Antler stem cells as a novel stem cell source for reducing liver fibrosis

Mesenchymal stem cells-extracellular vesicles alleviate pulmonary fibrosis by regulating immunomodulators

BACKGROUND

Pulmonary fibrosis (PF) is a chronic interstitial lung disease characterized by fibroblast proliferation and extracellular matrix formation, causing structural damage and lung failure. Stem cell therapy and mesenchymal stem cells-extracellular vesicles (MSC-EVs) offer new hope for PF treatment.

AIM

To investigate the therapeutic potential of MSC-EVs in alleviating fibrosis, oxidative stress, and immune inflammation in A549 cells and bleomycin (BLM)-induced mouse model.

METHODS

The effect of MSC-EVs on A549 cells was assessed by fibrosis markers [collagen I and α-smooth muscle actin (α-SMA), oxidative stress regulators [nuclear factor E2-related factor 2 (Nrf2) and heme oxygenase-1 (HO-1), and inflammatory regulators [nuclear factor-kappaB (NF-κB) p65, interleukin (IL)-1β, and IL-2]. Similarly, they were assessed in the lungs of mice where PF was induced by BLM after MSC-EV transfection. MSC-EVs ion PF mice were detected by pathological staining and western blot. Single-cell RNA sequencing was performed to investigate the effects of the MSC-EVs on gene expression profiles of macrophages after modeling in mice.

RESULTS

Transforming growth factor (TGF)-β1 enhanced fibrosis in A549 cells, significantly increasing collagen I and α-SMA levels. Notably, treatment with MSC-EVs demonstrated a remarkable alleviation of these effects. Similarly, the expression of oxidative stress regulators, such as Nrf2 and HO-1, along with inflammatory regulators, including NF-κB p65 and IL-1β, were mitigated by MSC-EV treatment. Furthermore, in a parallel manner, MSC-EVs exhibited a downregulatory impact on collagen deposition, oxidative stress injuries, and inflammatory-related cytokines in the lungs of mice with PF. Additionally, the mRNA sequencing results suggested that BLM may induce PF in mice by upregulating pulmonary collagen fiber deposition and triggering an immune inflammatory response. The findings collectively highlight the potential therapeutic efficacy of MSC-EVs in ameliorating fibrotic processes, oxidative stress, and inflammatory responses associated with PF.

CONCLUSION

MSC-EVs could ameliorate fibrosis in vitro and in vivo by downregulating collagen deposition, oxidative stress, and immune-inflammatory responses.

Mesenchymal stem cells-extracellular vesicles alleviate pulmonary fibrosis by regulating immunomodulators

BACKGROUND

Pulmonary fibrosis (PF) is a chronic interstitial lung disease characterized by fibroblast proliferation and extracellular matrix formation, causing structural damage and lung failure. Stem cell therapy and mesenchymal stem cells-extracellular vesicles (MSC-EVs) offer new hope for PF treatment.

AIM

To investigate the therapeutic potential of MSC-EVs in alleviating fibrosis, oxidative stress, and immune inflammation in A549 cells and bleomycin (BLM)-induced mouse model.

METHODS

The effect of MSC-EVs on A549 cells was assessed by fibrosis markers [collagen I and α-smooth muscle actin (α-SMA), oxidative stress regulators [nuclear factor E2-related factor 2 (Nrf2) and heme oxygenase-1 (HO-1), and inflammatory regulators [nuclear factor-kappaB (NF-κB) p65, interleukin (IL)-1β, and IL-2]. Similarly, they were assessed in the lungs of mice where PF was induced by BLM after MSC-EV transfection. MSC-EVs ion PF mice were detected by pathological staining and western blot. Single-cell RNA sequencing was performed to investigate the effects of the MSC-EVs on gene expression profiles of macrophages after modeling in mice.

RESULTS

Transforming growth factor (TGF)-β1 enhanced fibrosis in A549 cells, significantly increasing collagen I and α-SMA levels. Notably, treatment with MSC-EVs demonstrated a remarkable alleviation of these effects. Similarly, the expression of oxidative stress regulators, such as Nrf2 and HO-1, along with inflammatory regulators, including NF-κB p65 and IL-1β, were mitigated by MSC-EV treatment. Furthermore, in a parallel manner, MSC-EVs exhibited a downregulatory impact on collagen deposition, oxidative stress injuries, and inflammatory-related cytokines in the lungs of mice with PF. Additionally, the mRNA sequencing results suggested that BLM may induce PF in mice by upregulating pulmonary collagen fiber deposition and triggering an immune inflammatory response. The findings collectively highlight the potential therapeutic efficacy of MSC-EVs in ameliorating fibrotic processes, oxidative stress, and inflammatory responses associated with PF.

