Ghrelin accelerates wound healing in combined radiation and wound injury in mice

Ghrelin promotes chronic diabetic wound healing by regulating keratinocyte proliferation and migration through the ERK1/2 pathway

Delayed wound healing is a complication of diabetes mellitus and can lead to infection, sepsis, and amputation. Despite the currently available treatments, the global burden of diabetes-related wounds is growing; thus, more effective therapy for diabetic wounds is urgently needed. Ghrelin, an endogenous ligand for the growth hormone secretagogue receptor, is a 28-amino acid peptide hormone. Some reports have confirmed the therapeutic effects of ghrelin on diabetes mellitus and its complications. However, the effects and corresponding mechanisms of ghrelin on chronic diabetic wounds remain unknown. In this study, we explored the effect of ghrelin on diabetic wound healing and investigated the associated mechanisms. We showed that ghrelin accelerated wound healing in diabetic rats by promoting the proliferation and migration of keratinocytes. Re-epithelialization was accelerated in ghrelin-treated wounds, thicker and longer newly formed epidermis and more dividing keratinocytes were observed. We further confirmed that ghrelin regulated keratinocytes by activating the ERK1/2 pathway through its receptor growth hormone secretagogue receptor 1a (GHSR1a). Ghrelin also significantly reduced the levels of pro-inflammatory cytokines and increased the deposition of collagen in diabetic wounds. Our data provides preclinical evidence for the potential application of ghrelin as a compound to promote diabetic wound healing and clarifies the molecular mechanism.

A recombinant plasmid encoding human hepatocyte growth factor promotes healing of combined radiation-trauma skin injury involved in regulating Nrf2 pathway in mice

Combined radiation-trauma skin injury represents a severe and intractable condition that urgently requires effective therapeutic interventions. In this context, hepatocyte growth factor (HGF), a multifunctional growth factor with regulating cell survival, angiogenesis, anti-inflammation and antioxidation, may be valuable for the treatment of combined radiation-trauma injury. This study investigated the protective effects of a recombinant plasmid encoding human HGF (pHGF) on irradiated human immortalized keratinocytes (HaCaT) cells in vitro, and its capability to promote the healing of combined radiation-trauma injuries in mice. The pHGF radioprotection on irradiated HaCaT cells in vitro was assessed by cell viability, the expression of Nrf2, Bcl-2 and Bax, as well as the secretion of inflammatory cytokines. In vivo therapeutic treatment, the irradiated mice with full-thickness skin wounds received pHGF local injection. The injuries were appraised based on relative wound area, pathology, immunohistochemical detection, terminal deoxynucleotidyl transferase dUTP nick end labelling assay and cytokine content. The transfection of pHGF increased the cell viability and Nrf2 expression in irradiated HaCaT cells. pHGF also significantly upregulated Bcl-2 expression, decreased the Bax/Bcl-2 ratio and inhibited the expression of interleukin-1β and tumor necrosis factor-α in irradiated cells. Local pHGF injection in vivo caused high HGF protein expression and noticeable accelerated healing of combined radiation-trauma injury. Moreover, pHGF administration upregulated Nrf2, vascular endothelial growth factor, Bcl-2 expression, downregulated Bax expression and mitigated inflammatory response. In conclusion, the protective effect of pHGF may be related to inhibiting apoptosis and inflammation involving by upregulating Nrf2. Local pHGF injection distinctly promoted the healing of combined radiation-trauma injury and demonstrates potential as a gene therapy intervention for combined radiation-trauma injury in clinic.

Alleviation of radiation combined skin injury in rat model by topical application of ascorbate formulation

PURPOSE

This research endeavor was undertaken to elucidate the impact of an innovative ascorbate formulation on the regeneration process of full-thickness excision wounds in a rat model exposed to whole-body gamma irradiation, replicating conditions akin to combat or radiation emergency scenarios.

MATERIALS AND METHODS

We established a comprehensive rat model by optimizing whole body γ-radiation doses (5-9 Gy) and full-thickness excision wound sizes (1-3 cm2) to mimic radiation combined injury (RCI). The developed RCI model was used to explore the healing potential of ascorbate formulation. The study includes various treatment groups (i.e., sham control, radiation alone, wound alone, radiation + wound, and radiation + wound + formulation). The ascorbate formulation was applied twice daily, with a 12-hour gap between each application, starting 1 hour after the initiation of the wound. The healing potential of the formulation in the RCI context was evaluated over 14 days through hematological, molecular, and histological parameters.

