Surgical reconstruction in patients with cancer of the head and neck

Injectable cell/hydrogel microspheres induce the formation of fat lobule-like microtissues and vascularized adipose tissue regeneration

In this paper, we demonstrated that collagen/alginate microspheres could be generated by a non-contact microfabrication device and serve as excellent cell embedding and delivery devices as they were porous, injectable and able to provide growth- and differentiation-supporting matrix for human adipose-derived stem cells (hASCs). The microsphere matrix demonstrated highly porous structure and mechanical stability for as long as 90 days. hASCs demonstrated high viability after microsphere formation as well as higher proliferation and more mature adipocytes induction compared to two-dimensional culture. After four weeks culture in adipogenic differentiation medium, adipocytes/collagen/alginate microspheres highly mimicking natural fat lobules were obtained and injected subcutaneously into the head of node mice. The in vivo study demonstrated vascularized adipose tissue formation in four weeks. The regenerated vasculature among the transplantation showed functional anastomosis with host vasculature, suggesting that these cell/hydrogel microspheres present injectable adipocytes delivery devices capable of generating vascularized adipose tissue in vivo and thus suitable for cell transplantation and tissue regeneration.

Skin graft take rates, granulation, and epithelialization: dependence on myeloid cell hypoxia-inducible factor 1alpha

OBJECTIVE

To compare the "take" rates of skin grafts between myeloid-selective hypoxia-inducible factor (HIF) 1alpha knockout (KO) and wild-type (WT) mice. Production of the alpha subunit of HIF-1alpha is increased in healing wounds, which stimulates expression of vascular endothelial growth factor (VEGF) to promote angiogenesis. Therefore, the take rate of skin grafts may be closely associated with the presence or absence of HIF-1alpha production in the recipient bed.

DESIGN

The percentage of healthy graft areas obtained by planimetry and scores for epithelialization and granulation tissue formation obtained by histopathologic analysis were compared in 12 KO and 12 WT mice following skin grafting.

RESULTS

The graft take rate was significantly impaired in the KO group (P = .009), whereas epithelialization (P = .46) or granulation (P = .41) tissue formation scores did not reveal any significant differences.

CONCLUSION

Hypoxia-inducible factor 1alpha in myeloid cells may be an important molecule for revascularization of avascular tissues such as skin grafts, probably owing to its stimulating effect on angiogenesis.

Vascularized adipose tissue grafts from human mesenchymal stem cells with bioactive cues and microchannel conduits

Vascularization is critical to the survival of engineered tissues. This study combined biophysical and bioactive approaches to induce neovascularization in vivo. Further, we tested the effects of engineered vascularization on adipose tissue grafts. Hydrogel cylinders were fabricated from poly(ethylene glycol) diacrylate (PEG) in four configurations: PEG alone, PEG with basic fibroblast growth factor (bFGF), microchanneled PEG, or both bFGF-adsorbed and microchanneled PEG. In vivo implantation revealed no neovascularization in PEG, but substantial angiogenesis in bFGF-adsorbed and/or microchanneled PEG. The infiltrating host tissue consisted of erythrocyte-filled blood vessels lined by endothelial cells, and immunolocalized to vascular endothelial growth factor (VEGF). Human mesenchymal stem cells were differentiated into adipogenic cells, and encapsulated in PEG with both microchanneled and adsorbed bFGF. Upon in vivo implantation subcutaneously in immunodeficient mice, oil red O positive adipose tissue was present and interspersed with interstitial fibrous (IF) capsules. VEGF was immunolocalized in the IF capsules surrounding the engineered adipose tissue. These findings suggest that bioactive cues and/or microchannels promote the genesis of vascularized tissue phenotypes such as the tested adipose tissue grafts. Especially, engineered microchannels may provide a generic approach for modifying existing biomaterials by providing conduits for vascularization and/or diffusion.

Plastische Deckung von Weichteildefekten im Gesicht

The difficulties in facial reconstruction derive from the unique character of the face and the availability of local matching tissues. Facial reconstructive surgery must aim at a functionally and aesthetically rehabilitated patient. The performance of facial plastic surgery requires an understanding and the application of many important principles. The aim of this paper is to review the critical factors to be considered in the management of surgical wounds by second-intention healing, primary closure, skin grafting, and repair with local or distant free flaps. The key concepts useful in flap choice and implementation are discussed. In addition, an overview of new developments in tissue engineering and gene therapy as they relate to facial plastic surgery is provided.