An assessment of human epidermal repair in elderly normal subjects using immunohistochemical methods

Low-level laser treatment stimulates hair growth via upregulating Wnt10b and β-catenin expression in C3H/HeJ mice

This study was conducted in order to evaluate the role of low-level laser treatment (LLLT) in hair growth in C3H/HeJ mice. Healthy C57BL/6 mice were randomly divided into two groups: with and without low-level laser treatment. The skin color of each mouse was observed each day. Skin samples were collected for H&E, immunofluorescence, PCR, and western blot analysis, to observe the morphology of hair follicles and detect the expression levels of Wnt10b and β-catenin. Observation of skin color demonstrated that black pigmentation started significantly earlier in the laser group than in the control group. Hair follicle number in both groups showed no difference; however, the hair follicle length presented a significant difference. Wnt10b protein was detected on the second day in hair matrix cells in the LLLT group but not in the control group. PCR and western blot results both illustrated that expression of Wnt10b and β-catenin was significantly higher in the LLLT group than in the control group. Our study illustrated that low-level laser treatment can promote hair regrowth by inducing anagen phase of hair follicles via initiating the Wnt10b/β-catenin pathway.

Quantifying the effect of pore size and surface treatment on epidermal incorporation into percutaneously implanted sphere-templated porous biomaterials in mice

The sinus between skin and a percutaneous medical device is often a portal for infection. Epidermal integration into an optimized porous biomaterial could seal this sinus. In this study, we measured epithelial ingrowth into rods of sphere-templated porous poly(2-hydroxyethyl methacrylate) implanted percutaneously in mice. The rods contained spherical 20-, 40-, or 60-μm pores with and without surface modification. Epithelial migration was measured 3, 7, and 14 days post-implantation utilizing immunohistochemistry for pankeratins and image analysis. Our global results showed average keratinocyte migration distances of 81 ± 16.85 μm (SD). Migration was shorter through 20-μm pores (69.32 ± 21.73) compared with 40 and 60 μm (87.04 ± 13.38 μm and 86.63 ± 8.31 μm, respectively). Migration was unaffected by 1,1' carbonyldiimidazole surface modification without considering factors of pore size and healing duration. Epithelial integration occurred quickly showing an average migration distance of 74.13 ± 12.54 μm after 3 days without significant progression over time. These data show that the epidermis closes the sinus within 3 days, migrates into the biomaterial (an average of 11% of total rod diameter), and stops. This process forms an integrated epithelial collar without evidence of marsupialization or permigration.

Basement membrane dissolution and reassembly by limbal corneal epithelial cells expanded on amniotic membrane

PURPOSE

To investigate basement membrane (BM) formation during ex vivo expansion of limbal corneal epithelial cells on intact amniotic membrane (iAM) and epithelially denuded (d)AM.

METHODS

Human limbal explants were cultured on iAM and dAM. Expression of BM components, including laminin-5, type IV collagen, type VII collagen, perlecan, integrin alpha6, and epithelial cell differentiation markers such as p63, cytokeratin 3 (K3), and cytokeratin 12 (K12), were investigated by immunostaining. Levels of matrix metalloproteinase (MMP)-2 and MMP-9 and tissue inhibitor of matrix metalloproteinase (TIMP)-1 in the conditioned media were determined by ELISA and gelatin zymography.

RESULTS

All four BM components were preserved in both iAM and dAM before culturing, but dissolved 1 week afterward when MMP-2 was increased. Epithelial outgrowth correlated with increased expression of MMP-2 and -9 for both cultures. Resynthesis of BM began with laminin-5 followed by other components. This process took place at 1 week on iAM but at 2 weeks on dAM after culturing. At 4 weeks, BM was more maturely deposited as a linear band from the explant toward the leading edge on iAM and temporally correlated with a sharp decline of MMP-9 levels. In contrast, such BM deposition began at the leading edge on dAM only when TIMP-1 levels were increased. Epithelial cell outgrowth on iAM expressed more p63 but less K3 and K12 than did that on dAM.

CONCLUSIONS

After dissolution of original amniotic BM, new BM formed by ex vivo expanded human limbal corneal epithelial cells on iAM deposits much faster and is more mature, resulting in regeneration of a limbal epithelial phenotype. In contrast, BM deposition is delayed and remains immature on dAM, resembling wound healing by a corneal epithelial phenotype. Thus, BM resynthesis may be used as another objective readout for assessing the success of ex vivo expansion of limbal epithelial progenitor cells on AM.