RESULTS

The combination of a 5 Gy radiation dose and a 1 cm2 wound was identified as the optimal setting to develop the RCI model for subsequent studies. The formulation was used topically immediately following RCI, and then twice daily until complete healing. Treatment with the ascorbate formulation yielded noteworthy outcomes and led to a substantial reduction (p < .05) in the wound area, accelerated epithelialization periods, and an increased wound contraction rate. The formulation's localized healing response improved organ weights, normalized blood parameters, and enhanced hematopoietic and immune systems. A gene expression study revealed the treatment up-regulated TGF-β and FGF, and down-regulated PDGF-α, TNF-α, IL-1β, IL-6, MIP-1α, and MCP-1 (p < .05). Histopathological assessments supported the formulation's effectiveness in restoring cellular architecture and promoting tissue regeneration.

CONCLUSION

Topical application of the ascorbate formulation in RCI resulted in a significant improvement in delayed wound healing, leading to accelerated wound closure by mitigating the expression of inflammatory responses.

Injectable multifunctional chitosan/dextran-based hydrogel accelerates wound healing in combined radiation and burn injury

Clinical wound management of combined radiation and burn injury (CRBI) remains a huge challenge due to serious injuries induced by redundant reactive oxygen species (ROS), the accompanying hematopoietic, immunologic suppression and stem cell reduction. Herein, the injectable multifunctional Schiff base cross-linked with gallic acid modified chitosan (CSGA)/oxidized dextran (ODex) hydrogels were rationally designed to accelerate wound healing through elimination of ROS in CRBI. CSGA/ODex hydrogels, fabricated by mixing solutions of CSGA and Odex, displayed good self-healing ability, excellent injectability, strong antioxidant activity, and favorable biocompatibility. More importantly, CSGA/ODex hydrogels exhibited excellent antibacterial properties, which is facilitated for wound healing. Furthermore, CSGA/ODex hydrogels significantly suppressed the oxidative damage of L929 cells in an H₂O₂-induced ROS microenvironment. The recovery of mice with CRBI in mice demonstrated that CSGA/ODex hydrogels significantly reduced the hyperplasia of epithelial cells and the expression of proinflammatory cytokine, and accelerated wound healing which was superior to the treatment with commercial triethanolamine ointment. In conclusion, the CSGA/ODex hydrogels as a wound dressing could accelerate the wound healing and tissue regeneration of CRBI, which provides great potential in clinical treatment of CRBI.

Jia-Wei-Si-Miao-Yong-An Fang stimulates the healing of acute radiation-induced cutaneous wounds through MAPK/ERK pathway

ETHNOPHARMACOLOGICAL RELEVANCE

A famous traditional oral Chinese medicine formula, Si-Miao-Yong-An decoction, has been used to treat thromboangiitis obliterans from the Qing Dynasty. Because its therapeutic principles including clearing away heat, detoxification, accelerating blood circulation and relieving pains are consistent with acute radiation-induced cutaneous wounds in traditional Chinese medicine, we tried to add herbs and improve them into an external dosage form, called Jia-Wei-Si-Miao-Yong-An Fang (JWSMYA). However, its mechanism on radiation-induced cutaneous wounds is still unknown.

AIM OF THE STUDY

This study evaluated the therapeutic effect of JWSMYA and investigated the mechanism of repair and anti-fibrosis on acute radiation-induced cutaneous wounds with JWSMYA.

MATERIALS AND METHODS

Firstly, we prepared JWSMYA, and determined the composition through UHPLC LC-MS/MS. Then we used ionizing radiation to make a cutaneous wound model of rats, and observed wound healing through their skin injury score, wound contraction percentage and histological staining. In addition, immunohistochemical staining, Western blot analysis, qRT-PCR and Elisa were used to explore wound rehabilitation and anti-fibrosis mechanisms.

RESULTS

An in vivo assay revealed that JWSMYA promoted the repairment of acute radiation-induced cutaneous wounds, facilitated MAPK/ERK phosphorylation, inhibited PI3K/AKT activation, reduced the level of alpha-smooth muscle actin (a-sma), collagen type-I alpha 2 (Col1a2) and transforming growth factor-beta 1 (TGF-β1) in cutaneous tissues. However, no statistical difference was found in vascular endothelial growth factor (VEGF).

