Incisional wound healing in transforming growth factor-beta1 null mice

Epidermal stem cells: Interplay with the skin microenvironment during wound healing

Skin undergoes everyday turnover while often challenged by injuries. The wound healing process in the skin is a dynamic sequence of events that involves various cell types and signaling pathways. Epidermal stem cells (EpdSCs), the tissue-resident stem cells in the skin tissue, are at the center of this complicated process due to their special ability to self-renew and differentiate. During this process, EpdSCs interact actively with the tissue microenvironment, which is essential for proper re-epithelialization and skin barrier restoration. This review describes the intricate interplays between EpdSCs and various components of their surroundings, including extracellular matrix/fibroblasts, vasculature/endothelial cells, and immune cells, as well as their roles in tissue repair.

PRPF19 modulates morphology and growth behavior in a cell culture model of human skin

The skin provides one of the most visual aging transformations in humans, and premature aging as a consequence of oxidative stress and DNA damage is a frequently seen effect. Cells of the human skin are continuously exposed to endogenous and exogenous DNA damaging factors, which can cause DNA damage in all phases of the cell cycle. Increased levels of DNA damage and/or defective DNA repair can, therefore, accelerate the aging process and/or lead to age-related diseases like cancer. It is not yet clear if enhanced activity of DNA repair factors could increase the life or health span of human skin cells. In previous studies, we identified and characterized the human senescence evasion factor (SNEV)/pre-mRNA-processing factor (PRPF) 19 as a multitalented protein involved in mRNA splicing, DNA repair pathways and lifespan regulation. Here, we show that overexpression of PRPF19 in human dermal fibroblasts leads to a morphological change, reminiscent of juvenile, papillary fibroblasts, despite simultaneous expression of senescence markers. Moreover, conditioned media of this subpopulation showed a positive effect on keratinocyte repopulation of wounded areas. Taken together, these findings indicate that PRPF19 promotes cell viability and slows down the aging process in human skin.

A platelet-derived hydrogel improves neovascularisation in full thickness wounds

Platelets are a reservoir of growth factors, cytokines and chemokines involved in spontaneous wound repair. In this study, a platelet-rich and fibrin-rich hydrogel was generated from expired platelet components that would have otherwise been transfused. The material contained physiological concentrations of transforming growth factor β1 (TGF-β1, platelet-derived growth factor AB (PDGF-AB), PDGF-BB, insulin-like growth factor-1 (IGF-1), fibroblast growth factor 2 (FGF-2), and epidermal growth factor (EGF). The effect of the hydrogel on wound repair was investigated in SKH-1 mice. Full thickness dorsal wounds were created on the mice and treated with the hydrogel at various concentrations. Immunohistochemical staining with CD31 (endothelial cell marker) revealed that wounds treated with the hydrogel showed significantly enhanced vascularisation in the wound bed. Moreover, high levels of interleukin-6 (IL-6) and KC (IL-8 functional homologue) in treated wounds were sustained over a longer period of time, compared to untreated wounds. We postulate that sustained IL-6 is a driver, at least partly, of enhanced vascularisation in full thickness wounds treated with the hydrogel. Future work is needed to explore whether this hydrogel can be utilised as a treatment option when vascularisation is a critical limitation. STATEMENT OF SIGNIFICANCE: The economic cost of wound repair is estimated in billions of dollars each year. In many cases time required to vascularise wounds is a major contributor to slow wound repair. In this study, we developed a blood-derived platelet- and fibrin-rich hydrogel. It contains a number of growth factors actively involved in spontaneous wound healing. This hydrogel significantly improved dermal repair and vascularisation in a full-thickness wound mouse model. This study provides an action mechanism for modulation of localised inflammation.

Growth Factors, Reactive Oxygen Species, and Metformin-Promoters of the Wound Healing Process in Burns?

Burns can be caused by various factors and have an increased risk of infection that can seriously delay the wound healing process. Chronic wounds caused by burns represent a major health problem. Wound healing is a complex process, orchestrated by cytokines, growth factors, prostaglandins, free radicals, clotting factors, and nitric oxide. Growth factors released during this process are involved in cell growth, proliferation, migration, and differentiation. Reactive oxygen species are released in acute and chronic burn injuries and play key roles in healing and regeneration. The main aim of this review is to present the roles of growth factors, reactive oxygen species, and metformin in the healing process of burn injuries.

Role of TGF-β in Skin Chronic Wounds: A Keratinocyte Perspective

Chronic wounds are characterized for their incapacity to heal within an expected time frame. Potential mechanisms driving this impairment are poorly understood and current hypotheses point to the development of an unbalanced milieu of growth factor and cytokines. Among them, TGF-β is considered to promote the broadest spectrum of effects. Although it is known to contribute to healthy skin homeostasis, the highly context-dependent nature of TGF-β signaling restricts the understanding of its roles in healing and wound chronification. Historically, low TGF-β levels have been suggested as a pattern in chronic wounds. However, a revision of the available evidence in humans indicates that this could constitute a questionable argument. Thus, in chronic wounds, divergences regarding skin tissue compartments seem to be characterized by elevated TGF-β levels only in the epidermis. Understanding how this aspect affects keratinocyte activities and their capacity to re-epithelialize might offer an opportunity to gain comprehensive knowledge of the involvement of TGF-β in chronic wounds. In this review, we compile existing evidence on the roles played by TGF-β during skin wound healing, with special emphasis on keratinocyte responses. Current limitations and future perspectives of TGF-β research in chronic wounds are discussed.

Co-transfection of hepatocyte growth factor and truncated TGF-β type II receptor inhibit scar formation

Wound scarring remains a major challenge for plastic surgeons. Transforming growth factor (TGF)-β plays a key role in the process of scar formation. Previous studies have demonstrated that truncated TGF-β type II receptor (t-TGF-βRII) is unable to continue signal transduction but is still capable of binding to TGF-β, thereby blocking the TGF-β signaling pathway. Hepatocyte growth factor (HGF) is a multifunctional growth factor that promotes tissue regeneration and wound healing. Theoretically, the combination of HGF and t-TGF-βRII would be expected to exert a synergistic effect on promoting wound healing and reducing collagen formation. In the present study, lentivirus-mediated transfection of the two genes (t-TGF-βRII/HGF) into fibroblasts in vitro and in a rat model in vivo was used. The results demonstrated that the expression of t-TGF-βRII and HGF in NIH-3T3 cells was successfully induced. The expression of both molecules significantly reduced collagen I and III expression, and also inhibited fibroblast proliferation. Furthermore, histological examination and scar quantification revealed less scarring in the experimental wound in a rat model. Moreover, on macroscopic inspection, the experimental wound exhibited less visible scarring compared with the control. Therefore, the present study demonstrated that the combination gene therapy of t-TGF-βRII and HGF promoted wound healing, with less scarring and more epithelial tissue formation, not only by suppressing the overgrowth of collagen due to its antifibrotic effect, but also by promoting tissue regeneration.

