The effect of p38MAPK on cyclic stretch in human facial hypertrophic scar fibroblast differentiation

MicroRNA-155 mediates multiple gene regulations pertinent to the role of human adipose-derived mesenchymal stem cells in skin regeneration

Introduction: The role of Adipose-derived mesenchymal stem cells (AD-MSCs) in skin wound healing remains to be fully characterized. This study aims to evaluate the regenerative potential of autologous AD-MSCs in a non-healing porcine wound model, in addition to elucidate key miRNA-mediated epigenetic regulations that underlie the regenerative potential of AD-MSCs in wounds. Methods: The regenerative potential of autologous AD-MSCs was evaluated in porcine model using histopathology and spatial frequency domain imaging. Then, the correlations between miRNAs and proteins of AD-MSCs were evaluated using an integration analysis in primary human AD-MSCs in comparison to primary human keratinocytes. Transfection study of AD-MSCs was conducted to validate the bioinformatics data. Results: Autologous porcine AD-MSCs improved wound epithelialization and skin properties in comparison to control wounds. We identified 26 proteins upregulated in human AD-MSCs, including growth and angiogenic factors, chemokines and inflammatory cytokines. Pathway enrichment analysis highlighted cell signalling-associated pathways and immunomodulatory pathways. miRNA-target modelling revealed regulations related to genes encoding for 16 upregulated proteins. miR-155-5p was predicted to regulate Fibroblast growth factor 2 and 7, C-C motif chemokine ligand 2 and Vascular cell adhesion molecule 1. Transfecting human AD-MSCs cell line with anti-miR-155 showed transient gene silencing of the four proteins at 24 h post-transfection. Discussion: This study proposes a positive miR-155-mediated gene regulation of key factors involved in wound healing. The study represents a promising approach for miRNA-based and cell-free regenerative treatment for difficult-to-heal wounds. The therapeutic potential of miR-155 and its identified targets should be further explored in-vivo.

Study on promoting the regeneration of grafted fat by cell-assisted lipotransfer

Background

Cell-assisted lipotransfer (CAL), a modified adipose-derived stromal/stem cells (ADSCs)-based approach for autologous fat grafting that is an ideal option for soft tissue augmentation, has many shortcomings in terms of retention and adverse effects. The objective of our study was to improve the treatment efficacy of CAL by adding fibroblasts.

Methods

ADSCs and fibroblasts were isolated from human adipose and dermal tissues, with fibroblasts identified by immunofluorescence and ADSCs identified by the multilineage differentiation method. We performed cell proliferation, apoptosis, migration, adipogenic, and hemangioendothelial differentiation experiments, qPCR and Western blotting analysis in co-cultures of fibroblasts and ADSCs. Subsequently, we conducted animal experiments with BALB/c nude mice. Masson's staining, immunofluorescence staining and ultrasound were used to analyze the occurrence of adverse reactions of the grafted fat, and CT and three-dimensional reconstruction were used to accurately evaluate the volume of the grafted fat.

Results

We found that the co-culture of fibroblasts and ADSCs promoted their mutual proliferation, adipogenic differentiation, hemangioendothelial differentiation and proliferation and migration of HUVECs. Fibroblasts inhibit the apoptosis of ADSCs. Moreover, in animal experiments, the autografted adipose group combined with ADSCs and fibroblasts had the least occurrence of oily cysts, and fat had the best form of survival.

Conclusions

We enhanced adipocyte regeneration and angiogenesis in ADSCs and fibroblast cells after adding fibroblasts to conventional CAL autologous fat grafts. In turn, the volume retention rate of the grafted fat is improved, and the adverse reactions are reduced.

p38MAPK silencing attenuates scar proliferation after cleft palate repair surgery in rats via MRTF-A/SRF pathway

Scarring is the primary factor of maxilla growth restriction among people who have undergone cleft palate repair surgery. p38 mitogen-activated protein kinase (p38MAPK) promotes fibrosis in a variety of organs. However, its role in post-surgery scarring on the hard palate has not been fully understood. This study is designed to investigate the role of p38MAPK in scar formation and maxilla growth of rats. We removed the mucosa on the hard palate of rats and applied the p38MAPK silencing adenovirus vector on it two weeks after surgery. Then the scarring tissue and maxilla growth were evaluated by histological and morphological examination. The effect of p38MAPK silencing on scarring-related genes in fibroblasts was also studied. We found that local injection of Ad-p38MAPK-1 in vivo effectively reduces the expression of p38MAPK and scarring-related proteins and weakens the impact of scarring on the width of the hard palate. Mechanistically, p38MAPK silencing inhibits the expression of α-smooth muscle actin (α-SMA) via mediating the production and nuclear localization of myocardin-related transcription factor A (MRTF-A) in fibroblasts. These results reveal a molecular pathway of scar formation involving p38MAPK/MRTF-A stimulation and support targeting p38MAPK as a potentially effective treatment for post-surgery scarring on the hard palate.