Aging is associated with reduced deposition of specific extracellular matrix components, an upregulation of angiogenesis, and an altered inflammatory response in a murine incisional wound healing model

The concept that aging impairs wound healing is largely unsubstantiated, the literature being contradictory because of poor experimental design and a failure to adequately characterize animal models. This study tested the hypothesis that aging retards the rate of wound repair using standardized cutaneous incisional wounds in a well-characterized aging mouse colony. Against the background of age-related changes in normal dermal composition, marked differences in healing were observed. Immunostaining for fibronectin was decreased in the wounds of the old mice, with a delay in the inflammatory response, re-epithelialization, and the appearance of extracellular matrix components. Heparan sulfate and blood vessel staining were both unexpectedly increased in the wounds of the old animals at late time points. Despite an overall decrease in collagen I and III deposition in the wounds of old mice, the dermal organization was surprisingly similar to that of normal dermal basket-weave collagen architecture. By contrast, young animals developed abnormal, dense scars. Intriguingly, some of these age-related changes in scar quality and inflammatory cell profile are similar to those seen in fetal wound healing. The rate of healing in young animals appears to be increased at the expense of the scar quality, perhaps resulting from an altered inflammatory response.

Characterization of a new in vitro model for studies of reepithelialization in human partial thickness wounds

Reepithelialization of artificial partial thickness wounds made in biopsies of human skin was determined after 3, 5, or 7 d of incubation, submerged or elevated to the air-liquid interface. The biopsies were reepithelialized within 5-7 d, with a more complete epidermal healing in wounds exposed to air. Both types of wounds showed similar time-course in deposition of basement membrane components, as detected by immunofluorescence labeling. Laminin and collagen type VII were deposited underneath the migrating tips, whereas collagen type IV was detected after reepithelialization. Markers of terminal differentiation showed a pattern close to normal in the air-liquid incubated wounds after reepithelialization. Involucrin was detected in the suprabasal regions of the migrating epidermis and thereafter in the upper half of neo-epidermis in the air-liquid incubated wound. Filaggrin could not be detected in the submerged wounds at any time during healing, whereas wounds exposed to air showed a well-differentiated epidermis by Day 7. Tritiated thymidine-incorporation indicated proliferation of epidermal and dermal cells during reepithelialization and a maintained viability, as shown by cultivation of endothelial- and fibroblast-like cells obtained from the dermis 7 d after wounding. Reepithelialization in this human in vitro model is supported by a matrix close to normal with the possibility of extracellular influences and cell-cell interactions and, in addition, the technique is simple and reproducible. Therefore, we suggest this model for studies of regeneration in culture and as a complement to in vivo studies on epidermal healing.

Keratinocyte integrins in wound healing and chronic inflammation of the human periodontium

Periodontal epithelium plays a critical role in protection, destruction and repair of human periodontium. During optimal repair, epithelium migrates and covers the wound surface to prevent infection and damage of the vulnerable underlying connective tissue. During periodontal destruction, junctional epithelium undergoes transformation to pocket epithelium that has quite different characteristics from junctional epithelium. In the course of periodontal disease the epithelial attachment to the tooth surface is lost and the epithelium proliferates and extends pseudo-rete ridges deep into the inflamed connective tissue. Both scenarios, repair and destruction, involve active epithelial migration either in the wound provisional matrix or in the inflamed connective tissue matrix, respectively. This review covers recent research data on cellular receptors, integrins, that mediate epithelial cell migration during wound healing and destruction of human periodontium.

Histological study of lectin binding in regenerated rat junctional epithelium

We investigated the expression of carbohydrate residues in regenerated junctional epithelium (JE) cells histopathologically with lectin staining to clarify the mechanisms responsible for the changes in their expression in JE cells derived from residual oral epithelium. Curettage and root planing procedures were performed on the buccal gingival sulci of rat first lower molars, and JE and connective tissues were completely removed. The mandibles were resected after 12 h and 1, 2, 3, 4, 5, 7, 10 and 14 days, fixed with paraformaldehyde, decalcified with EDTA and embedded in paraffin. Serial sections were stained histochemically with four kinds of lectins (PNA, DBA, GS I, UEA I) to clarify the expression patterns of carbohydrate residues in regenerating epithelium. No binding of PNA or DBA was observed even when the regenerating epithelium was attached to the root surface, and they showed the same negative reactions as the basal cells of oral gingival epithelium (OGE). Positive reactions were, however, observed on the more stratified regenerating epithelium along the root surface. Positive reactions with GS I and negative reactions with UEA I were observed throughout the regeneration process, and these were the same as those observed in the basal cells of OGE. Therefore, we concluded that the basal cells and regenerated epithelium derived from OGE expressed the same carbohydrate residues. Furthermore, the expression of carbohydrate residues, one of the characteristics of JE, was related not only to the attachment to the tooth surface but also to changes of cell shape and cytoskeleton with stratification along the root surface.

