Platelet Lysate Activates Human Subcutaneous Adipose Tissue Cells by Promoting Cell Proliferation and Their Paracrine Activity Toward Epidermal Keratinocytes.

Alessio Romaldini,Maddalena Mastrogiacomo,Ranieri Cancedda,Fiorella Descalzi

doi:10.3389/fbioe.2018.00203

Alessio Romaldini, Maddalena Mastrogiacomo + Show 2 more

Open Access

https://doi.org/10.3389/fbioe.2018.00203

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Abstract

Skin chronic wounds are non-healing ulcerative defects, which arise in association with a morbidity state, such as diabetes and vascular insufficiency or as the consequence of systemic factors including advanced age. Platelet Rich Plasma, a platelet-rich blood fraction, can significantly improve the healing of human skin chronic ulcers. Given that the subcutaneous adipose tissue is located beneath the skin and plays a role in the skin homeostasis, in this study, we investigated the in vitro response of human subcutaneous adipose tissue cells to platelet content in a model mimicking in vitro the in situ milieu of a deep skin injury. Considering that, at the wound site, plasma turn to serum, platelets are activated and inflammation occurs, human adipose-derived stromal cells (hASC) were cultured with Human Serum (HS) supplemented or not with Platelet Lysate (PL) and/or IL-1α. We observed that HS sustained hASC proliferation more efficiently than FBS and induced a spontaneous adipogenic differentiation in the cells. PL added to HS enhanced hASC proliferation, regardless the presence of IL-1α. In the presence of PL, hASC progressively lessened the adipogenic phenotype, possibly because the proliferation of less committed cells was induced. However, these cells resumed adipogenesis in permissive conditions. Accordingly, PL induced in quiescent cells activation of the proliferation-related pathways ERK, Akt, and STAT-3 and expression of Cyclin D1. Moreover, PL induced an early and transient increase of the pro-inflammatory response triggered by IL-1α, by inducing COX-2 expression and secretion of a large amount of PGE2, IL-6, and IL-8. Media conditioned by PL-stimulated hASC exerted a chemotactic activity on human keratinocytes and favored the healing of an in vitro scratch wound. In order to bridge the gap between in vitro results and possible in vivo events, the stimuli were also tested in ex vivo cultures of in toto human adipose tissue biopsies (hAT). PL induced cell proliferation in hAT and outgrowth of committed progenitor cells able to differentiate in permissive conditions. In conclusion, we report that the adipose tissue responds to the wound microenvironment by activating the proliferation of adipose tissue progenitor cells and promoting the release of factors favoring wound healing.

Highlights

When a tissue or an organ is affected by an injury, the human body responds immediately by activating the wound-healing cascade
By focusing our attention on the molecular mechanisms activated by platelet-derived factors in skin wound healing, we previously investigated the effects of Platelet Lysate (PL) on human keratinocytes and we showed that PL-stimulated resting cells transiently produced increased levels of the inflammatory cytokine IL-8 and of the antimicrobial peptide NGAL, via p38 MAPK and NF-κB activation, and that the wound closure in an in vitro scratch assay was accelerated upon PL stimulation (El Backly et al, 2011)
We addressed the possible role played by the human subcutaneous adipose tissue in supporting the repair/regeneration process of skin wounds, given that such tissue is located beneath the skin and it physiologically contributes to re-establish the homeostasis of the damaged skin

Summary

Introduction

When a tissue or an organ is affected by an injury, the human body responds immediately by activating the wound-healing cascade. Repair of large and deep lesions often results in fibrosis and scar formation, leading to a function reduction or a loss. Regenerative medicine was born and is developing with the aim to promote the regeneration of a fully functional tissue or organ structure and to prevent or delay the scarring process. It is our believe that the new frontier of regenerative medicine should head toward approaches able to reactivate and enhance dormant endogenous regenerative mechanisms (Cancedda et al, 2017). The fundamental condition for designing and developing these new clinically relevant tools is to know in detail the natural tissue response to an injury in order to identify the pathways to be activated and the ones to be limited

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