Exosomal microRNAs from Mesenchymal Stem Cells: Novel Therapeutic Effect in Wound Healing

BACKGROUND

Wound healing is a complicated biological process that leads to the regeneration of damaged skin tissue. Determining the methods to promote wound healing has become a hot topic in medical cosmetology and tissue repair research. Mesenchymal stem cells (MSCs) are a group of stem cells with the potential of self-renewal and multi-differentiation. MSCs transplantation has a broad application prospect in wound healing therapy. Many studies have demonstrated that the therapeutic capacity of MSCs is mainly mediated by paracrine actions. Exosomes (EXOs), which are nanosized vesicles carrying a variety of nucleic acids, proteins and lipids, are an important component of paracrine secretion. It has been demonstrated that exosomal microRNAs (EXO-miRNAs) play a key role in the function of exosomes.

METHODS

In this review, we focus on current research on miRNAs from MSC-derived exosomes (MSC-EXO miRNAs) in terms of sorting, releasing and function and their effects on inflammation regulation, epidermal cell function, fibroblast function, and extracellular matrix formation. At last, we discuss the current attempts to improve the treatment of MSC-EXO-miRNAs.

RESULTS

Many studies have demonstrated that MSC-EXO miRNAs play a key role in promoting wound healing. They have been shown to regulate inflammation response, enhance epidermal cell proliferation and migration, stimulate fibroblast proliferation and collagen synthesis, and regulate extracellular matrix formation. Besides, there have been a number of strategies developed to promote MSC-EXO and MSC-EXO miRNAs for wound healing treatment.

CONCLUSION

Utilizing the association of exosomes from MSCs with miRNAs may be a promising strategy to promote trauma healing. MSC-EXO miRNAs may provide a new approach to promote wound healing and improve the quality of life for patients with skin injuries.

Screening and analysis of differentially expressed circRNAs and miRNAs in chronic diabetic extremity wounds

Increasing studies have shown that circular RNAs (circRNAs) and microRNAs (miRNAs) are related to the development of endocrine and metabolic diseases. However, there are few reports on the expression of circRNAs and miRNAs and their related co-expression and the expression of competitive endogenous RNA (ceRNA) in diabetic chronic refractory wounds. In this study, we compared the differential expression of circRNAs and miRNAs in diabetes chronic refractory wounds and normal skin tissues by high-throughput gene sequencing, and screened the differentially expressed circRNAs and miRNAs. Five abnormally expressed circRNAs and seven abnormally expressed miRNAs were detected by reverse transcription quantitative polymerase chain reaction PCR (RT-qPCR)to verify the results of RNA sequencing. We applied gene ontology (GO) to enrich and analyze dysregulated genes and elucidated their main functions via the Kyoto encyclopedia of genes and genomes analysis (KEGG). We constructed coding noncoding gene co-expression networks and ceRNA networks based on significantly abnormally expressed genes. According to the results of coding noncoding gene co-expression network analysis, hsa_circRNA_104175, hsa_circRNA_ 001588, hsa_circRNA_104330, hsa_circRNA_ 100141, hsa_circRNA_103107, and hsa_ circRNA_102044 may be involved in the regulation of the chronic intractable wound healing process in diabetes mellitus. This is particularly true in the regulation of vascular smooth muscle contraction-related pathways and the actin cytoskeleton, which affect the healing of chronic intractable wounds in diabetes. MiR-223-5p, miR-514a-3p, miR-205-5p, and miR-203-3p, which each have a targeting relationship with the above circRNAs, regulate the metabolism of nitrogen compounds in wound tissue by regulating NOD-like receptor signaling pathways, signaling pathways regulating the pluripotency of stem cells, microRNAs in cancer, and ECM-receptor interaction. This study showed circRNAs, miRNAs, and their network are associated with the development of chronic intractable wounds in diabetes, and our research identified the goals for new molecular biomarkers and gene therapy.

USP15 Enhances the Proliferation, Migration, and Collagen Deposition of Hypertrophic Scar-Derived Fibroblasts by Deubiquitinating TGF-βR1 In Vitro

Background:

Hypertrophic scar is a fibroproliferative disorder caused by skin injury. The incidence of hypertrophic scar following trauma or burns is 40 to 70 percent or 70 percent, respectively. It has been shown that transforming growth factor (TGF) β1/Smad signaling plays a crucial role in hypertrophic scar, and that USP15 can regulate the activity of TGFβ1/Smad signaling to affect the progression of the disease. However, the underlying mechanism of USP15 in hypertrophic scar remains unclear. The authors hypothesized that USP15 was up-regulated and enhanced the proliferation, migration, invasion, and collagen deposition of hypertrophic scar–derived fibroblasts by deubiquitinating TGF-β receptor I (TβRI) in vitro.

Methods:

Fibroblasts were isolated from human hypertrophic scars in vitro. The knockdown and overexpression of USP15 in hypertrophic scar–derived fibroblasts were performed using lentivirus infection. The effect of USP15 on hypertrophic scar–derived fibroblast proliferation, migration, and invasion, and the expression of TβRI, Smad2, Smad3, α-SMA, COL1, and COL3, were detected by Cell Counting Kit-8, scratch, invasion, quantitative real-time polymerase chain reaction, and Western blot assays. The interaction between USP15 and TβRI was detected by co-immunoprecipitation and ubiquitination assays.

