A review of the influence of growth factors and cytokines in in vitro human keratinocyte migration

Amniotic membrane stimulates cell migration by modulating transforming growth factor-β signalling

Keratinocyte migration is a mandatory aspect of wound healing. We have previously shown that amniotic membrane (AM) applied to chronic wounds assists healing through a process resulting in the overexpression of c-Jun at the wound's leading edge. We have also demonstrated that AM modifies the genetic programme induced by transforming growth factor-ß (TGF-ß) in chronic wounds. Here we used a scratch assay of mink lung epithelial cells (Mv1Lu) and a spontaneously immortalized human keratinocyte cell line (HaCaT) cells to examine the influence of AM application on the underlying signalling during scratch closure. AM application induced c-Jun phosphorylation at the leading edge of scratch wounds in a process dependent on MAPK and JNK signalling. Strikingly, when the TGF-ß-dependent Smad-activation inhibitor SB431542 was used together with AM, migration improvement was partially restrained, whereas the addition of TGF-ß had a synergistic effect on the AM-induced cell migration. Moreover, antagonizing TGF-ß with specific antibodies in both cell lines or knocking out TGF-ß receptors in Mv1Lu cells had similar effects on cell migration as using SB431542. Furthermore, we found that AM was able to attenuate TGF-ß-Smad signalling specifically at the migrating edge; AM treatment abated Smad2 and Smad3 nuclear localization in response to TGF-ß in a process dependent on mitogen-activated protein kinase kinase 1 (MEK1) activation but independent of EGF receptor or JNK activation. The involvement of Smad signalling on AM effects on HaCaT keratinocytes was further corroborated by overexpression of either Smad2 or Smad3 and the use of Smad phosphorylation-specific inhibitors, revealing a differential influence on AM-induced migration for each Smad. Thus, AM TGF-ß-Smad signalling abating is essential for optimal cell migration and wound closure.

IGF-I regulates HT1080 fibrosarcoma cell migration through a syndecan-2/Erk/ezrin signaling axis

Fibrosarcoma is a tumor of mesenchymal origin, originating from fibroblasts. IGF-I is an anabolic growth factor which exhibits significant involvement in cancer progression. In this study, we investigated the possible participation of syndecan-2 (SDC-2), a cell membrane heparan sulfate (HS) proteoglycan on IGF-I dependent fibrosarcoma cell motility. Our results demonstrate that SDC-2-deficient HT1080 cells exhibit attenuated IGF-I-dependent chemotactic migration (p < 0.001). SDC-2 was found to co-localize to IGF-I receptor (IGF-IR) in a manner dependent on IGF-I activity (P ≤ 0.01). In parallel, the downregulation of SDC-2 significantly inhibited both basal and due to IGF-I action ERK1/2 activation, (p < 0.001). The phosphorylation levels of ezrin (Thr567), which is suggested to act as a signaling bridge between the cellular membrane receptors and actin cytoskeleton, were strongly enhanced by IGF-I at both 1h and 24h (p < 0.05; p < 0.01). The formation of an immunoprecipitative complex revealed an association between SDC2 and ezrin which was enhanced through IGF-I action (p < 0.05). Immunoflourescence demonstrated a co-localization of IGF-IR, SDC2 and ezrin upregulated by IGF-I action. IGF-I enhanced actin polymerization and ezrin/actin specific localization to cell membranes. Finally, treatment with IGF-I strongly increased SDC2 expression at both the mRNA and protein level (p < 0.001). Therefore, we propose a novel SDC2-dependent mechanism, where SDC2 is co-localized with IGF-IR and enhances its' IGFI-dependent downstream signaling. SDC2 mediates directly IGFI-induced ERK1/2 activation, it recruits ezrin, contributes to actin polymerization and ezrin/actin specific localization to cell membranes, ultimately facilitating the progression of IGFI-dependent fibrosarcoma cell migration.

Effects of Prisma® Skin dermal regeneration device containing glycosaminoglycans on human keratinocytes and fibroblasts

Prisma® Skin is a new pharmaceutical device developed by Mediolanum Farmaceutici S.p.a. It includes alginates, hyaluronic acid and mainly mesoglycan. The latter is a natural glycosaminoglycan preparation containing chondroitin sulfate, dermatan sulfate, heparan sulfate and heparin and it is used in the treatment of vascular disease. Glycosaminoglycans may contribute to the re-epithelialization in the skin wound healing, as components of the extracellular matrix. Here we describe, for the first time, the effects of Prisma® Skin in in vitro cultures of adult epidermal keratinocytes and dermal fibroblasts. Once confirmed the lack of cytotoxicity by mesoglycan and Prisma® Skin, we have shown the increase of S and G2 phases of fibroblasts cell cycle distribution. We further report the strong induction of cell migration rate and invasion capability on both cell lines, two key processes of wound repair. In support of these results, we found significant cytoskeletal reorganization, following the treatments with mesoglycan and Prisma® Skin, as confirmed by the formation of F-actin stress fibers. Additionally, together with a significant reduction of E-cadherin, keratinocytes showed an increase of CD44 expression and the translocation of ezrin to the plasma membrane, suggesting the involvement of CD44/ERM (ezrin-radixin-moesin) pathway in the induction of the analyzed processes. Furthermore, as showed by immunofluorescence assay, fibroblasts treated with mesoglycan and Prisma® Skin exhibited the increase of Fibroblast Activated Protein α and a remarkable change in shape and orientation, two common features of reactive stromal fibroblasts. In all experiments Prisma® Skin was slightly more potent than mesoglycan. In conclusion, based on these findings we suggest that Prisma® Skin may be able to accelerate the healing process in venous skin ulcers, principally enhancing re-epithelialization and granulation processes.

