MicroRNA profiling of antler stem cells in potentiated and dormant states and their potential roles in antler regeneration

MiRNA Profiling and Its Potential Roles in Rapid Growth of Velvet Antler in Gansu Red Deer (Cervus elaphus kansuensis)

A significant variety of cell growth factors are involved in the regulation of antler growth, and the fast proliferation and differentiation of various tissue cells occur during the yearly regeneration of deer antlers. The unique development process of velvet antlers has potential application value in many fields of biomedical research. Among them, the nature of cartilage tissue and the rapid growth and development process make deer antler a model for studying cartilage tissue development or rapid repair of damage. However, the molecular mechanisms underlying the rapid growth of antlers are still not well studied. MicroRNAs are ubiquitous in animals and have a wide range of biological functions. In this study, we used high-throughput sequencing technology to analyze the miRNA expression patterns of antler growth centers at three distinct growth phases, 30, 60, and 90 days following the abscission of the antler base, in order to determine the regulatory function of miRNA on the rapid growth of antlers. Then, we identified the miRNAs that were differentially expressed at various growth stages and annotated the functions of their target genes. The results showed that 4319, 4640, and 4520 miRNAs were found in antler growth centers during the three growth periods. To further identify the essential miRNAs that could regulate fast antler development, five differentially expressed miRNAs (DEMs) were screened, and the functions of their target genes were annotated. The results of KEGG pathway annotation revealed that the target genes of the five DEMs were significantly annotated to the "Wnt signaling pathway", "PI3K-Akt signaling pathway", "MAPK signaling pathway", and "TGF-β signaling pathway", which were associated with the rapid growth of velvet antlers. Therefore, the five chosen miRNAs, particularly ppy-miR-1, mmu-miR-200b-3p, and novel miR-94, may play crucial roles in rapid antler growth in summer.

RNA sequencing-based identification of microRNAs in the antler cartilage of Gansu red deer (Cervus elaphus kansuensis)

Background

The velvet antler is a complex mammalian bone organ with unique biological characteristics, such as regeneration. The rapid growth stage (RGS) is a special period in the regeneration process of velvet antler.

Methods

To elucidate the functions of microRNAs (miRNAs) at the RGS of antler development in Gansu red deer (Cervus elaphus kansuensis), we used RNA sequencing (RNA-seq) to analyze miRNA expression profiles in cartilage tissues of deer antler tips at three different growth stages.

Results

The RNA-seq results revealed 1,073 known and 204 novel miRNAs, including 1,207, 1,242, and 1,204 from 30-, 60-, and 90-d antler cartilage tissues, respectively. To identify key miRNAs controlling rapid antler growth, we predicted target genes of screened 25 differentially expressed miRNAs (DEMs) and specifically expressed miRNAs (SEMs) in 60 d and annotated their functions. The KEGG results revealed that target genes of 25 DEMs and 30 SEMs were highly classified in the "Metabolic pathways", "Pathways in cancer", "Proteoglycans in cancer" and "PI3K-Akt signaling pathway". In addition, a novel miRNA (CM008039.1_315920), highly enriched in "NF-kappa B signaling pathway", may need further study.

Conclusions

The miRNAs identified in our study are potentially important in rapid antler growth. Our findings provide new insights to help elucidate the miRNA-mediated regulatory mechanisms involved during velvet antler development in C. elaphus kansuensis.

Progress of Noncoding RNA Regulating the Growth and Development of Antler Tissue Research

Antler is the secondary sexual characteristic of deer, which develops on the forehead at puberty. It is the only organ that can be regenerated entirely in mammals. Therefore, it is often used as a research model in the field of organ regeneration and wound repair. Many growth factors and proteins play an active role throughout the developmental process of antler regeneration. With the rapid development of sequencing technology, more and more noncoding RNAs (ncRNAs) have been discovered, and the relationship between ncRNA and antler regeneration has gradually become clear. This paper focuses on the research progress of several ncRNAs (including miRNA and lncRNA) in deer antler tissues, which are helpful to reveal the molecular mechanism of deer antler regeneration at the molecular level.