Histopathological, immunohistochemical, and molecular studies for determination of wound age and vitality in rats

In forensic medicine, it is vital to verify with the best attainable accuracy once injuries occurred during vital or post-mortem conditions. An immunohistochemical study was carried out to examine the time-dependent expression of macrophage-specific gene CD68 (cluster of differentiation 68), alpha-smooth muscle actin (α-SMA), and vascular endothelial growth factor (VEGF) in different skin wound timings (0, 1, 3, 5, 7, and 14 days) in rats. Histopathological studies were performed to assess the wound age and vitality. Eighteen male albino Wister rats (weighing 170-200 g) were used for wound induction. Rats (n = 3) were euthanised at 0, 1, 3, 5, 7, and 14 days from the starting point of wound induction. Histopathological examination showed that the epidermal re-epithelialisation was completed 14 days after skin incision. The inflammatory phase was recorded during the first 3 days of healing and reached the maximum levels at 5 days, then declined after 7 days, and completely removed at 14 days. The beginning of the proliferative phase was dated to day 3 and the peak at days 5 and 7. The initiation of the granulation tissue formation and remodelling phase of the healing process was observed 5 days after wounding. By immunohistochemical staining, negative VEGF gene expressions at early stages (0-3 days) were observed, as well as neither CD68+ macrophages nor α-SMA+ myofibroblast cells were detected. By increasing the wound ages (5-7 days), granulation tissue and angiogenesis were observed, with the migration of macrophages and fibroblast, which expressed VEGF, CD68, and α-SMA positive reaction. Time-dependent expression of the above markers suggested that they would be useful indicators for the determination of wound age. Both VEGF and transforming growth factor-beta 1 (TGFb1) mRNA levels were determined in different skin wound ages. The transcription of TGFb1 and VEGF increased shortly after wounding, until post-wounding day 7. It then declined constantly, reaching minimal values on day 14.

CTRP9 Regulates Growth, Differentiation, and Apoptosis in Human Keratinocytes through TGFβ1-p38-Dependent Pathway

Impairment of wound healing is a common problem in individuals with diabetes. Adiponectin, an adipocyte-derived cytokine, has many beneficial effects on metabolic disorders such as diabetes, obesity, hypertension, and dyslipidemia. C1q/TNF-Related Protein 9 (CTRP9), the closest paralog of adiponectin, has been reported to have beneficial effects on wound healing. In the current study, we demonstrate that CTRP9 regulates growth, differentiation, and apoptosis of HaCaT human keratinocytes. We found that CTRP9 augmented expression of transforming growth factor beta 1 (TGFβ1) by transcription factor activator protein 1 (AP-1) binding activity and phosphorylation of p38 in a dose-dependent manner. Furthermore, siRNA-mediated suppression of TGFβ1 reversed the increase in p38 phosphorylation induced by CTRP9. siRNA-mediated suppression of TGFβ1 or p38 significantly abrogated the effects of CTRP9 on cell proliferation and differentiation while inducing apoptosis, implying that CTRP9 stimulates wound recovery through a TGFβ1-dependent pathway in keratinocytes. Furthermore, intravenous injection of CTRP9 via tail vein suppressed mRNA expression of Ki67 and involucrin whereas it augmented TGFβ1 mRNA expression and caspase 3 activity in skin of type 1 diabetes animal models. In conclusion, our results suggest that CTRP9 has suppressive effects on hyperkeratosis, providing a potentially effective therapeutic strategy for diabetic wounds.

Characterization of Smad3 knockout mouse derived skin cells

TGF-β plays an important role in skin wound healing process, in which Smad3 acts as a signaling molecule. Smad3 knockout mice exhibit enhanced wound healing and less inflammatory process, but the intrinsic properties of the mouse derived skin cells are generally unexplored. The purpose of this study is to characterize the biological behavior of skin cells derived from Smad3 knockout mice and thus to define the mechanism of this particular wound healing process. Keratinocytes and dermal fibroblasts were harvested from the skin of Smad3 knockout (Smad3 KO) and wild-type (WT) mice and in vitro cultured for one and two passages for various experiments. The results showed that KO mouse serum contained significantly higher levels of TGF-β1 and lower level of IL-6 and IL-10 than WT mouse serum (p < 0.05), which were also supported by the same findings of more TGF-β1 and less IL-6 and IL-10 in the supernatant of cultured KO dermal fibroblasts than those of WT cells (p < 0.05). At gene levels, IL-6, IL-10, and TGF-β1 were significantly less expressed in KO fibroblasts than in WT fibroblasts (p < 0.05). In addition, KO dermal fibroblasts also exhibited stronger migration and proliferation potentials than WT fibroblasts (p < 0.05). Moreover, both KO fibroblasts and keratinocytes showed higher colony-forming efficiency than WT counterparts with significant difference (p < 0.05). These findings indicate that both systemic factors and intrinsic properties of skin cells contribute to enhanced wound healing and less inflammatory reaction observed in Smad3 knock-out mice.

TGF-β Signal Transduction in Oro-facial Health and Non-malignant Disease (Part I)

The transforming growth factor-beta (TGF-β) family of cytokines consists of multi-functional polypeptides that regulate a variety of cell processes, including proliferation, differentiation, apoptosis, extracellular matrix elaboration, angiogenesis, and immune suppression, among others. In so doing, TGF-β plays a key role in the control of cell behavior in both health and disease. In this report, we review what is known about the mechanisms of activation of the peptide, together with details of TGF-β signal transduction pathways. This review summarizes the evidence implicating TGF-β in normal physiological processes of the craniofacial complex—such as palatogenesis, tooth formation, wound healing, and scarring—and then evaluates its role in non-malignant disease processes such as scleroderma, submucous fibrosis, periodontal disease, and lichen planus.

Re-epithelialization of cutaneous wounds in adult zebrafish combines mechanisms of wound closure in embryonic and adult mammals

Re-epithelialization of cutaneous wounds in adult mammals takes days to complete and relies on numerous signalling cues and multiple overlapping cellular processes that take place both within the epidermis and in other participating tissues. Re-epithelialization of partial- or full-thickness skin wounds of adult zebrafish, however, is extremely rapid and largely independent of the other processes of wound healing. Live imaging after treatment with transgene-encoded or chemical inhibitors reveals that re-epithelializing keratinocytes repopulate wounds by TGF-β- and integrin-dependent lamellipodial crawling at the leading edges of the epidermal tongue. In addition, re-epithelialization requires long-range epithelial rearrangements, involving radial intercalations, flattening and directed elongation of cells - processes that are dependent on Rho kinase, JNK and, to some extent, planar cell polarity within the epidermis. These rearrangements lead to a massive recruitment of keratinocytes from the adjacent epidermis and make re-epithelialization independent of keratinocyte proliferation and the mitogenic effect of FGF signalling, which are only required after wound closure, allowing the epidermis outside the wound to re-establish its normal thickness. Together, these results demonstrate that the adult zebrafish is a valuable in vivo model for studying and visualizing the processes involved in cutaneous wound closure, facilitating the dissection of direct from indirect and motogenic from mitogenic effects of genes and molecules affecting wound re-epithelialization.