Results:

The authors demonstrated that USP15 knockdown significantly inhibited the proliferation, migration, and invasion of hypertrophic scar–derived fibroblasts in vitro and down-regulated the expression of TβRI, Smad2, Smad3, α-SMA, COL1, and COL3; in addition, USP15 overexpression showed the opposite trends (p < 0.05). Co-immunoprecipitation and ubiquitination assays revealed that USP15 interacted with TβRI and deubiquitinated TβRI.

Conclusion:

USP15 enhances the proliferation, migration, invasion, and collagen deposition of hypertrophic scar–derived fibroblasts by deubiquitinating TβRI in vitro.

Extracellular Vesicles from Adipose-Derived Stem Cells Promote Diabetic Wound Healing via the PI3K-AKT-mTOR-HIF-1α Signaling Pathway

BACKGROUND

Impaired potential of hypoxia-mediated angiogenesis lead poor healing of diabetic wounds. Previous studies have shown that extracellular vesicles from adipose derived stem cells (ADSC-EVs) accelerate wound healing with unelucidated mechanism. However, it is not yet clear about the underlying mechanism of ADSC-EVs in regulating the hypoxia-related PI3K/AKT/mTOR signaling pathway of vascular endothelial cells in diabetic wounds. Therefore, in this study, human derived ADSC-EVs (hADSC-EVs) isolated from adipose tissue were co-cultured with advanced glycosylation end product (AGE) treated human umbilical vein endothelial cells (HUVECs) in vitro and local injected into the wounds of diabetic rats.

METHODS

In vitro, the therapeutic potential of hADSC-EVs on AGE-treated HUVECs was evaluated by cell counting kit-8, scratching, and tube formation assay. Subsequently, the effects of hADSC-EVs on the PI3K/AKT/mTOR/HIF-1α signaling pathway were also assayed by qRT-PCR and western blot. In vivo, the effect of hADSC-EVs on diabetic wound healing in rats were also assayed by closure kinetics, Masson staining and HIF-1α-CD31 immunofluorescence.

RESULTS

hADSC-EVs were spherical in shape with an average particle size of 198.1 ± 91.5 nm, and were positive for CD63, CD9 and TSG101. hADSC-EVs promoted the expression of PI3K-AKT-mTOR-HIF-1α signaling pathway of AGEs treated HUVECs with improved the potential of proliferation, migration and tube formation, and improve the healing and angiogenesis of diabetic wound in rats. However, the effect of hADSC-EVs described above can be blocked by PI3K-AKT inhibitor both in vitro and vivo.

CONCLUSION

Our findings indicated that hADSC-EVs accolated the healing of diabetic wounds by promoting HIF-1α-mediated angiogenesis in the PI3K-AKT-mTOR depend manner.

Efficacy of hyperbaric oxygen therapy for diabetic foot ulcers: An updated systematic review and meta-analysis

The present systematic review and meta-analysis was performed to evaluate the efficacy of hyperbaric oxygen therapy (HBOT) in the treatment of diabetic foot ulcers (DFUs). Relevant articles were retrieved from PubMed, the Cochrane Library, EMBASE and other databases through November 2020. A total of 20 randomized clinical trials and 1263 trials were included in the meta-analysis. For each trial, the average difference, odds ratio and 95% confidence interval were calculated to evaluate the efficacy. Hyperbaric oxygen therapy increased the healing rate of diabetic foot ulcers (relative risk, 1.901; 95% CI = 1.484-2.435, p < 0.0001), shortened the healing time (MD = -19.360; 95% CI = -28.753~-9.966, p < 0.001), and reduced the incidence of major amputation (relative risk, 0.518, 95% CI = 0.323-0.830, P < 0.01). In summary, our meta-analysis confirmed that hyperbaric oxygen therapy offers great benefits in the treatment of DFU and the reduction of amputation. In addition, larger and well-designed randomized controlled trials need to be planned and conducted to verify this conclusion.

Mesenchymal stem cell-derived exosomes: An emerging therapeutic strategy for normal and chronic wound healing

Skin wound healing is a complex biological process. Mesenchymal stem cells (MSCs) play an important role in skin wound repair due to their multidirectional differentiation potential, hematopoietic support, promotion of stem cell implantation, self-replication, and immune regulation. Exosomes are vesicles with diameters of 40-100 nm that contain nucleic acids, proteins, and lipids and often act as mediators of cell-to-cell communication. Currently, many clinical scientists have carried out cell-free therapy for skin wounds, especially chronic wounds, using exosomes derived from MSCs. This review focuses on the latest research progress on the mechanisms of action associated with the treatment of wound healing with exosomes derived from different MSCs, the latest research progress on the combination of exosomes and other biological or nonbiological factors for the treatment of chronic skin wounds, and the new prospects and development goals of cell-free therapy.

[Research advances in the role of ubiquitin-proteasome pathway in hypertrophic scar]

The ubiquitin-proteasome pathway is a protein degradation pathway that relies on ATP and non-lysosomal pathway in eukaryotic cells. It participates in the regulation of multiple biological processes, including cell cycle, apoptosis, DNA repair, antigen presentation, receptor endocytosis, intracellular signal transduction. Recent studies have found that the ubiquitin-proteasome pathway can participate in the formation and development of hypertrophic scar by regulating transforming growth factor beta/Smad signal transduction and proliferation, differentiation, and apoptosis of fibroblasts. This article summarizes the effects of ubiquitin ligase enzyme, proteasome, and deubiquitinating enzyme in ubiquitin-proteasome pathway in hypertrophic scar, in order to provide new idea for the prevention and treatment of hypertrophic scar.