CONCLUSION

MSC-EVs could ameliorate fibrosis in vitro and in vivo by downregulating collagen deposition, oxidative stress, and immune-inflammatory responses.

Antler thymosin β10 reduces liver fibrosis via inhibiting TGF-β1/SMAD pathway

Hepatic stellate cell (HSC) activation is a crucial step in the development of liver fibrosis. Previous studies have shown that antler stem cells (AnSCs) inhibited HSC activation, suggesting that this may be achieved through secreting or releasing peptides. This study aimed to investigate whether AnSC-derived peptides (AnSC-P) could reduce liver fibrosis. The results showed that AnSC-P effectively reduced liver fibrosis in rats. Furthermore, we found that thymosin β10 (Tβ-10) was rich in AnSC-P, which may be the main component of AnSC-P contributing to the reduction in liver fibrosis. A further study showed that Tβ-10 reduced liver fibrosis in rats, with a reduction in HYP and MDA levels in the liver tissues, a decrease in the serum levels of ALP, ALT, AST, and TBIL and an increase in TP and ALB. Moreover, Tβ-10 decreased the expression levels of the genes related to the TGF-β/SMAD signaling pathway in vivo. In addition, Tβ-10 also inhibited TGF-β1-induced HSC activation and decreased the expression levels of the TGF-β/SMAD signaling pathway-related genes in HSCs in vitro. In conclusion, antler Tβ-10 is a potential drug candidate for the treatment of liver fibrosis, the effect of which may be achieved via inhibition of the TGFβ/SMAD signaling pathway.

The Current Proceedings of PSC-Based Liver Fibrosis Therapy

Liver fibrosis was initially considered to be an irreversible process which will eventually lead to the occurrence of liver cancer. So far there has been no effective therapeutic approach to treat liver fibrosis although scientists have put tremendous efforts into the underlying mechanisms of this disease. Therefore, in-depth research on novel and safe treatments of liver fibrosis is of great significance to human health. Pluripotent stem cells (PSCs) play important roles in the study of liver fibrosis due to their unique features in self-renewal ability, pluripotency, and paracrine function. This article mainly reviews the applications of PSCs in the study of liver fibrosis in recent years. We discuss the role of PSC-derived liver organoids in the study of liver fibrosis, and the latest research advances on the differentiation of PSCs into hepatocytes or macrophages. We also highlight the importance of exosomes of PSCs for the treatment of liver fibrosis.

Antler stem cell exosomes alleviate pulmonary fibrosis via inhibiting recruitment of monocyte macrophage, rather than polarization of M2 macrophages in mice

Pulmonary fibrosis (PF), a chronic interstitial lung disease, is characterized by over-abundant deposition of extracellular matrix consisting mainly of collagen I. In previous studies, we demonstrated that deer antler stem cells (AnSCs), a novel type of adult stem cell, are capable of significantly down-regulating collagen formation in different organs and tissues and speculated that they could effectively treat PF via reducing collagen deposition in the lung tissue. In the present study, we found that administration of AnSCs improved the survival rate of PF mice and reduced lung fibrosis, collagen deposition and myofibroblast differentiation. The effects of AnSC treatment were significantly better than the positive control (adipose-derived stem cells). Interestingly, AnSC-Exos were almost equally effective as AnSCs in treating PF, suggesting that the effects of AnSCs on reduction of PF may be mainly through a paracrine mechanism. Further, AnSC-Exos reduced the number of M2 macrophages, a type of macrophage that secrets pro-fibrotic factors to accelerate fibrotic progression, in the lung tissues. In vitro experiments showed that the effects of AnSC-Exos on macrophage modulation were likely achieved via inhibition of the recruitment of circulating monocyte-derived macrophages (reducing the number of macrophages), rather than via inhibition of M2 polarization of macrophages. Inhibition of macrophage recruitment by AnSCs may be achieved indirectly via inhibiting CCL7 expression in fibroblasts; both let-7b and let-7a were highly enriched in AnSC-Exos and may play a critical role in the inhibition of CCL7 expression of fibroblasts. Collectively, the use of antler stem cells or their exosomes opens up a novel strategy for PF treatment in the clinical setting.

