Xenogenic induction of adipose tissue and maintenance through pre- and post-conditioning using external volume expansion

Date Published:

2022 Oct 07

Abstract:

External volume expansion (EVE) has been shown to improve fat graft survival. In this study, we investigated the xenogenic implantation of human allograft adipose matrix (AAM) in non-immunocompromised mice in combination with pre- and post-conditioning with EVE to assess long-term adipose tissue survival. Sixty-eight recipient sites in thirty-four eight-week-old wild type (C57BL/6J) mice were separated into four groups. Thirty-four sites received no conditioning and either a subcutaneous injection of 300 μl saline (n= 17; PBS group) or AAM (n= 17; AAM group). Thirty-four sites received pre-conditioning with EVE (Day -7-3 pre-grafting) and 300 μl of AAM. Seventeen of these sites received immediate post-conditioning (Day 1-5 post-grafting) and 17 delayed post-conditioning (Day 28-32 post-grafting). Tissue was harvested at week 12 for analysis. At 12 weeks, immediate and delayed post-conditioning enabled higher volume retention (p= 0.02 andp< 0.0001, respectively). Adipose Stem Cells were greater in the AAM+Del-EVE group compared to the AAM (p= 0.01). Microvessel density was lower in the AAM group compared to the AAM+Imm-EVE (p= 0.04) and AAM+Del-EVE group (p= 0.02). Macrophage infiltration was lower in the AAM+Imm-EVE (p= 0.002) and AAM+Del-EVE (p= 0.003) groups compared to the AAM group. PCR analysis and Western blotting identified a significantly higher expression of PPAR-γ, LPL and VEGF with delayed-conditioning. Pre- and post-conditioning, particularly delayed-post-conditioning, of the recipient site optimized the microenvironment allowing significant adipogenesis and survival of neo-adipose tissue through robust angiogenesis. This study supports that xenogenic transplantation of adipose matrix allows adipose tissue formation and survival with EVE as an adjuvant.