The Role of TGFβ Signaling in Wound Epithelialization

Significance: Transforming growth factor β (TGFβ) has a crucial role in maintaining skin homeostasis. TGFβ signaling is important for re-epithelialization, inflammation, angiogenesis, and granulation tissue formation during wound healing. This review will discuss the most important findings regarding the role of TGFβ in epidermal maintenance and its restoration after injury. Recent Advances: Latest findings on the role of TGFβ signaling in normal and impaired wound healing, including the role of TGFβ pathway in tissue regeneration observed in super-healer animal models, will be reviewed. Critical Issues: The TGFβ pathway is attenuated in nonhealing wounds. Observed suppression of TGFβ signaling in chronic ulcers may contribute to the loss of tissue homeostasis and the inability of keratinocytes to migrate and close a wound. Future Directions: A better understanding of TGFβ signaling may provide new insights not only in the normal epithelialization process, but also in tissue regeneration. Future studies focused on TGFβ-mediated crosstalk between multiple cell types involved in wound healing may lead to development of novel therapeutic advances for chronic wounds.

Knockout of endothelial cell-derived endothelin-1 attenuates skin fibrosis but accelerates cutaneous wound healing

Endothelin (ET)-1 is known for the most potent vasoconstrictive peptide that is released mainly from endothelial cells. Several studies have reported ET-1 signaling is involved in the process of wound healing or fibrosis as well as vasodilation. However, little is known about the role of ET-1 in these processes. To clarify its mechanism, we compared skin fibrogenesis and wound repair between vascular endothelial cell-specific ET-1 knockout mice and their wild-type littermates. Bleomycin-injected fibrotic skin of the knockout mice showed significantly decreased skin thickness and collagen content compared to that of wild-type mice, indicating that bleomycin-induced skin fibrosis is attenuated in the knockout mice. The mRNA levels of transforming growth factor (TGF)-β were decreased in the bleomycin-treated skin of ET-1 knockout mice. On the other hand, skin wound healing was accelerated in ET-1 knockout mice, which was indicated by earlier granulation tissue reduction and re-epithelialization in these mice. The mRNA levels of TGF-β, tumor necrosis factor (TNF)-α and connective tissue growth factor (CTGF) were reduced in the wound of ET-1 knockout mice. In endothelial ET-1 knockout mouse, the expression of TNF-α, CTGF and TGF-β was down-regulated. Bosentan, an antagonist of dual ET receptors, is known to attenuate skin fibrosis and accelerate wound healing in systemic sclerosis, and such contradictory effect may be mediated by above molecules. The endothelial cell-derived ET-1 is the potent therapeutic target in fibrosis or wound healing, and investigations of the overall regulatory mechanisms of these pathological conditions by ET-1 may lead to a new therapeutic approach.

Transforming Growth Factor Beta Signaling in Cutaneous Wound Healing: Lessons Learned from Animal Studies

SIGNIFICANCE

Wound healing is a complex physiological process involving a multitude of growth factors, among which transforming growth factor beta (TGF-β) has the broadest spectrum of effects. Animal studies have provided key information on the mechanisms of TGF-β action in wound healing and have guided the development of therapeutic strategies targeting the TGF-β pathway to improve wound healing and scarring outcome.

RECENT ADVANCES

Development of tissue-specific expression systems for overexpression or knockout of TGF-β signaling pathway components has led to novel insight into the role of TGF-β signaling in wound healing. This work has also identified molecules that might serve as molecular targets for the treatment of pathological skin conditions such as chronic wounds and excessive scarring (fibrosis).

CRITICAL ISSUES

Many of the mouse models with genetic alterations in the TGF-β signaling pathway develop an underlying skin abnormality, which may pose some limitations on the interpretation of wound-healing results obtained in these animals. Also, TGF-β's pleiotropic effects on many cell types throughout all phases of wound healing present a challenge in designing specific strategies for targeting the TGF-β signaling pathway to promote wound healing or reduce scarring.

FUTURE DIRECTIONS

Further characterization of TGF-β signaling pathway components using inducible tissue-specific overexpression or knockout technology will be needed to corroborate results obtained in mouse models that display a skin phenotype, and to better understand the role of TGF-β signaling during distinct phases of the wound-healing process. Such studies will also provide a better understanding of how TGF-β mediates its autocrine, paracrine, and double paracrine effects on cellular responses in vivo during wound healing.

Preventive and therapeutic effects of Smad7 on radiation-induced oral mucositis

We report that K5.Smad7 mice, which express Smad7 transgene by a keratin-5 promoter, were resistant to radiation-induced oral mucositis, a painful oral ulceration. In addition to NF-κB activation known to contribute to oral mucositis, we found activated TGF-β signaling in oral mucositis. Smad7 dampened both pathways to attenuate inflammation, growth inhibition and apoptosis. Additionally, Smad7 promoted oral epithelial migration to close the wound. Further analyses revealed that TGF-β signaling Smads and their co-repressor CtBP1 transcriptionally repressed Rac1, and Smad7 abrogated this repression. Knocking down Rac1 in mouse keratinocytes abrogated Smad7-induced migration. Topically applying Smad7 protein with a cell permeable Tat-tag (Tat-Smad7) to oral mucosa showed preventive and therapeutic effects on radiation-induced oral mucositis in mice. Thus, we have identified novel molecular mechanisms involved in oral mucositis pathogenesis and our data suggest an alternative therapeutic strategy to block multiple pathological processes of oral mucositis.

Upregulation of ski in fibroblast is implicated in the peroxisome proliferator--activated receptor δ-mediated wound healing

BACKGROUND/AIM

Both peroxisome proliferator-activated receptor (PPAR) δ and Ski are investigate the interaction of PPARδ and Ski and this interaction-associated effect in wound healing.

METHODS

Effect of PPARδ activation on Ski expression was detected in rat skin fibroblasts by real-time PCR and western blot. Luciferase assay, electrophoretic mobility shift assay (EMSA) and chromatin immunoprecipitation (ChIP) assay were performed to identify the binding site of PPARδ in the promoter region of rat Ski gene. And the functional activity of PPARδ regulation to Ski was detected in fibroblast proliferation and rat skin wound healing model.

RESULTS

PPARδ agonist GW501516 upregulated Ski expression in a dose-dependent manner. Direct repeat-1 (DR1) response element locating at -865∼-853 in Ski promoter region was identified to mediate PPARδ binding to Ski and associated induction of Ski. Furthermore, PPARδ upregulated Ski to promote fibroblasts proliferation and rat skin wound repair, which could be largely blocked by pre-treated with Ski RNA interference.

CONCLUSION

This study demonstrates that Ski is a novel target gene for PPARδ and upregulation of Ski to promote fibroblast proliferation is implicated in the PPARδ-mediated wound healing.