The characteristics and medical applications of antler stem cells

Antlers are the only fully regenerable mammalian appendages whose annual renewal is initiated by antler stem cells (ASCs), defined as a specialized type of mesenchymal stem cells (MSCs) with embryonic stem cell properties. ASCs possess the same biological features as MSCs, including the capacity for self-renewal and multidirectional differentiation, immunomodulatory functions, and the maintenance of stem cell characteristics after multiple passages. Several preclinical studies have shown that ASCs exhibit promising potential in wound healing, bone repair, osteoarthritis, anti-tissue fibrosis, anti-aging, and hair regeneration. Medical applications based on ASCs and ASC-derived molecules provide a new source of stem cells and therapeutic modalities for regenerative medicine. This review begins with a brief description of antler regeneration and the role of ASCs. Then, the properties and advantages of ASCs are described. Finally, medical research advances regarding ASCs are summarized, and the prospects and challenges of ASCs are highlighted.

Mechanism of annexin A1/N-formylpeptide receptor regulation of macrophage function to inhibit hepatic stellate cell activation through Wnt/β-catenin pathway

BACKGROUND

Hepatic fibrosis is a common pathological process of chronic liver diseases with various causes, which can progress to cirrhosis.

AIM

To evaluate the effect and mechanism of action annexin (Anx)A1 in liver fibrosis and how this could be targeted therapeutically.

METHODS

CCl₄ (20%) and active N-terminal peptide of AnxA1 (Ac2-26) and N-formylpeptide receptor antagonist N-Boc-Phe-Leu-Phe-Leu-Phe (Boc2) were injected intraperitoneally to induce liver fibrosis in eight wild-type mice/Anxa1 knockout mice, and to detect expression of inflammatory factors, collagen deposition, and the role of the Wnt/β-catenin pathway in hepatic fibrosis.

RESULTS

Compared with the control group, AnxA1, transforming growth factor (TGF)-β1, interleukin (IL)-1β and IL-6 expression in the liver of mice with hepatic fibrosis induced by CCl₄ was significantly increased, which promoted collagen deposition and expression of α-smooth muscle actin (α-SMA), collagen type I and connective tissue growth factor (CTGF), and increased progressively with time. CCl₄ induced an increase in TGF-β1, IL-1β and IL-6 in liver tissue of AnxA1 knockout mice, and the degree of liver inflammation and fibrosis and expression of α-SMA, collagen I and CTGF were significantly increased compared with in wild-type mice. After treatment with Ac2-26, expression of liver inflammatory factors, degree of collagen deposition and expression of a-SMA, collagen I and CTGF were decreased compared with before treatment. Boc2 inhibited the anti-inflammatory and antifibrotic effects of Ac2-26. AnxA1 downregulated expression of the Wnt/β-catenin pathway in CCl₄-induced hepatic fibrosis. In vitro, lipopolysaccharide (LPS) induced hepatocyte and hepatic stellate cell (HSC) expression of AnxA1. Ac2-26 inhibited LPS-induced RAW264.7 cell activation and HSC proliferation, decreased expression of α-SMA, collagen I and CTGF in HSCs, and inhibited expression of the Wnt/β-catenin pathway after HSC activation. These therapeutic effects were inhibited by Boc2.

CONCLUSION

AnxA1 inhibited liver fibrosis in mice, and its mechanism may be related to inhibition of HSC Wnt/β-catenin pathway activation by targeting formylpeptide receptors to regulate macrophage function.

Deer Antler Reserve Mesenchyme Cell-Conditioned Medium Reduces the Destruction of Periodontitis in Mice

Reserve mesenchyme cells (RMCs) are a type of antler stem cells (ASCs) that contribute to the rapid growth of deer antlers, the only known mammalian organ that can fully regenerate annually. Based on the prior evidence, ASC-conditioned medium could improve regenerative cutaneous healing in rats. The purpose of the study was to evaluate the therapeutic effects of RMC-conditioned medium (RMC-CM) on reducing the destruction in the mice periodontitis (PD) model and the underlying mechanisms. The lipopolysaccharide (LPS)-stimulated RAW264.7 cells were used in vitro to verify the effects of RMC-CM. The results revealed that RMC-CM could significantly reduce bone resorption and osteoclast activation, upregulate anti-inflammatory macrophages (M2) related interleukin (IL)-10 and CD206, and downregulate pro-inflammatory macrophages (M1) related tumor necrosis factor alpha (TNF-α) and inducible nitric oxide synthase in vivo. In vitro, RMC-CM could significantly promote LPS-stimulated RAW264.7 cells migration, reduce osteoclast differentiation, downregulate the expression of TNF-α, IL-6, and IL-1β, and upregulate the expression of IL-10 and arginase 1. According to the results, we concluded that RMC-CM could significantly reduce alveolar bone resorption and inhibit inflammation in gingival tissue by decreasing the activation of osteoclasts and inducing macrophage polarization toward the M2 phenotype. This study may serve as the experimental foundation for RMC-CM in the treatment of PD.