Oleanolic acid induces migration in Mv1Lu and MDA-MB-231 epithelial cells involving EGF receptor and MAP kinases activation

During wound healing, skin function is restored by the action of several cell types that undergo differentiation, migration, proliferation and/or apoptosis. These dynamics are tightly regulated by the evolution of the extra cellular matrix (ECM) contents along the process. Pharmacologically active flavonoids have shown to exhibit useful physiological properties interesting in pathological states. Among them, oleanolic acid (OA), a pentacyclic triterpene, shows promising properties over wound healing, as increased cell migration in vitro and improved wound resolution in vivo. In this paper, we pursued to disclose the molecular mechanisms underlying those effects, by using an in vitro scratch assay in two epithelial cell lines of different linage: non-malignant mink lung epithelial cells, Mv1Lu; and human breast cancer cells, MDA-MB-231. In every case, we observed that OA clearly enhanced cell migration for in vitro scratch closure. This correlated with the stimulation of molecular pathways related to mitogen-activated protein (MAP) kinases, as ERK1,2 and Jun N-terminal kinase (JNK) 1,2 activation and c-Jun phosphorylation. Moreover, MDA-MB-231 cells treated with OA displayed an altered gene expression profile affecting transcription factor genes (c-JUN) as well as proteins involved in migration and ECM dynamics (PAI1), in line with the development of an epithelial to mesenchymal transition (EMT) status. Strikingly, upon OA treatment, we observed changes in the epidermal growth factor receptor (EGFR) subcellular localization, while interfering with its signalling completely prevented migration effects. This data provides a physiological framework supporting the notion that lipophilic plant extracts used in traditional medicine, might modulate wound healing processes in vivo through its OA contents. The molecular implications of these observations are discussed.

Hypoxia enhances the wound-healing potential of adipose-derived stem cells in a novel human primary keratinocyte-based scratch assay

Preclinical studies have suggested that paracrine factors from adipose-derived stem cells (ASCs) promote the healing of chronic wounds, and that the exposure of ASCs to hypoxia enhances their wound healing effect. To aid the translation of these findings into clinical use, robust wound models are necessary to explore each aspect of wound healing. The aspect of re-epithelization is often studied in a scratch assay based on transformed keratinocytes. However, there are concerns regarding the validity of this model, since these cell lines differ from normal keratinocytes, both in terms of proliferative capacity and differentiation, and sensitivity to environmental cues. In this study, the main challenge of using primary keratinocytes to examine the effects of ASCs was identified to be their different requirements for calcium in the culture media. We confirmed that a high calcium content led to morphological and cytoskeletal changes in primary keratinocytes, and demonstrated that a low calcium content compromised the growth of ASCs. We found that it is possible to perform the wound healing assay with primary keratinocytes, if the conditioned media from the ASCs is dialyzed to reduce the calcium concentration. Additionally, using this model of re-epithelization, conditioned media from normoxic ASCs was shown to markedly increase the rate of wound closure by primary keratinocytes, and this effect was significantly enhanced with media from the hypoxia-exposed ASCs. These findings, which are in line with the observations from previous in vivo studies, highlight the validity of this modified assay to investigate the wound healing properties of ASCs in vitro.

Epidermal grafting for wound healing: a review on the harvesting systems, the ultrastructure of the graft and the mechanism of wound healing

Epidermal grafting for wound healing involves the transfer of the epidermis from a healthy location to cover a wound. The structural difference of the epidermal graft in comparison to the split-thickness skin graft and full-thickness skin graft contributes to the mechanism of effect. While skin grafting is an epidermal transfer, little is known about the precise mechanism of wound healing by epidermal graft. This paper aims to explore the evolution of the epidermal graft harvesting system over the last five decades, the structural advantages of epidermal graft for wound healing and the current hypotheses on the mechanism of wound healing by epidermal graft. Three mechanisms are proposed: keratinocyte activation, growth factor secretion and reepithelialisation from the wound edge. We evaluate and explain how these processes work and integrate to promote wound healing based on the current in vivo and in vitro evidence. We also review the ongoing clinical trials evaluating the efficacy of epidermal graft for wound healing. The epidermal graft is a promising alternative to the more invasive conventional surgical techniques as it is simple, less expensive and reduces the surgical burden for patients in need of wound coverage.

Mesenchymal Stem Cells from Adipose Tissue in Clinical Applications for Dermatological Indications and Skin Aging

Operating at multiple levels of control, mesenchymal stem cells from adipose tissue (ADSCs) communicate with organ systems to adjust immune response, provide signals for differentiation, migration, enzymatic reactions, and to equilibrate the regenerative demands of balanced tissue homeostasis. The identification of the mechanisms by which ADSCs accomplish these functions for dermatological rejuvenation and wound healing has great potential to identify novel targets for the treatment of disorders and combat aging. Herein, we review new insights into the role of adipose-derived stem cells in the maintenance of dermal and epidermal homeostasis, and recent advances in clinical applications of ADSCs related to dermatology.