Detection and analysis of angiogenesis pathway‑associated lncRNA expression profiles in human skin fibroblasts under high‑glucose conditions

Accumulating evidence has indicated that long non‑coding RNAs (lncRNAs) have crucial roles in wound healing and that vascular lesions in diabetic wounds are frequently difficult to heal. However, the role of angiogenesis pathway‑associated lncRNAs in wound healing in diabetic patients has remained to be fully elucidated. In the present study, human skin fibroblasts were cultured under high‑glucose conditions in vitro to mimic a diabetic environment and the angiogenesis pathway‑associated lncRNA expression profile in the high‑ and normal‑glucose groups was examined. The microarray data indicated that 14 lncRNAs and 22 mRNAs were differentially expressed. Several candidate lncRNAs and mRNAs were then analyzed by reverse transcription‑quantitative PCR and the results were consistent with the microarray data. Furthermore, the University of California Santa Cruz Genome Browser was used to identify mRNAs linked to angiogenesis pathways near the transcriptional region of lncRNAs. The results suggested that lncRNAs RP4‑791C19.1 and CTD‑2589O24.1 may act on their target genes epidermal growth factor receptor and p21 (RAC1) activated kinase 1, respectively, as enhancers and cis‑regulate their expression. Therefore, the present study confirmed that several angiogenesis pathway‑associated lncRNAs were differentially expressed under high‑glucose conditions, which may have a key role in wound healing in patients with diabetes.

Long non‑coding RNA HOTAIR promotes burn wound healing by regulating epidermal stem cells

Local transplantation of epidermal stem cells (ESCs) exerts a therapeutic effect on burn wounds. However, cell viability can impede their clinical application. HOX antisense intergenic RNA (HOTAIR) is involved in regulating adult tissue stem cells, as well as in developmental patterning and pluripotency. However, little is known about its role in regulating ESCs. The present study was performed to investigate the effects of HOTAIR in the modulation of ESCs and wound repair. Firstly, reverse transcription-quantitative PCR was used to detect the relative expression of HOTAIR during burn wound healing in mice to determine whether HOTAIR is associated with wound healing. Subsequently, ESCs derived from mouse skin were transfected with a lentiviral vector to overexpress or knockdown HOTAIR. The effects of HOTAIR on cell proliferation and differentiation were measured by 5-bromodeoxyuridine and MTT assays, and by assessing NANOG mRNA expression. Lastly, mice with burns were administered a subcutaneous injection of HOTAIR-overexpressing ESCs. Images were captured and histological analyses were performed to evaluate wound healing. The results revealed that the expression of HOTAIR gradually increased and peaked at day 7 post-burn and maintained at relatively high levels until day 14 post-burn during wound healing. Furthermore, overexpression of HOTAIR promoted ESC proliferation and maintained the stem cell state in vitro. By contrast, suppression of HOTAIR inhibited cell proliferation and cell stemness. It was also identified that HOTIR-overexpressing ESCs accelerated re-epithelialization and facilitated burn wound repair. In conclusion, the present findings confirmed an essential role of HOTAIR in the regulation of ESC proliferation and stemness. Therefore, targeting HOTAIR in ESCs may be a potentially promising therapy for burn wound healing.

[Effects and mechanism of rat epidermal stem cells treated with exogenous vascular endothelial growth factor on healing of deep partial-thickness burn wounds in rats]

