Lysates from cultured allogeneic keratinocytes stimulate wound healing after tympanoplasty

Role of keratinocyte?fibroblast cross-talk in development of hypertrophic scar

The ability to generate or repair injured tissue is essential to the continuity of human life. As in all other organs, wound healing in the skin is a dynamic process involving tissue response to different types of insults. This process involves a continuous sequence of signals and responses in which platelets, fibroblasts, epithelial, endothelial, and immune cells come together outside their usual domains to orchestrate a very complex event that results in tissue repair. These signals, which are mainly growth factors and cytokines, orchestrate the initiation, continuation, and termination of wound healing. An imbalance in the synthesis and release of these cytokines and growth factors at the wound site, therefore, may result in either retarded wound healing, as is seen in diabetic patients and the elderly population, or overhealing wounds such as fibroproliferative disorders frequently seen following surgical incision, traumatic wounds, and severe electrical and thermal injury. In general, regardless of the site of injury, in any phase of the dynamic healing process, a fine balance between synthesis of extracellular matrix and degradation by a large family of enzymes, known as matrix metalloproteinases, is required for maintaining the structural integrity of healing tissue. The availability of new models such as organotypic co-culture systems have allowed us to gain new insight into the cell-cell interactions at both cellular and molecular levels. Recent evidence indicates that mesenchymal-epithelial interactions play a critical role in regulation of skin homeostasis and this cross-talk is mediated by soluble factors acting as autocrine/paracrine regulators of fibroblast and keratinocyte growth, function, and differentiation. In this review we address the question of how keratinocyte-fibroblast interaction plays a role in controlling the expression of key extracellular matrix molecules such as matrix metalloproteinases, which are critical in the healing process following any types of insults to the skin.

Interaction of keratinocytes and fibroblasts modulates the expression of matrix metalloproteinases-2 and -9 and their inhibitors

Disruption of epidermal-mesenchymal communication due to a delay in epithelialization, increases the frequency of developing fibrotic conditions in skin. As matrix metalloproteinases-2 (MMP-2) and -9 (MMP-9) are two key enzymes involved in wound healing and tissue remodeling, here we examined the efficacy of keratinocyte-fibroblast interaction on modulation of these enzymes and their inhibitors. The conditioned media derived from keratinocytes and fibroblasts grown in upper and lower chambers of a co-culture system, respectively, were analyzed for MMP-2 and -9. Keratinocyte or fibroblast conditioned medium (FCM) was used as a control. Gelatinolytic activity analyzed by zymography showed that keratinocytes mainly express MMP-9 and to a lesser extent MMP-2; while fibroblasts express only MMP-2. In a co-culture system, the activities of both MMP-2 and MMP-9 markedly increased in conditioned media collected from bottom chambers. These findings were consistent with the level of MMP-2 and MMP-9 measured by Western blot. Using the same experimental setting, the levels of tissue inhibitors of MMPs (TIMPs) secreted by keratinocytes and fibroblasts grown in the same co-culture system were also evaluated. Western blot showed that fibroblasts secrete only TIMP-1 and TIMP-2 whose levels were increased by co-culturing fibroblasts with keratinocytes. In contrary the level of TIMP-3, which was mainly expressed by keratinocytes, increased by co-culturing these cells with fibroblasts. In conclusion, interaction of fibroblast-keratinocyte modulates the levels of MMP-2 and -9 and their inhibitors produced by these cells and this interaction may be critical for a better healing quality at a late stage of the wound healing process.

Efficacy and safety of the freeze-dried cultured human keratinocyte lysate, LyphoDermtm 0.9%, in the treatment of hard-to-heal venous leg ulcers

LyphoDerm (XCELLentis, Belgium) is an end-sterilized, freeze-dried lysate from cultured allogeneic epidermal keratinocytes, formulated into a hydrophilic gel. Its efficacy and safety were evaluated, in combination with standard care (hydrocolloid dressing and compression therapy), in 194 patients suffering from hard-to-heal (lasting more than 6 weeks and not responding to conventional therapy) venous leg ulcers. Two control groups received standard care, with or without vehicle, respectively. Patients had a median age of 67.5 years and the majority were females (61%). The median duration of the ulcer was 43 weeks and in 39% of the subjects it had been present for more than 1 year. Thirty-eight percent of the patients in the standard care + LyphoDerm group had complete ulcer healing within 24 weeks (primary end point) compared to 27% of patients in the standard care + vehicle pooled groups (P = 0.114) in the "as treated" intent-to-treat cohort (37% vs. 27% in the "as randomized intent-to-treat cohort; p = 0.137). In the subgroup of patients with enlarging ulcers, the difference between the two groups was significant (30% vs. 11%; p = 0.024 in the "as treated" intent-to-treat cohort and 31% vs. 9%; p = 0.005 in the "as randomized" intent-to-treat cohort). LyphoDerm was well tolerated and safe, and no differences in the frequency of adverse events were noted between the treatment groups. Although the primary objective of the study was not achieved, the exploratory analysis carried out in patients with enlarging ulcers suggests that LyphoDerm could offer a new prospect for the treatment of patients with venous ulcers that may prove to be a significant adjunct to the overall provision of care.