Inhibition of p38 mitogen-activated protein kinases may attenuate scar proliferation after cleft lip surgery in rabbits via Smads signaling pathway

Background

Cleft lip repair surgery always results in visible scarring. It has been proved that scar formation can be reduced by inhibiting the p38 mitogen-activated protein kinases (p38MAPKs) signaling pathway. However, the interaction between p38MAPK and Smads in scar formation is still controversial.

Methods

This study was designed to investigate whether inhibition of p38MAPK reduces postoperative scar formation of cleft lips on rabbits via the Smads signaling pathway. Scar models in rabbits after cleft lip surgery were created and their fibroblasts were extracted. Then the expression of p38MAPK was disturbed by adenovirus in vitro and Vivo. The scar thickness was measured and scar tissues were excised for Sirius red staining and immunohistochemistry to detect the expression of type I collagen (col I), type III collagen (col III), and α-smooth muscle actin (α-SMA). The underlying mechanisms of p38MAPK knockdown on the extracellular matrix and Smad signaling pathway were invested in vitro using the EdU assay, Western blot, RT PCR, and immunofluorescence.

Results

p38MAPK knockdown suppresses the expression of p-smad3 and p-smad2 in fibroblasts, modulating the expression of its target genes, such as α-SMA, col I, and col III. When Ad-P38MAPK-1 was injected into lip scar, it reduced the expression of scar-related genes and scar thickness when compared to the negative control groups.

Conclusions

In rabbits, inhibiting p38MAPK expression prevents scar proliferation through inhibiting the Smad signaling pathway after cleft lip surgery.

3D-printed dermis-specific extracellular matrix mitigates scar contraction via inducing early angiogenesis and macrophage M2 polarization

Scar contraction frequently happens in patients with deep burn injuries. Hitherto, porcine dermal extracellular matrix (dECM) has supplied microenvironments that assist in wound healing but fail to inhibit scar contraction. To overcome this drawback, we integrate dECM into three-dimensional (3D)-printed dermal analogues (PDA) to prevent scar contraction. We have developed thermally gelled, non-rheologically modified dECM powder (dECMp) inks and successfully transformed them into PDA that was endowed with a micron-scale spatial structure. The optimal crosslinked PDA exhibited desired structure, good mechanical properties as well as excellent biocompatibility. Moreover, in vivo experiments demonstrated that PDA could significantly reduced scar contraction and improved cosmetic upshots of split thickness skin grafts (STSG) than the commercially available dermal templates and STSG along. The PDA has also induced an early, intense neovascularization, and evoked a type-2-like immune response. PDA's superior beneficial effects may attribute to their desired porous structure, the well-balanced physicochemical properties, and the preserved dermis-specific ECM cues, which collectively modulated the expression of genes such as Wnt11, ATF3, and IL1β, and influenced the crucial endogenous signalling pathways. The findings of this study suggest that PDA is a clinical translatable material that possess high potential in reducing scar contraction.

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Current dermal analogues have supplied microenvironments that assist in wound healing but cannot inhibit scar contraction.

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dECMp ink was formulated and transformed into PDA endowed with a micron-scale designed spatial structure.

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The PDAs were neatly superior to split thickness skin grafts and commercial dermal templates in hindering scar contraction.

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The transcriptome data may reveal how at the molecular level the IS and skin wounds respond to biomaterial stimuli.

Long non-coding RNA H19 acts as a microRNA-194 sponge to inhibit the apoptosis and promote the proliferation of hypertrophic scar fibroblasts