Objective: To explore the effects and mechanism of rat epidermal stem cells (ESCs) that were treated with exogenous vascular endothelial growth factor (VEGF) on the healing of deep partial-thickness burn wounds in rats. Methods: ESCs were isolated and cultured from the trunk skin of a 3-month-old female Sprague-Dawley (SD) rat. The third passage of cultured cells in the logarithmic growth phase was used in experiments (1)-(3). (1) The cells were routinely cultured in keratinocytes-specified serum-free medium (K-SFM) (the same routine culture condition below). The morphology of cells cultured for 3 and 5 days was observed under the inverted optical microscope. (2) After 24 hours in routine culture, the expression of cell surface markers CD44, CD45, CD11b, and CD11c was detected by flow cytometer, with triplicate samples. (3) Four batches of cells were collected, and each batch was divided into VEGF group or blank control group according to the random number table. The cells in blank control group were routinely cultured, while the cells in VEGF group were cultured in K-SFM containing VEGF in the final mass concentration of 10 ng/mL. The protein expressions of cytokeratin 19 (CK19) and CK10 in cells cultured for 10 days were detected by Western blotting. The Nanog mRNA expression in cells cultured for 0 (immediately), 2, 4, 6, 8, and 10 day (s) was detected by real-time fluorescent quantitative reverse transcription polymerase chain reaction. The absorbance value was detected with cell counting kit-8 in cells cultured for 2, 4, 6, 8, and 10 days. The clone number of more than 50 cells was observed and counted under the optical microscope in cells cultured for 10 days, and the cell colony formation rate was calculated. Three samples at each time point was analysed. (4) Thirty-six 3-month-old SD rats (either male or female) were used for the study, and two deep partial-thickness burn wounds (10 mm in diameter) were created in each rat by pressing a 100 ℃ electric iron plate on symmetric dorsal side. According to the random number table, the injured rats were divided into VEGF+ ESCs group, ESCs alone group, and blank control group, with 12 rats and 24 wounds in each group. From 0 (immediately) to 2 day (s) after injury, 20 μL phosphate buffer solution (PBS) was injected into each wound in the three groups in one time, once a day, with the solution in VEGF+ ESCs group containing 0.8×10(6) cells/mL of ESCs treated by 10 ng/mL VEGF for 10 days, the solution in ESCs alone group containing 0.8×10(6) cells/mL of ESCs without any treatment, and the solution in blank control group being PBS only. On post first injection day (PFID) 0 (immediately), 3, 7, and 14, three rats from each group were taken respectively according to the random number table for wound healing assessment, and the wound healing rates on PFID 3, 7, and 14 were calculated. The mice at each time point were sacrificed with wound tissue harvested for histology, and the skin structure was observed by hematoxylin-eosin staining. Data were statistically analyzed with independent sample t test, analysis of variance for factorial design, least significant difference test, and Bonferroni correction. Results: (1) By day 3 in culture, cells distributed in slowly-growing clusters. By day 5, the clusters were large and round, in which the cells mainly with large and round nuclei and little cytoplasm were observed. The above results were consistent with the morphological characteristics of ESCs. (2) The positive expression rate of CD44 was (94.3±1.2) %, and the expressions of CD45, CD11b, and CD11c were negative. The cells were confirmed as ESCs. (3) Compared with those of blank control group, the protein expression of CK19 in the cells of VEGF group was significantly increased after 10 days in culture (t=3.756, P<0.05), while the protein expression of CK10 was significantly decreased (t=3.149, P<0.05). Compared with those of blank control group, the Nanog mRNA expression in the cells cultured for 0 and 2 day (s) and absorbance values of the cells cultured for 2 and 4 day (s) were not significantly changed in VEGF group (t=0.58, 0.77, 0.53, 3.02, P>0.05), while the Nanog mRNA expression in the cells cultured for 4, 6, 8, and 10 days and absorbance values of the cells cultured for 6, 8, and 10 days were significantly increased in VEGF group (t=6.34, 5.00, 5.58, 4.61, 5.65, 10.78, 15.51, P<0.01). After 10 days in culture, the cell colony-forming rate in VEGF group was (56.4±1.3) %, significantly higher than (31.5±1.3) % of blank control group (t=13.96, P<0.01). (4) The burn wounds of rats in the three groups were confined to the superficial dermis of the skin on PFID 0. On PFID 3, normal skin tissue at wound margins slightly contracted in the rats of VEGF+ ESCs group, which was earlier than that in the other two groups. On PFID 7, the newly generated epidermis covered most parts of the rat wounds in VEGF+ ESCs group, and some of the epithelium crawled around the rat wounds in ESCs alone group, but no obvious epithelialization was observed in the rat wounds in blank control group. On PFID 14, the rat wounds in VEGF+ ESCs group were basically healed, while some parts of the rat wounds were unhealed in ESCs alone group, and most parts of the rat wounds were unhealed in blank control group. On PFID 3, the wound healing rates of rats in the three groups were similar (P>0.05). On PFID 7 and 14, the wound healing rates of rats in ESCs alone group, respectively (26.0±2.0) % and (64.4±4.7) %, were obviously higher than (12.4±1.1) % and (29.1±3.3) % of blank control group (P<0.01), all of which were obviously lower than (41.0±2.4) % and (91.3±3.5) % of VEGF+ ESCs group (P<0.01). On PFID 3, infiltration of a large number of inflammatory cells were observed in the rat wounds in VEGF+ ESCs group, which was earlier than those in the other two groups. On PFID 7, a large number of endothelial cells were observed in the rat wounds in VEGF+ ESCs group, while proliferation of a few endothelial cells were observed in the rat wounds in ESCs alone group, and a large number of inflammatory cells infiltrated the rat wounds in blank control group. On PFID 14, the newly generated epidermal cells covered nearly all the rat wounds in VEGF+ ESCs group and most parts of the rat wounds in ESCs alone group, while a large number of endothelial cells were observed and the newly generated epidermal cells covered some parts of the rat wounds in blank control group. Conclusions: ESCs of rats treated with exogenous VEGF can promote the healing of deep partial-thickness burn wounds in rats, which may be related to VEGF's roles in promoting the proliferation of ESCs and reducing its differentiation level, so as to maintain the potency of stem cells.

