Tranexamic acid reduces inflammation, edema and burn wound conversion in a rodent model

Abstract

Burn wound conversion is the observed process where superficial partial thickness burns convert into deep partial or full thickness burn injuries. This conversion process often involves surgical excision to achieve timely wound healing. Unfortunately, the pathophysiology of this phenomenon is multifactorial and poorly understood. Thus, a therapeutic intervention that may prevent secondary progression and cell death in burn-injured tissue is desirable. Recent work by our group and others has established that tranexamic acid (TXA) has significant anti-inflammatory properties in addition to its well-known anti-fibrinolytic effects. This study investigates TXA as a novel therapeutic treatment to mitigate burn wound conversion and reduce systemic inflammation. Sprague-Dawley rats were subjected to a hot comb burn contact injury. A subset of animals underwent a similar comb burn with an adjacent 30%TBSA contact injury. The interspaces represent the ischemic zones simulating the zone of stasis. The treatment group received injections of TXA (100 mg/kg) immediately after injury and once daily until euthanasia. Animals were harvested for analyses at 6 h and 7 days after injury. Full-thickness biopsies from the ischemic zones and lung tissue were assessed with established histological techniques. Plasma was collected for measurement of damage associated molecular patterns (DAMPs), and liver samples were used to study inflammatory cytokines expression. Treatment with TXA was associated with reduced burn wound conversion and decreased burn-induced systemic inflammatory response syndrome (SIRS). Lung inflammation and capillary leak were also significantly reduced in TXA treated animals. Future research will elucidate the underlying anti-inflammatory properties of TXA responsible for these findings.

Keywords: Burn wound conversion; Comb burn; Edema; SIRS; Tranexamic acid; Zone of stasis.

Figure 1.

TXA decreases skin necrosis after 10% TBSA burn. Rats underwent 10% TBSA burn injury followed by TXA or PBS (control) injection. During the following 5 days rats received daily injections of TXA or PBS. Animals were euthanized 7 days after burn injury and full thickness ischemia zones of skin were examined by histology. A. Burned skin areas on rat backs. Necrotic areas are dark-brown or black. B. H&E staining of skin ischemia zones. Necrotic areas are highly eosinophilic. Bar=200µ. The % of dermis occupied by necrotic area was quantified. N=5 for burn and burn+TXA groups. C. Immunohistochemical staining for CTHRC1 positive cells (brown) in skin sections is shown. The number of CTHRC1 positive cells per field under the 40x objective in the dermis was determined. N=5 for burn and burn+TXA rat groups. N=2 for control group. Bar=50µ.

Figure 2.

TXA decreases skin necrosis after 30% TBSA burn. Rats underwent 30% TBSA burn injury followed by daily injections of TXA or PBS (control). Animals were euthanized 7 days after burn injury and full thickness ischemia zones of skin were examined by histology. A. Burned skin areas on rat backs. Necrotic areas are dark-brown or black. B. H&E staining of skin ischemia zones. Necrotic areas are highly eosinophilic. Bar=200µ. The % of dermis occupied by necrotic area was quantified. N=5 for burn and burn + TXA groups.

Figure 3.

TXA suppresses the burn-induced release of nuclear DNA to bloodstream and the expression of IL1β and TNFα genes in liver. Rats underwent 30% TBSA burn injury followed by TXA or PBS (control) injection. Six hours later the animals were sacrificed with harvest of livers for RNA analysis. A. qPCR was used to determine circulating nuclear DNA in plasma. Plasma samples from two identical experiments were studied together. N=11 for burn group. N=10 for burn+TXA group. N=4 for control group. B. Total RNA was prepared and RT-qPCR was used to study the expression of IL1β and TNFα genes. N=5 for burn group and burn+TXA groups. N=2 for control group.

Figure 4.

TXA suppresses the burn-induced invasion of neutrophils to lungs. Rats underwent 30% TBSA burn injury followed by TXA or PBS (control) injection. Six hours later the animals were sacrificed, lungs were removed and processed for histology. Immunohistochemistry for MPO was performed. The number of MPO positive cells per field under the 40x objective in dermis was determined. N=5 for burn and burn+TXA rat groups. N=2 for control group. Bar=50µ

Figure 5.

TXA suppresses the burn-induced vessel leakage in lungs. Rats underwent 30% TBSA burn injury followed by TXA or PBS (control) injection. Six hours later the animals were injected with Evans blue. After thirty minutes the animals were anesthetized and the circulatory system perfused. The leakage of Evans blue to lungs was determined. N=5 for burn and burn+TXA rat groups. N=2 for control group. A. Perfused lungs. TXA decreases the red-brownish coloration of lungs. B. Fluorimetric measurement of Evans blue eluted from lungs.