Delay In Re-epithelialization Research Articles

NaHS-Hydrogel and Encapsulated Adipose-Derived Stem Cell Evaluation on an Ex Vivo Second-Degree Burn Model

Second-degree burns result in the loss of the epidermal barrier and could lead to delayed complications during the healing process. Currently, therapeutic options to treat severe burns are limited. Thus, this work aims to evaluate the effect of NaHS, a hydrogen sulfide (H2S) donor, in poloxamer hydrogel in topical application and the potentiating effect of injected encapsulated adipose-derived stem cells (ASCs) compared to monolayer ASCs using our previous second-degree burn model on human skin explants. Indeed, our model allows testing treatments in conditions similar to a clinical application. The observed benefits of NaHS may include an antioxidant role, which might be beneficial in the case of burns. Concerning ASCs, their interest in wound healing is more than well documented. In order to evaluate the efficiency of our treatments, we analyzed the kinetics of wound closure, keratinocyte proliferation, and dermal remodeling. The effect of NaHS led to a delay in re-epithelialization, with a decrease in the number of proliferating cells and a decrease in the synthesis of procollagen III. On the contrary, intradermal injection of ASCs, encapsulated or not, improves wound healing by accelerating re-epithelialization and collagen I synthesis; however, only encapsulated ASCs accelerate keratinocyte migration and increase the rate of procollagen III and collagen III. In conclusion, NaHS treatment did not improve burn healing. However, the injection of ASCs stimulated wound healing, which is encouraging for their therapeutical use in burn treatment.

Surface-optimized free flaps for complex facial defects after skin cancer

Advanced non-melanocytic skin cancer (NMSC) in the facial region causes extensive tissue loss, possibly coverable by local flaps. Remote free flaps are the reconstructive method of choice, despite disadvantages such as color and texture mismatch, and bulkiness with regard to facial skin. Post-ablative facial NMSC defects in four patients were reconstructed using remote free flaps, including radial forearm, scapular, parascapular, and anterolateral thigh flaps. Four months later, a split-thickness skin graft (STSG) was acquired from the retroauricular region to generate a non-cultured autologous epidermal cell (NCAEC) suspension. The flap surfaces were de-epithelialized, and the NCAEC suspension was sprayed onto the flap surface to improve the mismatch between facial and flap color. Debulking was also carried out. The aesthetic outcome was examined by photography and clinical examination 3, 6, 9, and 12 months after the first operation. All flaps survived the 11- to 21-month follow-up. The secondary operation was accompanied by a delay in re-epithelialization in one case. No STSG donor-site problems occurred. Follow-up photographs showed significant improvements in the color and texture of the flaps. Facial reconstruction with a free flap results in a mismatch of color and texture. Secondary correction of the flap surface by de-epithelialization and NCAEC application significantly improves the aesthetic outcome.

Topical Steroids in Bacterial Keratitis, A Retrospective Cohort Study.

Purpose: To review the outcomes, risk factors and morbidity of bacterial keratitis treated with and without topical steroids. Design and Methods: Retrospective cohort study. Demographics, risk factors, culture results, ulcer characteristics, time to epithelialization, visual-acuity and recurrences were recorded. Patients were classified into 2 groups: 1.Topical antibiotics/steroids (ASG), 2.Antibiotics only group (AOG). Results: Seventy two eyes were identified; 37 were classified in the ASG and 35 in the AOG. Predisposing factors were identified in 87.5% of cases, Penetrating keratoplasty, previous surgery, contact-lens wear and Herpes-simplex keratitides were the most common overall; Microorganisms were indentified in 85.5% and 60% of ASG and AOG respectively. Epithelialization was completed at a mean 17.62 and 16.06 days in ASG and AOG respectively (p= 0.533); Final mean BSCVA was 1.59±1.07 and 1.64±1.21 logMAR in ASG and AOG respectively (p= 0.864). The number of gained Snellen lines was 0.13±0.22 in ASG and 0.14±.0.24 in AOG (p= 0.860). There were no recurrences. Conclusion: Although a non statistical significant delay in re-epithelialization was noted in the ASG, this did not translate into a statistical difference in final BSCVA, gained Snellen lines or recurrence of infection. In our series, adjuvant topical steroids were not associated with an increase in unfavorable outcomes.