The effects of long non-coding RNAs (lncRNAs) on the proliferation of hypertrophic scars have been described. However, the underlying mechanisms are not well characterized. The present study aimed to investigate the mechanisms of lncRNA H19 in hypertrophic scars. The effects of the lncRNA H19 on the proliferation and apoptosis of hypertrophic scar fibroblasts (HSFs) were analyzed using 5'-Ethynyl-2'-deoxyuridine staining, flow cytometry, and MTT. The results revealed H19 promoted the proliferation and inhibited the apoptosis in HSF. In addition, the binding associations between H19 and microRNA-194 (miR-194), and miR-194 and insulin-like growth factor-I receptor (IGF1R) were identified using bioinformatics screening and verified using dual-luciferase assays. Furthermore, the effects of the IGF1R knockdown on H19-induced HSF phenotypes and regulation over the p38 MAPK pathway were determined. Mechanistically, miR-194 was identified as the downstream effector of the H19-mediated phenotypes of HSFs through its ability to directly target IGF1R, thus modulating the p38 MAPK signaling pathway. In conclusion, the findings suggested that H19 may inhibit the apoptosis and promote the proliferation of HSFs through the miR-194/IGF1R/p38 MAPK signaling axis, thereby contributing to the progression of hypertrophic scars. These findings may provide novel targets for the treatment of hypertrophic scars.

Investigation of the role of platelets in the aetiopathogenesis of adenomyosis

RESEARCH QUESTION

Do platelets aggregate in adenomyotic lesions and participate in adenomyosis pathogenesis and related fibrosis?

DESIGN

Eutopic and ectopic endometrium from 17 patients with adenomyosis and endometrium from 23 healthy controls were collected. Immunohistochemical analyses of platelet marker CD41, transforming growth factor beta 1 (TGF-β1) and vascular endothelial growth factor (VEGF) were performed to investigate aggregation and activation of platelets in the stroma. Picrosirius staining was carried out to evaluate the extent of fibrotic tissue.

RESULTS

Stroma in the control group showed higher CD41 staining levels than ectopic stroma from patients with adenomyosis (P < 0.001). In patients with adenomyosis, eutopic stroma expressed more extensive CD41 staining than ectopic stroma (P < 0.0001). Stroma in the control group exhibited higher TGF-β1 expression than eutopic and ectopic stroma from adenomyosis patients (P = 0.009 and P < 0.0001). Stroma in the control group also expressed higher VEGF levels than ectopic stroma from patients with adenomyosis (P < 0.001). In patients with adenomyosis, eutopic stroma showed higher VEGF expression than ectopic stroma (P = 0.021). Stroma in ectopic endometrium from adenomyosis patients displayed greater Picrosirius staining compared with both eutopic stroma from adenomyosis patients and stroma in the control group (P < 0.0001).

CONCLUSION

The results of this study did not detect a primary role for platelet activation or aggregation in the pathophysiological process of adenomyosis. Higher rates of collagen fibres were found in adenomyotic lesions, likely to be related to a TGF-β1-independent pathway. Collagen fibre deposition was more extensive in adenomyotic lesions, consistent with fibrosis.

[Mechanism of p38 mitogen activated protein kinase signaling pathway on promoting the hypertrophy of human lumbar ligamentum flavum via transforming growth factor β 1/connective tissue growth factor]

Objective

To investigate the mechanism of p38 mitogen activated protein kinase (MAPK) signaling pathway in regulating the hyperplasia and hypertrophy of human lumbar ligamentum flavum via transforming growth factor β ₁ (TGF-β ₁)/connective tissue growth factor (CTGF).

Methods

The lumbar ligamentum flavum tissue taken from patient with lumbar intervertebral disc herniation was isolated by collagenase-predigested explant cultures. The ligamentum flavum cells were treated with the extracellular regulated protein kinase pathway blocker PD98059, c-Jun N-terminal kinase pathway blocker SP600125, and p38 pathway blocker SB203580, and then the mRNA expressions of CTGF, collagen type Ⅰ, and collagen type Ⅲ were detected by real-time fluorescence quantitative PCR (qRT-PCR). The ligamentum flavum cells were divided into 4 groups, and transfected with small interfering RNA (siRNA), p38 siRNA, siRNA+3 ng/mL TGF-β ₁, and p38 siRNA+3 ng/mL TGF-β ₁ in groups A, B, C, and D, respectively. After 24 hours of transfection, immunofluorescence staining was performed to observe the expressions of p38 and phosphorylation p38 (p-p38); the relative mRNA expressions of CTGF, collagen type Ⅰ, and collagen type Ⅲ in each group were detected by qRT-PCR; the protein expression of CTGF in each group was detected by Western blot.