CONCLUSION

JWSMYA accelerated the repair of acute radiation-induced cutaneous wounds, which might be associated with the MAPK/ERK pathway. In addition, PI3K/AKT might be associated with the inhibition of fibrosis and the promotion of high-quality wound healing.

Modulation of Burn Hypermetabolism in Preclinical Models

Severe burns elicit a state of physiological stress and increased metabolism to help the body compensate for the changes associated with the traumatic injury. However, this hypermetabolic state is associated with increased insulin resistance, cardiovascular dysfunction, skeletal muscle catabolism, impaired wound healing, and delayed recovery. Several interventions were attempted to modulate burn hypermetabolism, including nutritional support, early excision and grafting, and growth hormone application. However, burn hypermetabolism still imposes significant morbidity and mortality in burn patients. Due to the limitations of in vitro models, animal models are indispensable in burn research. Animal models provide researchers with invaluable tools to test the safety and efficacy of novel treatments or advance our knowledge of previously utilized agents. Several animal studies evaluated novel therapies to modulate burn hypermetabolism in the last few years, including recombinant human growth hormone, erythropoietin, acipimox, apelin, anti-interleukin-6 monoclonal antibody, and ghrelin therapies. Results from these studies are promising and may be effectively translated into human studies. In addition, other studies revisited drugs previously used in clinical practice, such as insulin and metformin, to further investigate their underlying mechanisms as modulators of burn hypermetabolism. This review aims to update burn experts with the novel therapies under investigation in burn hypermetabolism with a focus on applicability and translation. Furthermore, we aim to guide researchers in selecting the correct animal model for their experiments by providing a summary of the methodology and the rationale of the latest studies.

Promoting effect of pomegranate peel extract on second-degree burn wound-healing through VEGF-A and TGF-β1 regulation

Pomegranate peel extract (PPE), a polyphenolic compound derived from pomegranate, has been widely concerned for its anti-oxidant, anti-inflammatory, and bacteriostatic effects. The potential therapeutic effect of PPE on burn injury was investigated, and its possible mechanisms were explored. Minipigs with second-degree burn were treated with PPE, Jing Wan Hong, and silver sulfadiazine. Hematoxylin-eosin (HE) staining was performed to detect burn severity, and then biological tissues were biopsied on days 0, 7, 14, 21, and 28 after administration. Immunohistochemistry, western blot, and real-time polymerase chain reaction (RT-PCR) were used to detect the protein and mRNA expression levels of VEGF-A and TGF-β1 in skin tissues after treatment with PPE. Furthermore, the skin wound healing at different time points was monitored by macroscopic observation. HE showed that after 28-day PPE treatment, the morphology of the skin tissue showed a significant improvement. Macroscopic data monitoring indicated that the decrustation and fur growing time was shortened. Meanwhile, the rate of wound healing increased after PPE treatment. The combination of immunohistochemistry, western blotting, and RT-PCR showed that after PPE treatment, expression of VEGF-A and TGF-β1 increased sharply on day 7, maintaining a high level until day 14, showing a downward trend on day 21, and approaching normal levels on day 28. However, in the model group, the protein and mRNA expression levels of VEGF-A and TGF-β1 increased on day 28 after burn injury, which was a slow process. Results indicated that compared with the model group, the peak expression level of VEGF-A and TGF-β1 was earlier, which was consistent with decrustation, shortening of fur growing time, and improvement of wound healing rate in minipig second-degree burn model. PPE showed a significant promoting effect on minipig second-degree burn model, which might be associated with the upregulation of the protein and gene expression levels of VEGF-A and TGF-β1.

Ghrelin Represses Thymic Stromal Lymphopoietin Gene Expression through Activation of Glucocorticoid Receptor and Protein Kinase C Delta in Inflamed Skin Keratinocytes