Dynamic regulation of Wnt7a expression in the primate endometrium: implications for postmenstrual regeneration and secretory transformation.

Despite the vital physiological role of endometrial regeneration during the menstrual cycle and the various pathological implications of abnormal growth of endometrial epithelial cells, the local factors and regulatory mechanisms involved in endometrial regeneration and growth have not been well characterized. Here, we examine the pattern, hormone dependence, and potential functions of Wnt7a (wingless-type MMTV integration site family member 7a), which is known to play a critical role in the formation of the mouse endometrial epithelium during embryonic development, in both human and artificially cycling rhesus macaque endometrium, and using a potent Wnt-antagonist in a mouse model of endometrial regeneration. Wnt7a transcript levels were examined using quantitative real-time PCR and in situ hybridization, and immunohistochemistry was performed to detect Ki-67 and 3,5-bromodeoxyuridine. Stringent, fully conditional Wnt inhibition was achieved by adenoviral expression of Dickkopf-1 during artificial endometrial regeneration in mice. In macaques, Wnt7a expression was confined to the newly formed luminal epithelium (LE) and upper glands during the postmenstrual repair phase. The signal increased in the LE during the proliferative phase but decreased in the upper glands and was undetectable in the glands by the late proliferative phase. Interestingly, Wnt7a was completely suppressed in the LE and remained undetectable in other cell types after 7 d of progesterone treatment. The pattern of Wnt7a expression in the human endometrium was similar to that in macaques. Blockade of Wnt signaling during endometrial regeneration in mice resulted in a dramatic delay in reepithelialization and degeneration of glands and LE. These results strongly suggest, for the first time, a role for Wnt7a in postmenstrual regeneration and proliferation of endometrial glands and LE in primates, and its dramatic suppression by progesterone is likely essential for secretory transformation of the epithelium.

FGF receptors 1 and 2 are key regulators of keratinocyte migration in vitro and in wounded skin

Efficient wound repair is essential for the maintenance of the integrity of the skin. The repair process is controlled by a variety of growth factors and cytokines, and their abnormal expression or activity can cause healing disorders. Here, we show that wound repair is severely delayed in mice lacking fibroblast growth factor receptors (FGFR) 1 and 2 in keratinocytes. As the underlying mechanism, we identified impaired wound contraction and a delay in re-epithelialization that resulted from impaired keratinocyte migration at the wound edge. Scratch wounding and transwell assays demonstrated that FGFR1/2-deficient keratinocytes had a reduced migration velocity and impaired directional persistence owing to inefficient formation and turnover of focal adhesions. Underlying this defect, we identified a significant reduction in the expression of major focal adhesion components in the absence of FGFR signaling, resulting in a general migratory deficiency. These results identify FGFs as key regulators of keratinocyte migration in wounded skin.

Delayed Re-Epithelialization in Periostin-Deficient Mice during Cutaneous Wound Healing

BackgroundMatricellular proteins, including periostin, are important for tissue regeneration.Methods and FindingsPresently we investigated the function of periostin in cutaneous wound healing by using periostin-deficient (−/−) mice. Periostin mRNA was expressed in both the epidermis and hair follicles, and periostin protein was located at the basement membrane in the hair follicles together with fibronectin and laminin γ2. Periostin was associated with laminin γ2, and this association enhanced the proteolytic cleavage of the laminin γ2 long form to produce its short form. To address the role of periostin in wound healing, we employed a wound healing model using WT and periostin−/− mice and the scratch wound assay in vitro. We found that the wound closure was delayed in the periostin−/− mice coupled with a delay in re-epithelialization and with reduced proliferation of keratinocytes. Furthermore, keratinocyte proliferation was enhanced in periostin-overexpressing HaCaT cells along with up-regulation of phosphorylated NF-κB.ConclusionThese results indicate that periostin was essential for keratinocyte proliferation for re-epithelialization during cutaneous wound healing.