Results

p38 pathway blocker SB203580 could significantly reduce the relative mRNA expressions of CTGF, collagen type Ⅰ, and collagen type Ⅲ ( P<0.05). After 24 hours of transfection, immunofluorescence staining showed positive staining with p38 and p-p38 expressions in groups A, C, and D and negative staining in group B. Compared with group A, the relative mRNA expressions of CTGF, collagen type Ⅰ, and collagen type Ⅲ and relative protein expression of CTGF in group B decreased significantly ( P<0.05), while those in groups C and D increased significantly ( P<0.05); and those indicators significantly increased in group C than in group D ( P<0.05).

Conclusion

TGF-β ₁/CTGF based on the p38 MAPK signaling pathway play an important role in the occurance and development of hypertrophy of human lumbar ligamentum flavum.

Adipose-Derived Tissue in the Treatment of Dermal Fibrosis: Antifibrotic Effects of Adipose-Derived Stem Cells

Treatment of hypertrophic scars and other fibrotic skin conditions with autologous fat injections shows promising clinical results; however, the underlying mechanisms of its antifibrotic action have not been comprehensively studied. Adipose-derived stem cells, or stromal cell-derived factors, inherent components of the transplanted fat tissue, seem to be responsible for its therapeutic effects on difficult scars. The mechanisms by which this therapeutic effect takes place are diverse and are mostly mediated by paracrine signaling, which switches on various antifibrotic molecular pathways, modulates the activity of the central profibrotic transforming growth factor β/Smad pathway, and normalizes functioning of fibroblasts and keratinocytes in the recipient site. Direct cell-to-cell communications and differentiation of cell types may also play a positive role in scar treatment, even though they have not been extensively studied in this context. A more thorough understanding of the fat tissue antifibrotic mechanisms of action will turn this treatment from an anecdotal remedy to a more controlled, timely administered technology.

Effect of Plastrum Testudinis Extracts on the Proliferation and Osteogenic Differentiation of rBMSCs by Regulating p38 MAPK-Related Genes

Extracts from plastrum testudinis (PTE) are active compounds that have been used to treat bone diseases in traditional Chinese medicine for thousands of years. In previous studies, we demonstrated their effects on glucocorticoid-induced osteoporosis both in vivo and in vitro. However, the mechanisms by which PTE regulates the osteogenic differentiation of rat bone marrow-derived mesenchymal stem cells (rBMSCs) in vitro remain poorly understood. In this study, rBMSCs were treated with medium (CON), PTE, osteogenic induction (OI), and a combination of PTE and OI (PTE+OI) over a 21-day period. We found that PTE significantly promoted rBMSCs osteogenic differentiation and mineralisation after 21 days of culturing. Moreover, PTE+OI further enhanced the differentiation and mineralisation process. PTE upregulated STE20, IGF1R, and p38 MAPK mRNA expression and downregulated TRAF6 mRNA expression. The extracts inhibited TRAF6 protein expression and promoted STE20, IGF1R, and phosphorylated p38 MAPK protein expression. Our results imply that PTE promotes the proliferation and osteogenic differentiation of rBMSCs by upregulating p38 MAPK, STE20, and IGF1R and downregulating TRAF6 expression, which may provide experimental evidence of the potential of PTE in the treatment of osteoporosis.

Early cessation of pressure garment therapy results in scar contraction and thickening

Pressure garment therapy is often prescribed to improve scar properties following full-thickness burn injuries. Pressure garment therapy is generally recommended for long periods of time following injury (1-2 years), though it is plagued by extremely low patient compliance. The goal of this study was to examine the effects of early cessation of pressure garment therapy on scar properties. Full-thickness burn injuries were created along the dorsum of red Duroc pigs. The burn eschar was excised and wound sites autografted with split-thickness skin. Scars were treated with pressure garments within 1 week of injury and pressure was maintained for either 29 weeks (continuous pressure) or for 17 weeks followed by cessation of pressure for an additional 12 weeks (pressure released); scars receiving no treatment served as controls. Scars that underwent pressure garment therapy were significantly smoother and less contracted with decreased scar height compared to control scars at 17 weeks. These benefits were maintained in the continuous pressure group until week 29. In the pressure released group, grafts significantly contracted and became more raised, harder and rougher after the therapy was discontinued. Pressure cessation also resulted in large changes in collagen fiber orientation and increases in collagen fiber thickness. The results suggest that pressure garment therapy effectively improves scar properties following severe burn injury; however, early cessation of the therapy results in substantial loss of these improvements.