Cell-matrix interactions modulate interstitial collagenase expression by human keratinocytes actively involved in wound healing

We reported that interstitial collagenase is produced by keratinocytes at the edge of ulcers in pyogenic granuloma, and in this report, we assessed if production of this metalloproteinase is a common feature of the epidermal response in a variety of wounds. In all samples of chronic ulcers, regardless of etiology, and in incision wounds, collagenase mRNA, localized by in situ hybridization, was prominently expressed by basal keratinocytes bordering the sites of active re-epithelialization indicating that collagenolytic activity is a characteristic response of the epidermis to wounding. No expression of mRNAs for 72- and 92-kD gelatinases or matrilysin was seen in keratinocytes, and no signal for any metalloproteinase was detected in normal epidermis. Immunostaining for type IV collagen showed that collagenase-positive keratinocytes were not in contact with an intact basement membrane and, unlike normal keratinocytes, expressed alpha 5 beta 1 receptors. These observations suggest that cell-matrix interactions influence collagenase expression by epidermal cells. Indeed, as determined by ELISA, primary cultures of human keratinocytes grown on basement membrane proteins (Matrigel; Collaborative Research Inc., Bedford, MA) did not express significant levels of collagenase, whereas cells grown on type I collagen produced markedly increased levels. These results suggest that migrating keratinocytes actively involved in re-epithelialization acquire a collagenolytic phenotype upon contact with the dermal matrix.

Expression of integrins and basement membrane components by wound keratinocytes

Extracellular matrix proteins and their cellular receptors, integrins, play a fundamental role in keratinocyte adhesion and migration. During wound healing, keratinocytes detach, migrate until the two epithelial sheets confront, and then regenerate the basement membrane. We examined the expression of different integrins and their putative ligands in keratinocytes during human mucosal wound healing. Migrating keratinocytes continuously expressed kalinin but not the other typical components of the basement membrane zone: type IV collagen, laminin, and type VII collagen. When the epithelial sheets confronted each other, these missing basement membrane components started to appear gradually through the entire wound area. The expression of integrin beta 1 subunit was increased in keratinocytes during migration. The beta 1-associated alpha 2 and alpha 3 subunits were expressed constantly by wound keratinocytes whereas the alpha 5 subunit was present only in keratinocytes during reepithelialization. Furthermore, migrating cells started to express alpha v-integrins which were not present in the nonaffected epithelium. All keratinocytes also expressed the alpha 6 beta 4 integrin during migration. In the migrating cells, the distribution of integrins was altered. In normal mucosa, beta 1-integrins were located mainly on the lateral plasma membrane and alpha 6 beta 4 at the basal surface of basal keratinocytes in the nonaffected tissue. In wounds, integrins were found in filopodia of migrating keratinocytes, and also surrounding cells in several cell layers of the migrating sheet. The results indicate that migrating keratinocytes, in deep human wounds enlarge their integrin repertoire. The changes in integrin expression take place concomitantly with changes in the basement membrane composition, suggesting a close interplay of these two groups of molecules during wound healing.

Accelerated epithelization under a highly vapor-permeable wound dressing is associated with increased precipitation of fibrin(ogen) and fibronectin

In a previous study we showed that the use of a newly developed, highly water vapor permeable, PEU wound dressing accelerates the epithelization of partial-thickness wounds more than an occlusive wound dressing (OpSite) in comparison with air exposure. The purpose of this study was to investigate the distribution of fibrin(ogen), fibronectin, and type IV collagen during the epithelization process under these three conditions. The breathable PEU film enabled coagulation of the wound exudate, preserving it into a semisolid gelatinous state. This coagulum layer contained an abundant amount of fibrin(ogen) and fibronectin. In wounds occluded with OpSite film, depositions of fibrin(ogen) and fibronectin were less extensive. Migrating keratinocytes contained intracellular depositions of fibrin(ogen), suggesting that these cells phagocytize components of the provisional fibrin matrix during wound healing. It was concluded that accelerated epithelization underneath the highly water vapor permeable polyetherurethane film dressing is associated with the presence of a gelatinous coagulum containing fibrin(ogen) and fibronectin. We speculate that the enhanced healing rate might be caused by an increased concentration of growth-promoting factors present in the residual exudate underneath the PEU dressing.