MIC-1 Antlerogenic Stem Cells Homogenate from Cervus elaphus Accelerate Corneal Burn Reepithelization in Rabbits

Deer antler is the only mammalian organ that can fully grow back once lost from its pedicle. Antler regeneration is a stem cell-based process. Therefore, antlers probably offer the most pertinent model for studying organ regeneration in mammals. Evaluation of the effect of deer antler stem cells on the healing of superficial and deep rabbit corneal wounds was performed. Thirty-six New Zealeand White rabbits were used in this study in superficial and deep denaturation models, and corneal erosion was performed with n-heptanol placed on the cornea for 30 and NaOH for 90 s. Antler stem cells in drop formulation with hyaluronate was used. As a control, sodium hyaluronate in the superficial model and protein-free calf blood dialysate (Solcoseryl) in the deep model were administered. In superficial corneal damage, a reduction in the area of the damaged cornea was observed from day 3 of the experiment to an adequate level: 45% in the test group and 52% in the control group relative to the baseline damage (100%). Between days 3 and 7, on average, a smaller lesion area was observed in the group receiving antler stem cells. The use of antler stem cells has resulted in a marked improvement in cornea clarity. According to the 5-point scale of corneal opacity evaluation, where 1 is completely clear and 5 is completely opaque, the first statistically significant changes were observed after 4 weeks of treatment: 3.0 in the study group, 4.1 in the control with Solcoseryl, and 4.4 in the control group. After 9 weeks, these values were, 2.5, 3.8, and 4.1, respectively. The present preliminary study shows the promising results of antlerogenic stem cells of Cervus elaphus topically applied for the treatment of corneal injury. A deeper understanding of the developmental mechanisms involved in antler renewal can be useful for controlling regeneration cornea processes.

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.

Residual antler periosteum holds the potential to partially regenerate lost antler tissue

Deer antlers are the only mammalian organs that can fully regenerate, which relies on pedicle periosteum (PP). Interestingly during the growing phase, antlers themselves can regenerate partially lost antler tissue. However, what tissue type in the growing antlers fulfills this role is not known. Following antler removal during the growing phase, a "second" antler regenerates from the stump. In this study, the "second" antler growing from the cut antler base (AB) was examined in both red and sika deer. The results showed that all regenerating antlers were formed from the peripheral edge of the AB, where the antler periosteum (AnP) is located. The growth center showed a clear demarcation from the AB bone in red deer. Therefore, it is highly likely that AnP is the tissue that possesses the potential. Factors that might affect this potential were explored and the main factor was found to be AB calcification, which was controlled by rising androgens. Thus, the ultimate antler regeneration potential of the AnP was assessed through castration and repeated antler removal. The results demonstrated that the regeneration potential of AnP was somewhat limited and inferior to that of the PP. The ability of AnP to achieve partial regeneration may be evolutionarily conserved, as the regeneration of partially lost antlers within the season is secured; whereas, with PP, a new set of antlers in the next season is guaranteed. This two-level mechanism may signify how evolutionarily important it is for deer to possess reasonably intact antlers.

Integrated analysis of miRNA and mRNA transcriptomic reveals antler growth regulatory network

The growth of antler is driven by endochondral ossification in the growth center of the apical region. Antler grows faster than cancer tissues, but it can be stably regulated and regenerated periodically. To elucidate the molecular mechanisms of how antler grows rapidly without carcinogenesis, in this study, we used RNA-seq technology to evaluate the changes of miRNA and mRNA profiles in antler at four different developmental stages, including 15, 60, 90, and 110 days. We identified a total of 55004 unigenes and 246 miRNAs of which, 10182, 13258, 10740 differentially expressed (DE) unigenes and 35, 53, 27 DE miRNAs were identified in 60-day vs. 15-day, 90-day vs. 60-day, and 110-day vs. 90-day. GO and KEGG pathway analysis indicated that DE unigenes and DE miRNA were mainly associated with chondrogenesis, osteogenesis and inhibition of oncogenesis, that were closely related to antler growth. The interaction networks of mRNA-mRNA and miRNA-mRNA related to chondrogenesis, osteogenesis and inhibition of oncogenesis of antler were constructed. The results indicated that mRNAs (COL2A1, SOX9, WWP2, FGFR1, SPARC, LOX, etc.) and miRNAs (miR-145, miR-199a-3p, miR-140, miR-199a-5p, etc.) might have key roles in chondrogenesis and osteogenesis of antler. As well as mRNA (TP53, Tpm3 and ATP1A1, etc.) and miRNA (miR-106a, miR-145, miR-1260b and miR-2898, etc.) might play important roles in inhibiting the carcinogenesis of antler. In summary, we constructed the mRNA-mRNA and miRNA-mRNA regulatory networks related to chondrogenesis, osteogenesis and inhibition of oncogenesis of antler, and identified key candidate mRNAs and miRNAs among them. Further developments and validations may provide a reference for in-depth analysis of the molecular mechanism of antler growth without carcinogenesis.