Ghrelin, a peptide hormone secreted from enteroendocrine cells of the gastrointestinal tract, has anti-inflammatory activity in skin diseases, including dermatitis and psoriasis. However, the molecular mechanism underlying the beneficial effect of ghrelin on skin inflammation is not clear. In this study, we found that ghrelin alleviates atopic dermatitis (AD)-phenotypes through suppression of thymic stromal lymphopoietin (TSLP) gene activation. Knockdown or antagonist treatment of growth hormone secretagogue receptor 1a (GHSR1a), the receptor for ghrelin, suppressed ghrelin-induced alleviation of AD-like phenotypes and suppression of TSLP gene activation. We further found that ghrelin induces activation of the glucocorticoid receptor (GR), leading to the binding of GR with histone deacetylase 3 (HDAC3) and nuclear receptor corepressor (NCoR) NCoR corepressor to negative glucocorticoid response element (nGRE) on the TSLP gene promoter. In addition, ghrelin-induced protein kinase C δ (PKCδ)-mediated phosphorylation of p300 at serine 89 (S89), which decreased the acetylation and DNA binding activity of nuclear factor- κB (NF-κB) p65 to the TSLP gene promoter. Knockdown of PKCδ abolished ghrelin-induced suppression of TSLP gene activation. Our study suggests that ghrelin may help to reduce skin inflammation through GR and PKCδ-p300-NF-κB-mediated suppression of TSLP gene activation.

Effect of Bacterial Infection on Ghrelin Receptor Regulation in Periodontal Cells and Tissues

The effect of bacterial infection on the expression of growth hormone secretagogue receptor (GHS-R) was investigated in periodontal cells and tissues, and the actions of ghrelin were evaluated. GHS-R was assessed in periodontal tissues of rats with and without periodontitis. Human gingival fibroblasts (HGFs) were exposed to Fusobacterium nucleatum in the presence and absence of ghrelin. GHS-R expression was determined by real-time PCR and immunocytochemistry. Furthermore, wound healing, cell viability, proliferation, and migration were evaluated. GHS-R expression was significantly higher at periodontitis sites as compared to healthy sites in rat tissues. F. nucleatum significantly increased the GHS-R expression and protein level in HGFs. Moreover, ghrelin significantly abrogated the stimulatory effects of F. nucleatum on CCL2 and IL-6 expressions in HGFs and did not affect cell viability and proliferation significantly. Ghrelin stimulated while F. nucleatum decreased wound closure, probably due to reduced cell migration. Our results show original evidence that bacterial infection upregulates GHS-R in rat periodontal tissues and HGFs. Moreover, our study shows that ghrelin inhibited the proinflammatory actions of F. nucleatum on HGFs without interfering with cell viability and proliferation, suggesting that ghrelin and its receptor may act as a protective molecule during bacterial infection on periodontal cells.

A balanced charged hydrogel with anti-biofouling and antioxidant properties for treatment of irradiation-induced skin injury

Skin injury caused by large doses of ionizing radiation is the common and severe side effect of radiotherapy. However, its therapeutic efficacy is always hindered by early reactive oxygen species generation, repetitive inflammatory microenvironment and bacterial infection risk. Herein, we report an anti-biofouling hydrogel with anti-inflammation and anti-oxidative properties for the treatment of irradiation-induced skin injury. The anti-biofouling hydrogel can be achieved by balancing oppositely charged alginate, hyaluronic acid (HA) and polylysine (PLL) at the optimal ratio, which effectively resist protein and bacterial adhesion, and evades immune response. Moreover, curcumin and epigallocatechin gallate (EGCG) can be facially encapsulated and substantially released from the hydrogel. Results showed that the resulting AHP-Cur/EGCG hydrogel can significantly weaken the development of skin injury and accelerate its healing process by alleviating inflammation, scavenging ROS and promoting angiogenesis. Therefore, the findings presented in this work provide an effective strategy for clinical management and treatment of ionizing radiation-induced skin injury.

Peptides from Animal Origin: A Systematic Review on Biological Sources and Effects on Skin Wounds

Background

Skin wounds are closely correlated with opportunistic infections and sepsis risk. Due to the need of more efficient healing drugs, animal peptides are emerging as new molecular platforms to accelerate skin wound closure and to prevent and control bacterial infection.

Aim

The aim of this study was to evaluate the preclinical evidence on the impact of animal peptides on skin wound healing. In addition, we carried out a critical analysis of the studies' methodological quality. Main Methods. This systematic review was performed according to the PRISMA guidelines, using a structured search on the PubMed-Medline, Scopus, and Web of Science platforms to retrieve studies published until August 25, 2020 at 3 : 00 pm. The studies included were limited to those that used animal models, investigated the effect of animal peptides with no association with other compounds on wound healing, and that were published in English. Bias analysis and methodological quality assessments were examined through the SYRCLE's RoB tool.

