Control of scarring in adult wounds by neutralising antibody to transforming growth factor beta.
Shah M, Foreman DM, Ferguson MW (1992).
In this paper, the researchers injected the margins of healing dermal wounds in adult male rats with antibodies that neutralize transforming growth factor-Beta (TGF-β), known as neutralizing antibodies, or NAs. As a result, the wounds healed without scar formation but were as strong as scarred tissue.
The purpose of this experiment was to test whether early manipulation of the concentration of certain cytokines, such as TGF-β, would be effective in controlling scarring. The researchers chose TGF-β because it affects all phases of the healing process, and it induces scarring in fetal wounds, which is significant because fetal wounds normally heal without scarring and with a lesser cytokine response.
The experiment involved reducing the concentration of TGF-β within the healing wound by using NAs to inhibit its activity. First, they obtained adult male rats and made four incisions on each. In each animal, one wound was not manipulated (control), another was injected with an irrelevant antibody (rabbit IgG) (sham control), the third was injected with TGF-β (positive control) and the final incision was injected with NAs to TGF-β. The wounds were analyzed using histology/immunocytochemistry, tensiometry, and biochemical analysis.
The tensiometry involved cutting strips from each wound at identical sites for all wounds and extending the strips until they ruptured. All strips ruptured at the site of the healing wound.
The biochemical analysis involved cutting strips, microdissecting the scar tissue or normal skin from underlying fat and muscle, drying and weighing the samples. The hydroxyproline content was measured to calculate the amount of collagen present (assuming collagen contains 13.6% hydroxyproline).
A week after wounding, NA-treated wounds contained much less collagen than the other wounds in the same animal. In the rats killed 14 days after wounding, the NA-treated wounds had much fewer macrophages and blood vessels than the other wounds. Despite this, there was no significant difference in tensile strength between NA-treated wounds and the control wounds. Fourteen days after wounding onwards all wounds had similar tensile strength and collagen content, but the NA-treated wounds had a normal orientation of their extracellular matrix and hence a permanent reduction in scarring. Additionally, the advantageous effects on scarring in the NA-treated wounds were not accompanied by a delay in wound healing or a reduction in wound strength.
The underlying mechanism is that the NAs inhibit the autocatalytic and autoinductive cascades of TGF-β amplification by neutralizing TGF-β such that it cannot interact with its own promoter to upregulate its own synthesis. Therefore, the early application of NAs to TGF-β leads to lower numbers of blood vessels, macrophages, and monocytes at the wound site.
With today’s hygiene and care, the speed of wound healing is not as essential as it was evolutionarily. Characteristics that expedited the healing process were probably selected for at the expense of scar quality. Cytokines can accelerate the healing process, and lowering cytokine concentration may inhibit wound healing. Today, however, the reduction of particular cytokines does not result in deleterious effects on the speed or strength of wound healing. Therefore, these findings suggest an important approach to control of scarring in normal wound healing.
Analysis of the PaperI enjoyed this paper as it was very easy to read, and its clarity and concise presentation strengthened its readability. As a follow-up of this paper, I looked it up on Web of Science and discovered it had been cited 400 times since it was published in 1992. One of the most recent papers that cited it mentioned that a product has been developed based on this concept that is currently undergoing clinical trials (2). Avotermin is in clinical development for the improvement of scar appearance in the skin. To date, there are no data from studies of Avotermin applied to wounds that raise any safety concerns.
References
2. Laverty, H. G. et al. (2009). TGF-β3 and cancer: A review. Accessed 17 November 2009.
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