An injectable adipose matrix for soft-tissue reconstruction

Abstract

Background: Soft-tissue repair is currently limited by the availability of autologous tissue sources and the absence of an ideal soft-tissue replacement comparable to native adipose tissue. Extracellular matrix-based biomaterials have demonstrated great potential as instructive scaffolds for regenerative medicine, mechanically and biochemically defined by the tissue of origin. As such, the distinctive high lipid content of adipose tissue requires unique processing conditions to generate a biocompatible scaffold for soft-tissue repair.

Methods: Human adipose tissue was decellularized to obtain a matrix devoid of lipids and cells while preserving extracellular matrix architecture and bioactivity. To control degradation and volume persistence, the scaffold was cross-linked using hexamethylene diisocyanate and 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide. In vitro studies with human adipose-derived stem cells were used to assess cell viability and adipogenic differentiation on the biomaterial. In vivo biocompatibility and volume persistence were evaluated by subcutaneous implantation over 12 weeks in a small-animal model.

Results: The scaffold provided a biocompatible matrix supporting the growth and differentiation of adipose-derived stem cells in vitro. Cross-linking the matrix increased its resistance to enzymatic degradation. Subcutaneous implantation of the acellular adipose matrix in Sprague-Dawley rats showed minimal inflammatory reaction. Adipose tissue development and vascularization were observed in the implant, with host cells migrating into the matrix indicating the instructive potential of the matrix for guiding tissue remodeling and regeneration.

Conclusions: With its unique biological and mechanical properties, decellularized adipose extracellular matrix is a promising biomaterial scaffold that can potentially be used allogenically for the correction of soft-tissue defects.

Figures

Figure 1

Processed adipose tissue matrix (left) and histological image of decellularized adipose tissue showing no remnants of cellular components (center). Immunostaining for type I collagen confirms it as the predominant component of adipose extracellular matrix (right).

Figure 2

Scanning electron microscopy images of processed adipose ECM without cells (left) and 48 hours after seeding with cells (right).

Figure 3

Crosslinked matrices show increased resistance to enzymatic degradation. Percent of total collagen degraded over 24 hours when incubated with collagenase for uncrosslinked control tissue and matrices crosslinked with 5-100 mM EDC (above), 1% and 5% HMDC in Tween 20 (center), 1% and 5% HMDC in 2-propanol (below). Error bars denote standard deviation.

Figure 4

Gross (above) and histological images (below) of adipose matrix from the in vivo rat study for uncrosslinked control (left), 5 mM EDC crosslinked (center), and 1% HMDC crosslinked ECM (right). Specimens are stained with Masson’s trichrome and the adiposederived matrix is denoted by an asterisk.

Figure 5

Histology of adipose ECM implants after four weeks in Sprague Dawley rats stained with hematoxylin and eosin (left), Oil red O for lipids (center), CD31 (above, right), and CD44 (below, right).

Figure 6

At 12 weeks in the subcutaneous rat study, adipose matrix implants show substantial areas of adipose tissue development and collagen remodeling by host cells.