A concise review

Runt-related transcription factor-1 (Runx1) is well known for its functions in hematopoiesis and leukemia but recent research has focused on its role in skeletal development and osteoarthritis (OA). Deficiency of the Runx1 gene is fatal in early embryonic development, and specific knockout of Runx1 in cell lineages of cartilage and bone leads to delayed cartilage formation and impaired bone calcification. Runx1 can regulate genes including collagen type II (Col2a1) and X (Col10a1), SRY-box transcription factor 9 (Sox9), aggrecan (Acan) and matrix metalloproteinase 13 (MMP-13), and the up-regulation of Runx1 improves the homeostasis of the whole joint, even in the pathological state. Moreover, Runx1 is activated as a response to mechanical compression, but impaired in the joint with the pathological progress associated with osteoarthritis. Therefore, interpretation about the role of Runx1 could enlarge our understanding of key marker genes in the skeletal development and an increased understanding of Runx1 could be helpful to identify treatments for osteoarthritis. This review provides the most up-to-date advances in the roles and bio-mechanisms of Runx1 in healthy joints and osteoarthritis from all currently published articles and gives novel insights in therapeutic approaches to OA based on Runx1.

Relationship between osteoporosis and Cushing syndrome based on bioinformatics

BACKGROUND

Many clinical studies have reported a relatively high incidence of osteoporosis and fragility fractures in patients with Cushing syndrome (CS). However, few papers have investigated osteoporosis and CS in terms of pathogenesis, so this study explores the association between the 2 and predicts upstream micro-ribonucleic acids (miRNAs) through bioinformatics, which provides potential targets for simultaneous pharmacological interventions in both diseases and also provides a basis for pathological screening.

METHODS

We used Genecards, Online Mendelian Inheritance in Man and Therapeutic Target Database databases to screen the targets of osteoporosis and Cushing syndrome; import target genes to Database for Annotation, Visualization and Integrated Discovery for Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway analysis; the intersecting genes were uploaded to Search Tool for the Retrieval of Genes and Genomes database to construct protein-protein interaction network; Cytoscape software was used to screen core genes, and Molecular Complex Detection module was used to analyze cluster modules; finally, the NetworkAnalyst data platform was used to predict the miRNAs that interact with core genes.

RESULTS

The core genes of osteoporosis and Cushing syndrome were insulin, tumor necrosis factor, signal transducer and activator of transcription 3 (STAT3), interleukin-6, insulin-like growth factor 1, etc. A total of 340 upstream miRNAs including hsa-let-7a-5p, hsa-mir-30a-5p and hsa-mir-125b-5p were predicted. The biological processes involved include regulating the transcription of ribonucleic acid polymerase II promoter and participating in the transduction of cytokine signaling pathways, which focus on the binding of nerve system ligand, JAK-STAT signaling pathway, Rap1 signaling pathway, PI3K-Akt signaling pathway, etc.

CONCLUSION

Osteoporosis and Cushing syndrome are closely related in terms of targets and molecular mechanisms. In this study, bioinformatics methods were used to identify their targets and mechanisms, providing potential targets for drug simultaneous regulation of the 2 diseases, and providing a new direction for exploring the relationship between diseases.

Exploring the relationship between osteoporosis and polycystic ovary syndrome based on bioinformatics

BACKGROUND

In recent years, clinical studies have found that there is a close relationship between osteoporosis and polycystic ovary syndrome. However, there are few literature on the pathogenesis of osteoporosis and polycystic ovary syndrome. In order to clarify their common pathogenic mechanism and provide potential targets for drugs to regulate them at the same time, bioinformatics methods are used to explore, so as to provide a new direction for the study of the relationship between diseases in the future.

METHODS

To screen the targets of osteoporosis and polycystic ovary syndrome by Genecards, Online Mendelian Inheritance in Man databases and Therapeutic Target Database to take the intersection of the two mappings and upload the intersection targets to the STRING database to construct protein-protein interaction network; to screen the core targets by degree value and import them to Metascape database for Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway analysis; and finally, to construct the visualization network of core targets and pathways by Cytoscape software. Ethical approval and informed consent of patients are not required because the data used in this study is publicly available and does not involve individual patient data or privacy.

