Stem cells derived from fat - or adipose tissue derived stem cells (ADSCs) - have been reported to greatly accelerate the wound healing process. It is thought that they help the body to repair by secreting beneficial biomolecules such as growth factors and cytokines. Dr Wenxin Wang’s group aim to develop a scaffold material that can easily encapsulate ADSCs so that they can be delivered effectively to chronic wounds.
Firstly, the team set out to develop a suitable hydrogel system that can provide support to human ADSCs. The material needs to be able to maintain these hADCs as stem cells and encourage them to secrete factors that promote blood vessel formation. They designed and made a material (a PEG-based thermo-responsive hyperbranched copolymer PEGMEMA475-MEO2MA-PEGDA258) through a ‘one-pot and one-step’ DE-ATRP and RAFT method that developed in their laboratory.
When this polymer solution is applied as a liquid to the wound and adjusts to body temperature, the dressing becomes more gel-like. In addition, this polymer can be further chemically cross-linked in minutes to make the hydrogel more mechanically robust.
Next, the team looked at how human ADSCs behave when they are encapsulated in the delivery material. They found that when cells were in the hydrogel scaffold, they survived and grew well with more than 83% viability and maintenance of proliferation (figures 1 & 2) and secreted molecules called growth factors. Also, within 7 days of the cells being encapsulated in the hydrogel, there was an increased production of blood-vessel promoting growth factors (PlGF, VEGF) (figure 3), which suggests great potential for stem cell therapy via an in situ topical delivery system for wound healing applications.
The next objective is to show that the stem cells can maintain their ‘stemness’ or ability to form new cell types when they are within the hydrogel scaffold. Their preliminary results show that human ADSCs make molecules that act as stem cell markers (Oct-4, Sox-2 and Klf-4) after the cells have been encapsulated in the scaffold material, and that the cells can be induced to mature as other cell types, suggesting that they are keeping their ‘stemness’ in the material.