Inhibitory effects of serum from sepsis patients on epithelial cell migration in vitro: a case control study

Background

Sepsis delays wound re-epithelialization. In this study we explored the effect of human sepsis sera as well as the effects of cytokines, growth factors and exosomes of sepsis sera treated normal fibroblasts (NF) on keratinocyte migration and proliferation in vitro.

Methods

Serum samples were taken on days 1, 4, and 9 from 44 patients diagnosed with severe sepsis, and from 14 matching healthy controls. We evaluated the effects of sepsis serum with or without TNF-α, EGF, EGF receptor inhibitor or exosomes of sepsis sera treated NF on human keratinocyte (HaCaT) proliferation (BrdU assay), viability (MTT assay), and migration (horizontal wound healing model). Cytokine levels of sepsis and healthy sera were measured by multiplex assay. Comparisons between groups were carried out using SPSS statistics and P < 0.05 was considered significant.

Results

Severe-sepsis sera collected on days 1, 4, and 9 reduced keratinocyte proliferation by 6% (P = 0.005), 20% (P = 0.001), and 18% (P = 0.002), respectively, compared to control sera. Cell viability in cultures exposed to sepsis sera from days 4 and 9 was reduced by 38% (P = 0.01) and 58% (P < 0.001), respectively. Open-surface wounds exposed to sepsis sera from days 1 and 4 were larger than those exposed to sera from healthy controls (60 vs. 31%, P = 0.034 and 66 vs. 31%, P = 0.023, respectively). Exosomes of sepsis or healthy sera treated NF inhibited keratinocyte migration. We detected higher serum levels of cytokines TNF-α (5.7 vs. 0.7 pg/ml, P < 0.001), IL-6 (24.8 vs. 3.8 pg/ml, P < 0.001), IL-10 (30.0 vs. 11.9 pg/ml, P = 0.040), and VEGF (177.9 vs. 48.1 pg/ml, P = 0.018) in sepsis sera. Levels of EGF were significantly lower in sepsis sera than in that of healthy controls (6.5 vs. 115.6 pg/ml, P < 0.001). Sepsis serum supplemented with EGF 5 ng/ml and TNF-α in all concentrations improved keratinocyte migration.

Conclusions

Keratinocyte viability, proliferation and migration were reduced in severe sepsis in vitro. Exosomes from NF added in healthy or sepsis serum media inhibited keratinocyte migration. Decreased levels of EGF in sepsis sera may partially explain the delay of wound healing with severe-sepsis patients. Increased levels of TNF-α in sepsis sera do not explain diminished keratinocyte migration.

Male pattern baldness and risk of incident skin cancer in a cohort of men

We examined the association between male-pattern baldness and risk of incident skin cancer, including invasive melanoma, invasive squamous cell carcinoma (SCC), and basal cell carcinoma (BCC) in a prospective analysis, based on 36,032 participants from the Health Professionals' Follow-up Study. In 1992, participants reported their status of male-pattern baldness at age 45 years by choosing from five crown-view pictograms based on Norwood's classification. Diagnosis of skin cancers was reported biennially and information on melanoma and SCC was pathologically confirmed. We identified 327 melanoma cases, 1324 SCC cases, and 8438 BCC cases during the follow-up. Male-pattern baldness was not significantly associated with risk of incident melanoma, but was significantly associated with increased risk of SCC and BCC. The multivariate-adjusted hazard ratio (HR) (95% confidence interval, CI) for the highest category of baldness (frontal plus severe vertex baldness) was 1.33 (1.06-1.68) for SCC (p_trend  = 0.001) and 1.23 (1.12-1.35) for BCC (p_trend  < 0.0001), compared with no baldness. Analyses by body sites found significant associations between frontal plus moderate to severe vertex baldness and risk of melanoma (HR = 1.83, 95% CI: 1.01-3.34) and SCC (HR = 1.30, 95% CI: 1.02-1.66) at head and neck. The associations were particularly stronger for scalp melanoma (HR = 7.15, 95% CI: 1.29-39.42) and scalp SCC (HR = 7.09, 95% CI: 3.84-13.08), but not for non-scalp head and neck sites. Information on body sites was not available for BCC. In conclusion, male pattern baldness may be associated with increased risk of skin cancer, but the associations may only exist for those occurring at head and neck, particularly at scalp.

Influence of Birch Bark Triterpenes on Keratinocytes and Fibroblasts from Diabetic and Nondiabetic Donors

Impaired wound healing is one of the main risk factors associated with diabetes mellitus. Few options are available to treat diabetic wounds, and therefore efficient remedies are urgently needed. An interesting option might be an extract of birch bark (TE) that has been clinically proven to accelerate acute wound healing. We investigated the effects of TE and its main components betulin and lupeol in cultured normal keratinocytes and dermal fibroblasts from diabetic and nondiabetic donors. These in vitro models can provide insights into possible beneficial effects in wound healing. TE and betulin treatment led to increased mRNA levels of chemokines, pro-inflammatory cytokines, and mediators important in wound healing, e.g., IL-6, TNFα, IL-8, and RANTES. We observed a pronounced upregulation of MIF, IL-8, and RANTES on the protein level. Furthermore, a shape change of the actin cytoskeleton was seen in keratinocytes and fibroblasts, and the Rho-GTPases and p38-MAPK were found to be activated in keratinocytes. On the basis of our results, TE is worthy of further study as a potential option to influence wound-healing processes under diabetic conditions. These first insights need to be confirmed by clinical studies with diabetic patients.