Identification of differentially expressed miRNAs associated with thermal injury in epidermal stem cells based on RNA-sequencing

Current research indicates that epidermal stem cells (EpSCs) play an important role in promoting wound healing, but the mechanism of action of these cells during wound repair following thermal damage remains unclear. In the present study, the trypsin digestion method was used to isolate human EpSCs and the cells were incubated in a 51.5°C water tank for 35 sec to construct a thermal injury model. The differentially expressed miRNAs were identified using high-throughput sequencing technology, and bioinformatic methods were used to predict their target genes and signaling pathways that may be involved in wound repair. A total of 33 miRNAs including, hsa-miR-1973, hsa-miR-4485-3p, hsa-miR-548-5p, hsa-miR-212-3p and hsa-miR-4461 were upregulated, whereas 21 miRNAs including, hsa-miR-4520-5p, hsa-miR-4661-5p, hsa-miR-191-3p, hsa-miR-129-5p, hsa-miR-147b and hsa-miR-6868-3p were downregulated following thermal injury of the human EpSCs. The bioinformatic analysis indicated that the differentially expressed miRNAs are involved in biological processes such as cell proliferation and differentiation, cell growth apoptosis, cell adhesion and migration. The results showed that there is a differential expression pattern of miRNAs after thermal injury of human EpSCs and these differences are involved in the regulation of the wound healing process. These findings provide new clues for further study of the wound healing mechanism and targeted therapy.

tRNA‑derived small RNAs: A novel class of small RNAs in human hypertrophic scar fibroblasts

tRNA-derived small RNAs (tsRNAs) have been shown to play regulatory roles in many physiological and pathological processes. However, their roles in hypertrophic scars remain unclear. The present study investigated differentially expressed tsRNAs in human hypertrophic scar fibroblasts and normal skin fibroblasts via high-throughput sequencing. Several dysregulated tsRNAs were validated by reverse transcription-quantitative polymerase chain reaction (RT-qPCR). Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment, target prediction, coexpression networks and competing endogenous RNA (ceRNA) networks were evaluated to discover the principal functions of significantly differentially expressed tsRNAs. In total, 67 differentially expressed tsRNAs were detected, of which 27 were upregulated and 40 downregulated in hyper-trophic scar fibroblasts. The GO analysis indicated that the dysregulated tsRNAs are associated with numerous biological functions, including 'nervous system development', 'cell adhesion', 'focal adhesion', 'protein binding', 'angiogenesis' and 'actin binding'. KEGG pathway analysis revealed that the most altered pathways include 'Ras signaling pathway', 'Rap1 signaling pathway' and 'cGMP-PKG signaling pathway'. The target genes of the differentially expressed tsRNAs participate in several signaling pathways important for scar formation. The results of RT-qPCR were consistent with those of sequencing. MicroRNA (miR)-29b-1-5p was identified as a target of tsRNA-23678 and was downregulated in hypertrophic scar fibroblasts, constituting a negative regulatory factor for scar formation. Furthermore, tsRNA-23761 acted as a ceRNA and bound to miR-3135b to regulate the expression of miR-3135b targets, including angiotensin-converting enzyme. Collectively, these findings reveal that tsRNAs are differentially expressed in human hypertrophic scar fibroblasts, and may contribute to the molecular mechanism and treatment of hypertrophic scars.

Detection and Analysis of the Hedgehog Signaling Pathway-Related Long Non-Coding RNA (lncRNA) Expression Profiles in Keloid

BACKGROUND Hedgehog (Hh) signaling pathway-related genes have important roles in several physiological and disease processes that involve cell proliferation. Long non-coding region RNAs (lncRNAs) have a regulatory role on gene expression. Keloid is characterized by excessive proliferation of scar tissue following trauma. The aims of this study were to evaluate the Hh signaling pathway in keloid skin tissues and its downstream gene expression and lncRNAs, compared with normal skin. MATERIAL AND METHODS Four pairs of keloids and adjacent normal skin epidermis underwent total RNA extraction. Gene chip high-throughput real-time quantitative polymerase chain reaction (qPCR) was used to examine the differential expression profiles of the Hh signaling pathway-related lncRNAs and mRNAs in the human keloid and normal skin. The differentially expressed mRNAs were analyzed by Gene Ontology (GO) and the Kyoto Encyclopedia of Genes and Genomes (KEGG) to identify their biological roles. RESULTS In keloid tissue, differential expression of 33 mRNAs and 30 lncRNAs relating to the Hh pathway, were verified by gene chip qPCR. The results of GO and KEGG analysis showed that the upregulated mRNAs were involved in cell proliferation, cell growth, and tissue repair, and down-regulated mRNAs were involved in apoptosis. The lncRNA, AC073257.2, affected cell keloid growth and proliferation by its upstream target the GLI2 gene at the transcriptional level. The lncRNA, HNF1A-AS1, affected cell keloid growth and proliferation by its neighboring target gene, HNF1A. CONCLUSIONS Differential expression occurred in Hh signaling pathway-related lncRNAs and mRNAs, which may provide further insight into the development of keloid.

High‑throughput sequencing reveals differentially expressed lncRNAs and circRNAs, and their associated functional network, in human hypertrophic scars