Therapeutic Potential of Mesenchymal Stem Cells versus Omega n − 3 Polyunsaturated Fatty Acids on Gentamicin-Induced Cardiac Degeneration

This study compared the cardioprotective action of mesenchymal stem cells (MSCs) and PUFAs in a rat model of gentamicin (GM)-induced cardiac degeneration. Male Wistar albino rats were randomized into four groups of eight rats each: group I (control group), group II (gentamicin-treated rats receiving gentamicin intraperitoneally (IP) at dose of 100 mg/kg/day for 10 consecutive days), group III (gentamicin and PUFA group receiving gentamicin IP at dose of 100 mg/kg/day for 10 consecutive days followed by PUFAs at a dose of 100 mg/kg/day for 4 weeks), and group IV (gentamicin and MSC group receiving gentamicin IP at dose of 100 mg/kg/day followed by a single dose of MSCs (1 × 10⁶)/rat IP). Cardiac histopathology was evaluated via light and electron microscopy. Immunohistochemical detection of proliferating cell nuclear antigen (PCNA), caspase-3 (apoptosis), Bcl2, and Bax expression was performed. Moreover, cardiac malonaldehyde (MDA) content, catalase activity, and oxidative stress parameters were biochemically evaluated. Light and electron microscopy showed that both MSCs and PUFAs had ameliorative effects. Their actions were mediated by upregulating PCNA expression, downregulating caspase-3 expression, mitigating cardiac MDA content, catalase activity, and oxidative stress parameters. MSCs and PUFAs had ameliorative effects against gentamicin-induced cardiac degeneration, with MSCs showing higher efficacy compared to PUFAs.

Ferulic Acid Combined With Bone Marrow Mesenchymal Stem Cells Attenuates the Activation of Hepatic Stellate Cells and Alleviates Liver Fibrosis

Bone marrow mesenchymal stem cells (BMSCs) can effectively alleviate liver fibrosis, but the efficacy of cell therapy alone is insufficient. In recent years, a combination of traditional Chinese medicine (TCM) and cell therapy has been increasingly used to treat diseases in clinical trials. Ferulic acid (FA) is highly effective in treating liver fibrosis, and a combination of cells and drugs is being tested in clinical trials. Therefore, we combined BMSCs and Ferulic acid to treat CCl₄-induced fibrosis and determine whether this combination was more effective than single treatment. We used BMSCs and FA to treat CCl₄-induced fibrosis in rat models, observed their therapeutic effects, and investigated the specific mechanism of this combination therapy in liver fibrosis. We created a BMSC/hepatic stellate cell (HSC) coculture system and used FA to treat activated HSCs to verify the specific mechanism. Then, we used cytochalasin D and angiotensin II to investigate whether BMSCs and FA inactivate HSCs through cytoskeletal rearrangement. MiR-19b-3p was enriched in BMSCs and targeted TGF-β receptor II (TGF-βR2). We separately transfected miR-19b-3p into HSCs and BMSCs and detected hepatic stellate cell activation. We found that the expression of the profibrotic markers α-SMA and COL1-A1 was significantly decreased in the combination group of rats. α-SMA and COL1-A1 levels were also significantly decreased in the HSCs with the combination treatment. Cytoskeletal rearrangement of HSCs was inhibited in the combination group, and RhoA/ROCK pathway gene expression was decreased. Following angiotensin II treatment, COL1-A1 and α-SMA expression increased, while with cytochalasin D treatment, profibrotic gene expression decreased in HSCs. The expression of COL1-A1, α-SMA and RhoA/ROCK pathway genes was decreased in the activated HSCs treated with a miR-19b-3p mimic, indicating that miR-19b-3p inactivated HSCs by suppressing RhoA/ROCK signalling. In contrast, profibrotic gene expression was significantly decreased in the BMSCs treated with the miR-19b-3p mimic and FA or a miR-19b-3p inhibitor and FA compared with the BMSCs treated with the miR-19b-3p mimic alone. In conclusion, the combination therapy had better effects than FA or BMSCs alone. BMSC and FA treatment attenuated HSC activation and liver fibrosis by inhibiting cytoskeletal rearrangement and delivering miR-19b-3p to activated HSCs, inactivating RhoA/ROCK signalling. FA-based combination therapy showed better inhibitory effects on HSC activation.

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.

Bone marrow derived-mesenchymal stem cell improves diabetes-associated fatty liver via mitochondria transformation in mice

Background

Non-alcoholic fatty liver disease (NAFLD) has become a global epidemic disease. Its incidence is associated with type 2 diabetes mellitus (T2DM). Presently, there is no approved pharmacological agents specially developed for NAFLD. One promising disease-modifying strategy is the transplantation of stem cells to promote metabolic regulation and repair of injury.

