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The Biointegration of a Porcine Acellular Dermal Matrix in a Novel Radiated Breast Reconstruction Model.

BACKGROUND
Ideal acellular dermal matrices (ADM) for breast reconstruction exhibit native extracellular matrix (ECM) structure to allow rapid biointegration and appropriate mechanical properties for desired clinical outcomes. In a novel in vivo model of irradiated breast reconstruction, we describe the cellular and vascular ingrowth of Artia, a porcine product chemically prepared to mimic the biomechanics of human ADM, with retained natural ECM structure to encourage cellular ingrowth.


METHODS
Utilizing the murine dorsal skinfold model, Artia was implanted into 16 C57bl/6 mice. Eight of the mice received a single dose 35 Gy radiation to the skin, followed by 12 weeks to produce radiation fibrosis and 8 mice served as nonradiated controls. Real-time photoacoustic microscopy of vascular integration and oxygen saturation within the ADM were made over 14 days. At 21 days, vascular ingrowth (CD31), fibroblast scar tissue formation (alpha smooth-muscle actin α-SMA, vimentin), and macrophage function (M2/M1 ratio) were evaluated. Scanning electron microscopy images of Artia were produced to help interpret the potential orientation of cellular and vascular ingrowth.


RESULTS
Repeated photoacoustic microscopy imaging demonstrated vascular ingrowth increasing over 14 days, with a commensurate increase in oxygen saturation within both radiated and nonradiated ADM-albeit at an insignificantly lower rate in the radiated group. By day 21, robust CD31 staining was seen that was insignificantly greater in the nonradiated group. Of the fibroblast markers, vimentin expression was significantly greater in the radiated group (P < 0.05). Macrophage lineage phenotype was consistent with remodeling physiology in both radiated and nonradiated groups. Scanning electron microscopy demonstrated transversely organized collagen fibrils with natural porous ECM structure to allow cellular ingrowth.


CONCLUSIONS
Artia demonstrates appropriate biointegration, with increased oxygen saturation by 14 days, consistent with the performance of other collagen substrates in this model. Radiation fibrosis resulted in higher vimentin expression yet did not impact macrophage phenotype while only modestly decreasing Artia biointegration suggesting that ADM may have a role in reconstructive efforts in a radiated setting. Taken together with its enhanced biomechanics, this porcine ADM product is well poised to be clinically applicable to breast reconstruction.