Elsevier

Burns

Volume 40, Issue 7, November 2014, Pages 1365-1374
Burns

Repetitive extracorporeal shock wave applications are superior in inducing angiogenesis after full thickness burn compared to single application

https://doi.org/10.1016/j.burns.2014.01.019Get rights and content

Abstract

Objective

Burn wounds remain a challenge due to subsequent wound infection and septicemia, which can be prevented by acceleration of wound healing. The aim of the study was to analyze microcirculation and leukocyte endothelium interaction with particular focus on angiogenesis after full-thickness burn using three different repetitions of low energy shock waves.

Methods

Full-thickness burns were inflicted to the ears of hairless mice (n = 44; area: 1.6 ± 0.05 mm2 (mean ± SEM)). Mice were randomized into four groups: the control group received a burn injury but no shock waves; group A received ESWA (0.03 mJ/mm2) on day one after burn injury; group B received shock waves on day one and day three after burn injury; group C ESWA on day one, three and seven after burn injury. Intravital fluorescent microscopy was used to assess microcirculatory parameters, angiogenesis and leukocyte interaction. Values were obtained before burn (baseline value) immediately after and on days 1, 3, 7 and 12 after burn.

Results

Shock-wave treated groups showed significantly accelerated angiogenesis compared to the control group. The non-perfused area (NPA) is regarded as a parameter for angiogenesis and showed the following data on day 12 2.7 ± 0.4% (group A, p = 0.001), 1.4 ± 0.5% (group B, p < 0.001), 1.0 ± 0.3% (group C, p < 0.001), 6.1 ± 0.9% (control group). Edema formation is positively correlated with the number of shock wave applications: day 12: group A: 173.2 ± 9.8%, group B: 184.2 ± 6.6%, group C: 201.1 ± 6.9%, p = 0.009 vs. control: 162.3 ± 8.7% (all data: mean ± SEM).

Conclusion

According to our data shock waves positively impact the wound healing process following burn injury. Angiogenesis showed significantly improved activity after shock wave application. In all three treatment groups angiogenesis was higher compared to the control group. Within the ESWA groups, double applications showed better results than single application and three applications showed better results than single or double applications.

Introduction

Extracorporeal shock wave application (ESWA) has the potential to qualify as an adjuvant therapy option for soft tissue disorders such as chronic wounds in experimental settings [1], [2]. Initially, extracorporeal shock waves have been applied in the treatment of urolithiasis, using synergistic interactions between stress waves and cavitation as a key therapy principal [3].

Shock waves are single acoustic pulses, characterized by alternating rapid increase (ns) and decrease (μs) of positive and negative pressures. One of the main differences between the treatment of urolithiasis and the use of ESWA in soft tissue disorders is the applied energy flux density (EFD). Low doses of ESWA with an EFD below 0.15 mJ/mm2 release significantly less energy than extracorporeal shock wave lithotripsy (ESWL).

Although ESWA has proven to accelerate tissue repair in acute and chronic wounds [4], until today only little is known about its exact wound healing mechanisms especially in burn injuries. The effect of ESWA on angiogenesis and inflammation is crucial for the enhanced results in skin flap tissue survival. Kuo et al. could show in the dorsal skin random flap model in rodents that shock waves can increase topical blood perfusion. This increase correlated with suppression of tumor necrosis factor alpha and reduced leukocyte infiltration [5]. Similar examples may be found in previously conducted studies, where for instance ESWA was applied in murine isografts [6] and its tissue response was analyzed in terms of microcirculatory parameters. Yet a comparative analysis of angiogenic gene expression in normal versus diabetic mice with impaired wound healing has failed to show any impact of ESWA on tissue repair and wound closure. Multiple doses of ESWA have shown to improve wound healing [7]. Until today, there is no consensus on which type of wounds are most likely to benefit from shock waves as well as on how shock wave parameters such as energy, degree of focus and frequency or number of cycles must be chosen in order to achieve excellent results [8].