New physiological insights into the phenomena of deer antler: A unique model for skeletal tissue regeneration

Generally, mammals are unable to regenerate complex tissues and organs however the deer antler provides a rare anomaly to this rule. This osseous cranial appendage which is located on the frontal bone of male deer is capable of stem cell-based organogenesis, annual casting, and cyclic de novo regeneration. A series of recent studies have classified this form of regeneration as epimorphic stem cell based. Antler renewal is initiated by the activation of neural crest derived pedicle periosteal cells (PPCs) found residing within the pedicle periosteum (PP), these PPCs have the potential to differentiate into multiple lineages. Other antler stem cells (ASCs) are the reserve mesenchymal cells (RMCs) located in the antlers tip, which develop into cartilage tissue. Antlerogenic periosteal cells (APCs) found within the antlerogenic periosteum (AP) form the tissues of both the pedicle and first set of antlers. Antler stem cells (ASCs) further appear to progress through various stages of activation, this coordinated transition is considered imperative for stem cell-based mammalian regeneration. The latest developments have shown that the rapid elongation of the main beam and antler branches are a controlled form of tumour growth, regulated by the tumour suppressing genes TP73 and ADAMTS18. Both osteoclastogenesis, as well as osteogenic and chondrogenic differentiation are also involved. While there remains much to uncover this review both summarises and comprehensively evaluates our existing knowledge of tissue regeneration in the deer antler. This will assist in achieving the goal of in vitro organ regeneration in humans by furthering the field of modern regenerative medicine.

The Translational potential of this article

As a unique stem cell-based organ regeneration process in mammals, the deer antler represents a prime model system for investigating mechanisms of regeneration in mammalian tissues. Novel ASCs could provide cell-based therapies for regenerative medicine and bone remodelling for clinical application. A greater understanding of this process and a more in-depth defining of ASCs will potentiate improved clinical outcomes.

MicroRNAomic Transcriptomic Analysis Reveal Deregulation of Clustered Cellular Functions in Human Mesenchymal Stem Cells During in Vitro Passaging

Clinical trials using human mesenchymal stem/stromal cells (hMSCs) for cell replacement therapy showed varied outcomes, where cells' efficacy has been perceived as the limiting factor. In particular, the quality and number of the expanded cells in vitro. In this study, we aimed to determine molecular signatures of hMSCs derived from the pulp of extracted deciduous teeth (SHED) and Wharton's jelly (WJSCs) that associated with cellular ageing during in vitro passaging. We observed distinct phenotypic changes resembling proliferation reduction, cell enlargement, an increase cell population in G2/M phase, and differentially expressed of tumor suppressor p53 in passage (P) 6 as compared to P3, which indicating in vitro cell senescence. The subsequent molecular analysis showed a set of diverse differentially expressed miRNAs and mRNAs involved in maintaining cell proliferation and stemness properties. Considering the signaling pathway related to G2/M DNA damage regulation is widely recognized as part of anti-proliferation mechanism controlled by p53, we explored possible miRNA-mRNA interaction in this regulatory pathway based on genomic coordinates retrieved from miRanda. Our work reveals the potential reason for SHED underwent proliferation arrest due to the direct impinge on the expression of CKS1 by miRNAs specifically miR-22 and miR-485-5p which lead to down regulation of CDK1 and Cyclin B. It is intended that our study will contribute to the understanding of these miRNA/mRNA driving the biological process and regulating different stages of cell cycle is beneficial in developing effective rejuvenation strategies in order to obtain quality stem cells for transplantation.