RESULTS

The core targets of polycystic ovary syndrome and osteoporosis were insulin gene, insulin-like growth factor 1, CTNNB1, serine/threonine kinase 1, signal transducer and activator of transcription 3, LEP, etc. The biological processes involved include the regulation of protein phosphorylation, cell proliferation and differentiation, hormone endocrine, reproductive system and skeletal system. The related pathways were concentrated in Foxo signaling pathway, HTLV-I infection, PI3K-AKT signaling pathway, MAPK signaling pathway and AGE-RAGE signaling pathway in diabetic complications.

CONCLUSIONS

There is a close relationship between osteoporosis and polycystic ovary syndrome in terms of target and molecular mechanism. This study used bioinformatics to clarify their targets and mechanisms, providing potential targets for drugs to regulate both diseases simultaneously and providing new directions to explore the relationship between the diseases.

Transcriptome Analysis Reveals Novel Genes Associated with Cartilage Degeneration in Posttraumatic Osteoarthritis Progression

OBJECTIVE

The current therapeutic strategy for posttraumatic osteoarthritis (PTOA) focuses on early intervention to attenuate disease progression, preserve joint function, and defer joint replacement timing. Sequential transcriptomic changes of articular cartilage in a rat model were investigated to explore the molecular mechanism in early PTOA progression.

DESIGN

Anterior cruciate ligament transection and medial meniscectomy (ACLT + MMx)-induced PTOA model was applied on male Wistar rats. Articular cartilages were harvested at time 0 (naïve), 2 week, and 4 weeks after surgery. Affymetrix Rat genome 230 2.0 array was utilized to analyze the gene expression changes of articular cartilages.

RESULTS

We identified 849 differentially expressed genes (DEGs) at 2 weeks and 223 DEGs at 4 weeks post-ACLT + MMx surgery compared with time 0 (naïve group). Gene ontology and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis were performed to gain further insights from these DEGs. 22 novel genes and 1 novel KEGG pathway (axon guidance) in cartilage degeneration of osteoarthritis were identified. Axon guidance molecules-Gnai1, Sema4d, Plxnb1, and Srgap2 commonly dysregulated in PTOA progression. Gnai1 gene showed a concordant change in protein expression by immunohistochemistry staining.

CONCLUSIONS

Our study identified 22 novel dysregulated genes and axon guidance pathway associated with articular cartilage degeneration in PTOA progression. These findings provide the potential candidates of biomarkers and therapeutic targets for further investigation.

Integrating transcriptome-wide association study and mRNA expression profile identified candidate genes related to hand osteoarthritis

Background

Osteoarthritis (OA) is a common skeletal system disease that has been partially attributed to genetic factors. The hand is frequently affected, which seriously affects the patient’s quality of life. However, the pathogenetic mechanism of hand osteoarthritis (hand OA) is still elusive.

Methods

A genome-wide association study (GWAS) summary of hand OA was obtained from the UK Biobank dataset, which contains data from a total of 452,264 White British individuals, including 37,782 OA patients. The transcriptome-wide association study (TWAS) of hand OA was performed using FUnctional Summary-based ImputatiON (FUSION) with the skeletal muscle and blood as gene expression references. The significant genes identified by TWAS were further subjected to gene set enrichment analysis (GSEA) with the Database for Annotation, Visualization and Integrated Discovery (DAVID) tool. Furthermore, we compared the genes and gene sets identified by our TWAS with that of a knee OA mRNA expression profile to detect the genes and gene sets shared by TWAS and mRNA expression profiles in OA. The mRNA expression profiles of 18 normal knee cartilages and 20 OA knee cartilages were acquired from the Gene Expression Omnibus database (accession number: GSE114007).

Results

TWAS identified 177 genes with P < 0.05 for the skeletal muscle, including ANKRD44 (P = 0.0001), RIC3 (P = 0.0003), and AC005154.6 (P = 0.0004). TWAS identified 423 genes with P < 0.05 for the blood, including CRIM1 (P = 0.0002), ZNF880 (P = 0.0002), and NCKIPSD (P = 0.0003). After comparing the results of the TWAS to those of the mRNA expression profiling of OA, we identified 5 common genes, including DHRS3 (log2fold = − 1.85, P = 3.31 × 10^− 9) and SKP2 (log2fold = 1.36, P = 1.62 × 10^− 8). GSEA of TWAS identified 51 gene ontology (GO) terms for hand OA, for example, protein binding (P = 0.0003) and cytosol (P = 0.0020). We also detected 6 common GO terms shared by TWAS and mRNA expression profiling, including protein binding (P_TWAS = 2.54 × 10^− 4, P_mRNA = 3.42 × 10^− 8), extracellular exosome (P_TWAS = 0.02, P_mRNA = 1.18 × 10^− 4), and cytoplasm (P_TWAS = 0.0183, P_mRNA = 0.0048).