Transforming growth factor beta1 gene expression during vaginal wound healing in a rabbit menopause model

OBJECTIVE

Surgical outcome following reconstructive pelvic surgery is largely dependent on the vaginal wound healing process. As peri- and post-menopausal women are the most likely candidates to undergo these surgeries, it is important to understand the effect of estrogen deficiency on this process. Transforming growth factor beta (TGFβ) is an important mediator of wound healing. We sought to assess TGFβ1 gene expression during the vaginal incisional wound healing process in a rabbit menopause model.

DESIGN

Animal study.

SETTING

Animal laboratory.

SAMPLE

Sixty-three rabbits were used for this study.

METHODS

Twenty-one underwent bilateral oophorectomy, 21 underwent a sham surgery, and 21 served as controls. Eight weeks later, standardised full-thickness 6-mm diameter circular segments were excised from the vagina of all rabbits. Animals were killed sequentially, before wounding, and at 0, 4, 7, 14, 21 and 35 days after wounding, and the wounds were harvested.

MAIN OUTCOME MEASURES

Wound closure and TGFβ1 gene transcription, as measured by real-time polymerase chain reaction (PCR).

RESULTS

Wound closure was significantly protracted (P < 0.02), whereas TGFβ1 gene expression was significantly increased (P < 0.0001) during the wound healing process in oophorectomised rabbits, as compared with both control and sham groups.

CONCLUSION

Oophorectomised rabbits show protracted incisional vaginal wound healing associated with increased TGFβ1 gene transcription.

Wound-induced TGF-β1 and TGF-β2 enhance airway epithelial repair via HB-EGF and TGF-α

The abundance of transforming growth factor-beta (TGF-β) in normal airway epithelium suggests its participation in physiological processes to maintain airway homeostasis. The current study was designed to address the hypothesis that TGF-β1 and TGF-β2 might contribute to normal reparative response of airway epithelial cells (AECs). Treatments with exogenous TGF-β1 or TGF-β2 significantly enhanced wound repair of confluent AEC monolayers. Mechanical injury of AEC monolayers induced production of both TGF-β1 and TGF-β2. Wound repair of AECs was significantly reduced by a specific inhibitor of TGF-β type I receptor kinase activity. We investigated whether the TGF-β-enhanced repair required epidermal growth factor receptor (EGFR) transactivation and secretion of EGFR ligands. Both TGF-β1 and TGF-β2 enhanced EGFR phosphorylation and induced production of heparin-binding EGF-like growth factor (HB-EGF) and transforming growth factor-alpha (TGF-α) in AECs. Moreover, treatment with a broad-spectrum metalloproteinase inhibitor or anti-HB-EGF and anti-TGF-α antibodies inhibited the wound repair and the EGFR phosphorylation by TGF-β1 and TGF-β2, indicating that the TGF-β1 and TGF-β2 effects on wound repair required the release of HB-EGF and TGF-α. Our data, for the first time, have shown that both TGF-β1 and TGF-β2 play a stimulatory role in airway epithelial repair through EGFR phosphorylation following autocrine production of HB-EGF and TGF-α. These findings highlight an important collaborative mechanism between TGF-β and EGFR in maintaining airway epithelial homeostasis.

The role of p21 in regulating mammalian regeneration

The MRL (Murphy Roths Large) mouse has provided a unique model of adult mammalian regeneration as multiple tissues show this important phenotype. Furthermore, the healing employs a blastema-like structure similar to that seen in amphibian regenerating tissue. Cells from the MRL mouse display DNA damage, cell cycle G2/M arrest, and a reduced level of p21^CIP1/WAF. A functional role for p21 was confirmed when tissue injury in an adult p21^-/- mouse showed a healing phenotype that matched the MRL mouse, with the replacement of tissues, including cartilage, and with hair follicle formation and a lack of scarring. Since the major canonical function of p21 is part of the p53/p21 axis, we explored the consequences of p53 deletion. A regenerative response was not seen in a p53^-/- mouse and the elimination of p53 from the MRL background had no negative effect on the regeneration of the MRL.p53^-/- mouse. An exploration of other knockout mice to identify p21-dependent, p53-independent regulatory pathways involved in the regenerative response revealed another significant finding showing that elimination of transforming growth factor-β1 displayed a healing response as well. These results are discussed in terms of their effect on senescence and differentiation.

Platelet-rich fibrin versus albumin in surgical wound repair: a randomized trial with paired design

OBJECTIVE

To study the effects of autologous platelet-rich fibrin (PRF) versus human albumin on incisional wound breaking strength and subcutaneous collagen deposition in patients undergoing laparoscopic cholecystectomy in a randomized trial.

SUMMARY BACKGROUND DATA

Platelet peptidic growth factors may stimulate collagen synthesis and tissue repair.

METHODS

One expanded polytetrafluoroethylene (ePTFE) tube was inserted subcutaneously from the edge of each of the two 10-mm trocar incisions in 51 patients. Treatment with PRF prepared from the patient's own blood or human albumin was randomized to respective wound site by concealed allocation. On postoperative day 10, breaking strength of the incisional wounds as well as the collagen concentration, type I procollagen mRNA, type III procollagen mRNA, matrix metalloproteinase-1 mRNA, and fibroblast density in the ePTFE tubes were determined. All analyses were assessor-blinded. The trial was registered in the Current Controlled Trials Registry (ISRCTN34481461).

RESULTS

Local PRF had no significant effect on incisional wound-breaking strength. In the ePTFE tubes, PRF treatment decreased collagen concentration by 24% (P=0.046) and type I procollagen mRNA level by 29% (P=0.003), but had no significant impact on type III procollagen mRNA, matrix metalloproteinase-1 mRNA or fibroblast infiltration. The profibrotic transforming growth factor-beta1 level increased (P<0.0001) 2-fold with PRF. Collagen concentration in albumin-treated ePTFE tubes correlated with breaking strength of the skin incisions (rs=0.48, P=0.03).

CONCLUSIONS

PRF did not improve wound strength significantly compared with albumin but suppressed subcutaneous collagen synthesis and deposition during early repair of surgical wounds in humans. Furthermore, deposition of reparative collagen in the subcutaneous ePTFE tube model partly predicted the breaking strength of an incisional skin wound.

Mice lacking beta6 integrin in skin show accelerated wound repair in dexamethasone impaired wound healing model

Integrin alphavbeta6 is an epithelial-specific receptor that is absent from the healthy epidermis but synthesized de novo during wound repair. However, its function in wound repair is unknown. Integrin-mediated transforming growth factor-beta1 (TGF-beta1) activation is the main activation mechanism of this key cytokine in vivo. Impaired wound healing caused by glucocorticoids is a major clinical problem and is associated with a disturbed balance of TGF-beta1 activity. Therefore, alphavbeta6 integrin-mediated regulation of TGF-beta1 activity may be involved in this process. To determine the function of alphavbeta6 integrin in glucocorticoid-induced impaired wound healing, both beta6 integrin-deficient (beta6-/-) and wild-type mice were exposed to dexamethasone treatment. Multiple wound parameters, keratinocyte proliferation, inflammation, and TGF-beta1 activation were assessed. Wound healing was significantly accelerated in the dexamethasone-treated beta6-/- mice compared with the corresponding wild-type mice. The dexamethasone-treated beta6-/- mice showed enhanced keratinocyte proliferation in both wound epithelium and hair follicles while the production of proinflammatory cytokines and TGF-beta1 activation were reduced. Accelerated wound repair in the dexamethasone-treated beta6-/- mice might be associated with the reduced antiproliferative and proinflammatory effects of TGF-beta1. Inhibition of alphavbeta6 integrin may provide a future target for treatment of impaired wound healing.