An Extended Epidermal Response Heals Cutaneous Wounds in the Absence of a Hair Follicle Stem Cell Contribution

Hair follicles have been observed to provide a major cellular contribution to epidermal healing, with emigration of stem-derived cells from the follicles aiding in wound reepithelialization. However, the functional requirements for this hair follicle input are unknown. Here we have characterized the keratinocyte stem cell status of mutant mice that lack all hair follicle development on their tail, and analyzed the consequent alterations in epidermal wound healing rate and mechanisms. In analyzing stem cell behavior in embryonic skin we found that clonogenic keratinocytes are relatively frequent in the ectoderm prior to hair follicle formation. However, their frequency in the interfollicular epidermis drops sharply by birth, at which time the majority of stem cells are present within the hair follicles. We find that in the absence of hair follicles cutaneous wounds heal with an acute delay in reepithelialization. This delay is followed by expansion of the region of activated epidermis, beyond that seen in normal haired skin, followed by appropriate wound closure. JID Journal Club article: for questions, answers, and open discussion about this article please go to http://network.nature.com/group/jidclub.

β2‐Adrenergic receptor activation delays wound healing

Keratinocytes migrate directionally into the wound bed to initiate re-epithelialization, necessary for wound closure and restoration of barrier function. They solely express the beta2-adrenergic receptor (beta2-AR) subtype of beta-ARs and can also synthesize beta-AR agonists generating a hormonal mediator network in the skin. Emerging studies from our laboratory demonstrate that beta-AR agonists decrease keratinocyte migration via a protein phosphatase (PP) 2A-dependent mechanism. Here we have extended our investigations to observe the effects of beta2-AR activation on keratinocyte polarization, migration, and ERK phosphorylation at the wound edge, cytoskeletal organization, phospho-ERK intracellular localization, proliferation, human skin wound re-epithelialization, wound-induced ERK phosphorylation, and murine skin wound healing. We demonstrate that in keratinocytes, beta2-AR activation is anti-motogenic and anti-mitogenic with both mechanisms being PP2A dependent. beta2-AR activation dramatically alters the organization of the actin cytoskeleton and prevents localization of phospho-ERK to the lamellipodial edge and its colocalization with vinculin. Finally, we demonstrate a beta2-AR-mediated delay in re-epithelialization and decrease in wound-induced epidermal ERK phosphorylation in human skin wounds and a delay in re-epithelialization in murine tail-clip wounds. Our work uncovers novel keratinocyte biology and a previously unrecognized role for the adrenergic hormonal mediator network in the wound repair process.

Sympathetic denervation accelerates wound contraction but delays reepithelialization in rats

Participation of the peripheral nervous system in wound healing is not well understood. The aim of this study was to investigate the effects of sympathetic denervation on rat excisional cutaneous wound healing. Male rats were chemically denervated with intraperitoneal administration of 6-hydroxydopamine (6-OHDA) in 1% ascorbic acid. 6-OHDA or vehicle was administered twice a week until euthanasia, beginning 7 days before wounding. A full-thickness excisional lesion was performed and the lesion area measured to evaluate wound contraction. After euthanasia, the lesion and adjacent normal skin were formalin-fixed and paraffin-embedded. Sections were stained with hematoxylin and eosin or toluidine blue, or immunostained for alpha-smooth muscle actin. Animals treated with 6-OHDA showed acceleration in wound contraction, increase in myofibroblastic differentiation, reduction in mast cell migration, and a delay in reepithelialization. To investigate the effects of neurogenic inflammation, a group of animals was treated with 6-OHDA only after the acute inflammatory phase, and these animals showed delayed wound contraction 3 and 7 days after wounding when compared to those treated before the lesion. In conclusion, the present study shows that sympathetic denervation affects cutaneous wound healing, probably by a decrease in neurogenic inflammation during the initial phase of healing and the absence of catecholamines throughout the final phase.

Naltrexone, an opioid antagonist, facilitates reepithelialization of the cornea in diabetic rat.