Conclusion

In this study, we identified 5 candidate genes and 6 GO terms related to hand OA, which may help to uncover the pathogenesis of hand OA. It should be noted that the possible difference in the gene expression profiles between hand OA and knee OA may affect our study results, which should be interpreted with caution.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13075-021-02458-2.

Altered IHH signaling contributes to reduced chondrocyte proliferation in the growth plate of MPS VII mice

Bone elongation is driven by chondrocyte proliferation and hypertrophy in the growth plate. Both processes are modulated by multiple signaling pathways including the Indian Hedgehog (IHH) signaling pathway. Mucopolysaccharidoses (MPS) are a group of lysosomal storage disorders characterized by accumulation of glycosaminoglycans (GAGs) in multiple tissues and organs, leading to a range of clinical symptoms including bone shortening through mechanisms that are not fully understood. Using MPS VII mice, we previously observed a reduction in the number of proliferating and hypertrophic chondrocytes and a reduced gene expression of Ihh in the tibial growth plate. We further demonstrate here that IHH secretion by MPS VII chondrocytes was reduced both in vitro and in vivo. While normal chondrocytes showed no response to exogenous IHH, proliferation of MPS VII chondrocytes was stimulated in response to exogenous IHH in vitro. This was accompanied by an elevated gene expression of patched receptor (Ptch1). The results from this study suggested that reduced proliferation in MPS VII growth plate may be partially due to dysfunction of the IHH signaling pathway.

Genome sequence and comparative analysis of reindeer (Rangifer tarandus) in northern Eurasia

Reindeer are semi-domesticated ruminants that have adapted to the challenging northern Eurasian environment characterized by long winters and marked annual fluctuations in daylight. We explored the genetic makeup behind their unique characteristics by de novo sequencing the genome of a male reindeer and conducted gene family analyses with nine other mammalian species. We performed a population genomics study of 23 additional reindeer representing both domestic and wild populations and several ecotypes from various geographic locations. We assembled 2.66 Gb (N50 scaffold of 5 Mb) of the estimated 2.92 Gb reindeer genome, comprising 27,332 genes. The results from the demographic history analysis suggested marked changes in the effective population size of reindeer during the Pleistocene period. We detected 160 reindeer-specific and expanded genes, of which zinc finger proteins (n = 42) and olfactory receptors (n = 13) were the most abundant. Comparative genome analyses revealed several genes that may have promoted the adaptation of reindeer, such as those involved in recombination and speciation (PRDM9), vitamin D metabolism (TRPV5, TRPV6), retinal development (PRDM1, OPN4B), circadian rhythm (GRIA1), immunity (CXCR1, CXCR2, CXCR4, IFNW1), tolerance to cold-triggered pain (SCN11A) and antler development (SILT2). The majority of these characteristic reindeer genes have been reported for the first time here. Moreover, our population genomics analysis suggested at least two independent reindeer domestication events with genetic lineages originating from different refugial regions after the Last Glacial Maximum. Taken together, our study has provided new insights into the domestication, evolution and adaptation of reindeer and has promoted novel genomic research of reindeer.

Novel insights into Dhh signaling in antler chondrocyte proliferation and differentiation: Involvement of Foxa

The desert hedgehog (Dhh) is crucial for spermatogenesis and Leydig cell differentiation, but little is known regarding its physiological function in cartilage. In this study, Dhh mRNA was abundant in antler chondrocytes, where it advanced cell proliferation concomitant with accelerated transition from the G1 to the S phase and induced elevation of the hypertrophic chondrocyte markers, Col X and Runx2. Silencing of Ptch1 resulted in appreciable Smo accumulation and enhanced rDhh stimulation of Smo, whose impediment by cyclopamine obscured the proliferative function of Dhh and alleviated its guidance of chondrocyte differentiation. Further analysis evidenced the noteworthy positive action of Smo in the bridging between Dhh and Gli transcription factors. Obstruction of Gli1 by GANT58 caused the failed stimulation of Col X and Runx2 by rDhh. Analogously, siRNA against Gli1-3 hindered chondrocyte differentiation in the context of rDhh. Simultaneously, Gli transcription factors mediated the regulation of Dhh on Foxa1, Foxa2, and Foxa3, whose knockdown impaired chondrocyte differentiation. Attenuation of Foxa antagonized the augmentation of Col X and Runx2 generated by rDhh. Collectively, Dhh signaling through its target Foxa appears to induce antler chondrocyte proliferation and differentiation.

