Pre clinical Research

The aim of the preclinical research is to develop new treatment strategies for healing of (deep) burn wounds which improve the outcome of healing.

Wound healing is a cascade of different processes that have to be closely orchestrated in order to regain normal functional restoration of the damaged tissue. Derailment of this system results in impaired wound healing and hypertrohic scar formation. A number of factors seem to be responsible for the generation of often invalidating scars, such as the depth and location of the wound and an excessive inflammatory reaction (possibly as a result of an infection). Although ample research has been performed on many aspects of wound healing, the precise mechanism of scar formation or scarless healing is still lacking.

Our attention is focused on fundamental research and efforts are made to detect the cellular and molecular mechanisms of wound healing and scarring. When the underlying processes which lead to scarring are understood, new treatments can be developed in which scarring is decreased or even prevented. In addition, the insight in processes which lead to a normal functioning skin are of interest in developing optimal skin substitutes, our second major focus of research.

To be able to develop treatment strategies to reduce scar formation, understanding the mechanisms leading to skin regeneration or scar formation is important. To study the healing process in great detail different model systems are used. These wound model systems are important for the development of treatments preventing scarring, and to understand the different processes leading to scar formation.

Several in vivo and in vitro models are used in this research. The in vitro studies allow detailed research on the effect of individual cell types and individual (growth) factors.

Current state of affairs

Burn wound model
We have developed an ex vivo burn wound model which is based on in vitro culture of normal human skin. All the cellular elements of the skin, including skin appendages and matrix elements, are present. We showed that this model can be supplemented with other factors important in wound healing e.g. by the addition of the LPS to mimic bacterial infection. Especially re-epithelialisation can be studied in great detail.

Inhibition of Fibrosis
Fibrosis is a result of a derailed healing process after tissue injury. Common processes which are necessary for normal regeneration of the damaged tissues have become uncontrollable, which results in excessive collagen accumulation. Although the mechanisms leading to fibrosis in different tissues are different they also share many common features.

TGF-beta is one of the main effectors in fibrosis. This cytokine is involved in the transition of fibroblasts (or smooth muscle cells) into myo-fibroblasts. The (sustained) presence of this cell type is one of the shared characteristics in fibrosis of different tissues. Studies in other areas than skin wound healing have explored various agents which where shown to have beneficial effects on inhibiting the process of fibrosis. This could be a direct effect by influencing collagen deposition or by influencing the inflammatory response.

A literature search yielded several potential mechanisms for intervention. In an in vivo model the efficacy of different approved drugs which interfere with the selected processes were assessed on their scar reducing potential.

Itch
Itching (pruritus) following burns is a well known clinical problem. The lack of detailed knowledge about the mechanisms causing this harassment hampers the development of proper treatment methods.

Several data indicate that the skin nerve system is significantly involved in the wound healing process, most probably via neuro-peptides affecting vasodilatation and inflammation but also by stimulation of proliferation of epithelial and connective tissue cells.

Bacterial Infection
Wound infection is an important problem in burn wound management. In wounds which would normally heal without scar formation, contamination with micro-organisms can have disastrous effects on the process of wound healing. However not all colonised wounds experience the same problems. The mechanisms underlying the differences in wound healing are largely unknown. E.g. it is not clear whether all micro-organisms are harmful and thus should be eliminated, also the wound environment might play an important role.

To analyse the impact of the problem a retrospective analysis of the patients charts and the incidence of recurring bacterial contamination in combination with delayed healing was performed. Patients with problematic wound healing with sustained bacterial contamination (P. aeruginosa) were found to have higher TBSA, higher % full thickness wounds and more frequent inhalation trauma when compared with a patient group without healing problems despite contamination with P. aeruginosa. Surprisingly the study group acquired the bacterial contamination significantly later than the control group. Also the bacteria were less sensitive to antimicrobial treatment.

There are several possible factors which cause the differences in healing between the two patient groups such as; wound environment/condition or the bacterial strain.

Computer aided digital imaging
To be able to evaluate different treatment strategies on their efficacy evaluations tools have to be developed.

Histo-pathological analysis by microscopic visualisation is a technique that is used by many scientists in wound healing research. It often is the basis for many strategic decisions in clinical burn care as well as pre-clinical research. However, the results that are obtained by this technique most often have descriptive or at the most a semi-quantitative nature. In order to get quantitative data digital, image analysis can be used. When reliable, quantification can be done be a single person and in a short time and more accurate and numerical data can be generated. After validation this technique will be implemented in clinical as well as preclinical research.