Biomedical Engineering Reference
In-Depth Information
excellent retention properties. Whilst macrophages were
observed inside the gel after the first week, the inflamma-
tory response was weak, with small levels of cytokines such as
transforming growth factor-
β
(TGF-
β
). Mature adipocytes were
observed after week 8, with significant numbers of cells at week
12 of varying dimensions, indicating
de novo
adipogenesis rather
thanrecruitmentofmaturecells.Itisconcludedthattheamidated
hyaluronongelisanexcellentmaterialforregeneratingsofttissue,
which actively drives adipogenesis.
5.1 Introduction
There is a major clinical need for the reconstruction of soft tis-
sues, mainly to repair congenital defects (e.g., Romberg's disease or
Poland syndrome),
1
,
2
burns, injury, or resection of tumors. Tradi-
tional therapeutic practices have generally been found not to func-
tion adequately. Transplantation of mature, autologous fat tissue or
free-fat transplantation,
3
,
4
for example, has an unreliable outcome
ranging from complete resorption and gross shrinkage of the graft
to the formation of oily cysts. Common fillers of small defects, such
as collagen, native hyaluronic acid, or synthetic polymers such as
poly(methyl methacrylate) (PMMA) and silicone, generally have a
shortresidencetimeinsubcutaneoustissueandcancauseachronic
host response.
5
-
8
In contrast, cell-based tissue engineering and regenerative
therapeutic strategies have been heralded as a novel and promis-
ingapproachtothereconstructionofdefectivetissues,includingsoft
tissue.Thestromal-vascularfractionofadiposetissuecontainslarge
quantitiesofpluripotentmesenchymalprogenitorcells
9
,
10
thathave
a high proliferative and differentiation potential, making them ideal
candidatescellsforthisapplication.Inaddition,ithasbeenreported
that adipogenic progenitor cells have a lower oxygen consump-
tion than mature adipocytes,
11
constructive for engineered tissues,
which have an inadequate vascular supply.
However, whilst various published
in vitro
studies clearly
demonstrate that preadipocytes within a range of polymers will
differentiate into mature fat tissue,
in vivo
results have not been as
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