Reclassification of velvet antler portions following transcriptomic analysis

Context Commercially, velvet antlers along the longitudinal axis are divided into four portions, namely, wax-like (WL), blood-colour (BC), honeycomb-like (HL) and bone (B) slices from the top to the base. However, there is no evidence at a molecular level showing the accuracy of this classification. Aims The aim of the present study was to take transcriptional approach to assess the accuracy of the traditional classification for these four portions of velvet antler, and to link the expressed mRNAs of each portion with possible functions by using bioinformatics analysis. Methods Three sticks of three-branched velvet antlers of sika deer were harvested from three anaesthetised 4-year-old sika deer. On the basis of the traditional methods used commercially, the velvet antler sticks were divided into the four portions of WL, BC, HL and B. Transcriptome sequencing was performed using Illumina HiSeq × Ten at BGI (Shenzheng, China). Key results In total, 5647 genes were obtained from the four portions. Spearman correlation analysis grouped these four portions into three clusters (WL, BC, HL+B). C-means analysis further confirmed a similar trend, indicating the accuracy of the new classification based on transcriptome analysis. Further functional analysis showed that highly expressed genes in WL, BC and HL+B were mainly related to cell cycle, cartilage development, and bone development respectively. Conclusions Four-portion classification based on traditional methods should be replaced by three-portion classification based on the mRNA expression levels. Implications We believe that this new classification can contribute to velvet antler industry, providing more accuracy in the use of velvet antlers as pharmaceuticals.

Altered chondrocyte differentiation, matrix mineralization and MEK-Erk1/2 signaling in an INPPL1 catalytic knock-out mouse model of opsismodysplasia

Opsismodysplasia (OPS) is a rare but severe autosomal recessive skeletal chondrodysplasia caused by inactivating mutations in the Inppl1/Ship2 gene. The molecular mechanism leading from Ship2 gene inactivation to OPS is currently unknown. Here, we used our Ship2^Δ/Δ mouse expressing reduced amount of a catalytically-inactive SHIP2 protein and a previously reported SHIP2 inhibitor to investigate growth plate development and mineralization in vivo, ex vivo and in vitro. First, as observed in OPS patients, catalytic inactivation of SHIP2 in mouse leads to reduced body length, shortening of long bones, craniofacial dysmorphism, reduced height of the hyperthrophic chondrocyte zone and to defects in growth plate mineralization. Second, intrinsic Ship2^Δ/Δ bone defects were sufficient to induce the characteristic OPS alterations in bone growth, histology and mineralization ex vivo. Third, expression of osteocalcin was significantly increased in SHIP2-inactivated chondrocyte cultures whereas production of mineralized nodules was markedly decreased. Targeting osteocalcin mRNA with a specific shRNA increased the production of mineralized nodules. Fourth, levels of p-MEK and p-Erk1/2 were significantly increased in SHIP2-inactivated chondrocytes in response to serum and IGF-1, but not to FGF2, as compared to control chondrocytes. Treatment of chondrocytes and bones in culture with a MEK inhibitor partially rescued the production of mineralized nodules, the size of the hypertrophic chondrocyte zone and bone growth, raising the possibility of a treatment that could partially reduce the phenotype of this severe condition. Altogether, our results indicate that Ship2^Δ/Δ mice represent a relevant model for human OPS. They also highlight the important role of SHIP2 in chondrocytes during endochondral ossification and its different differentiation steps. Finally, we identified a role of osteocalcin in mineralized nodules production and for the MEK-Erk1/2 signaling pathway in the OPS phenotype.

Advances in understanding of presbycusis

The pathophysiology of age-related hearing loss (ARHL), or presbycusis, involves a complex interplay between environmental and genetic factors. The fundamental biomolecular mechanisms of ARHL have been well described, including the roles of membrane transport, reactive oxygen species, cochlear synaptopathy, vascular insults, hormones, and microRNA, to name a few. The genetic basis underlying these mechanisms remains under-investigated and poorly understood. The emergence of genome-wide association studies has allowed for the identification of specific groups of genes involved in ARHL. This review highlights recent advances in understanding of the pathogenesis of ARHL, the genetic basis underlying these processes and suggests future directions for research and potential therapeutic avenues.