Results

Thirty studies were identified using the PRISMA workflow. In general, animal peptides were effective in accelerating skin wound healing, especially by increasing cellular proliferation, neoangiogenesis, colagenogenesis, and reepithelialization. Considering standardized methodological quality indicators, we identified a marked heterogeneity in research protocols and a high risk of bias associated with limited characterization of the experimental designs.

Conclusion

Animal peptides show a remarkable healing potential with biotechnological relevance for regenerative medicine. However, rigorous experimental approaches are still required to clearly delimit the mechanisms underlying the healing effects and the risk-benefit ratio attributed to peptide-based treatments.

Platelet-rich plasma improves the therapeutic efficacy of mesenchymal stem cells by enhancing their secretion of angiogenic factors in a combined radiation and wound injury model

Delayed wound healing after radiation exposure can cause serious cutaneous damage, and its treatment is a major clinical challenge. Although mesenchymal stem cells (MSCs) have emerged as a promising therapeutic agent in regenerative medicine, they alone do not produce satisfactory effects in a combined radiation and wound injury (CRWI) model. Here, we investigated the therapeutic effect of combined umbilical cord blood-derived (UCB)-MSCs and platelet-rich plasma (PRP) treatment on wound healing in a CRWI mouse model. First, we assessed the release of cytokines from UCB-MSCs cultured with PRP and observed changes in the expression of angiogenic factors. The angiogenic paracrine factors from UCB-MSCs cultured with PRP were assessed in human umbilical vein endothelial cells (HUVECs). To assess therapeutic efficacy, UCB-MSCs and PRP were topically implanted into a CRWT mouse model. Vascular endothelial growth factor (VEGF), a pro-angiogenic growth factor, urokinase-type plasminogen activator and contributor to VEGF-induced signalling were more highly expressed in conditioned media of UCB-MSCs cultured with PRP than in that of UCB-MSCs alone. Furthermore, conditioned media of UCB-MSCs cultured with PRP increased the formation of tube-like structures in HUVECs. Co-treatment of UCB-MSCs and PRP in a CRWI mouse model increased the wound closure rate and angiogenesis compared with an untreated irradiated group. Moreover, increased expression of VEGF and CD31 were observed in the wound tissue of co-treated mice compared with untreated irradiated mice. PRP stimulates the release of angiogenic factors from UCB-MSCs, and combined therapy of UCB-MSCs and PRP improves regeneration efficacy by enhancing angiogenesis in a CRWI model.

An herbal-compound-based combination therapy that relieves cirrhotic ascites by affecting the L-arginine/nitric oxide pathway: A metabolomics-based systematic study

ETHNOPHARMACOLOGICAL RELEVANCE

Traditional Chinese medicine boasts a 440-year-long history of treating refractory ascites via combinations of herbal medicines, called formulae. Xiaozhang Tie (XT) is a proprietary herbal-compound-based formula that has been proven to be very effective in the treatment of cirrhosis-associated ascites in clinical practice, but the mechanism of action of XT remains unknown.

AIM OF THE STUDY

In this study, we used a metabolomics-based systematic method to elucidate the mechanism of XT in the treatment of cirrhotic ascites.

METHODS

Decompensated liver cirrhosis was induced in rats by intraperitoneal injection of Carbon tetrachloride (CCl₄). Ultra performance liquid chromatography-mass spectrometry (UPLC-MS) combined with pattern recognition approaches were used to determine differentiating metabolites relevant to XT treatment. Biomarkers were further validated by a targeted quantitative method and by the results from serum and urine analyses. Pathway analysis and correlation network construction were used to reveal the therapeutic targets associated with XT treatment, and the potential mechanisms were verified by the results from biochemical, histopathological and immunohistochemical assays.

RESULTS

XT synergistically mediated the abnormalities of amino acid metabolic pathways in cirrhotic rats. XT significantly elevated the arginine levels, reduced the serum nitric oxide (NO) levels and alleviated the gastrointestinal motility disorder of cirrhotic rats. This effect of XT has been confirmed by the inhibition of the activities of inducible NO synthase and neuronal NO synthase in the small intestine.

CONCLUSIONS

These results reveal that XT promotes gastrointestinal motility by acting on multiple targets in multiple pathways, of which the L-arginine/NO pathway is most affected.