Use of becaplermin in the closure of pharyngocutaneous fistulas

BACKGROUND

We report on the contribution of recombinant platelet-derived growth factor-BB (becaplermin) in treating recalcitrant postlaryngectomy fistulas in two patients with head and neck cancer.

METHODS

Topical becaplermin was applied daily, with periodic wound assessment and photodocumentation.

RESULTS

The two patients with persistent fistula refractory to conventional management have demonstrated rapid improvement after topical application of becaplermin. Each wound exhibited an exuberant granulation response, with a 50% decrease in the size of wound at 1 week. The patients experienced eventual closure, with none having local recurrence of their cancer at 2 years' follow-up.

CONCLUSIONS

Becaplermin seems to be a promising addition to traditional methods of treatment for postlaryngectomy fistulas. In patients with delayed healing, future studies will be required to determine the overall efficacy of such biologic response modifiers in the treatment of pharyngocutaneous fistulas and other chronic wounds of the head and neck.

Miringoplastia com a utilização de um novo material biossintético

A miringoplastia é uma cirurgia com a finalidade de controlar a infecção no ouvido médio, reconstruir o mecanismo de transmissão sonora para a janela oval e proteger a janela redonda. São descritos diversos materiais para reconstruir a membrana timpânica, destacando-se a fáscia do músculo temporal, pericôndrio do tragus, cartilagem, dura-máter, tecido placentário, entre outros. OBJETIVO: Este trabalho tem objetivo de demonstrar o efeito de um novo biomaterial, a membrana de látex natural com polilisina, desenvolvida no laboratório de Neuroquímica do Departamento de Bioquímica da Faculdade de Medicina de Ribeirão Preto da Universidade de São Paulo - USP. FORMA DE ESTUDO: Coorte Longitudinal. MATERIAL E MÉTODO: O biomaterial utilizado é estimulante da neovascularização e crescimento tecidual organizado em diferentes órgãos e tecidos, sendo um material inócuo e não rejeitado pelo organismo. Foi usada a biomembrana de látex com polilisina como um implante transitório para o fechamento da perfuração da membrana timpânica. A membrana foi colocada na face externa dos bordos da membrana timpânica e a fáscia temporal na face interna da mesma. Foram estudadas 238 orelhas com perfuração de membrana timpânica por seqüela de otite média crônica, submetidas a miringoplastia com enxerto de fáscia de músculo temporal e a membrana de látex natural, com idades de 7 a 76 anos. Apresentavam uma ou mais miringoplastias anteriores sem sucesso 41 dos casos. RESULTADO: Como ressaltamos preliminarmente, verificamos pega do enxerto em 90,5% das orelhas (181), sendo fechamento de perfuração amplas, 96; médias, 73 e 12 pequenas. Verificamos intensa vascularização em 100% dos enxertos, o que não é habitual quando não se usa a membrana de látex natural. CONCLUSÃO: Conclue-se que o biomaterial usado merece nossa atenção quanto ao seu uso como implante transitório em miringoplastias, melhorando o processo de revascularização da membrana timpânica remanescente.

Expression of a releasable form of annexin II by human keratinocytes

Annexin II is a multifunctional calcium-dependent phospholipid binding protein whose presence in epidermis has previously been reported. However, like other members of annexin family, annexin II has been regarded as either an intracellular protein or associated with the cellular membrane. Here, we report the presence of a releasable annexin II and p11, two monomers of annexin II tetramer, in keratinocyte-conditioned medium (KCM). Proteins present in KCM were fractionated on a gel filtration column and following further evaluation, a releasable protein with apparent MW of 36 kDa was identified. Further characterization identified this protein as the p36 monomer of annexin II tetramer. The phospho-tyrosine antibody did not visualize this protein as the phosphorylated form of p36. Several experiments were conducted to examine whether this protein is soluble or associated with keratinocyte cell membranes in the conditioned medium. A centrifugation of conditioned medium was not able to bring this protein down into the pellet. Surprisingly, the results of Western analysis identified p36 and p11, two monomers of the annexin II tetramer, in conditioned medium derived from either keratinocytes cultured alone or keratinocytes co-cultured with fibroblasts. In contrast to the keratinocyte-conditioned medium in which annexin II was easily detectable, both monomers were barely detectable in conditioned medium collected from dermal fibroblasts. This finding was in contrast to the cell lysates in which p36 was detectable in both keratinocytes and fibroblasts. However, the amount of this protein was markedly higher in keratinocyte lysate relative to that of dermal fibroblasts. Conditioned medium derived from keratinocyte established from adult showed a higher level of annexin II compared to that of keratinocytes established from newborn babies. The expression of p11 seems to increase with differentiation of keratinocytes derived from either adult or newborn skin samples. When the site of annexin synthesis in human skin was examined by immunohistochemical staining, the antibody for p36 localized the annexin to the keratinocyte cell members in the basal and suprabasal keratinocytes. In conclusion, Western blot detection of both p36 and p11 in conditioned medium from skin cells revealed that human keratinocytes, but not fibroblasts, express a releasable monomer form of annexin II which is regulated by differentiation status of keratinocytes. This finding is consistent with the localization of annexin II detected by immunohistochemical staining.

