Abstract
Cell-based therapies involving the delivery of adipose-derived stromal cells (ASCs) on decellularized adipose tissue (DAT) scaffolds are a promising approach for soft tissue augmentation and reconstruction. Our lab has recently shown that culturing human ASCs on DAT scaffolds within a perfusion bioreactor prior to implantation can enhance their capacity to stimulate in vivo adipose tissue regeneration. Building from this previous work, the current study investigated the effects of bioreactor preconditioning on the ASC phenotype and secretory profile in vitro, as well as host cell recruitment following implantation in an athymic nude mouse model. Immunohistochemical analyses indicated that culturing within the bioreactor increased the percentage of ASCs co-expressing inducible nitric oxide synthase (iNOS) and arginase-1 (Arg-1), as well as tumor necrosis factor-alpha (TNF-α) and interleukin-10 (IL-10), within the peripheral regions of the DAT relative to statically cultured controls. In addition, bioreactor culture altered the expression levels of a range of immunomodulatory factors in the ASC-seeded DAT. In vivo testing revealed that culturing the ASCs on the DAT within the perfusion bioreactor prior to implantation enhanced the infiltration of host CD31+ endothelial cells and CD26+ cells into the DAT implants, but did not alter CD45+F4/80+CD68+ macrophage recruitment. However, a higher fraction of the CD45+ cell population expressed the pro-regenerative macrophage marker CD163 in the bioreactor group, which may have contributed to enhanced remodeling of the scaffolds into host-derived adipose tissue. Overall, the findings support that bioreactor preconditioning can augment the capacity of human ASCs to stimulate regeneration through paracrine-mediated mechanisms.
Highlights
Tissue-engineering strategies represent a promising approach for the long-term augmentation and regeneration of damaged or deficient subcutaneous adipose tissue for applications in plastic and reconstructive surgery
Consistent with our previous findings that there was a significant increase in the density of erythrocyte-containing blood vessels in the decellularized adipose tissue (DAT) implants in the dynamic group at 4 and 8 weeks (Han and Flynn, 2020), CD31+ endothelial cell recruitment was significantly enhanced in the dynamic group at all three timepoints in the current study, suggesting that culturing within the bioreactor augmented the capacity of the adipose-derived stromal cells (ASCs) to stimulate angiogenesis within the implants
The findings of the current study support that dynamic preconditioning of human ASCs on the DAT scaffolds within the perfusion bioreactor under 2% O2 altered their phenotype and paracrine profile relative to controls cultured under static conditions
Summary
Tissue-engineering strategies represent a promising approach for the long-term augmentation and regeneration of damaged or deficient subcutaneous adipose tissue for applications in plastic and reconstructive surgery. While applying DAT as an off-the-shelf scaffold is appealing, studies have suggested that the rate and extent of adipose tissue regeneration can be enhanced by seeding the scaffolds with pro-regenerative progenitor cells (Young et al, 2014; Wang et al, 2013). This strategy may be critical for the larger volume augmentation that is required for many reconstructive applications in the clinic, as a lack of angiogenesis and host cell infiltration can result in implant failure. Through careful consideration of the cell culture microenvironment, it may be possible to design systems for cell expansion and preconditioning that would augment the capacity of the ASCs to stimulate regeneration, resulting in a more robust and predictable response that would justify the additional costs and regulatory hurdles involved
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