Ulcers and erosions of the corneal epithelium, as well as delays in resurfacing of the cornea after wounding, are major causes of ocular morbidity and visual loss in diabetes. To study whether intervention by the opioid antagonist naltrexone (NTX; 30 mg/kg, twice daily) can restore reepithelialization in diabetic cornea, we induced diabetes in rats by intravenous injection of 65 mg/kg streptozotocin. After confirmation of diabetes, 5-mm-diameter epithelial defects that did not include the limbus were created by mechanical scraping of the cornea. At 4 and 8 weeks, corneal reepithelialization was markedly subnormal, with delays ranging from 11% to 17-fold in the diabetic animals compared with control counterparts. Rats that were diabetic for 8 weeks also had a significant decrease in the incidence of complete wound closure. At 4 and 8 weeks, diabetic animals that were receiving NTX had an acceleration in reepithelialization compared with diabetic animals that were receiving vehicle and even surpassed controls. DNA synthesis in the corneal epithelium of diabetic rats was decreased up to 90% of control levels, and NTX exposure of diabetic subjects elevated the labeling index by up to eightfold from diabetic animals that were receiving vehicle. Opioid growth factor and opioid growth factor receptor distribution were comparable in diabetic and control animals. These results indicate a delay in reepithelialization that is dependent on the duration of diabetes and that intervention of endogenous opioid-receptor interfacing with an opioid antagonist can facilitate the process of wound healing.

The effect of fibrin sealant on the healing of laser-resurfaced skin

Background: Fibrin sealant is an effective hemostatic agent and a useful tissue sealant. Studies have also suggested that fibrin sealant may accelerate the normal wound-healing process. Objective: This study was designed to ascertain whether fibrin sealant would enhance wound healing after CO 2 laser resurfacing in a guinea pig model. Methods: The CO 2 laser was used to create equal areas of skin resurfacing on both sides of 14 Dunkin Hartley guinea pigs. Fibrin sealant was applied to the treatment side, whereas bacitracin was applied to the control side. Biopsies of these areas were performed on days 1, 3, 7, and 10. A histologic evaluation was performed with the use of a grading scale that compared acute and chronic inflammation, granulation tissue, collagen deposition, and epidermal regeneration. Results: The wounds treated with fibrin sealant demonstrated a statistically significant reduction in the degree of acute and chronic inflammation as well as collagen deposition. At day 7, fibrin sealant was noted to enhance neovascularization and result in a slight delay in reepithelialization. All wounds were completely reepithelialized at day 10. No wound infections or other complications were noted as a result of the application of fibrin sealant. Conclusions: Although wound healing was not accelerated, the application of fibrin sealant after CO 2 laser resurfacing diminished the acute and chronic inflammatory response, enhanced neovascularization, and reduced collagen accumulation. Further research is needed to assess whether the effects of fibrin sealant noted in this study result in improved cosmetic healing after CO 2 laser resurfacing. ( Aesthetic Surg J 2001;21:509-517.)

Delayed wound healing in keratin 6a knockout mice.

Keratin 6 (K6) expression in the epidermis has two components: constitutive expression in the innermost layer of the outer root sheath (ORS) of hair follicles and inducible expression in the interfollicular epidermis in response to stressful stimuli such as wounding. Mice express two K6 isoforms, MK6a and MK6b. To gain insight into the functional significance of these isoforms, we generated MK6a-deficient mice through mouse embryonic stem cell technology. Upon wounding, MK6a was induced in the outer ORS and the interfollicular epidermis including the basal cell layer of MK6a(+/+) mice, whereas MK6b induction in MK6a(-/-) mice was restricted to the suprabasal layers of the epidermis. After superficial wounding of the epidermis by tape stripping, MK6a(-/-) mice showed a delay in reepithelialization from the hair follicle. However, the healing of full-thickness skin wounds was not impaired in MK6a(-/-) animals. Migration and proliferation of MK6a(-/-) keratinocytes were not impaired in vitro. Furthermore, the migrating and the proliferating keratinocytes of full-thickness wounds in MK6a(-/-) animals expressed neither MK6a nor MK6b. These data indicate that MK6a does not play a major role in keratinocyte proliferation or migration but point to a role in the activation of follicular keratinocytes after wounding. This study represents the first report of a keratin null mutation that results in a wound healing defect.