Topical treatment with growth factors for tympanic membrane perforations: progress towards clinical application

Basic scientific research has demonstrated that epidermal growth factor (EGF), basic fibroblast growth factor (bFGF), platelet-derived growth factor-AA (PDGF-AA) and transforming growth factor-alpha (TGF-alpha) are induced by acute tympanic membrane (TM) perforation. The expression of these growth factors peaks during the inflammatory phase and then declines, suggesting their involvement in the healing process of the TM. Expression of EGF receptor, bFGF receptor, PDGF receptor and keratinocyte growth factor (KGF) receptor in the TM has also been reported. Identification of these receptors indicates that the target cells in the TM may be stimulated during the process of healing by the corresponding exogenous growth factor in vivo. Some reports from animal studies showed encouraging effects of EGF, bFGF and PDGF-AA in terms of accelerated or enhanced healing of acute and chronic TM perforations without significant adverse effects. Two reports of clinical trials of topical application of EGF or bFGF for TM perforations revealed mixed results. In this article special considerations for future directions of research into growth factors are discussed and related articles on healing of skin wounds and other lesions are reviewed. Further experimental and clinical studies on the mechanism of action of growth factors, timing of application, selection (either singly or in combination), delivery mode, dose and safety aspects, as well as more clinical trials, are warranted, and will pave the way for clinical application.

Keratinocyte differentiation inversely regulates the expression of involucrin and transforming growth factor beta1

Extensive skin loss from a variety of conditions such as severe thermal injury is associated with significant functional morbidity and mortality. In recent years, the healing quality has been improved for patients who suffer burns due in part to the usage of skin replacement mainly prepared from multi-layered sheets of cultured keratinocytes. Although it is known that keratinocytes are a rich source of wound healing promoting factors such as transforming growth factor-beta1 (TGF-beta1), it is not clear whether differentiated keratinocytes in a multi-layer form release this multi-functional growth factor and has any functional influence on dermal fibroblasts. This study examined the hypothesis that keratinocytes in mono- and multi-layer forms express different levels of TGF-beta1. To address this hypothesis, keratinocytes were grown in serum free medium (KSFM) supplemented with bovine pituitary extract (50 microg/ml) and EGF (5 microg/ml). When cells reached confluency, conditioned medium was removed and replaced with 50% KSFM with no additives and 50% DMEM without serum and cells were allowed to form multi-layers and differentiate. The conditioned medium was then collected every 48 h up to 24 days and the level of TGF-beta1 and the efficacy of a keratinocyte released fibroblast mitogenic factor were evaluated by ELISA and (3)H-thymidine incorporation, respectively. Northern analysis was also employed to evaluate the expression of TGF-beta1, involucrin, TIMP-1, and 18 S ribosomal RNA in keratinocytes at different times of the onset of differentiation. The microscopic morphology of keratinocytes at different times of induction of cell differentiation showed detachments (nodules) of many regions of keratinocyte sheet from culture substratum within 1-2 weeks. The numbers and sizes of these nodules were increased as the process of keratinocyte differentiation proceed. The results of TGF-beta1 evaluation revealed that mono-layers of cultured keratinocytes which were round, attached, and proliferating in KSFM + BPE and EGF containing medium released a significantly higher level of TGF-beta1 (196 +/- 58 pg /ml) relative to those grown in multi-layer forms (28 +/- 7.8 pg/ml). A longitudinal experiment was then conducted and the results showed that cells on the onset of differentiation released even greater level of TGF-beta1 (388 +/- 53 pg/ml) relative to those grown in KSFM + BPE and EGF. This finding was consistent with the expression of TGF-beta1 mRNA evaluated in keratinocytes grown in test medium for various duration. In general, the level of TGF-beta1 protein and mRNA gradually reduced to its lowest level within 12 days of growing cells in our test medium. When aliquots of the collected keratinocyte conditioned medium were added to dermal fibroblasts, the level of (3)H-thymidine incorporation increased only in those cells receiving aliquots of conditioned medium containing high levels of TGF-beta1. When involucrin was used as a differentiation marker for keratinocytes at different time points, the highest level of involucrin mRNA expression was found at the later stage of cell differentiation. In conclusion, high involucrin expressing differentiated keratinocytes seem to be quiescent in releasing both TGF-beta1 and a fibroblast mitogenic factor.