Therapeutic potential of a biomatrix (Askina gel) in regenerative medicine

Neovascularization is a critical determinant in wound-healing outcomes for several kinds of injuries. Tissue engineering is continuously searching for matrixes, scaffolds, cells and growth factors to create microenvironment able to promote tissue regeneration. Moreover, an adequate vascularization of the wound milieu is a necessary goal in regenerative medicine also in the case of transplanted cells utilization. A new focus of interest in regenerative medicine research is represented by the use of mesenchymal stem cells (MSCs). They are capable of self-renewal and multi-lineage differentiation and can be considered a potential autologous cell source. Adipose-derived stem cells (ASCs) represent an abundant source of MSCs easily accessible from subcutaneous and visceral adipose tissue. ASCs can be cultured as monolayers on tissue culture plastic loosing in this way cell-specific properties and so poorly reflect in vivo ASCs behaviour. We suggest that a sterile hydrogel (Askina® Gel) containing a modified starch polymer and commonly used in surgery, could serve as scaffold to improve neovascularization and cell regeneration. Therefore, we first evaluated the ability of this hydrogel to promote tubule formation in vitro using mouse endothelial cells (MS-1). We observed that when cultured on hydrogel, MS-1 form spontaneously capillary-like structures after 36-48 h from seeding. Conversely, MS-1 pretreated with an inhibitor of VEGFR2 (SU 1498) were not able to make tubules at the same times. In parallel, hydrogel samples were surgically implanted in the back of CD-1 mouse, and harvested at 7-10 days post-implantation. The analysis of hydrogel plugs cryosections by H&E staining and by immunofluorescence revealed a remarkable neovascularization in hydrogel plugs preloaded with growth factors. Finally, since ACSs can form three-dimensional spheroids with increased stemness capability when cultured on biomaterials, we tested the ability of ASCs isolated from human abdominal adipose tissue recovered from obese subjects (35-45 years old), to form spheroids on hydrogel. We demonstrated that hydrogel was effectively able to promote spherical cell aggregates formation that most of the cells into spheroids were viable. In conclusion, these preliminary results suggest that hydrogel, besides conventional use in surgery, could be used as good vehicle for the retention of transplanted stem cells at the cell graft promoting neo-angiogenesis and tissue regeneration.