Transforming growth factor beta (TGF-β) isoforms in wound healing and fibrosis

Scar formation, with persistent alteration of the normal tissue structure, is an undesirable and significant result of both wound healing and fibrosing disorders. There are few strategies to prevent or to treat scarring. The transforming growth factor beta (TGF-β) superfamily is an important mediator of tissue repair. Each TGF-β isoform may exert a different effect on wound healing, which may be context-dependent. In particular, TGF-β1 may mediate fibrosis in adults' wounds, while TGF-β3 may promote scarless healing in the fetus and reduced scarring in adults. Thus, TGF-β3 may offer a scar-reducing therapy for acute and chronic wounds and fibrosing disorders.

Aberrant Wound Healing in an Epidermal Interleukin-4 Transgenic Mouse Model of Atopic Dermatitis

Wound healing in a pre-existing Th2-dominated skin milieu was assessed by using an epidermal specific interleukin-4 (IL-4) transgenic (Tg) mouse model, which develops a pruritic inflammatory skin condition resembling human atopic dermatitis. Our results demonstrated that IL-4 Tg mice had delayed wound closure and re-epithelialization even though these mice exhibited higher degrees of epithelial cell proliferation. Wounds in IL-4 Tg mice also showed a marked enhancement in expression of inflammatory cytokines/chemokines, elevated infiltration of inflammatory cells including neutrophils, macrophages, CD3+ lymphocytes, and epidermal dendritic T lymphocytes. In addition, these mice exhibited a significantly higher level of angiogenesis as compared to wild type mice. Furthermore, wounds in IL-4 Tg mice presented with larger amounts of granulation tissue, but had less expression and deposition of collagen. Taken together, an inflamed skin condition induced by IL-4 has a pronounced negative influence on the healing process. Understanding more about the pathogenesis of wound healing in a Th2- dominated environment may help investigators explore new potential therapeutic strategies.

Hepatocyte Growth Factor and Satellite Cell Activation

Satellite cells are the "currency" for the muscle growth that is critical to meat production in many species, as well as to phenotypic distinctions in development at the level of species or taxa, and for human muscle growth, function and regeneration. Careful research on the activation and behaviour of satellite cells, the stem cells in skeletal muscle, including cross-species comparisons, has potential to reveal the mechanisms underlying pathological conditions in animals and humans, and to anticipate implications of development, evolution and environmental change on muscle function and animal performance.

Chemical characterization and in vitro toxicity of diesel exhaust particulate matter generated under varying conditions

Epidemiologic studies have linked diesel exhaust (DE) to cardiovascular and respiratory morbidity and mortality, as well as lung cancer. DE composition is known to vary with many factors, although it is unclear how this influences toxicity. We generated eight DE atmospheres by applying a 2×2×2 factorial design and altering three parameters in a controlled exposure facility: (1) engine load (27 vs 82 %), (2) particle aging (residence time ~5 s vs ~5 min prior to particle collection), and (3) oxidation (with or without ozonation during dilution). Selected exposure concentrations of both diesel exhaust particles (DEPs) and DE gases, DEP oxidative reactivity via DTT activity, and in vitro DEP toxicity in murine endothelial cells were measured for each DE atmosphere. Cell toxicity was assessed via measurement of cell proliferation (colony formation assay), cell viability (MTT assay), and wound healing (scratch assay). Differences in DE composition were observed as a function of engine load. The mean 1-nitropyrene concentration was 15 times higher and oxidative reactivity was two times higher for low engine load versus high load. There were no substantial differences in measured toxicity among the three DE exposure parameters. These results indicate that alteration of applied engine load shifts the composition and can modify the biological reactivity of DE. While engine conditions did not affect the selected in vitro toxicity measures, the change in oxidative reactivity suggests that toxicological studies with DE need to take into account engine conditions in characterizing biological effects.

Enhanced expression of hepatocyte growth factor in the healing of experimental acute tympanic membrane perforation

OBJECTIVES

The present study was performed to investigate the expression of hepatocyte (HGF), epidermal (EGF) and vascular endothelial (VEGF) growth factors in the course of healing of experimental tympanic membrane (TM) perforations in rats. The goal was to explain the role of these growth factors in the healing process of TM and to assess the possibility of their future application as healing promoters.

METHODS

Seventy rats were used, of which 10 served as controls and the others had their TM perforated. The experimental animals were divided into six subgroups on the basis of time points (01, 03, 05, 07, 09, 15 day after injury). Videootoscopy and histology were employed to assess the morphology of the healing process. The expressions of HGF, EGF and VEGF were evaluated using Western blot analysis. Tissue localization of HGF was determined by the immunofluorescence method.

RESULTS

HGF was hardly detectable in normal TM; however, a significant increase was noted in its expression starting from the third day after injury throughout the follow-up period, with the highest level on day 05. The analysis of HGF tissue localization with immunofluorescence revealed diffuse staining in the cytoplasm of proliferating epithelial cells. The expression of EGF was elevated on the first day after injury, not reaching statistical significance, and then returned to the level observed in the control TM. No significant differences were noted in the expression of VEGF.

CONCLUSION

High expression of HGF during the healing process of acute TM perforations makes it a promising candidate for further studies oriented towards its possible use in augmentation of TM healing.

