The stretching of skin studied with 3D microscopy.
Can we make 3D movies of collagen and elastin bundles in skin tissue to eventually help patients with large skin defects? To answer this question, PhD student Ludo van Haasterecht set out 4 years ago to study human healthy and scar tissue, in a collaboration between LaserLab from the Vrije Universiteit, the Rode Kruis Ziekenhuis, Humeca BV, and the Dutch Burn foundation.
In clinical practice, plastic surgeons are often faced with large skin defects that are difficult to close primarily. Different techniques have become available but most of them have a poor cosmetic outcome. For certain indications the skin stretching technique can be used. By stretching the adjacent healthy skin the availability of surrounding skin is increased and the tension at the wound edges is reduced. But this technique has its limitations with respect to the size of reconstruction. These limitations are most likely related to the adaptability of the collagen network. Collagen is considered to be predominantly responsible for qualities of healthy skin and the unique combination of strength and suppleness. To explore the limits of such stretching procedure and to be able to optimise this approach, we need a better understanding of the architecture and function of the dermal architecture.
To this end, Ludo built a so-called skin-stretching microscope, with which he could follow the structural change of collagen, elastin and cells 'live' with sub-micron resolution, while it was being stretched, with sub-micron resolution, in 3D. The imaging techniques were 2nd harmonic generation and multi-photon auto-fluorescence. Measurements in which skin was stretched in one direction up to 150% showed that the collagen bundles align in the stretch direction, lengthen and eventually break. The total force at which this happened varied between 1 and 4 MPa. This is the first study ever of this kind on human skin.
The exact behavior of the stress-strain curves and the associated structural changes under stress will be reported in two separate scientific publications. The first focuses on collagen, the second reports on a larger dataset and includes the role of elastin. In addition, they are preparing a publication on a neural network to predict the stress-strain behavior from the 2D microscopic images. The study has led to ideas to improve the clinical skin stretching device, and how to translate the insights into clinical practice.