Re-epithelialization of Human Oral Keratinocytes in vitro

Re-epithelialization involves interactions between keratinocytes and the extracellular matrix upon which these cells move. It is hypothesized that keratinocytes are activated when wounded, and the resultant phenotypic change directs re-epithelialization. We have adapted organotypic cultures, in which oral gingival keratinocytes are fully differentiated, to study re-epithelialization following wounding. To elucidate keratinocyte behavior and phenotype during re-epithelialization, we have investigated this process in the presence and absence of the growth factor TGF-beta 1 and have monitored expression of MMP-1 (Type I collagenase) mRNA by in situ hybridization. In addition, we have followed proliferation and migration of wound keratinocytes by genetically marking these cells with a retroviral vector and by measuring their proliferative index. We found that keratinocytes grown without TGF-beta 1 were hyperproliferative in response to wounding, and re-epithelialization was complete by 24 h. However, 2.5 ng/mL TGF-beta 1 induced a transient delay in re-epithelialization, a reduction in proliferation, and fewer clusters of genetically marked cells. Keratinocytes expressed MMP-1 mRNA only when they covered the wounded surface, suggesting that the cells acquire a collagenolytic phenotype during re-epithelialization and that contact with different ECM components may modulate keratinocyte expression of MMP-1. We conclude that the phenotype of oral keratinocytes is altered during re-epithelialization in vitro and that this process is modulated by TGF-beta 1. Re-epithelialization occurs as keratinocytes are activated to move over the wound bed. Understanding the phenotype of wounded keratinocytes may facilitate treatment of chronic oral wounds and periodontal disease.

Effect of TGF-β1 on Re-Epithelialization of Human Keratinocytes In Vitro: An Organotypic Model

Transforming growth factor beta-1 (TGF-beta 1) has been shown to inhibit keratinocyte proliferation in vitro yet and migration was investigated in organotypic cultures after incisional wounding. Organotypic cultures provide a more in vivo-like epidermal tissue and may therefore respond in a different manner than previous culture models in which epidermal differentiation is incomplete. Without TGF-beta 1, keratinocytes were hyperproliferative in response to wounding. At doses of 2.5 ng/ml or greater, a delay in re-epithelialization was seen at 24 h post-wounding along with a reduction in hyperproliferation. By 48 h, however, re-epithelialization was complete in all cultures treated with TGF-beta 1. In particular, 7 ng/ml TGF-beta 1 inhibited proliferation yet had no effect on re-epithelialization by 48 h. These studies demonstrate that i) TGF-beta 1 induced a delay in re-epithelialization, ii) proliferation of wounded keratinocytes was not inhibited at 2.5 ng/ml doses of TGF-beta 1, and iii) at 7 ng/ml TGF-beta 1, re-epithelialization was complete by 48 h in spite of the profound inhibition of cell proliferation. In the organotypic model, TGF-beta 1 appears to alter re-epithelialization.

Delayed healing in full-thickness wounds treated with aluminum chloride solution: A histologic study with evaporimetry correlation

Optimizing wound healing parameters seems to be the utmost importance in the present age of sophisticated wound care and dressings. We studied the effect of two hemostatics: 30% aluminum chloride and ferric subsulfate (Monsel's solution) on the rate of wound healing in Yucatan miniature hairless pigs. Wound healing was examined in occluded and nonoccluded full-thickness 3-mm punch biopsy wounds. Wounds were treated either with 30% aluminum chloride solution or ferric subsulfate solution or were allowed to clot with minimal pressure from a gauze pad. The course of wound healing was followed utilizing evaporimetry readings from the wound sites in addition to periodic histologic examination in an attempt to correlate the evaporimetry readings with corresponding histology. Delay in reepithelialization was noted histologically both in wounds treated with aluminum chloride and in those treated with ferric subsulfate compared to controls. Presumably this delay was the result of tissue necrosis caused by these hemostatic agents, resulting in slightly larger and less cosmetically acceptable scars. Plots of evaporimetry data revealed a biphasic pattern of water loss during healing, with an initial rapid decline in water loss followed by a much slower decline. Histologic reepithelialization seemed to correlate best with the point on the evaporimery curve where the slope changed from the phase of rapid water loss to a slower rate.