Mechanisms of growth-promoting and tumor-protecting effects of epithelial nicotinic acetylcholine receptors

Although the role of nicotine as a carcinogen is debatable, it is widely accepted that it contributes to cancer by promoting growth and survival of mutated cell clones and protecting them from the chemo- and radiotherapy-induced apoptosis. On the cell membrane (cm), the nicotinic acetylcholine (ACh) receptors (nAChRs) implement upregulation of proliferative and survival genes. Nicotine also can permeate cells and activate mitochondrial (mt)-nAChRs coupled to inhibition of the mitochondrial permeability transition pore (mPTP) opening, thus preventing apoptosis. In this study, we sought to pin down principal mechanisms mediating the tumor-promoting activities of nicotine resulting from activation of cm- and mt-nAChRs in oral and lung cancer cells, SCC25 and SW900, respectively. Activated cm-nAChRs were found to form complexes with receptors for EGF and VEGEF via the α7 and β2 nAChR subunits, respectively, whereas activated mt-nAChRs physically associated with the intramitochondrial protein kinases PI3K and Src via the α7 and β4 subunits. This was associated with upregulated expression of cyclin D1/activation of ERK1/2 and inhibition of mPTP opening, respectively, as well as upregulated proliferation and resistance to H(2)O(2)-induced apoptosis. The molecular synergy between cm-nAChRs and growth factor receptors helps explain how one biological mediator, such as ACh, can modulate activity of the other, such as a growth factor, and vice versa. Establishment of functional coupling of mt-nAChRs to regulation of mPTP opening provides a novel mechanism of nicotine-dependent protection from cell death. Further elucidation of this novel mechanism of tumor-promoting activities of nicotine should have a strong translational impact, because extraneuronal nAChRs may provide a novel molecular target to prevent, reverse, or retard progression of both nicotine-related and unrelated cancers.

High-voltage pulsed current stimulation enhances wound healing in diabetic rats by restoring the expression of collagen, α-smooth muscle actin, and TGF-β1

Impaired wound healing is a common complication of diabetes mellitus and a major morbidity that leads to pain and severely diminished quality of life. Diabetic wounds are commonly associated with defective immune cell responses or abnormality of extracellular matrix. Various types of electrical stimulation interventions have been used to promote tissue healing. However, it is unclear whether high-voltage pulsed current stimulation (HVPCS) enhances diabetic wound healing. In this study, the effects of HVPCS on wound healing were investigated in diabetic rats. Three groups of rats (10 per group) were used: non-diabetic control, diabetic control, and diabetic rats that were administered HVPCS for 40 minutes daily for 1 week. Rats from control groups were administered sham interventions. Dorsal incision wounds were generated in all animals, and wound-healing rate was determined during one-week intervention. After interventions, we measured the relative expression levels of collagen type I (collagen-I), α-smooth muscle actin (α-SMA), and transforming growth factor-β1 (TGF-β1) mRNAs in the wounded skin. Wound closure was delayed in diabetic control rats compared to the non-diabetic control rats, and the diabetic control rats showed the reduced expression levels of collagen-I, α-SMA and TGF-β1 mRNAs. Importantly, compared to diabetic control rats, rats with HVPCS showed accelerated wound closure and healing (p < 0.01) and restored expression levels of collagen-I (p = 0.02), α-SMA (p = 0.04), and TGF-β1 (p = 0.01) mRNAs. In conclusion, HVPCS may be beneficial for enhancing the healing of diabetic wounds by restoring the expression levels of TGF-β1, collagen-I, and α-SMA.

Chemokine-like factor 1-derived C-terminal peptides induce the proliferation of dermal microvascular endothelial cells in psoriasis

Psoriasis is an inflammatory disease characterized by the abnormal proliferation of skin cells, including dermal microvascular endothelial cells. Recently, chemokine-like factor 1 (CKLF1) was found to participate in the local inflammation and cell proliferation. To explore its role in the pathogenesis of psoriasis, the expression of both CKLF1 and its receptor (CCR4) was determined in the psoriatic lesions. Also, the effect of the C-terminal peptides (C19 and C27) of CKLF1 on the proliferation of human umbilical vein endothelial cells was studied in vitro. By immunohistochemistry and immunofluorescence, the expression of both CKLF1 and CCR4 was determined in the psoriatic lesions. The effect of C-terminal peptides on human umbilical vein endothelial cells (HUVECs) was studied in vitro by the evaluation of cell proliferation and apoptosis. The in vivo assessment was performed accordingly through the subcutaneous injection peptides on BALB/c mice. The results showed that, by immunohistochemistry, both CKLF1 and CCR4 were increasingly expressed in psoriatic lesions as compared to normal skins. Moreover, the primary umbilical vein endothelial cells exhibited higher proliferation ratio under the C19 or C27 stimulation, which was even enhanced by the addition of psoriatic sera or TNF-α. Furthermore, the enhancement of peptide simulation was accompanied with the activation of ERK1/2-MAPKs pathway. In addition, such effect of C19 and C27 was mirrored by the hyperproliferation of cutaneous microvessels in BALB/c mice that were subcutaneously injected with the two peptides. Therefore, we concluded that CKLF1 plays a role in the pathogenesis of psoriasis by promoting the proliferation of microvascular endothelial cells that possibly correlates with ERK1/2-MAPKs activation.