Longitudinal Study of Scar Hyperplasia Formation Following Cleft Lip Wound Healing

The purpose of this study was to observe the hyperplasia trend of scar after the cleft lip surgery in a rabbit animal model, and determine the time-point of the highest hypertrophic degree of scar after cleft lip repair. Forty New Zealand white rabbits from the same offspring were used to establish a cleft lip wound healing model using Millard surgery procedure. The scar volumes were measured and granulation tissues were observed visually in the 2, 3, 4, and 5 weeks after operation. The scar tissues were harvested at the indicated time-points. Immunohistochemical (IHC) and Western Blot analyses were performed to detect the expression level of α-smooth muscle actin (α-SMA) in the scar tissue. The scars shrunk and the volumes reduced at 3 to 4 weeks after surgery; however, at 5 weeks postsurgery, the volumes increased. IHC and Western blot analyses indicated the expression of α-SMA was significantly enhanced 3 to 4 weeks, but reduced in the 5 weeks after surgery. Overall, the degree of scar hyperplasia after cleft lip surgery in rabbits was normally distributed and the scarring was most severe in the 3 to 4 weeks after cleft lip surgery. The study confirms a novel animal model for the assessment of therapies for the treatment of scar hyperplasia of human cleft lip in future.

A Systematic Review on the Effect of Mechanical Stretch on Hypertrophic Scars after Burn Injuries

Objective/Background

To review the effect of mechanical stretch on hypertrophic scars after burn injuries.

Methods

A systematic review of all controlled trials related to the effect of mechanical stretch on post burn hypertrophic scars was conducted. Studies of conservative scar managements that applied mechanical forces parallel to the scar surface, including stretching exercise, massage, and splinting, were appraised. Eligible studies published in English between 1995 and 2016 were extracted from The Cochrane Library, MEDLINE, CINAHL, Science direct, SPORTDiscus, and Physiotherapy Evidence Database Scale (PEDro). The journals were further screened with inclusion and exclusion criteria. PEDro was selected for further analysis and appraisal.

Results

There were 853 articles identified. After a standardized screening mechanism stipulated, only nine full-text articles were selected for critical appraisal using PEDro. There were five articles of high quality, two of fair quality, and two of poor quality. Detailed training regime and outcomes of nine studies were summarised, including two studies with stretching exercise, six studies with massage, and one study with splinting. The physical parameters of scar assessments and the range of motion on affected areas were compared.

Conclusion

From extensive literature search, there was no strong evidence indicating the positive effect of mechanical stretch using stretching exercise, massage, or splinting on hypertrophic scars. A firm conclusion cannot be drawn for the discrepancy of outcome measures and varied effectiveness. Most of the included studies lacked objective evaluation or control group for comparison. Further high quality studies with larger sample size and using standardized measurements are needed.

Adipose tissue-derived stem cells suppress hypertrophic scar fibrosis via the p38/MAPK signaling pathway

BACKGROUND

Hypertrophic scars (HS) generally occur after injury to the deep layers of the dermis, resulting in functional deficiency for patients. Growing evidence has been identified that the supernatant of adipose tissue-derived stem cells (ADSCs) significantly ameliorates fibrosis of different tissues, but limited attention has been paid to its efficacy on attenuating skin fibrosis. In this study, we explored the effect and possible mechanism of ADSC-conditioned medium (ADSC-CM) on HS.

METHOD

Real-time quantitative polymerase chain reaction (qRT-PCR) and Western blotting were used to detect the expression of collagen I (Col1), collagen III (Col3), and α-smooth muscle actin (α-SMA) after fibroblasts and cultured HS tissues were stimulated with ADSC-CM and p38 inhibitor/activator. Immunofluorescence staining was performed to test the expression of α-SMA. Masson's trichrome staining, hematoxylin and eosin (H&E) staining, and immunohistochemistry staining were carried out to assess the histological and pathological change of collagen in the BALB/c mouse excisional model. All data were analyzed by using SPSS17.0 software. Statistical analysis was performed by Student's t tests.

RESULTS

The in vitro and ex vivo study revealed ADSC-CM decreased the expression of Col1, Col3, and α-SMA. Together, thinner and orderly arranged collagen was manifested in HS tissues cultured with ADSC-CM. Dramatically, the assessed morphology showed an accelerated healing rate, less collagen deposition, and col1- and col3-positive cells in the ADSC-CM treated group. Importantly, the protein level of p-p38 was downregulated in a concentration-dependent manner in HS-derived fibroblasts with ADSC-CM treatment, which further decreased the expression of p-p38 after the application of its inhibitor, SB203580. SB203580 led to an obvious decline in the expression of Col1, Col3, and α-SMA in fibroblasts and cultured HS tissues and presented more ordered arrangement and thinner collagen fibers in BALB/c mice. Lastly, anisomycin, an agonist of p38, upregulated the expression of fibrotic proteins and revealed more disordered structure and denser collagen fibers.