Effects of Ghrelin on the Oxidative Stress and Healing of the Colonic Anastomosis in Rats

BACKGROUND

Anastomotic leakage is the deadliest complication of colonic procedures. Ghrelin is an orexigenic hormone with potent actions on growth hormone release and functions in the processes of growth, tissue inflammation, repair, and oxidative stress. We evaluated the hypothesis that the exogenous administration of ghrelin causes beneficial effects on the healing of colonic anastomosis.

MATERIALS AND METHODS

Sixty-four male Wistar rats were randomly assigned to eight subgroups receiving postoperative intraperitoneal administration of ghrelin (23 μg/kg/d) or saline after a colonic anastomosis. The anastomotic tissue was evaluated on the third, seventh, and 14th postoperative days. Anastomotic bursting pressure, histological parameters, hydroxyproline content, and tissue oxidative stress markers were compared.

RESULTS

There was a significant increase in the mean anastomotic bursting pressure in the ghrelin subgroup on the seventh postoperative day (P = 0.035). Histological evaluation demonstrated a significant difference in the neutrophilic infiltrate (P = 0.035) on the third and 14th d and in apoptosis (P = 0.004), granulation tissue (P = 0.011) and peritoneal inflammation (P = 0.014) on the 14th postoperative day. There was a statistically significant increase in the hydroxyproline content in the ghrelin subgroup on the 14th postoperative day (P = 0.043). There were significant differences in the nitrite tissue levels (P = 0.021) on day 3 and in reactive oxygen species (P = 0.012) on day 14.

CONCLUSIONS

The administration of ghrelin had beneficial anti-inflammatory and antioxidant effects, increasing the resistance of the anastomosis and the hydroxyproline tissue content in the postoperative period.

Polymorphism of regulatory region of GHRL gene (-2531C>T) as a promising predictive factor for radiotherapy-induced oral mucositis in patients with head neck cancer

BACKGROUND

The purpose of this study was to investigate the relationship between single nucleotide polymorphisms (SNP; rs1629816) in the regulatory region (c.-2531C>T) of the ghrelin (GHRL) gene and the occurrence and severity of oral mucositis caused by radiotherapy (RT) in patients with head and neck cancer.

METHODS

Oral mucositis in 65 patients with head and neck cancer who underwent irradiation were assessed according to Radiation Therapy Oncology Group (RTOG)/European Organisation for Research and Treatment of Cancer (EORTC) scale. The DNA from patients with head and neck cancer was isolated from whole blood. The genotypes were determined using the minisequencing method (SNaPshot PCR).

RESULTS

The frequency of occurrence of the GHRL gene (c.-2531C>T, rs1629816) genotypes were as follows: AA = 21.5%; GA = 40%; and GG = 38.5%. In case of AA genotype, there was a 7-fold decrease of the risk of occurrence of oral mucositis (of grades 2 and 3) in the sixth week of RT (AA vs GA or GG, respectively: 17.9% vs 82.1% patients; odds ratio [OR] 0.14; 95% confidence interval [CI] 0.02-0.98; P = .0481). No statistically significant differences were observed between the volume of oral cavity contours (V30, V40, and V50) depending on the GHRL genotype in patients with head and neck cancer.

CONCLUSION

The study results have demonstrated an association between the AA genotype of the GHRL gene and the risk of more severe oral mucositis attributed to RT in patients with head and neck cancer.

Ghrelin protects against nucleus pulposus degeneration through inhibition of NF-κB signaling pathway and activation of Akt signaling pathway

The objective of the present study was to examine the potential role of ghrelin in degeneration of nucleus pulposus (NP). Lower expression levels of ghrelin were found in human NP cells stimulated with interleukin-1β (IL-1β). Moreover, exogenous ghrelin suppressed IL-1β induced degeneration and inflammation associated biomarkers in human NP cells, including matrix metalloproteinase-13, a disintegrin and metalloproteinase with thrombospondin motifs-5, tumor necrosis factor-α and iNOS, which was possibly mediated by antagonization of NF-κB signaling. Moreover, ghrelin enhanced production of critical extracellular matrix of NP cells, including collagen 2, aggrecan, and Sox-9 in NP cells. Ghrelin also promoted NP tissue regeneration in a rabbit IVD degeneration model, which seems to be associated with growth hormone secretagogue receptor. Additionally, the protective role of ghrelin in anabolism potentially relies on activation of Akt signaling pathway. Taken together, ghrelin may represent a molecular target for prevention and treatment of intervertebral disc degeneration.