Bioengineering a human plasma-based epidermal substitute with efficient grafting capacity and high content in clonogenic cells

Cultured epithelial autografts (CEAs) produced from a small, healthy skin biopsy represent a lifesaving surgical technique in cases of full-thickness skin burn covering >50% of total body surface area. CEAs also present numerous drawbacks, among them the use of animal proteins and cells, the high fragility of keratinocyte sheets, and the immaturity of the dermal-epidermal junction, leading to heavy cosmetic and functional sequelae. To overcome these weaknesses, we developed a human plasma-based epidermal substitute (hPBES) for epidermal coverage in cases of massive burn, as an alternative to traditional CEA, and set up critical quality controls for preclinical and clinical studies. In this study, phenotypical analyses in conjunction with functional assays (clonal analysis, long-term culture, or in vivo graft) showed that our new substitute fulfills the biological requirements for epidermal regeneration. hPBES keratinocytes showed high potential for cell proliferation and subsequent differentiation similar to healthy skin compared with a well-known reference material, as ascertained by a combination of quality controls. This work highlights the importance of integrating relevant multiparameter quality controls into the bioengineering of new skin substitutes before they reach clinical development.

SIGNIFICANCE

This work involves the development of a new bioengineered epidermal substitute with pertinent functional quality controls. The novelty of this work is based on this quality approach.

The Roles of Growth Factors in Keratinocyte Migration

Significance: The re-epithelialization of wounded skin requires the rapid and coordinated migration of keratinocytes (KC) into the wound bed. Almost immediately after wounding, cells present at or attracted to the wound site begin to secrete a complex milieu of growth factors. These growth factors exert mitogenic and motogenic effects on KCs, inducing the rapid proliferation and migration of KCs at the wound edge. Recent Advances: New roles for growth factors in KC biology are currently being discovered and investigated. This review will highlight the growth factors, particularly transforming growth factor-α (TGF-α), heparin-binding epidermal growth factor (HB-EGF), insulin-like growth factor 1 (IGF-1), fibroblast growth factor 7 (FGF-7), FGF-10, and hepatocyte growth factor (HGF), which have conclusively been shown to be the most motogenic for KCs. Critical Issues: The cellular and molecular heterogeneity of wounded tissue makes establishing direct relationships between specific growth factors and KC migration difficult in situ. The absence of this complexity in simplified in vitro experimental models of migration makes the clinical relevance of the results obtained from these in vitro studies ambiguous. Future Directions: Deciphering the relationship between growth factors and KC migration is critical for understanding the process of wound healing in normal and disease states. Insights into the basic science of the effects of growth factors on KC migration will hopefully lead to the development of new therapies to treat acute and chronic wounds.

Mesenchymal stem cell-conditioned medium improves the proliferation and migration of keratinocytes in a diabetes-like microenvironment

The impairment of wound healing in diabetic patients is an important clinical problem. Proper keratinocyte migration and proliferation are the crucial steps during reepithelialization, and these steps may be impaired in diabetes mellitus (DM) due to hyperglycemia and chronic inflammation in wound site. In this study, we explored the effects of diabetes-like microenvironment with high glucose (HG) and intense inflammation on the migration and proliferation of keratinocytes in vitro. We found that the migration and proliferation of rat keratinocytes were reduced with HG and lipopolysaccharide (LPS) stimulation via Erk signaling pathway in a reactive oxygen species (ROS)-dependent manner. Nevertheless, mesenchymal stem cell-conditioned medium (MSC-CM) counteracts the effects of HG and LPS. Treatment of rat keratinocyte with MSC-CM decreased HG- and/or LPS-induced ROS overproduction. Furthermore, MSC-CM reversed the downregulation of phosphorylation of MEK1/2 and Erk 1/2, which was induced by HG and/or LPS without affecting total levels. Our results may provide a possible mechanism for delayed wound healing in DM and provide a foundation to develop MSC-CM as an alternative therapeutic strategy to ameliorate the poor wound-healing conditions.

Role of dermatopontin in re-epithelialization: implications on keratinocyte migration and proliferation

Re-epithelialization is a key event in wound healing and any impairment in that process is associated with various pathological conditions. Epidermal keratinocyte migration and proliferation during re-epithelialization is largely regulated by the cytokines and growth factors from the provisional matrix and dermis. Extracellular matrix consists of numerous growth factors which mediate cell migration via cell membrane receptors. Dermatopontin (DPT), a non-collagenous matrix protein highly expressed in dermis is known for its striking ability to promote cell adhesion. DPT also enhances the biological activity of transforming growth factor beta 1 which plays a central role in the process of wound healing. This study was designed to envisage the role of DPT in keratinocyte migration and proliferation along with its mRNA and protein expression pattern in epidermis. The results showed that DPT promotes keratinocyte migration in a dose dependant fashion but fail to induce proliferation. Further, PCR and immunodetection studies revealed that the mRNA and protein expression of DPT is considerably negligible in the epidermis in contrast to the dermis. To conclude, DPT has a profound role in wound healing specifically during re-epithelialization by promoting keratinocyte migration via paracrine action from the underlying dermis.

The effects of insulin-like growth factor-1 gene therapy and cell transplantation on rat acute wound model

BACKGROUND

Wound healing is a complex process. Different types of skin cells, extracellular matrix and variety of growth factors are involved in wound healing. The use of recombinant growth factors in researches and production of skin substitutes are still a challenge.

