Microfragmented adipose tissue is associated with improved ex vivo performance linked to HOXB7 and b-FGF expression

Abstract

Introduction Adipose tissue (AT) has become a source of mesenchymal stromal/stem cells (MSC) for regenerative medicine applications, in particular skeletal disorders. Several enzymatic or mechanical procedures have been proposed to process AT with the aim to isolate cells that can be locally implanted. How AT is processed may impact its properties. Thus, we compared AT processed by centrifugation (C-AT) to microfragmentation (MF-AT). Focusing on MF-AT, we subsequently assessed the impact of synovial fluid (SF) alone on both MF-AT and isolated AT-MSC to better understand their cartilage repair mechanisms. Materials and methods MF-AT and C-AT from the same donors were compared by histology and qRT-PCR immediately after isolation or as ex vivo cultures using a micro-tissue pellet system. The in vitro impact of SF on MF-AT and AT-MSC was assessed by histological staining and molecular analysis. Results The main AT histological features (i.e., increased extracellular matrix and cellularity) of the freshly isolated or ex vivo-cultured MF-AT persisted compared to C-AT, which rapidly deteriorated during culture. Based on our previous studies of HOX genes in MSC, we investigated the involvement of Homeobox Protein HOX-B7 (HOXB7) and its target basic Fibroblast Growth Factor (bFGF) in the molecular mechanism underlying the improved performance of MF-AT. Indeed, both these biomarkers were more prominent in freshly isolated MF-AT compared to C-AT. SF alone preserved the AT histological features of MF-AT, together with HOXB7 and bFGF expression. Increased cell performance was also observed in isolated AT-MSC after SF treatment concomitant with enhanced HOXB7 expression, although there was no apparent association with bFGF. Conclusions Our findings show that MF has a positive effect on the maintenance of AT histology and may trigger the expression of trophic factors that improve tissue repair by processed AT.

HOX genes in stem cells: Maintaining cellular identity and regulation of differentiation

“…Interestingly, HOXB7 turned out to be an “universal MSC” HOX gene as it was reported to be expressed in all the different types of MSCs ( Liedtke et al, 2010 ; Klein et al, 2013 ; Foppiani et al, 2019 ). An induced expression of HOXB7 was identified as a master player driving proliferation and differentiation of human BM- and AT-MSCs ( Foppiani et al, 2019 ; Casari et al, 2021 ), and accounts for the high proliferation and sprouting potential of VW-MSCs ( Klein et al, 2013 ; Klein, 2016 ). However, rather than accounting for stem cell type-specific functions, HOX genes specify various regional properties of a tissue along the rostral-caudal axis by regulating a wide range of cellular activities such as proliferation and differentiation, cellular adhesion, migration and invasion, as well as cell death ( Parrish et al, 2009 ).…”

Molecular Mechanisms of Cartilage Repair and Their Possible Clinical Uses: A Review of Recent Developments

“…Bringing into sharp focus MF-AT, Casari et al afterward evaluated the effect of synovial fluid (SF) alone on both MF-AT and isolated AT-MSC to better comprehend their cartilage repair processes. The findings of this study showed that MF has a positive impact on the preservation of AT histology and might activate the expression of trophic factors that ameliorate tissue repair by processed AT [19].…”

“…Casari et al [19] These authors compared adipose tissue (AT) processed by centrifugation (C-AT) to microfragmentation (MF-AT). They evaluated the impact of synovial fluid (SF) alone on both MF-AT and isolated AT-MSC to better comprehend their cartilage repair processes.…”