Hyaluronan orchestrates transforming growth factor-beta1-dependent maintenance of myofibroblast phenotype

The differentiation of resident fibroblasts to myofibroblasts is central to wound healing. In the context of organ fibrosis, however, persistence of these myofibroblasts is associated with progressive disease. This study examines mechanisms controlling the maintenance of the myofibroblast phenotype. Myofibroblasts were induced by adding transforming growth factor-beta1 (TGF-beta1) (10 ng/ml) to fibroblasts for 72 h. The phenotype was maintained for up to 120 h following removal of TGF-beta1. Western blot for pSmad2 and -3 demonstrated persistent phosphorylation despite removal of exogenous TGF-beta1. This persistence was because of autocrine synthesis of TGF-beta1, which was inhibited by both anti-TGF-beta1 antibody and the ALK5 inhibitor SB431542. Persistence of phenotype was also associated with increased hyaluronan (HA) generation, synthesis of the hyaladherin TSG6, and HA pericellular coat formation. These were all inhibited by TGF-beta receptor blockade. To further investigate the importance of HA synthesis, 4-methylumbelliferone was used to deplete the cytoplasmic pool of UDP-glucuronic acid, essential for HA chain elongation. This prevented formation of the pericellular HA matrix and decreased expression of alpha-SMA. 4-Methylumbelliferone had no effect, however, on Smad2 and -3 phosphorylation. Similarly inhibition of HAS2 by short interfering RNA prevented phenotypic activation without altering TGF-beta1-dependent Smad phosphorylation, thus suggesting that HA-dependent regulation of cell phenotype was independent of Smad activation. These data suggest that myofibroblasts in areas of fibrosis maintain their own phenotype through autocrine TGF-beta1 action and that extracellular HA matrices are an essential mediator of this. We propose a model in which the formation of the pericellular HA matrix regulates the outcome of Smad-dependent autocrine TGF-beta1-activated signaling, and therefore persistence of the myofibroblast phenotype.

Avotermin: A Novel Antiscarring Agent

Published literature shows that both physicians and their patients are highly concerned about scarring, even relatively minor scars and those that can be concealed by clothing. Furthermore, both patients and their physicians value any opportunities to improve or minimize scarring. While a range of treatment paradigms have been evaluated, no single therapy has been adopted as a universally accepted standard of care and, currently, there are no marketed pharmaceuticals for the prophylactic reduction of scarring. Many of the available treatments are used empirically and most have not been evaluated in robust prospective, randomized, controlled clinical trials. To address this unmet medical need, translational research into the molecular mechanisms of scarring has led to the discovery and commercial development of a new class of prophylactic medicines that promote the regeneration of normal skin and improve scar appearance. Avotermin, the first agent identified in this class, is the clinical application of human recombinant transforming growth factor β3 (TGFβ3), a key protein involved in scar-free healing observed in embryos. Controlled, double-blind, randomized phase I/II clinical studies have shown that avotermin, administered as an intradermal injection at the time of surgery, leads to both short-term and longer-term (at ≥12 months) improvements in the appearance of scars compared with placebo and standard wound care.

Effects of adiponectin on growth and differentiation of human keratinocytes--implication of impaired wound healing in diabetes

Impaired wound healing is one of the most common complications associated with diabetes. Adiponectin is an abundant circulating adipocyte-derived cytokine that has beneficial effects on disorders accompanying diabetes. Herein we report that adiponectin has a regulatory effect on the growth and differentiation of HaCaT human keratinocyte cells. Furthermore, adiponectin regulated the expression of TGFbeta isoforms in keratinocytes in a dose-dependent manner, which implies that adiponectin modulates other types of cells related to wound repair via secretion of growth factors from keratinocytes. Moreover, TUNEL assay results revealed that adiponectin enhances apoptosis of keratinocytes. Taken together, the present results indicate that adiponectin has suppressive effects on the formation of hyperkeratosis commonly seen in patients with diabetic foot and its application may be beneficial for developing treatment for that disorder.

Creating thick linear scar by inserting a gelatin sponge into rat excisional wounds

The rat incisional wound is an important model for wound scarring research, but it is also difficult to mimic thick human incisional scarring. We hypothesized that such a thick linear scarring can be generated by inserting a gelatin sponge into a rat excisional wound. The results demonstrated that the new wound model could generate 11 times wider wound width (at day 7) and 4-5 times wider scar width (at days 14, 21, and 60), respectively, than the widths of incisional wounds (p<0.05) in adult Sprague-Dawley rats. The thick linear scar created was grossly apparent in contrast to the grossly unobvious scar of the incisional wound, and a regular linear shape could be achieved with a similar scar width along the wound. The mechanism study revealed several factors that might contribute to the enhanced scarring, including delayed wound healing, enhanced inflammation, increased expression of fibrotic factors, and abnormal wound remodeling due to the insertion of the gelatin sponge. These results indicate that the new wound model of thick linear scar might be valuable for clinically relevant study of scar manipulation. Moreover, this model may serve as a tool for studying gene-mediated tissue regeneration during wound repair using inserted gelatin sponge as a gene carrier.

Loss of TGFbeta signaling destabilizes homeostasis and promotes squamous cell carcinomas in stratified epithelia

Although TGFbeta is a potent inhibitor of proliferation, epithelia lacking the essential receptor (TbetaRII) for TGFbeta signaling display normal tissue homeostasis. By studying asymptomatic TbetaRII-deficient stratified epithelia, we show that tissue homeostasis is maintained by balancing hyperproliferation with elevated apoptosis. Moreover, rectal and genital epithelia, which are naturally proliferative, develop spontaneous squamous cell carcinomas with age when TbetaRII is absent. This progression is associated with a reduction in apoptosis and can be accelerated in phenotypically normal epidermis by oncogenic mutations in Ras. We show that TbetaRII deficiency leads to enhanced keratinocyte motility and integrin-FAK-Src signaling. Together, these mechanisms provide a molecular framework to account for many of the characteristics of TbetaRII-deficient invasive SQCCs.

Platelet-rich plasma: growth factors and pro- and anti-inflammatory properties

BACKGROUND

Platelet-rich plasma (PRP) promotes regeneration of bone, presumably through the action of concentrated growth factors. However, it is not clear how PRP affects the inflammatory response. The purpose of this study was to analyze the growth factors in PRP and to study the effects of PRP on monocyte cytokine release and lipoxin A(4) (LXA(4)) generation.