OBJECTIVES

Much research has been done on the effects of gene therapy and cell therapy on wound healing. In this experimental study, the effect of insulin-like growth factor (IGF-1) gene transfer in fibroblast cells was assessed on acute dermal wound healing.

MATERIALS AND METHODS

Fibroblasts were cultured and transfected with IGF-1. Lipofectamine 2000 was used as a reagent of transfection. Transgene expression levels were measured by the enzyme linked immunosorbent assay (ELISA). To study in vivo, rats (weighing 170-200 g) were randomly divided into three groups (five/group) and full-thickness wounds were created on the dorsum region. Suspensions of transfected fibroblast cells were injected into the wound and were compared with wounds treated with native fibroblast cells and normal saline. For the microscopic examination, biopsy was performed on day seven.

RESULTS

In vitro, the maximum expression of IGF1 (96.95 pg/mL) in transfected fibroblast cells was 24 hours after gene transfer. In vivo, it was clear that IGF-1 gene therapy caused an increase in the number of keratinocyte cells during the wound healing process (mean of group A vs. group B with P value = 0.01, mean of group A vs. group C with P value = 0.000). Granulation of tissue formation in the transfected fibroblast group was more organized when compared with the normal saline group and native fibroblast cells.

CONCLUSIONS

This study indicated that the optimization of gene transfer increases the expression of IGF-1. High concentrations of IGF-1, in combination with cell therapy, have a significant effect on wound healing.

Dental pulp stem cells' secretome enhances pulp repair processes and compensates TEGDMA-induced cytotoxicity

OBJECTIVES

Aim of this study was to investigate the effects of dental pulp stem cells' (DPSCs) secretome, expressed through their culture conditioned medium (CM), on biological endpoints related to pulp repair and on TEGDMA-induced cytotoxicity.

METHODS

DPSCs cultures were established and characterized for stem cell markers with flow cytometry. CM was collected from DPSCs under serum deprivation conditions (SDC) and normal serum conditions (NSC) at various time-points. CM effects on DPSCs viability, migration and mineralization potential were evaluated by MTT assay, transwell insert and in vitro scratch assay and Alizarin Red staining/quantification respectively. TEGDMA (0.25-2.0mM) cytotoxicity regarding the same biological endpoints was tested in the presence/absence of CM. TGF-β1 and FGF-2 secretion in CM was measured by ELISA.

RESULTS

CM collected under SDC (4d) was able to increase cell viability by 20-25% and to reduce TEGDMA cytotoxicity by 20% (p<0.05). CM positive effects were not obvious when collected under NSC. Transwell assay showed significant increase (26%, p<0.05) of DPSCs' migration after CM exposure, whereas both migration assays could not support a migration rate improvement in TEGDMA-treated cultures exposed to CM compared to TEGDMA alone. CM significantly (p<0.01) increased DPSCs mineralization potential and completely counteracted TEGDMA cytotoxicity on this process. ELISA analysis showed a time-dependent increase of TGF-β1 and a TEGDMA concentration-dependent increase of both TGF-β1 and FGF-2 in CM.

SIGNIFICANCE

These findings suggest that DPSCs secretome increases their viability, migration and mineralization potential and counteracts TEGDMA-induced cytotoxicy, revealing a novel mechanism of DPSCs autocrine signaling on pulp repair processes.

FOXO1, TGF-β regulation and wound healing

Re-epithelialization is a complex process that involves migration and proliferation of keratinocytes, in addition to the production of cytokines and growth factors that affect other cells. The induction of transcription factors during these processes is crucial for successful wound healing. The transcription factor forkhead boxO-1 (FOXO1) has recently been found to be an important regulator of wound healing. In particular, FOXO1 has significant effects through regulation of transforming growth factor-beta (TGF-β) expression and protecting keratinocytes from oxidative stress. In the absence of FOXO1, there is increased oxidative damage, reduced TGF-β1 expression, reduced migration and proliferation of keratinocytes and increased keratinocytes apoptosis leading to impaired re-epithelialization of wounds.

Mesenchymal stem cells ameliorate impaired wound healing through enhancing keratinocyte functions in diabetic foot ulcerations on the plantar skin of rats

AIMS/HYPOTHESIS

Although the initial healing stage involves a re-epithelialization in humans, diabetic foot ulceration (DFU) has been investigated using rodent models with wounds on the thigh skin, in which a wound contraction is initiated. In this study, we established a rodent model of DFU on the plantar skin and evaluated the therapeutic efficacy of bone-marrow-derived mesenchymal stem cells (BM-MSCs) in this model.

METHODS

The wounds made on the hind paws or thighs of streptozotocin induced diabetic or control rats were treated with BM-MSCs. Expression levels of phosphorylated focal adhesion kinase (pFAK), matrix metaroprotease (MMP)-2, EGF, and IGF-1, were evaluated in human keratinocytes, which were cultured in conditioned media of BM-MSCs (MSC-CM) with high glucose levels.

RESULTS

Re-epithelialization initiated the healing process on the plantar, but not on the thigh, skin. The therapy utilizing BM-MSCs ameliorated the delayed healing in diabetic rats. In the keratinocytes cultured with MSC-CM, the decreased pFAK levels in the high glucose condition were restored, and the MMP2, EGF, and IGF-1 levels increased.