Due to inflammation and undersupply with O2 and other vital nutrients caused by the microcirculatory breakdown, burn wounds remain a special challenge in wound care. The main treatment consists of substitution of physiological saline solution as well as local antiseptics and symptomatic medication [9], [10].

Due to this lack of a causal therapy, the aim of this study was to assess the potential of ESWA in inducing angiogenesis in such wounds and therefore allow for faster healing. This could potentially be not only applied to the burn wounds itself, but also secondary wounds resulting from skin grafts and their donor sites. While excision and grafting remains the standard for deep dermal or full thickness burns, even burn specialists might disagree on the treatment of more superficial burns. For example, scalding burns with their mix in depth are often hard to assess and the both grafting as well as allowing for primary healing might lead to good results. Also technical support to objectify a wound assessment often fail [11]. These areas could benefit by a stimulus of ESWA. By treating grafts with ESWA the take rate as well as the velocity of ingrowth could be improved. By treating the donor sites wound healing and epithelialization could be accelerated, allowing potential reharvesting, reducing potential infections and reducing the open total body surface.

In a previously conducted study it was possible to show how ESWA positively impact angiogenesis following burn injury. Until now, nothing is known about the potential benefit or disadvantage for angiogenesis of repetitive applications of extracorporeal shock waves. Therefore, the main purpose of this study was to examine whether increased repetitive extracorporeal shock wave applications result in improved angiogenic activity compared to fewer repetitions following full thickness burn [12]. Another aim was to investigate possible changes in the inflammatory response caused by ESWA.

Section snippets

Materials and methods

44 male hairless SKH-1/hr mice (four groups, n = 11 per group, bodyweight: 22.1 ± 0.3 g (mean ± SEM), age 4–5 weeks) were obtained from Charles River Laboratories (Sulzfeld, Germany). Mice were sustained in accordance to German animal welfare regulations, which comply with international guidelines of animal welfare and their use in scientific experiments. Regional authorities have also approved of all investigations. All mice underwent single housing in standard polycarbonate cages (21 °C, 12 h

Results

Three animals, one from group A, one from group C and one from control group, were excluded from the study as they showed ear perforations.

Discussion

To reduce the likeliness of hypertrophic scars and dissatisfactory aesthetic results as well as to prevent local and systemic infections, fast re-epithelialization—which represents the last step of the wound healing process—is of key importance. However, therapies specifically targeting acceleration of wound healing are still missing [10].

Conflict of interest statement

My coworker and I herewith certify that there is no financial or proprietary interest in the subjected matter or materials discussed in this manuscript.

Acknowledgements

The authors thank the Vogelsang Foundation, Bochum, Germany for their financial support.

References (32)

  • A. Rawlingson et al.

    Functional significance of inducible nitric oxide synthase induction and protein nitration in the thermally injured cutaneous microvasculature

    Am J Pathol

    (2003)
  • F. Di Meglio et al.

    Cardiac shock wave therapy: assessment of safety and new insights into mechanisms of tissue regeneration

    J Cell Mol Med

    (2012)
  • M.A. Reichenberger et al.

    Comparison of extracorporal shock wave pretreatment to classic surgical delay in a random pattern skin flap model

    Plast Reconstr Surg

    (2011)
  • R. Mittermayr et al.

    Extracorporeal shock wave therapy (ESWT) minimizes ischemic tissue necrosis irrespective of application time and promotes tissue revascularization by stimulating angiogenesis

    Ann Surg

    (2011)
  • Y.R. Kuo et al.

    Extracorporeal shock-wave therapy enhanced wound healing via increasing topical blood perfusion and tissue regeneration in a rat model of STZ-induced diabetes

    Wound Repair Regener

    (2009)
  • A. Stojadinovic et al.

    Angiogenic response to extracorporeal shock wave treatment in murine skin isografts

    Angiogenesis

    (2008)
  • Cited by (0)

    1

    O. Goertz and L. von der Lohe contributed equally to the study.

    View full text