Growing evidence suggests that long noncoding RNAs (lncRNAs) and circular RNAs (circRNAs) are involved in the occurrence and development of tumors and fibrotic diseases. However, the integrated analysis of lncRNA and circRNA expression, alongside associated co-expression and competing endogenous RNA (ceRNA) networks, has not yet been performed in human hypertrophic scars (HS). The present study compared the expression levels of lncRNAs, circRNAs and mRNAs in human HS and normal skin tissues by high-throughput RNA sequencing. Numerous differentially expressed lncRNAs, circRNAs and mRNAs were detected. Subsequently, five aberrantly expressed lncRNAs and mRNAs, and six circRNAs were measured to verify the RNA sequencing results by reverse transcription-quantitative polymerase chain reaction. Furthermore, Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analyses were performed for the dysregulated genes, in order to elucidate their principal functions. In addition, a coding-noncoding gene co-expression (CNC) network and ceRNA network were constructed for specific significantly altered genes. The CNC network analysis suggested that AC048380.1 and LINC00299 were associated with metastasis-related genes, including inhibin subunit βA (INHBA), SMAD family member 7 (SMAD7), collagen type I α1 chain (COL1A1), transforming growth factor β3 (TGFβ3) and MYC proto-oncogene, bHLH transcription factor (MYC). Inhibitor of DNA binding 2 was associated with the lncRNAs cancer susceptibility 11, TGFβ3-antisense RNA 1 (AS1), INHBA-AS1, AC048380.1, LINC00299 and LINC01969. Circ-Chr17:50187014_50195976_-, circ-Chr17:50189167_50194626_-, circ-Chr17:50189167_ 50198002_- and circ-Chr17:50189858_50195330_- were also associated with INHBA, SMAD7, COL1A1, TGFβ3 and MYC. COL1A1 and TGFβ3 were associated with circ-Chr9:125337017_125337591_+ and circ-Chr12:120782654_120784593_-. The ceRNA network indicated that INHBA-AS1 and circ-Chr9:125337017_125337591_+ were ceRNAs of microRNA-182-5p targeting potassium voltage-gated channel subfamily J member 6, ADAM metallopeptidase with thrombospondin type 1 motif 18, SRY-box 11, MAGE family member L2, matrix metallopeptidase 16, thrombospondin 2, phosphodiesterase 11A and collagen type V a1 chain. These findings suggested that lncRNAs and circRNAs may act as ceRNAs, which are implicated in the pathophysiology and development of human HS, and lay a foundation for further insight into the novel regulatory mechanism of lncRNAs and circRNAs in hypertrophic scarring.

[Advances in the research of the application of induced pluripotent stem cells in tissue engineering skin as seed cells]

Tissue engineering skin has a wide application prospect on the clinical treatment of all sorts of skin defect, especially large area burn. The shortage of seed cells and their function improvement are the main problems in this field. The existing seed cells of tissue engineering skin are difficult to meet the needs of clinical application due to the limitations of acquisition, proliferation, and aging. Subsequently, the generation of induced pluripotent stem cells (iPSCs) provides a safe and efficient cell source for tissue engineering skin. Our article focuses on the origin of iPSCs and its characteristics of differentiating into keratinocytes, fibroblasts, melanocytes, vascular smooth muscle cells, nerve cells, and hair follicle, and discusses the main problems and prospects of iPSCs in establishment of tissue engineering skin and application in wound repair.

Aberrantly expressed long noncoding RNAs in hypertrophic scar fibroblasts in vitro: A microarray study

A hypertrophic scar is the result of abnormal repair of the body after trauma. Histopathologically, it is mostly the result of the excessive proliferation of fibroblasts and the accumulation of extracellular matrix. Accumulating evidence has demonstrated that long non-coding RNAs (lncRNAs) have a critical role in the regulation of gene expression and in the pathogenesis of diseases. However, the roles of lncRNAs in hypertrophic scars have remained elusive. The present study investigated the profiles of differentially expressed lncRNAs between fibroblasts derived from a hypertrophic scar and normal skin, and explored the possible mechanisms underlying the development of hypertrophic scars. Microarray data indicated that 6,104 lncRNAs and 2,952 mRNAs were differentially expressed. A set of differentially expressed transcripts as confirmed by reverse transcription-quantitative polymerase chain reaction. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analyses were performed to determine the principal functions of the significantly deregulated genes. Furthermore, associated expression networks, including subgroup analysis, competing endogenous RNAs (ceRNAs) and coding-noncoding co-expression networks were constructed using bioinformatics methods. The homology between differentially expressed lncRNAs and mRNAs was assessed and two exon lncRNA were selected to explore their regulatory mechanisms. The ceRNA network inferred that NR_125715 acted as a competing endogenous RNA, bound to microRNA (miR)-141-3p, miR-200a-3p and miR-29 to regulate the expression of the miRs' targets, including transforming growth factor β2 (TGFB2). Similarly, NR_046402 acted as a competing endogenous RNA, which bound to miR-133a-3p.1 and miR-4469 to then regulate the expression of the miRs' targets, including DNA polymerase δ1, catalytic subunit (POLD1). In addition, co-expression analysis indicated that the expression of lncRNAs NR_125715 and NR_046402 was correlated with that of TGFB2 and POLD1 mRNA. The identification of these differentially expressed lncRNAs in the hypertrophic scar-derived fibroblasts in the present study, may provide novel insight into the functional interactions of lncRNA, miRNA and mRNA, and lead to novel theories for the pathogenesis and treatment of hypertrophic scars.