CONCLUSIONS/INTERPRETATION

Our study established a novel rat DFU model. The impaired healing process in diabetic rats was ameliorated by transplantation of BM-MSCs. This amelioration might be accounted for by the modification of keratinocyte functions.

NADPH oxidases in redox regulation of cell adhesion and migration

SIGNIFICANCE

Adhesion and migration induced by cytokines or growth factors are well-organized processes in cellular motility. Reactive oxygen species (ROS) are specifically produced by the Nox family of NADPH oxidases.

RECENT ADVANCES

The signal transduction of migration and adhesion depends on ROS produced by Nox enzymes and factors that initiate migration and adhesion and stimulate cellular ROS formation.

CRITICAL ISSUES

The identification of molecular targets of ROS formation in the signal transduction of adhesion and migration is still in its beginnings, but a site and isoform-specific contribution of Nox enzymes to this process becomes apparent. Nox-derived ROS, therefore, act as second messengers that are specifically modifying signaling proteins involved in adhesion and migration.

FUTURE DIRECTIONS

Individual protein targets of Nox-mediated redox signaling in different cell types and tissues will be identified. Isoform-specific Nox inhibitors will be developed to modulate the ROS-dependent component of migration and adhesion. These compounds might be suited to elicit differential effects between pathophysiologic and physiologic adhesion and migration.

Crosstalk between adrenergic and toll-like receptors in human mesenchymal stem cells and keratinocytes: a recipe for impaired wound healing

Previous studies demonstrate that skin wounds generate epinephrine (EPI) that can activate local adrenergic receptors (ARs), impairing healing. Bacterially derived activators of Toll-like receptors (TLRs) within the wound initiate inflammatory responses and can also impair healing. In this study, we examined the hypothesis that these two pathways crosstalk to one another, using EPI and macrophage-activating lipopeptide-2 (MALP2) to activate ARs and TLR2, respectively, in human bone marrow-derived mesenchymal stem cells (BM-MSCs) and neonatal keratinocytes (NHKs). BM-MSCs exposed to EPI significantly (p < .05) increased TLR2 message (sevenfold BM-MSCs), TLR2 protein (twofold), and myeloid differentiation factor 88 (MyD88) (fourfold). Conversely, activation of TLR2 by MALP2 in these cells increased β2-AR message (twofold in BM-MSCs, 2.7-fold in NHKs), β2-AR protein (2.5-fold), phosphorylation of β-AR-activated kinase (p-BARK, twofold), and induced release of EPI from both cell types (twofold). Treating cells with EPI and MALP2 together, as would be encountered in a wound, increased β2-AR and p-BARK protein expression (sixfold), impaired cell migration (BM-MSCs- 21%↓ and NHKs- 60%↓, p < .002), and resulted in a 10-fold (BM-MSCs) and 51-fold (NHKs) increase in release of IL-6 (p < .001) responses that were remarkably reduced by pretreatment with β2-AR antagonists. In vivo, EPI-stressed animals exhibited impaired healing, with elevated levels of TLR2, MyD88, and IL-6 in the wounds (p < .05) relative to nonstressed controls. Thus, our data describe a recipe for decreasing cell migration and exacerbating inflammation via novel crosstalk between the adrenergic and Toll-like receptor pathways in BM-MSCs and NHKs.

The Human Umbilical Cord Tissue-Derived MSC Population UCX(®) Promotes Early Motogenic Effects on Keratinocytes and Fibroblasts and G-CSF-Mediated Mobilization of BM-MSCs When Transplanted In Vivo

Mesenchymal stromal cells (MSCs) play an important role in tissue regeneration mainly through the secretion of trophic factors that enhance the repair of damaged tissues. The main goal of this work was to study the paracrine mechanisms by which an umbilical cord tissue-derived MSC population (UCX(®)) promotes the migration capacity of human dermal fibroblasts and keratinocytes, which is highly relevant for skin regeneration. Furthermore, the differences between paracrine activities of MSCs from the umbilical cord tissue and the bone marrow (BM-MSCs) were also evaluated. In vitro scratch assays revealed that conditioned media (CM) obtained from both growing and stationary-phase UCX(®) cultures induced human dermal fibroblast (HDF) and keratinocyte (HaCaT) migration. These assays showed that the motogenic activity of UCX(®) CM to HaCaTs was significantly higher than to HDFs, in opposition to the effect seen with CM produced by BM-MSCs that preferentially induced HDF migration. Accordingly, a comparative quantification of key factors with vital importance in the consecutive stages of wound healing revealed very different secretome profiles between UCX(®) and BM-MSCs. The relatively higher UCX(®) expression of EGF, FGF-2, and KGF strongly supports early induction of keratinocyte migration and function, whereas the UCX(®)-specific expression of G-CSF suggested additional roles in mobilization of healing-related cells including CD34(-)/CD45(-) precursors (MSCs) known to be involved in tissue regeneration. Accordingly, in vitro chemotaxis assays and an in vivo transplantation model for chemoattraction confirmed that UCX(®) are chemotactic to CD34(-)/CD45(-) BM-MSCs via a cell-specific mobilization mechanism mediated by G-CSF. Overall, the results strongly suggest different paracrine activities between MSCs derived from different tissue sources, revealing the potential of UCX(®) to extend the regenerative capacity of the organism by complementing the role of endogenous BM-MSCs.