Method

In this study, a T2DM model was established through 28-week high-fat diet (HFD) feeding resulting in T2DM-associated NAFLD, followed by the injection of bone marrow mesenchymal stem cells (BMSCs). The morphology, function, and transfer of hepatocyte mitochondria were evaluated in both vivo and in vitro.

Results

BMSC implantation resulted in the considerable recovery of increasing weight, HFD-induced steatosis, liver function, and disordered glucose and lipid metabolism. The treatment with BMSC transplantation was accompanied by reduced fat accumulation. Moreover, mitochondrial transfer was observed in both vivo and vitro studies. And the mitochondria-recipient steatotic cells exhibited significantly enhanced OXPHOS activity, ATP production, and mitochondrial membrane potential, and reduced reactive oxygen species levels, which were not achieved by the blocking of mitochondrial transfer.

Conclusion

Mitochondrial transfer from BMSCs is a feasible process to combat NAFLD via rescuing dysfunction mitochondria, and has a promising therapeutic effect on metabolism-related diseases.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-021-02663-5.

The Provocative Roles of Platelets in Liver Disease and Cancer

Both platelets and the liver play important roles in the processes of coagulation and innate immunity. Platelet responses at the site of an injury are rapid; their immediate activation and structural changes minimize the loss of blood. The majority of coagulation proteins are produced by the liver—a multifunctional organ that also plays a critical role in many processes: removal of toxins and metabolism of fats, proteins, carbohydrates, and drugs. Chronic inflammation, trauma, or other causes of irreversible damage to the liver can dysregulate these pathways leading to organ and systemic abnormalities. In some cases, platelet-to-lymphocyte ratios can also be a predictor of disease outcome. An example is cirrhosis, which increases the risk of bleeding and prothrombotic events followed by activation of platelets. Along with a triggered coagulation cascade, the platelets increase the risk of pro-thrombotic events and contribute to cancer progression and metastasis. This progression and the resulting tissue destruction is physiologically comparable to a persistent, chronic wound. Various cancers, including colorectal cancer, have been associated with increased thrombocytosis, platelet activation, platelet-storage granule release, and thrombosis; anti-platelet agents can reduce cancer risk and progression. However, in cancer patients with pre-existing liver disease who are undergoing chemotherapy, the risk of thrombotic events becomes challenging to manage due to their inherent risk for bleeding. Chemotherapy, also known to induce damage to the liver, further increases the frequency of thrombotic events. Depending on individual patient risks, these factors acting together can disrupt the fragile balance between pro- and anti-coagulant processes, heightening liver thrombogenesis, and possibly providing a niche for circulating tumor cells to adhere to—thus promoting both liver metastasis and cancer-cell survival following treatment (that is, with minimal residual disease in the liver).

Extracellular vesicles derived from umbilical cord mesenchymal stromal cells alleviate pulmonary fibrosis by means of transforming growth factor-β signaling inhibition

Background

Pulmonary fibrosis (PF), the end point of interstitial lung diseases, is characterized by myofibroblast over differentiation and excessive extracellular matrix accumulation, leading to progressive organ dysfunction and usually a terminal outcome. Studies have shown that umbilical cord-derived mesenchymal stromal cells (uMSCs) could alleviate PF; however, the underlying mechanism remains to be elucidated.

Methods

The therapeutic effects of uMSC-derived extracellular vesicles (uMSC-EVs) on PF were evaluated using bleomycin (BLM)-induced mouse models. Then, the role and mechanism of uMSC-EVs in inhibiting myofibroblast differentiation were investigated in vivo and in vitro.

Results

Treatment with uMSC-EVs alleviated the PF and enhanced the proliferation of alveolar epithelial cells in BLM-induced mice, thus improved the life quality, including the survival rate, body weight, fibrosis degree, and myofibroblast over differentiation of lung tissue. Moreover, these effects of uMSC-EVs on PF are likely achieved by inhibiting the transforming growth factor-β (TGF-β) signaling pathway, evidenced by decreased expression levels of TGF-β2 and TGF-βR2. Using mimics of uMSC-EV-specific miRNAs, we found that miR-21 and miR-23, which are highly enriched in uMSC-EVs, played a critical role in inhibiting TGF-β2 and TGF-βR2, respectively.

Conclusion

The effects of uMSCs on PF alleviation are likely achieved via EVs, which reveals a new role of uMSC-EV-derived miRNAs, opening a novel strategy for PF treatment in the clinical setting.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-021-02296-8.

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.