CONCLUSION

This study demonstrated that ADSC-CM could decrease collagen deposition and scar formation in in vitro, ex vivo and in vivo experiments. The regulation of the p38/MAPK signaling pathway played an important role in the process. The application of ADSC-CM may provide a novel therapeutic strategy for HS treatment, and the anti-scarring effect can be achieved by inhibition of the p38/MAPK signaling pathway.

Missense Variant in MAPK Inactivator PTPN5 Is Associated with Decreased Severity of Post-Burn Hypertrophic Scarring

BACKGROUND

Hypertrophic scarring (HTS) is hypothesized to have a genetic mechanism, yet its genetic determinants are largely unknown. The mitogen-activated protein kinase (MAPK) pathways are important mediators of inflammatory signaling, and experimental evidence implicates MAPKs in HTS formation. We hypothesized that single-nucleotide polymorphisms (SNPs) in MAPK-pathway genes would be associated with severity of post-burn HTS.

METHODS

We analyzed data from a prospective-cohort genome-wide association study of post-burn HTS. We included subjects with deep-partial-thickness burns admitted to our center who provided blood for genotyping and had at least one Vancouver Scar Scale (VSS) assessment. After adjusting for HTS risk factors and population stratification, we tested MAPK-pathway gene SNPs for association with the four VSS variables in a joint regression model. In addition to individual-SNP analysis, we performed gene-based association testing.

RESULTS

Our study population consisted of 538 adults (median age 40 years) who were predominantly White (76%) males (71%) admitted to our center from 2007-2014 with small-to-moderate-sized burns (median burn size 6% total body surface area). Of 2,146 SNPs tested, a rare missense variant in the PTPN5 gene (rs56234898; minor allele frequency 1.5%) was significantly associated with decreased severity of post-burn HTS (P = 1.3×10-6). In gene-based analysis, PTPN5 (P = 1.2×10-5) showed a significant association and BDNF (P = 9.5×10-4) a borderline-significant association with HTS severity.

CONCLUSIONS

We report PTPN5 as a novel genetic locus associated with HTS severity. PTPN5 is a MAPK inhibitor expressed in neurons, suggesting a potential role for neurotrophic factors and neuroinflammatory signaling in HTS pathophysiology.

The role of aldo-keto reductase 1C3 (AKR1C3)-mediated prostaglandin D2 (PGD2) metabolism in keloids

Keloids are progressively expanding scars, mostly prevalent in individuals of African descent. Previous data identified increased mast cell number and activation state in keloids suggesting a role in disease progression. The major eicosanoid secreted by mast cells is prostaglandin D2 (PGD2), a relatively unstable pro-inflammatory mediator which can be spontaneously converted to 15-deoxy-(Delta12,14)-prostaglandin J2(15d-PGJ2) or enzymatically metabolized to 9α,11β-PGF2 by aldo-keto reductase 1C3 (AKR1C3). In this work, we investigated the possible role of PGD2 and its metabolites in keloids using CRL1762 keloid fibroblasts (KF) and immunohistochemical staining. Our data suggested approximately 3-fold increase of tryptase-positive mast cell count in keloids compared with normal skin. Furthermore, AKR1C3 was overexpressed in the fibrotic area of keloids while relatively weak staining detected in normal skin. Metabolism of PGD2 to 9α,11β-PGF2 by both, KF and normal fibroblasts, was dependent on AKR1C3 as this reaction was attenuated in the presence of the AKR1C3 inhibitor, 2'-hydroxyflavanone, or in cells with decreased AKR1C3 expression. 15d-PGJ2, but not the other tested PGs, inhibited KF proliferation, attenuated KF-mediated collagen gel contraction and increased caspase-3 activation. In addition, treatment with 15d-PGJ2 activated P38-MAPK, induced reactive oxygen species and upregulated superoxide dismutase-1 (SOD-1). Finally, inhibition of P38-MAPK further augmented 15d-PGJ2-induced caspase-3 cleavage and attenuated its effect on SOD-1 transcription. This work suggests that localized dual inhibition of AKR1C3 and P38-MAPK may inhibit keloid progression. Inhibiting AKR1C3 activity may generate oxidative environment due to redirection of PGD2 metabolism towards 15d-PGJ2 while inhibition of P38-MAPK will sensitize keloid cells to ROS-induced apoptosis.