@article {17810, title = {Gellan Gum-Hyaluronic Acid Spongy-Like Hydrogels And Adipose Tissue-Derived Lineages Synergise Towards Skin Regeneration}, journal = {TERMIS AM13}, year = {2013}, month = {2013-11-15 00:00:00}, abstract = {

Upon massive loss/burns adult human skin heals mainly by repair mechanisms that lead to undesirable wound contraction and evident scar formation. Therefore, strategies capable of promoting skin regeneration are of major importance in this field. It is believed that insufficient re-vascularization after grafting is one of the events that most contribute to fibrosis (1, 2). Pre-vascularization of skin substitutes, despite the limitation still encountered with the source of endothelial cells, turned out to be a promising approach for a more efficient inosculation, consequently improving wound healing. Under this context, we proposed a skin tissue engineering (TE) strategy that combines an off-the-shelf scaffold with human adipose stem cells (hASCs) and microvascular endothelial cells (hAMECs) to promote skin tissue regeneration by modulating neovascularization and the intricate cascade of events that drive skin wound healing. The innovative character of the proposed approach relies on taking advantage of a powerful cell-machinery obtained from a single cell source, yet holding a potential immunomodulatory capacity, combined with a gellan gum-hyaluronic acid spongy-like hydrogel (GG-HA), which, unlike traditional hydrogels, depict cell adhesive properties and\  attractive mechanical performance.

Materials and Methods

GG-HA Spongy-like hydrogels were obtained, following a patented methodology (3), from GG-HA hydrogels and upon re-hydration of a freeze dried polymeric network. These structures, stable for more than one year, were analyzed in terms of microarchitecture by micro-CT and scanning electron microscopy (SEM), of water uptake ability. hASCs and hAMECs were isolated from the digestion of same human lipoaspirate with collagenase and\  characterized by flow cytometry considering the mesenchymal and endothelial phenotypic markers.\  Spongy-like hydrogels were formed by hydration of the dried polymeric structures, at the time of cell seeding, either by dropwise addition of the hASCs and hASCs plus hAMECs suspensions respectively forming homotypic \ \ and heterotypic constructs, or culture medium forming acellular structures used as control. Constructs were implanted in nude mice skin full-thickness excisional wounds and analyzed at day 3, 7, 14 and 21 post surgery regarding wound closure, repithelialization and vascularization.\  Empty wounds were set as control group.

Results

Obtained dried GG-HA polymeric networks were able to reach 2000\% of the initial weight within 15 minutes of hydration in culture medium, forming the spongy-like hydrogels and yet enabling the natural\ 

entrapment/encapsulation and consequent attachment of the cells within its porous microarchitecture

After transplantation to full-thickness wounds in mice, GG-HA spongy-like hydrogels showed to facilitate the early inflammatory cell infiltration, translated by a dense granulation tissue formation. With time this resulted in a rapid degradation and matrix remodeling, and complete wound closure and reepithelization. More importantly, the combination of the hASCS and GG-HA spongy-like hydrogels promoted neovascularization (Fig. 1A) that was further enhanced by the incorporation of hAMECs that were found incorporated in the neovessels (Fig. 1B).

Discussion and Conclusions

This work proposes a strategy that takes advantage of a abundant cell source, adipose tissue, and of improved GG-HA structures to promote skin regeneration. The\  significant amount of granulation tissue formed upon implantation contributed to faster matrix degradation and remodelling, thus accelerating the healing process. This effect synergized with the transplanted endothelial cells signalling towards the formation of an improved vascular network. By gathering an off-the-shelf dried network and two cell types obtained in a relatively short timeframe from the same source, we were able to demonstrate the possibility of creating a clinically relevant skin tissue substitute that acts in promoting neotissue vascularization

References:\ 

1.Boyce ST (2001) Burns 27(5):523-533,

2. Metcalfe AD \& Ferguson MW (2007) Biomaterials 28(34):5100-5113.

3. da Silva, L., Gellan Gum-based spongy-like hydrogels: methods and biomedical applications thereof, patent submitted 20131000027163

}, keywords = {gellan gum spongy-like hydrogel, Human adipose stem cells}, author = {Cerqueira, M. T. and da Silva, L. P. and Santos, T. C. and Pirraco, R. P. and Correlo, V. M. and Marques, A. P. and Reis, R. L.} }