METHODS

PRP was prepared from healthy donors. Platelet-derived growth factor (PDGF)-AB, PDGF-BB, transforming growth factor-beta1, insulin-like growth factor-I, fibroblast growth factor-basic (FGF-b), epidermal growth factor (EGF), vascular endothelial growth factor, interleukin-12 (p40/70), and regulated on activation, normal T-cell expressed and secreted (RANTES) levels were evaluated by enzyme-linked immunosorbent assay and bead-based multiplexing. Peripheral blood monocytes were isolated and cultured with or without PRP. Cytokine, chemokine, and LXA(4) levels as well as monocyte chemotactic migration were analyzed.

RESULTS

Growth factors were increased significantly in PRP compared to whole blood (WB) and platelet-poor plasma. Monocyte chemotactic protein-1 (MCP-1) was suppressed significantly by PRP, whereas RANTES was increased significantly in monocyte cultures. LXA(4) levels were significantly higher in PRP compared to WB. PRP stimulated monocyte chemotaxis in a dose-dependent fashion, whereas RANTES, in part, was responsible for PRP-mediated monocyte migration.

CONCLUSIONS

PRP is a rich source of growth factors and promoted significant changes in monocyte-mediated proinflammatory cytokine/chemokine release. LXA(4) was increased in PRP, suggesting that PRP may suppress cytokine release, limit inflammation, and, thereby, promote tissue regeneration.

Role of TGF beta-mediated inflammation in cutaneous wound healing

Among many molecules known to influence wound healing, transforming growth factor beta 1 (TGF beta 1) has the broadest spectrum of actions, affecting all cell types that are involved in all stages of wound healing. Both positive and negative effects of TGF beta 1 on wound healing have been reported. However, the underlying mechanisms are largely unknown. We observed that endogenous TGF beta 1 was elevated in a narrow window of time after injury, and transgenic mice constitutively overexpressing wild-type TGF beta 1 in keratinocytes (K5.TGF beta 1wt) exhibited a significant delay in full-thickness wound healing as compared to non-transgenic mice. Delayed wound healing was associated with profound inflammation throughout all stages of wound healing in K5.TGF beta 1wt mice. Our data suggest that excessive and prolonged TGF beta 1 at the wound site does not benefit wound healing, which is partially owing to its pro-inflammatory effect. Future studies need to be conducted to assess whether tightly regulated TGF beta 1 expression will benefit wound healing. To this end, we have developed a gene-switch TGF beta 1 transgenic system that allows TGF beta 1 induction in keratinocytes temporally with desired levels. These mice will provide a tool to study stage-specific effects of TGF beta 1 on cutaneous wound healing.

The role of TGF-beta signaling in myocardial infarction and cardiac remodeling

Transforming Growth Factor (TGF)-beta is markedly induced and rapidly activated in the infarcted myocardium. However, understanding of the exact role of TGF-beta signaling in the infarcted and remodeling heart has been hampered by the complex and unusual biology of TGF-beta activation and by the diversity of its effects eliciting multiple, and often opposing cellular responses. Experimental studies suggest that TGF-beta signaling may be crucial for repression of inflammatory gene synthesis in healing infarcts mediating resolution of the inflammatory infiltrate. In addition, TGF-beta may play an important role in modulating fibroblast phenotype and gene expression, promoting extracellular matrix deposition in the infarct by upregulating collagen and fibronectin synthesis and by decreasing matrix degradation through induction of protease inhibitors. TGF-beta is also a key mediator in the pathogenesis of hypertrophic and dilative ventricular remodeling by stimulating cardiomyocyte growth and by inducing interstitial fibrosis. In this review we summarize the current knowledge on the role of TGF-beta in infarct healing and cardiac remodeling.

Smad3 deficiency alters key structural elements of the extracellular matrix and mechanotransduction of wound closure

The loss of TGFbeta or its downstream mediator, Smad3, key players in tissue repair, accelerates closure of incisional wounds in mice. In contrast, we now report that excisional ear wounds in mice lacking Smad3 enlarge compared with wild-type controls resulting from changes in extracellular matrix molecules, which alter the mechanotransduction properties of these wounds. Specifically, levels of elastin and glycosoaminoglycans are increased, collagen fibers are more compactly organized, and matrix modulators like integrins, TGFbeta1, and matrix metalloproteinases (MMPs) are altered both basally and after wounding in Smad3 knockout mice. Mechanical testing of dorsal skin correlates these changes in matrix composition with functional parameters, specifically an increased elastic modulus, suggesting an imbalance of tissue forces. We propose that the altered mechanical elastic properties translate into a persistent retractile force that is opposed by decreased wound contractile forces contributing to the enlarging ear wound in Smad3 knockout mice. These studies highlight a previously undescribed role for Smad3 in the mechanotransduction of matrix unsupported ear wound closure.

A "traffic control" role for TGFbeta3: orchestrating dermal and epidermal cell motility during wound healing

Cell migration is a rate-limiting event in skin wound healing. In unwounded skin, cells are nourished by plasma. When skin is wounded, resident cells encounter serum for the first time. As the wound heals, the cells experience a transition of serum back to plasma. In this study, we report that human serum selectively promotes epidermal cell migration and halts dermal cell migration. In contrast, human plasma promotes dermal but not epidermal cell migration. The on-and-off switch is operated by transforming growth factor (TGF) beta3 levels, which are undetectable in plasma and high in serum, and by TGFbeta receptor (TbetaR) type II levels, which are low in epidermal cells and high in dermal cells. Depletion of TGFbeta3 from serum converts serum to a plasmalike reagent. The addition of TGFbeta3 to plasma converts it to a serumlike reagent. Down-regulation of TbetaRII in dermal cells or up-regulation of TbetaRII in epidermal cells reverses their migratory responses to serum and plasma, respectively. Therefore, the naturally occurring plasma-->serum-->plasma transition during wound healing orchestrates the orderly migration of dermal and epidermal cells.

Biology of Langerhans cells and Langerhans cell histiocytosis

Langerhans cells (LC) are epidermal dendritic cells (DC). They play an important role in the initiation of immune responses through antigen uptake, processing, and presentation to T cells. Langerhans cell histiocytosis (LCH) is a rare disease in which accumulation of cells with LC characteristics (LCH cells) occur. LCH lesions are further characterized by the presence of other cell types, such as T cells, multinucleated giant cells (MGC), macrophages (MPhi), eosinophils, stromal cells, and natural killer cells (NK cells). Much has been learned about the pathophysiology of LCH by studying properties of these different cells and their interaction with each other through cytokines/chemokines. In this review we discuss the properties and interactions of the different cells involved in LCH pathophysiology with the hope of better understanding this enigmatic disorder.

