Chronic Cutaneous Wounds Research Articles

Ectopic localization of matrix metalloproteinase-9 in chronic cutaneous wounds

It has been hypothesized that excessive activity of matrix metalloproteinases (MMPs), in particular the gelatinases MMP-9 and MMP-2, contributes to poor healing of chronic skin ulcers. We compared MMP-9 and MMP-2 in wound margin biopsies of standardized acute partial-thickness wounds in healthy volunteers (n = 6) and in venous leg ulcer patients (n = 12) with those of chronic wounds of different etiologies (n = 34) by a combination of specific analyses of activity and protein localization. We also studied MMP-14 by immunohistochemistry and in situ hybridization in parallel. Neither MMP-9 (P =.814) nor MMP-2 (P =.742) endogenous activities differed significantly between acute and chronic wound tissues. Acute wound healing was characterized by induction of MMP-9 in the advancing epithelium. In chronic wounds, prominent MMP-9 immunostaining was seen in neutrophils and macrophages in the ulcer bed, but virtually no MMP-9 was detected in wound edge keratinocytes. MMP-2 was increased and activated with acute wound age. MMP-2 was found abundantly in dermal fibroblasts and endothelial cells beneath, but not in new epithelium of acute and chronic wounds. MMP-14 mRNA or protein was detected solely in the stroma of both acute and chronic wounds. In conclusion, the overall activity of gelatinases MMP-9 and MMP-2 was not increased in chronic wounds compared to normally healing wound tissues. Chronic nonhealing wounds may not be caused by excessive gelatinase activity, but are distinguished from healing wounds by an unfavorable distribution and persistance of MMP-9. HUM PATHOL 33:355-364. Copyright 2002, Elsevier Science (USA). All rights reserved.

Production de kératinocytes autologues à buts thérapeutiques au sein d’un établissement pharmaceutique

Because biotechnologies are growing and are becoming key players in the pharmaceutical industry scene, Genévrier Laboratories inaugurated in January 1998, a new department especially designed for the production of cultured cells as therapeutic agents. Meeting clinician therapeutic needs by providing autologous keratinocytes and chondrocytes in the near future, represents the primary aim of the Biotechnology department. Concrete cell-based products are already being used for the treatment of burns and cutaneous chronic wounds such as the EPIBASE graft, which corresponds to an epidermis sheet composed of cultured autologous keratinocytes.

Hepatocyte growth factor/scatter factor (HGF/SF) increases cutaneous wound healing in the diabetes mouse

HGF/SF is a heparin binding polypeptide that stimulates cell proliferation, motility and morphogenesis via activation of it's receptor c-Met tyrosine kinase. It has also been shown that HGF/SF is a potent angiogenic factor in a sponge implant model in rats. To evaluate the potential HGF/SF has to heal chronic cutaneous wounds we have topically applied recombinant murine HGF/SF to full thickness excisional injuries using the diabetes mouse model. The diabetes mouse is the result of a spontaneous mutation in an inbred mouse strain. Homozygote animals (db/db) are obese, hyperglycemic and exhibit impaired cutaneous wound healing compared to their wildtype littermates.

Physiology and healing dynamics of chronic cutaneous wounds

In the last few decades, a great deal of progress has been made in understanding the cellular and biochemical interplay that comprises the normal wound healing response. This response is a complex process involving intricate interactions among a variety of different cell types, structural proteins, growth factors, and proteinases. The normal wound repair process consists of three phases—inflammation, proliferation, and remodeling—that occur in a predictable sequence and comprise a series of cellular and biochemical events. A review of the biochemical and physiologic processes that regulate wound healing and the cascade of cellular events that gives rise to the healing process is presented here.

Patterns of matrix metalloproteinase and TIMP expression in chronic ulcers.

Controlled proteolysis is needed for cell migration, angiogenesis, and matrix remodeling during normal wound repair. Our objective has been to investigate how chronic leg ulcers differ from normally healing wounds (pinch graft donor sites) with respect to their metalloproteinase expression patterns. Using in situ hybridization and immunohistochemistry, we found that collagenase-1 (MMP-1), stromelysin-1 (MMP-3) and stromelysin-2 (MMP-10) were expressed in keratinocytes bordering both acute and chronic wounds. Unlike MMP-1, signal for collagenase-3 (MMP-13) was not detected in keratinocytes but exclusively in fibroblasts deep in the ulcer bed of chronic wounds, suggesting that while MMP-1 production is important for migration, MMP-13 plays a role in matrix remodeling. Tissue inhibitor of metalloproteinase (TIMP)-1 was not detected in the epidermis of any chronic wound sample while it was expressed in keratinocytes bordering normally healing wounds. TIMP-3 was abundantly expressed in stromal fibroblast- and macrophage-like cells surrounding vessels and sweat glands in both types of wounds. Our results suggest that there are no qualitative differences in the expression of MMPs-1, -3 and -10 in the epidermis of chronic vs normally healing wounds. However, the number of stromal cells expressing MMP-1 and MMP-3 was greater in chronic vs acute wounds, whereas MMP-10 was never detected in the dermis. TIMP-1 expression near the basement membrane in acute, but not in chronic, wounds suggests that the balance between MMPs and their inhibitors may be altered in poorly healing wounds. Analogous to chronic cutaneous wounds, MMP-1 and -3 are abundantly expressed in chronic small and large bowel ulcers, while the migrating surface epithelium is negative for TIMP-1 expression.