Generation of human-induced pluripotent stem cells from burn patient-derived skin fibroblasts using a non-integrative method

Patient specific induced pluripotent stem cells (iPSCs) have been recognized as a possible source of cells for skin tissue engineering. They have the potential to greatly benefit patients with large areas of burned skin or skin defects. However, the integration virus-based reprogramming method is associated with a high risk of genetic mutation and mouse embryonic fibroblast feeder-cells may be a pollutant. In the present study, human skin fibroblasts (HSFs) were successfully harvested from patients with burns and patient-specific iPSCs were generated using a non-integration method with a feeder-free approach. The octamer-binding transcription factor 4 (OCT4), sex-determining region Y box 2 (SOX2) and NANOG transcription factors were delivered using Sendai virus vectors. iPSCs exhibited representative human embryonic stem cell-like morphology and proliferation characteristics. They also expressed pluripotent markers, including OCT4, NANOG, SOX2, TRA181, stage-specific embryonic antigen 4 and TRA-160, and exhibited a normal karyotype. Teratoma and embryoid body formation revealed that iPSCs were able to differentiate into cells of all three germ layers in vitro and in vivo. The results of the present study demonstrate that HSFs derived from patients with burns, may be reprogrammed into stem cells with pluripotency, which provides a basis for cell-based skin tissue engineering in the future.

[Advances in the research of effects of regulation of cell autophagy on wound healing]

As one of the self-protection mechanism, autophagy widely exists in eukaryotic cells. It plays an important role in maintaining cells survival, update, material recycling, and tissue homeostasis. A series of researches discovered that autophagy played dual function in fibrotic diseases. The induction of autophagy can promote the degradation of collagen on one hand, on the other hand, the regulation of autophagy through microRNA, transforming growth factor β, and other factors can promote the occurrence of fibrosis. In wound healing, autophagy may participate in the pathophysiological processes of inflammation, reepithlialization, and wound remodeling. The regulation of cell autophagy may become an effective way and the new target for treatment of wound and pathological scar.

Differential miRNA expression profiles in human keratinocytes in response to protein kinase C inhibitor

Aberrant expression of microRNAs (miRNAs) is widely accepted to be involved in keratinocyte differentiation and to be dependent on activation of the protein kinase C (PKC) pathway. However, the miRNA profiles and biological characteristics of keratinocytes induced by specific inhibitors of PKC have yet to be elucidated. The present study aimed to explore the differential miRNA expression profiles in keratinocytes treated with the PKC inhibitor GF109203X, by conducting a bioinformatics analysis. Parts of the GF109203X‑induced keratinocytes formed distinct clones after 2 days of culture, and the expression of intergrin β1, cytokeratin (CK)19 and CK14 were positive, whereas CK10 expression was negative. A total of 79 miRNAs were differentially expressed in keratinocytes treated with GF109203X, among which 45 miRNAs were upregulated and 34 were downregulated. The significantly upregulated microRNAs includedhsa‑miR‑1‑3p and miR‑181c‑5p, whereas hsa‑miR‑31‑5p and hsa‑let‑7c‑3p were significantly downregulated. In addition, the results of reverse transcription‑quantitative polymerase chain reaction exhibited consistency with the microarray results. An enrichment analysis demonstrated that certain target genes of the differentially expressed miRNAs serve an important role in cell proliferation and differentiation, cell cycle progression and apoptosis, etc. These results revealed that GF109203X induced the differential expression of certain miRNAs when keratinocytes began showing the characteristics of epidermal‑like stem cells, which may provide a novel approach for wound healing and regeneration of skin tissues.

[Advances in the research of effects of exosomes derived from stem cells on wound repair]

Exosomes are nano-vesicles released by many kinds of cells. Exosomes play a significant role in cell-to-cell communication and substance transportation through direct effect of signaling molecules on the cell membrane surface, intracellular regulation of cellular content during membrane fusion, or regulation of release of various bioactive molecules. Several studies have reported that culture supernatant of stem cells has some related exosomes to take part in wound repair. The secretion of exosomes is depended on the source and the physiological and pathological condition of deriving cells. How to stimulate the stem cells to produce exosomes maximally and their clinical application are worthy to explore. In this review, we summarize the biological function and application of exosomes derived from stem cells in wound repair.

[Long non-coding RNA and wound healing]

Long non-coding RNA (lncRNA) is a class of RNA molecules longer than 200 nucleotides which does not encode proteins or only encode a few proteins, and it plays important regulatory roles in the expression of genes at the epigenetic, transcriptional, and posttranscriptional levels. The recent reports suggest that lncRNA plays a significant role in growth and development of body, cellular biological processes including in cell proliferation, differentiation, migration, and apoptosis, and regulation of wound healing processes such as re-epithelialization, angiogenesis, and scar formation. The lncRNA has become a new research hotspot in wound healing. This article reviews the role of lncRNA in different stages of wound repair to get a further understanding of molecular mechanisms of wound healing and provide a new target spot for prevention and treatment of pathological scars and wound healing.

Substance P combined with epidermal stem cells promotes wound healing and nerve regeneration in diabetes mellitus

Exogenous substance P accelerates wound healing in diabetes, but the mechanism remains poorly understood. Here, we established a rat model by intraperitoneally injecting streptozotocin. Four wounds (1.8 cm diameter) were drilled using a self-made punch onto the back, bilateral to the vertebral column, and then treated using amniotic membrane with epidermal stem cells and/or substance P around and in the middle of the wounds. With the combined treatment the wound-healing rate was 100% at 14 days. With prolonged time, type I collagen content gradually increased, yet type III collagen content gradually diminished. Abundant protein gene product 9.5- and substance P-immunoreactive nerve fibers regenerated. Partial nerve fiber endings extended to the epidermis. The therapeutic effects of combined substance P and epidermal stem cells were better than with amniotic membrane and either factor alone. Our results suggest that the combination of substance P and epidermal stem cells effectively contributes to nerve regeneration and wound healing in diabetic rats.