Screening and functional identification of lncRNAs in antler mesenchymal and cartilage tissues using high-throughput sequencing

Long non-coding RNA (lncRNA) is a transcription product of the mammalian genome that regulates the development and growth in the body. The present study aimed to analyze the expression dynamics of lncRNA in sika antler mesenchymal and cartilage tissues by high-throughput sequencing. Bioinformatics was applied to predict differentially expressed lncRNAs and target genes and screen lncRNAs and mRNAs related to osteogenic differentiation, cell proliferation, and migration. Finally, the expression of the lncRNAs and target genes were analyzed by qRT-PCR. The results showed that compared to the cartilage tissue, the transcription levels of lncRNA and mRNA, 1212 lncRNAs and 518 mRNAs, in mesenchymal tissue were altered significantly. Thus, a complex interaction network was constructed, and the lncRNA-mRNA interaction network correlation related to osteogenic differentiation, cell proliferation, and migration was analyzed. Among these, the 26 lncRNAs and potential target genes were verified by qRT-PCR, and the results of qRT-PCR were consistent with high-throughput sequencing results. These data indicated that lncRNA promotes the differentiation of deer antler mesenchymal tissue into cartilage tissue by regulating the related osteogenic factors, cell proliferation, and migration-related genes and accelerating the process of deer antler regeneration and development.

Whole Transcriptome Analysis of Mesenchyme Tissue in Sika Deer Antler Revealed the CeRNAs Regulatory Network Associated With Antler Development

Deer antler is the only completely regenerable organ in mammals. During the rapid growth period, the antler proliferates even faster than cancerous tissue growth. However, the proliferation and development of antler have been in a stable and controllable growth cycle. In this study, we analyzed the time series expression data of nine samples from mesenchyme layer in three male sika deer in the early period of the antler with a saddle-like appearance (30 days), the rapid growth period of the antler with two branches (60 days), and the final period of the antler with three branches (90 days). Whole Transcriptome sequencing results show that in the 30 d versus 60 d group, 1,464 genes, 85 long noncoding RNAs (lncRNAs), and 61 miRNAs were identified as differentially expressed; 1,748 genes, 138 lncRNAs, and 78 miRNAs were identified as differentially expressed in 30d versus 90d group; and 816 differentially expressed genes (DEGs), 49 differentially expressed lncRNAs (DE lncRNAs), and 24 differentially expressed miRNA (DE miRNAs) were identified in 60d versus 90d group. A total of 182 miRNA-mRNA interaction pairs and 89 miRNA-lncRNA interaction pairs were screened from DEGs, DE miRNAs, and DE lncRNAs to construct the ceRNA regulatory network (ceRNET). In summary, we identified candidate mRNAs, miRNAs and lncRNAs that regulate the development of antler tip. It may lay the foundation for further investigating the molecular mechanism of antler rapid growth and development.

Effects of macrophage-conditioned medium on sika deer (Cervus nippon) antler stem cells

Context Immune system has been claimed as the ‘main switch’ of tissue or organ regeneration. Among immune cells, macrophages stand out as important modulators in mutiple regeneration models, such as planarian, axolotl, mammalian hair and liver. As a unique model for mammals, deer antler is considered to ideal for studying complete mammalian organ regeneration. Studies have found that antler regeneration is a stem cell-based process and antler stem cells locate in the pedicle periosteum (PP). Although the regulatory roles of the immune system in other regeneration models have been extensively studied, they remain unstudied in antler regeneration. Aims To explore the possible role of macrophages in the PP cells (PPCs). Methods We treated PPCs with a macrophage-conditioned medium (MCM) and detected effects of MCM on proliferation, migration and apoptosis of the PPCs, and identified differentially expressed genes by using the RNA-seq technique. Key results We found that MCM enhanced proliferation rate and migration rate significantly and stimulated apoptosis of the PPCs. Using the RNA-seq technique, we identified 112 differentially expressed genes in the PPCs (38 downregulated and 74 upregulated) after the MCM treatment. Furthermore, gene-ontology annotation analyses showed that the upregulated genes were mainly involved in cell adhesion, chemotaxis, wound healing, growth factor-stimulated responses, and bone formation, and the downregulated genes were involved in regulation of biosynthesis. Conclusions MCM had a great influence on the antler stem cells, and macrophages might regulate antler regeneration through altering the microenvironment and gene-expression profiles of the PPCs. Implications We believe that the results of the present study would facilitate the discovery of the roles of immune system in antler stem cells and, thus, mammalian organ regeneration in general.

miR-20b, miR-296, and Let-7f Expression in Human Adipose Tissue is Related to Obesity and Type 2 Diabetes

OBJECTIVE

This study aimed to analyze the potential association of different microRNA (miRNA) molecules with both type 2 diabetes (T2D) and obesity and determine their target genes.