DC electrical stimulation for chronic wound healing enhancement Part 1. Clinical study and determination of electrical field distribution in the numerical wound model

Notwithstanding several past clinical studies demonstrating the beneficial impact of electrical stimulation with steady direct current on the healing of chronic cutaneous wounds, the basic mechanisms underlying its effects on regenerative processes remain to be elucidated and the stimulation regime optimized. In the present study, an attempt is made towards the optimization of steady direct current stimulation of wound healing with respect to the shape and positioning of stimulation electrodes. The effects of direct current stimulation on wound healing were studied in a double-blind clinical trial involving fifty patients with spinal cord injuries, suffering from pressure ulcers. The therapeutic effect of electrical stimulation was found to depend on the positioning and shape of the electrodes. Healing of pressure ulcers was significantly enhanced by direct current, with the positive stimulation electrode overlaying the wound surface and the negative electrode placed on intact skin around the wound. By contrast, stimulation by the second type of electrode configuration - which assumed positioning of both stimulation electrodes on intact skin at the opposite sides of the wound - had only a non-significant effect on pressure ulcer healing. Numerical modelling showed that direct current stimulation using two types of electrode arrangements induced different electric field distributions in the stimulated tissue in the wound area. Endogenous electric conditions in the skin were closely approached with external electrical stimulation when the wound surface was covered with the positive stimulation electrode, while the negative electrode surrounded the wound. With such stimulation, highly significant acceleration of wound healing was observed in the clinical study, leading to the assumption that endogenous electrical phenomena in injured skin are not just side effects, but play an active role in healing. The agreement of the externally induced electric field with the endogenous electric field distribution in injured skin was adopted as the basis for optimization of direct current electrical stimulation for wound healing enhancement.

Immunopathogenesis of Psoriasis

IN THIS age of genetic engineering and transgenic and knockout mice, it is sobering to realize that the immunopathogenesis of psoriasis was discovered largely through clinical research in patients with psoriasis. Before the mid-1980s, the keratinocyte was the focus of scientific research in psoriasis because both the clinical and histologic phenotypes of this disease are dominated by the results of abnormal keratinocyte proliferation and differentiation.^1-6However, the results of research since then have demonstrated that if one eliminates the activated T lymphocyte in psoriatic plaques, keratinocyte proliferation and differentiation return to normal both clinically and histologically.^7-10Thus, the abnormalities in the keratinocytes are reversible. Clinically, psoriatic plaques are described as red, elevated, and scaly. Both the elevation and scale are direct results of the same altered keratinocyte proliferation and differentiation that have been observed in acute and chronic cutaneous wounds. This alternate pathway of keratinocyte differentiation has been

Collagen VII expression in human chronic wounds and scars.

Collagen VII is the major structural component of the anchoring fibrils that stabilize the cutaneous basement membrane on the dermis. Disruption and, more usually, destruction of the basement membrane are characteristic of wounds that are slow, or fail, to heal, such as chronic lower-limb or pressure ulcers. In this study, the expression of collagen VII was analysed in 28 human chronic cutaneous wounds or scars using a reverse transcription-polymerase chain reaction (RT-PCR) technique. Collagen VII expression was detected in 26 of these 28 cutaneous wounds, but not in two wounds, neither of which showed any clinical evidence of healing.

Pseudoepitheliomatous hyperplasia in chronic cutaneous wounds. A flow cytometric study.

Cutaneous squamous cell carcinomas (SCC) arising in a setting of chronic regeneration and repair tend to be highly aggressive lesions prognostically distinct from SCC arising in solar-damaged skin. Full thickness thermal injury and chronic nonhealing ulcers are predisposing conditions in up to 2% of SCC. A significant association has been suggested to exist between pseudoepitheliomatous hyperplasia (PH) and SCC. Three-hundred-eighty-six surgical cases of skin excised secondary to severe burns (n = 254) or chronic ulcers (n = 132) were reviewed, yielding 43 (11%) with PH. Flow cytometric DNA analysis was performed on paraffin-embedded sections. Thirty cases without PH were studied in addition to the 43 cases with PH. The majority (39/43) of the PH cases showed a single diploid population with a mean S-phase of 13.7%. Four cases (9.3%) showed an aneuploid peak. All cases without PH were diploid with a mean S-phase of 9.0%. In this study, PH was present in 11% of cases reviewed, and showed a 50% mean higher S-phase than comparable cases without PH. Aneuploidy was present in 9.3% of the PH cases studied. SCC may arise from a subgroup of PH in a background of rapidly proliferating keratinocytes.

Regulatory concerns in the development of topical recombinant ophthalmic and cutaneous wound healing biologics

The use of recombinant DNA technology has enabled the development of an increasing number of endogenous growth regulatory peptides for potential use as therapeutic biologics. Numerous such recombinant peptides are now licensed, and many are in various stages of pharmaceutical development. Although currently there are a number of "Points to Consider" and related guidance documents available concerning various issues of biotechnology-derived products, the purpose of this article is to focus on the use of these biologics in topical ophthalmic and chronic cutaneous wound healing. Regulatory expectations with respect to product quality, safety, and efficacy that may be particularly germane to these products will be discussed. Providing regulatory guidance on these issues may not only facilitate the introduction of safe and effective new biologic therapies into clinical trials at the investigational level but also provide appropriate information to aid in their eventual approval for licensure and widespread clinical use.