Inflammatory cells during wound repair: the good, the bad and the ugly

Damage to any tissue triggers a cascade of events that leads to rapid repair of the wound - if the tissue is skin, then repair involves re-epithelialization, formation of granulation tissue and contraction of underlying wound connective tissues. This concerted effort by the wounded cell layers is accompanied by, and might also be partially regulated by, a robust inflammatory response, in which first neutrophils and then macrophages and mast cells emigrate from nearby tissues and from the circulation. Clearly, this inflammatory response is crucial for fighting infection and must have been selected for during the course of evolution so that tissue damage did not inevitably lead to death through septicemia. But, aside from this role, exactly what are the functions of the various leukocyte lineages that are recruited with overlapping time courses to the wound site, and might they do more harm than good? Recent knockout and knockdown studies suggest that depletion of one or more of the inflammatory cell lineages can even enhance healing, and we discuss new views on how regulation of the migration of inflammatory cells to sites of tissue damage might guide therapeutic strategies for modulating the inflammatory response.

The temporal effects of anti-TGF-beta1, 2, and 3 monoclonal antibody on wound healing and hypertrophic scar formation

BACKGROUND

A number of studies have implicated transforming growth factor (TGF)-beta1, 2, and 3 (TGF-beta) in wound healing and hypertrophic scarring. We propose that TGF-beta has a temporal effect on these processes. To test this hypothesis, we applied anti-TGF beta1, 2, and 3 monoclonal antibody topically to our dermal ulcer model in the rabbit ear.

STUDY DESIGN

Rabbit ear wounds were treated intradermally with anti-TGF-beta1, 2, and 3 antibody at early, middle, and late time points. Treated and untreated control wounds were harvested at various time points and examined histologically to quantify wound healing and scar hypertrophy. Real-time polymerase chain reaction was performed to determine TGF-beta mRNA expression in the treated and control wounds.

RESULTS

The early treatment group demonstrated decreased new epithelium and granulation tissue (p < 0.05 versus controls). Scars harvested on days 28 and 40 displayed no difference in scar hypertrophy. Both the middle and late treatment groups demonstrated a significant decrease in scar hypertrophy (p < 0.05).

CONCLUSIONS

Treated wounds from the early treatment group displayed delayed wound healing, with no reduction in scar hypertrophy. Later treatment of wounds with the same antibody, beginning 7 days after wounding, resulted in a reduction in scar hypertrophy. These results support our hypothesis and clearly demonstrate that TGF-beta1, 2, and 3 have differential temporal effects during the wound-healing process, and are important for optimal wound healing in the first week after wounding; beyond 1 week, TGF-beta1, 2, and 3 play a critical role in hypertrophic scar formation.

Wound-healing defect of CD18(-/-) mice due to a decrease in TGF-beta1 and myofibroblast differentiation

We studied the mechanisms underlying the severely impaired wound healing associated with human leukocyte-adhesion deficiency syndrome-1 (LAD1) using a murine disease model. In CD18(-/-) mice, healing of full-thickness wounds was severely delayed during granulation-tissue contraction, a phase where myofibroblasts play a major role. Interestingly, expression levels of myofibroblast markers alpha-smooth muscle actin and ED-A fibronectin were substantially reduced in wounds of CD18(-/-) mice, suggesting an impaired myofibroblast differentiation. TGF-beta signalling was clearly involved since TGF-beta1 and TGF-beta receptor type-II protein levels were decreased, while TGF-beta(1) injections into wound margins fully re-established wound closure. Since, in CD18(-/-) mice, defective migration leads to a severe reduction of neutrophils in wounds, infiltrating macrophages might not phagocytose apoptotic CD18(-/-) neutrophils. Macrophages would thus be lacking their main stimulus to secrete TGF-beta1. Indeed, in neutrophil-macrophage cocultures, lack of CD18 on either cell type leads to dramatically reduced TGF-beta1 release by macrophages due to defective adhesion to, and subsequent impaired phagocytic clearance of, neutrophils. Our data demonstrates that the paracrine secretion of growth factors is essential for cellular differentiation in wound healing.

Analysis of rat calvaria defects implanted with a platelet-rich plasma preparation: histologic and histometric observations

OBJECTIVES

It has been suggested that degranulating platelet alpha-granules release growth factors having a potential to modulate bone formation. The objective of this study was to evaluate the osteoconductive potential of a platelet-rich plasma (PRP) preparation.

METHODS

Thirty adult male Sprague-Dawley rats were used. The PRP preparation was obtained from 10 ml of whole blood drawn from one age-matched donor rat. The preparation was processed by gradient density centrifugation and stored at -80 degrees C until use. Using aseptic techniques, the PRP preparation soak loaded onto an absorbable collagen sponge (ACS) or ACS alone was surgically implanted into contralateral critical size 6-mm calvaria osteotomies in 18 animals. Twelve animals received ACS versus sham surgery in contralateral defects. Animals were sacrificed at 4 and 8 weeks when biopsies were collected for histologic and histometric analysis.

RESULTS

The animals were maintained without adverse events. Bone formation was highly variable in sites receiving PRP and control treatments. Defect bone fill at 4 weeks averaged (+/-SD) 28.8+/-27.4% (PRP/ACS) versus 39.1+/-24.4% (ACS; p=0.2626) and 62.0+/-20.0% (ACS) versus 71.6+/-32.2% (sham surgery; p=0.1088), and at 8 weeks 81.0+/-12.9% (PRP/ACS) versus 64.5+/-28.1% (ACS; p=0.2626) and 75.6+/-34.1% (ACS) versus 74.1+/-24.2% (sham surgery; p=0.7353). Remnants of the ACS biomaterial were observed at both 4 and 8 weeks in sites implanted with PRP/ACS or ACS.

CONCLUSIONS

The results suggest that the PRP preparation has a limited potential to promote local bone formation.

Transforming growth factor-beta and its effect on reepithelialization of partial-thickness ear wounds in transgenic mice

Transforming growth factor-beta (TGF-beta) is known to affect nearly every aspect of wound repair. Many of the effects have been extensively investigated; however, the primary effect of endogenously derived TGF-beta on wound reepithelialization is still not completely understood. To examine this, two types of wounds were made on a transgenic mouse over-expressing TGF-beta1. Full-thickness back wounds were made to compare the wound healing process in the presence of compensatory healing mechanisms. Superficial partial-thickness ear wounds involving only the epidermis were made to determine the effect of TGF-beta on reepithelialization. In the partial-thickness ear wounds, at later time points, the transgenic group had smaller epithelial gaps than the wild-type mice. A greater number of actively proliferating cells, as determined by bromodeoxyuridine incorporation, was also found in the transgenic mice at post-injury day 8. These results show that TGF-beta1 stimulates the rate of reepithelialization at later time points in partial-thickness wounds. However, in the full-thickness back wounds, the transgenic animals exhibited a slower reepithelialization rate at all time points and the number of bromodeoxyuridine-positive cells was fewer. Our findings would suggest that the overexpression of TGF-beta1 speeds the rate of wound closure in partial-thickness wounds by promoting keratinocyte migration. In full-thickness wounds, however, the overexpression of TGF-beta1 slows the rate of wound reepithelialization.