METHODS

Quantitative PCR was used to analyze the miR-20b, miR-296, and Let-7f levels in human visceral and subcutaneous adipose tissues (ATs) in relation to obesity and T2D, miRTarBase 4.0 was used for validation of target genes, and the Protein Analysis Through Evolutionary Relationships (PANTHER) Classification System and the Database for Annotation, Visualization and Integrated Discovery (DAVID) were used to annotate the biological processes of the predicted targets.

RESULTS

In AT, miR-20b, miR-296, and Let-7f levels were significantly different between normoglycemic subjects and those with T2D. In visceral adipose tissue, miRNA levels were higher in normoglycemic/obesity samples than in T2D/obesity samples. miR-20b-miR-296 and Let-7f target genes that showed significant differences in both ATs in relation to obesity and T2D were CDKN1A, CX3CL1, HIF1A, PPP2R1B, STAT3, and VEGFA. These genes are known to be principally involved in the vascular endothelial growth factor (VEGF) and WNT pathways.

CONCLUSIONS

This study provides experimental evidence of the possible correlation between AT miR-20b-miR-296-Let-7f with obesity and T2D, which might involve vascular endothelial growth factor and WNT-dependent pathways that are regulated by six different genes, suggesting a novel signaling pathway that could be important for understanding the mechanisms underlying the AT dysfunction associated with obesity and T2D.

The red deer Cervus elaphus genome CerEla1.0: sequencing, annotating, genes, and chromosomes

We present here the de novo genome assembly CerEla1.0 for the red deer, Cervus elaphus, an emblematic member of the natural megafauna of the Northern Hemisphere. Humans spread the species in the South. Today, the red deer is also a farm-bred animal and is becoming a model animal in biomedical and population studies. Stag DNA was sequenced at 74× coverage by Illumina technology. The ALLPATHS-LG assembly of the reads resulted in 34.7 × 10³ scaffolds, 26.1 × 10³ of which were utilized in Cer.Ela1.0. The assembly spans 3.4 Gbp. For building the red deer pseudochromosomes, a pre-established genetic map was used for main anchor points. A nearly complete co-linearity was found between the mapmarker sequences of the deer genetic map and the order and orientation of the orthologous sequences in the syntenic bovine regions. Syntenies were also conserved at the in-scaffold level. The cM distances corresponded to 1.34 Mbp uniformly along the deer genome. Chromosomal rearrangements between deer and cattle were demonstrated. 2.8 × 10⁶ SNPs, 365 × 10³ indels and 19368 protein-coding genes were identified in CerEla1.0, along with positions for centromerons. CerEla1.0 demonstrates the utilization of dual references, i.e., when a target genome (here C. elaphus) already has a pre-established genetic map, and is combined with the well-established whole genome sequence of a closely related species (here Bos taurus). Genome-wide association studies (GWAS) that CerEla1.0 (NCBI, MKHE00000000) could serve for are discussed.

Protective effects and plausible mechanisms of antler-velvet polypeptide against hydrogen peroxide induced injury in human umbilical vein endothelial cells

Antler velvet polypeptide (VAP) is a prominent bioactive component of antler velvet. Whereas uncharacterized crude extracts have typically been used in pharmacological studies, in this study, the velvet polypeptide was isolated and purified by acid water extraction, ethanol precipitation, ammonium sulfate fractionation and precipitation, and chromatography, progressively. Human umbilical vein endothelial cells (HUVECs) were induced with H₂O₂ followed purified polypeptide treatment. Cell viability was evaluated by MTT assay. The apoptosis of cells was detected by fluorescence microscopy and flow cytometry. A cell analyzer was used to measure the mitochondrial membrane potential. The intracellular reactive oxygen species (ROS) levels were determined by flow cytometry. Oxidative stress related biochemical parameters were detected, and the expression of apoptosis-related proteins was examined by Western blot analysis. The results indicated that a 7.0 kDa polypeptide (VAP II) was isolated from antler velvet. VAP II enhanced cell viability, decreased cell apoptosis, reversed depolarization of mitochondrial membrane potential, decreased ROS levels, inhibited oxidative stress, and regulated the downstream signaling apoptotic cascade expression caused by H₂O₂. The protective effects of VAP II on HUVECs suggests a potential strategy for the treatment of cardiovascular disease.