Senescence of donor cells impairs fat graft regeneration by suppressing adipogenesis and increasing expression of senescence-associated secretory phenotype factors

Abstract

Background Fat grafting has been regarded as a promising approach for regenerative therapy. Given the rapidly aging population, better understanding of the effect of age on fat graft outcomes and the underlying mechanisms is urgently needed. Methods C57/BL6 mice [old (O, 18–20-month-old) and young (Y, 4-month-old)] were randomized to four fat graft groups [old-to-old (O-O), young-to-young (Y-Y), old-to-young (O-Y), and young-to-old (Y-O)]. Detailed cellular events before and after grafting were investigated by histological staining, RNA sequencing, and real-time polymerase chain reaction. The adipogenic differentiation potential of adipose-derived mesenchymal stem cells (AD-MSCs) from old or young donors was investigated in vitro. Additionally, adipogenesis of AD-MSCs derived from old recipients was evaluated in the culture supernatant of old or young donor fat tissue. Results After 12 weeks, the volume of fat grafts did not significantly differ between the O-O and O-Y groups or between the Y-Y and Y-O groups, but was significantly smaller in the O-O group than in the Y-O group and in the O-Y group than in the Y-Y group. Compared with fat tissue from young mice, senescence-associated secretory phenotype (SASP) factors were upregulated in fat tissue from old mice. Compared with the Y-O group, adipogenesis markers were downregulated in the O-O group, while SASP factors including interleukin (IL)-6, tumor necrosis factor-α, and IL-1β were upregulated. In vitro, AD-MSCs from old donors showed impaired adipogenesis compared with AD-MSCs from young donors. Additionally, compared with the culture supernatant of young donor fat tissue, the culture supernatant of old donor fat tissue significantly decreased adipogenesis of AD-MSCs derived from old recipients, which might be attributable to increased levels of SASP factors. Conclusions Age has detrimental effects on fat graft outcomes by suppressing adipogenesis of AD-MSCs and upregulating expression of SASP factors, and fat graft outcomes are more dependent on donor age than on recipient age. Thus, rejuvenating fat grafts from old donors or banking younger adipose tissue for later use may be potential approaches to improve fat graft outcomes in older adults.

Senescence induces fundamental changes in the secretome of mesenchymal stromal cells (MSCs): implications for the therapeutic use of MSCs and their derivates

“…Currently, optimized and combined algorithms of different senescence-related biomarkers are the better option for the identification and isolation of senescent cells within a cell population. The main parameters used to identify senescent cells are: i) cell morphology; ii) evaluation of the expression of cell cycle regulators, such as P53, P21-CIP1, P16-INK4A, P38-MAPK, P14-ARF, at their transcriptional and translational levels; iii) detection of the expression of retinoblastoma gene family (RB1, RB2/P130, P107); iv) determination of senescence associated lysosomal β-galactosidase activity (SA-β-gal); v) identification of critical shorting of telomere DNA sequence length; and vi) lipofuscin detection using GL13 staining ( Dimri et al, 1995 ; Debacq-Chainiaux et al, 2009 ; Georgakopoulou et al, 2013 ; Alessio et al, 2017 ; Evangelou et al, 2017 ; Salmonowicz and Passos, 2017 ; Son et al, 2019 ; Jannone et al, 2020 ; Chen et al, 2021 ; Ogrodnik, 2021 ; Guan et al, 2022 ; Wagner and Wagner, 2022 ; Weng et al, 2022 ). There are also website tools that may help in the identification of senescent cells.…”