The Role of Insulin-Like Growth Factor 1 in the Progression of Age-Related Hearing Loss

Aging is associated with impairment of sensorial functions and with the onset of neurodegenerative diseases. As pari passu circulating insulin-like growth factor 1 (IGF-1) bioavailability progressively decreases, we see a direct correlation with sensory impairment and cognitive performance in older humans. Age-related sensory loss is typically caused by the irreversible death of highly differentiated neurons and sensory receptor cells. Among sensory deficits, age-related hearing loss (ARHL), also named presbycusis, affects one third of the population over 65 years of age and is a major factor in the progression of cognitive problems in the elderly. The genetic and molecular bases of ARHL are largely unknown and only a few genes related to susceptibility to oxidative stress, excitotoxicity, and cell death have been identified. IGF-1 is known to be a neuroprotective agent that maintains cellular metabolism, activates growth, proliferation and differentiation, and limits cell death. Inborn IGF-1 deficiency leads to profound sensorineural hearing loss both in humans and mice. IGF-1 haploinsufficiency has also been shown to correlate with ARHL. There is not much information available on the effect of IGF-1 deficiency on other human sensory systems, but experimental models show a long-term impact on the retina. A secondary action of IGF-1 is the control of oxidative stress and inflammation, thus helping to resolve damage situations, acute or made chronic by aging. Here we will review the primary actions of IGF-1 in the auditory system and the underlying molecular mechanisms.

The Regulatory Mechanism of MLT/MT1 Signaling on the Growth of Antler Mesenchymal Cells

Melatonin (MLT) plays an important role in regulating the physiological cycle of seasonal breeding animals. Melatonin receptor I (MT1) is effectively expressed in the cambium layer of deer antler. However, the function and metabolic mechanism of MLT/MT1 signaling in the mesenchymal cells of sika deer remain to be further elucidated. In this work, we detected the effects of MLT/MT1 signaling on mesenchymal cells proliferation and the interaction between MLT/MT1 and IGF1/IGF1-R signaling. The results show that (1) deer antler mesenchymal cells actually express MT1; (2) exogenous melatonin significantly promotes mesenchymal cells proliferation, while MT1 knock-down significantly impairs the positive effects of melatonin; and (3) melatonin significantly enhanced IGF1/IGF1-R signaling, as both the expression of IGF1 and IGF-1R increased, while MT1 knock-down significantly decreased IGF1-R expression and IGF1 synthesis. In summary, these data verified that MLT/MT1 signaling plays a crucial role in antler mesenchymal proliferation, which may be mediated by IGF1/IGF1-R.

ATRA Signaling Regulates the Expression of COL9A1 through BMP2-WNT4-RUNX1 Pathway in Antler Chondrocytes

Although all-trans retinoic acid (ATRA) is involved in the regulation of cartilage growth and development, its regulatory mechanisms remain unknown. Here, we showed that ATRA could induce the expression of COL9A1 in antler chondrocytes. Silencing of cellular retinoic acid binding protein 2 (CRABP2) could impede the ATRA-induced upregulation of COL9A1, whereas overexpression of CRABP2 presented the opposite effect. RARα agonist Am80 induced the expression of COL9A1, whereas treatment with RARα antagonist Ro 41-5253 or RXRα small-interfering RNA (siRNA) caused an obvious blockage of ATRA on COL9A1. In antler chondrocytes, CYP26A1 and CYP26B1 weakened the sensitivity of ATRA to COL9A1. Simultaneously, Bone morphogenetic protein 2 (BMP2) and WNT4 mediated the regulation of ATRA on COL9A1 expression. Knockdown of WNT4 could abrogate the inhibitory effect of BMP2 overexpression on COL9A1. Conversely, constitutive expression of WNT4 reversed the upregulation of COL9A1 elicited by BMP2 siRNA. Together these data indicated that WNT4 might act downstream of BMP2 to mediate the effect of ATRA on COL9A1 expression. Further analysis evidenced that attenuation of runt-related transcription factor 1 (RUNX1) could prevent the stimulation of ATRA on COL9A1 expression, while exogenous rRUNX1 further enhanced this effectiveness. Moreover, RUNX1 might serve as an intermediate to mediate the regulation of BMP2 and WNT4 on COL9A1 expression. Collectively, ATRA signaling might regulate the expression of COL9A1 through BMP2-WNT4-RUNX1 pathway.