[Effects of recombinant human granulocyte-macrophage colony-stimulating factor on wound healing and microRNA expression in diabetic rats]

OBJECTIVE

To investigate the effects of recombinant human granulocyte macrophage colony-stimulating factor (rhGM-CSF) on wound healing and microRNA expression in diabetic rats.

METHODS

Eighteen male SD rats of clean grade were used to reproduce diabetes model. Four weeks later, a total of 64 full-thickness skin wounds were created on the back of 16 rats with established diabetes, with 4 wounds on each rat. Two symmetrical wounds on either side of the spine were created as a pair according to paired design. Then the wounds were divided into groups A and B according to the random number table and blind method (red and blue tags on the rhGM-CSF or the gel vehicle), with 32 wounds in each group. The ointment with red tag was applied on the wounds of group A and the blue one on group B. The application was conducted once a day, with a thickness of 3 mm, up to post injury day (PID) 14. Gross observation of wound healing was conducted on PID 3, 7, 14. The wound healing rate was determined on PID 3 and 7. On PID 3, 7, 14, tissues from 2, 4, and 8 wounds were harvested from each group respectively for the observation of the histopathological changes with HE staining, and also for analyzing the expression of proliferating cell nuclear antigen (PCNA) and CD31 with immunohistochemical staining (denoted as absorbance value). On PID 7, tissues from 6 wounds in each group were harvested for microarray gene chip to screen the differentially expressed microRNAs. Enrichment analysis of Kyoto encyclopedia of genes and genomes (KEGG) signaling pathway on the differentially expressed microRNAs were performed after the microRNA screening results were validated by real-time fluorescent quantitative RT-PCR. Data were processed with paired t test or two-sample t test.

RESULTS

(1) On PID 3, the wound area was significantly decreased, and the wound granulation was significantly proliferated in both groups. On PID 7, the wound area was further decreased, and the wound area was almost filled by granulation in both groups; the conditions in group A were better. On PID 14, all the wounds in group A were almost healed, while a small area of raw wound with incrustation still remained in some wounds of group B. On PID 3 and 7, the wound healing rates of group A were (41 ± 5)% and (75 ± 4)%, significantly higher than those of group B [(31 ± 9)% and (71 ± 4)%, with t values respectively 10.13 and 8.06, P values below 0.001]. (2) On PID 3, the epidermal cells, endothelial cells, and Fbs in the wounds of 2 groups were sparse, with heavy infiltration of inflammatory cells. The above condition in the wounds was better in group A than in group B. On PID 7, the epidermal cells, endothelial cells, and Fbs were gradually well arranged in group A; infiltration of inflammatory cells decreased, and the condition was better than that of group B. On PID 14, the wounds of group A were completely covered by epidermis, while infiltration of inflammatory cells still remained in some wounds of group B. (3) On PID 3, 7, 14, the positive expressions of CD31 and PCNA in group A were respectively 0.275 ± 0.018, 0.345 ± 0.034, 0.305 ± 0.023; 0.406 ± 0.063, 0.223 ± 0.011, 0.045 ± 0.022. They were significantly higher than those of group B (0.222 ± 0.020, 0.229 ± 0.018, 0.197 ± 0.015; 0.324 ± 0.039, 0.162 ± 0.012, 0.018 ± 0.020, with t values from 2.281 to 9.652, P < 0.05 or P < 0.01). (4) According to the microRNAs detection and screening, as compared with group B, 18 microRNAs were up-regulated while 13 were down-regulated in the wounds of group A. (5) The results of real-time fluorescent quantitative RT-PCR had good consistency with the results of microRNAs detection. (6) Enrichment analysis of KEGG signaling pathway showed that among the 31 differentially expressed microRNAs, 4 took part in the MAPK signaling pathway, 3 took part in the Wnt signaling pathway, 1 took part in the TGF-β signaling pathway, 3 took part in the epidermal growth factor receptor signaling pathway, 2 took part in the cell cycle pathway, 5 took part in the axon guidance signaling pathway, 6 took part in the focal adhesion pathway, 3 took part in the regulation of actin cytoskeleton pathway, 1 took part in the extracellular cell matrix receptor pathway, 3 took part in the adherens junction pathway, and 1 took part in the cell adhesion molecules pathway. After disclosing the blind, it showed that the ointment with red tag was the rhGM-CSF gel and the blue one was gel vehicle.

CONCLUSIONS

The rhGM-CSF gel can promote wound healing in diabetic rats, producing significant differential microRNA expression in wounds, and they may be the target at gene post-transcriptional level of rhGM-CSF gel in promoting wound healing.

[Advances in the research of the role of MicroRNAs in wound healing]

MicroRNAs are endogenous noncoding RNA molecules with 19-22 nucleotides in length. MicroRNAs can post-transcriptionally regulate gene and (or) protein expression by binding to their target messenger RNAs (mRNAs), leading to mRNA degradation or suppression of translation. As a huge family that regulates gene expression, microRNAs has recently been shown to not only participate in the normal healing processes of wounds but also closely related to pathologic wound healing, and formation of hypertrophic scars and keloids. This review focuses on the biogenesis of microRNA and its role in wound healing.