Wound-healing studies in transgenic and knockout mice

Injury to the skin initiates a cascade of events including inflammation, new tissue formation, and tissue remodeling, that finally lead to at least partial reconstruction of the original tissue. Historically, animal models of repair have taught us much about how this repair process is orchestrated and, over recent years, the use of genetically modified mice has helped define the roles of many key molecules. Aside from conventional knockout technology, many ingenious approaches have been adopted, allowing researchers to circumvent such problems as embryonic lethality, or to affect gene function in a tissue- or temporal-specific manner. Together, these studies provide us with a growing source of information describing, to date, the in vivo function of nearly 100 proteins in the context of wound repair. This article focuses on the studies in which genetically modified mouse models have helped elucidate the roles that many soluble mediators play during wound repair, encompassing the fibroblast growth factor (FGF) and transforming growth factor-beta (TGF-beta) families and also data on cytokines and chemokines. Finally, we include a table summarizing all of the currently published data in this rapidly growing field. For a regularly updated web archive of studies, we have constructed a Compendium of Published Wound Healing Studies on Genetically Modified Mice which is avaialble at http://icbxs.ethz.ch/members/grose/woundtransgenic/home.html.

Inhibiting Scar Formation in Rat Wounds by Adenovirus-Mediated Overexpression of Truncated TGF-?? Receptor II

The purpose of this study was to explore the possibility of inhibiting wound scarring by blocking TGFbeta signaling of wound cells by means of a gene therapy approach. Normal dermal fibroblasts were infected in vitro either with recombinant adenovirus encoding a truncated TGFbeta receptor II (Ad-tTGF-betaRII) or with [beta]-galactosidase adenovirus (Ad-beta-gal). TGF-beta1 gene expression in infected fibroblasts was analyzed by Northern blot. In vivo, 1x10(9) plaque-forming units of Ad-tTGF-betaRII were intradermally injected into the dorsal skin of 10-day-old newborn Sprague-Dawley rats (n = 10). For gene therapy, 1x10(9) plaque-forming units of Ad-tTGF-betaRII viruses were injected intradermally at the right side dorsal skin of another set of same aged Sprague-Dawley rats as the experimental group (n = 15). In the control group, 1x10(9) plaque-forming units of Ad-beta-gal (n = 11) or the same volume of saline (n = 4) was injected at the left side skin of the same rats. A 5-mm-long full-thickness incisional wound was created at the injection sites of each rat 2 days after injection. Wound tissues were harvested at day 3 (n = 2), day 7 (n = 2), and day 14 (n = 11) after wounding for histological analysis. Scar area of wound tissues harvested at day 14 was quantitatively analyzed. The results showed that TGF-beta1 gene expression was markedly down-regulated in Ad-tTGF-betaRII infected fibroblasts compared with Ad-beta-gal infected cells. In vivo, adenovirus-mediated transgene expression in rat skin reached a peak level at day 2 after injection and the expression gradually decreased afterward. Inhibited inflammatory reaction was also observed in the treated wounds with significantly reduced inflammatory cells (p < 0.05). Moreover, in all 11 rats, the experimental wound at day 14 had much less scarring than its control wound of the same rat, with an average of 49 percent reduction of the scar area (p < 0.05). Furthermore, more panniculus muscles were repaired in the experimental wounds (nine of 11) than in the control wounds (two of 11) (p < 0.05). These results indicate that gene therapy by targeting wound TGF-beta can effectively inhibit wound scarring and may potentially be applied to clinical scar treatment.

Genetic- or transforming growth factor-beta 1-induced changes in epidermal peroxisome proliferator-activated receptor beta/delta expression dictate wound repair kinetics

Advances in wound care are of great importance in clinical injury management. In this respect, the nuclear receptor peroxisome proliferator-activated receptor (PPAR)beta/delta occupies a unique position at the intersection of diverse inflammatory or anti-inflammatory signals that influence wound repair. This study shows how changes in PPARbeta/delta expression have a profound effect on wound healing. Using two different in vivo models based on topical application of recombinant transforming growth factor (TGF)-beta1 and ablation of the Smad3 gene, we show that prolonged expression and activity of PPARbeta/delta accelerate wound closure. The results reveal a dual role of TGF-beta1 as a chemoattractant of inflammatory cells and repressor of inflammation-induced PPARbeta/delta expression. Also, they provide insight into the so far reported paradoxical effects of the application of exogenous TGF-beta1 at wound sites.

The Tryptophan-rich Motifs of the Thrombospondin Type 1 Repeats Bind VLAL Motifs in the Latent Transforming Growth Factor-β Complex

Transforming growth factor-beta (TGF-beta) is secreted as a latent complex of the latency-associated peptide (LAP) and the mature domain, which must be activated for TGF-beta to signal. We previously identified thrombospondin 1 (TSP1) as a physiologic activator of TGF-beta in vitro and in vivo. The WSXW sequences in the type 1 repeats of TSP1 interact with the mature domain of TGF-beta, and WSXW peptides inhibit TSP1-mediated activation by blocking TSP1 binding to the TGF-beta latent complex. However, the binding site for the WSXW sequence was not identified. In this report, we show that the WSXW sequences bind the (61)VLAL sequence in mature TGF-beta and also bind (77)VLAL in LAP. A glutathione S-transferase (GST) fusion protein of the second TSP1 type 1 repeat (GST-TSR2) binds immobilized VLAL peptide. VLAL peptides inhibit binding of LAP and mature TGF-beta to soluble GST-TSR2 and immobilized WSXW peptide. VLAL peptide inhibits TSP1-mediated activation of recombinant and endothelial cell-derived latent TGF-beta. Furthermore, TGF-beta or LAP deleted in the VLAL sequence fails to bind immobilized WSXW or soluble GST-TSR2, indicating that binding to both VLAL sequences is important for association of TSP1 and the latent complex. Additionally, TSP1 is unable to activate latent TGF-beta when VLAL is deleted from the mature domain. These data show that the WSXW motif binds VLAL on both LAP and mature TGF-beta, and these interactions are critical for TSP1-mediated activation of the TGF-beta latent complex.

Essential role of Smad3 in the inhibition of inflammation-induced PPARbeta/delta expression

Wound healing proceeds by the concerted action of a variety of signals that have been well identified. However, the mechanisms integrating them and coordinating their effects are poorly known. Herein, we reveal how PPARbeta/delta (PPAR: peroxisome proliferator-activated receptor) follows a balanced pattern of expression controlled by a crosstalk between inflammatory cytokines and TGF-beta1. Whereas conditions that mimic the initial inflammatory events stimulate PPARbeta/delta expression, TGF-beta1/Smad3 suppresses this inflammation-induced PPARbeta/delta transcription, as seen in the late re-epithelialization/remodeling events. This TGF-beta1/Smad3 action involves an inhibitory effect on AP-1 activity and DNA binding that results in an inhibition of the AP-1-driven induction of the PPARbeta/delta promoter. As expected from these observations, wound biopsies from Smad3-null mice showed sustained PPARbeta expression as compared to those of their wild-type littermates. Together, these findings suggest a mechanism for setting the necessary balance between inflammatory signals, which trigger PPARbeta/delta expression, and TGF-beta1/Smad3 that governs the timely decrease of this expression as wound healing proceeds to completion.