Topically applied CMT-2 enhances wound healing in streptozotocin diabetic rat skin

A Novel Chemically Modified Curcumin "Normalizes" Wound-Healing in Rats with Experimentally Induced Type I Diabetes: Initial Studies

Introduction. Impaired wound-healing in diabetics can lead to life-threatening complications, such as limb amputation, associated in part with excessive matrix metalloproteinase- (MMP-) mediated degradation of collagen and other matrix constituents. In the current study, a novel triketonic chemically modified curcumin, CMC2.24, was tested for efficacy in healing of standardized skin wounds in streptozotocin-induced diabetic rats. Initially, CMC2.24 was daily applied topically at 1% or 3% concentrations or administered systemically (oral intubation; 30 mg/kg); controls received vehicle treatment only. Over 7 days, the diabetics exhibited impaired wound closure, assessed by gross and histologic measurements, compared to the nondiabetic controls. All drug treatments significantly improved wound closure with efficacy ratings as follows: 1% 2.24 > systemic 2.24 > 3% 2.24 with no effect on the severe hyperglycemia. In subsequent experiments, 1% CMC2.24 "normalized" wound-healing in the diabetics, whereas 1% curcumin was no more effective than 0.25% CMC2.24, and the latter remained 34% worse than normal. MMP-8 was increased 10-fold in the diabetic wounds and topically applied 1% (but not 0.25%) CMC2.24 significantly reduced this excessive collagenase-2; MMP-13/collagenase-3 did not show significant changes. Additional studies indicated efficacy of 1% CMC2.24 over more prolonged periods of time up to 30 days.

Neutrophil activity in chronic venous leg ulcers--a target for therapy?

Chronic venous leg ulcers (CVLUs) affect approximately 600,000 people annually in the United States and accrue yearly treatment costs of US $2.5-5 billion. As the population ages, demands on health care resources for CVLU treatments are predicted to drastically increase because the incidence of CVLUs is highest in those ≥65 years of age. Furthermore, regardless of current standards of care, healing complications and high recurrence rates prevail. Thus, it is critical that factors leading to or exacerbating CVLUs be discerned and more effective, adjuvant, evidence-based treatment strategies be utilized. Previous studies have suggested that CVLUs' pathogenesis is related to the prolonged presence of high numbers of activated neutrophils secreting proteases in the wound bed that destroy growth factors, receptors, and the extracellular matrix that are essential for healing. These events are believed to contribute to a chronically inflamed wound that fails to heal. Therefore, the purpose of this project was to review studies from the past 15 years (1996-2011) that characterized neutrophil activity in the microenvironment of human CVLUs for new evidence that could explicate the proposed relationship between excessive, sustained neutrophil activity and CVLUs. We also appraised the strength of evidence for current and potential therapeutics that target excessive neutrophil activity.

The Role of Doxycycline as a Matrix Metalloproteinase Inhibitor for the Treatment of Chronic Wounds

Many chronic wounds fail to heal with conventional therapy, resulting in disability and impaired quality of life. New technologies using recombinant growth factors, autologous growth factors, or bioengineered skin—tissue substitutes have been shown to be effective, but these treatments are costly. An effective, low-cost treatment to improve healing of chronic wounds is needed. The molecular environment of chronic wounds, like many other chronic inflammatory diseases, contains abnormally high levels of proinflammatory cytokines (tumor necrosis factor [TNF]-α and interleukin [IL]-1β]) and matrix metalloproteinases (MMPs), which impair normal wound healing. In animal models and clinical studies of ulcerative diseases, doxycycline, an inexpensive and Food and Drug Administration (FDA)-approved antibiotic, appears to inhibit members of the MMP superfamily like MMPs and TNF-α-converting enzyme (TACE). This article provides an overview of the roles of MMPs and intrinsic tissue inhibitors of metalloproteinases (TIMPs) in wound healing and the damaging effects of chronically elevated levels of MMPSs in chronic wounds. It also explores the use of topical doxycycline, a synthetic MMP inhibitor (MMPI), to enhance healing of chronic wounds.

