Scientists at Germany's Hohenstein Institute say that although liposuction has been a standard medical procedure in cosmetic surgery for many years, surgeons are still searching for fat tissue substitutes to provide better treatment for patients with large soft tissue defects.

Against this background researchers at the Institute for Hygiene and Biotechnology (IHB) at the Hohenstein Institute have now succeeded in establishing a reasonably sized fat implant under laboratory conditions for the first time. First of all, they successfully differentiated adult stem cells into fat cells while growing them on biodegradable fibres (Fig. 1). Using the same method, they were then able to grow human adult stem cells on three-dimensional implants and differentiated them into fat cells (Fig. 2).

Reconstructive surgery

In reconstructive surgery, replacing soft tissue to treat wounds with large tissue defects is said to represent a great challenge, e.g. in the case of pressure ulcers or large-scale scarring (Fig. 3). Until now, plastic surgeons have been using skin flaps for the reconstruction of soft tissue - a procedure that is said to strongly strain healthy surrounding tissue and therefore the whole patient.

"Depending on the size of the tissue defect, tissue expanders are used to stretch the healthy skin and fat tissue for several weeks. It also requires few surgical interventions in order to prepare the wound area and the tissue flaps before transplantation: these processes are associated with many risks for the patient such as hypothermia, cardiovascular problems or wound infections. Currently there is no suitable fat tissue substitute that can be easily transplanted and provides a long-term solution in the treatment of soft tissue defects," the Hohenstein Institute says.

Textile implants

The team of scientists led by Prof. Dr. Dirk Höfer, Director of the IHB, is dealing with the question of how textile implants could be complemented with patient's own stem cells so that it can therefore be used more effectively in plastic and reconstructive surgery. The scientists cultivated dense layers of human adult stem cells on fibres, meshes and nonwovens made of biodegradable biopolymers as shown in previous experiments (Fig. 4).

In addition they were able to show that fibre-bound stem cells release growth factors that promote the formation of new blood vessels at the implantation site by using hatched chicken eggs as a vascular model (CAM angiogenesis model). Within a very short time, the researchers say, new blood vessels grew into the biological modified textile implants and formed a functional capillary network (Fig. 5).

Against this background, the scientists at the IHB continued their work with regard to the development of a fat tissue substitute. Their objective was to establish a biopolymer fibre based soft tissue substitute with enhanced biocompatibility suitable for the treatment of extensive tissue defects. The challenges they face are:

• Growing patient's own stem cells on biodegradable textiles implants (future, cell-based medication)
• Rapid formation of new blood vessels into the fat tissue substitute to promote wound healing and to ensure an adequate supply of nutrients to the transplanted tissue
• Implant-induced differentiation of the patient's own stem cells into fat cells - preferable directly in the patient's body, and
• Adapting the implant individually to form, shape and three-dimensionality for each patient

Considering these results, the Hohenstein scientists aimed to grow patient's own stem cells on three dimensional implants made of biopolymers. These adult stem cells could be differentiated into fat cells in order to build a soft tissue substitute without causing inflammatory responses or transplant rejection.

Further information

Prof. Dr. Dirk Höfer, (Director of the Institute for Hygiene and Biotechnology at the Hohenstein Institute)

E-mail: [email protected]