Attenuation of protease activity in chronic wound fluid with bisphosphonate-functionalised hydrogels

Chronic ulcers are an important and costly medical issue, imposing considerable pain, reduced mobility and decreased quality of life. The common pathology in these chronic wounds is excessive proteolytic activity, resulting in degradation of key factors critical to the ulcer's ability to heal. Matrix metalloproteinases (MMPs), a large family of zinc-dependent endopeptidases, have been shown to have increased activity in chronic wound fluid (CWF), with many authors suggesting that they need to be inhibited for the ulcer to heal. The studies we report here show that the excessive MMP activity in CWF can be inhibited with the bisphosphonate alendronate, in the form of a sodium salt, a functionalised analogue, and tethered to a poly(2-hydroxy methacrylate) (PHEMA) hydrogel. Furthermore, these functionalised alendronate hydrogels appear to be biologically inert as assessed in a three-dimensional ex vivo human skin equivalent model. Together, these results highlight the potential use of a tethered MMP inhibitor to inhibit protease activity in wound fluid. This approach may improve wound healing as it still allows MMPs to remain active in the upper cellular layers of the ulcer bed where they perform vital roles in wound healing; thus may offer an attractive new device-orientated wound therapy.

Novel sulfonated hydrogel composite with the ability to inhibit proteases and bacterial growth

There is a growing interest in the development of wound dressings that possess functionality beyond providing physical protection and an optimal moisture environment for the wound. To this end, a novel dressing material based on a sulfonated triblock polymer has been developed. This versatile polymer possesses an ion-exchange capability that is amenable to binding and controlled release of a variety of therapeutic agents. This sulfonated polymer offers several advantages over existing commercial hydrogels used as wound dressings. These include (1) hydrophilicity that is proportional to sulfonation level, (2) easy preparation of fabric supported dressings (e.g., polyester, cotton, nylon), (3) excellent mechanical integrity of the materials when hydrated, (4) stability to a variety of chemistries, and (5) stability to a variety of sterilization methodologies. In this study, polymer was coated onto a polyester fabric and then modified by ion exchange to prepare the sodium, silver, or doxycycline salts. These sulfonated triblock polymer formulations were then evaluated for their capacity to sequester the neutrophil proteases, elastase, and collagenase-2 (MMP-8). Several of the formulations were found to sequester significant amounts of either elastase or collagenase. These formulations were demonstrated to be tested against a commercially available dressing that is currently marketed for its protease-inhibiting capability. The experimental dressing was statistically superior to the commercial dressing at inhibiting MMP-8 and elastase under the same conditions.

Chemically modified tetracycline (CMT-8) and estrogen promote wound healing in ovariectomized rats: effects on matrix metalloproteinase-2, membrane type 1 matrix metalloproteinase, and laminin-5 gamma2-chain

Estrogen deficiency is associated with impaired cutaneous wound healing. Remodeling of the extracellular matrix in wound healing involves the action of matrix metalloproteinases on basement membrane zone components, especially laminin-5. We studied the effects of estrogen and a potent matrix metalloproteinase inhibitor, chemically modified non-antimicrobial tetracycline, CMT-8, on wound healing in ovariectomized rats. At the tissue level, laminin-5 gamma2-chain expression was decreased and the migration-inductive 80 kDa form of laminin-5 gamma2-chain was absent in ovariectomized rats when compared with sham and CMT-8- or estrogen-treated ovariectomized animals as detected by Western blotting. The highest levels of gelatinolytic activity (matrix metalloproteinase-2 and -9) were found in sham animals. Levels were reduced in ovariectomized rats and were lowest after treating ovariectomized rats with CMT-8 or estrogen as analyzed by functional activity assay and zymography. The total amount of membrane type 1-matrix metalloproteinase was unchanged in all groups. We conclude that CMT-8 and estrogen can promote wound healing in ovariectomized rats, not only by normalizing wound bed total collagen content and structure, but also by recovering the expression and processing of key molecules in wound healing, i.e., laminin-5 gamma2-chain. This study shows, for the first time, the role of estrogen and CMT-8 in laminin-5 gamma2-chain modulation in vivo.

The proteolytic environment of chronic wounds

A consistent feature of chronic leg and pressure ulcers is chronic inflammation associated with an elevated infiltration of neutrophils. Neutrophils and their proteases have been implicated in mediating the tissue damage associated with a variety of chronic inflammatory diseases. This review discusses our current understanding of the proteolytic enzymes found in chronic wounds and attempts to relate this information to the abundant presence of neutrophils. In addition, the implications that the proteolytic environment may have for current and future treatment strategies of chronic nonhealing wounds are discussed.