ABSTRACT
Inflammation is a normal phase of the wound healing process, which likely occurs following tissue transplantation. For reconstructive surgery purposes, engineered adipose tissues represent promising alternatives to autologous fat grafts. It is therefore important to study the impact of an inflammatory microenvironment on the cellular functions of the different cell types comprised within matrix-rich reconstructed tissues. In this study, human reconstructed adipose tissues (hrATs) featuring a preformed capillary network formed by microvascular endothelial cells (hMVECs) were produced from adipose-derived stem/stromal cells (ASCs) by the self-assembly approach of tissue engineering. We hypothesized that a prolonged inflammatory context, mediated by tumor necrosis factor (TNF) and interleukin-1ß (IL-1ß), would impact hrATs' secretory profile and mediate detrimental effects on the microvascular network in vitro. Analysis of conditioned media established tissue responsiveness through the increased secretion of monocyte chemoattractant protein-1 (up to 23 fold), interleukin-6 (up to 69 fold) and angiopoietin-1 (up to 2.7 fold) after 3 and 6 days of cytokine exposure, along with a significant reduction in adiponectin secretion. Imaging of the preformed capillary network within the hrATs revealed increased disorganization in the presence of TNF/IL-1ß, featuring a less extended and less ramified network with apoptotic hMVECs in the remaining capillary structures. These results indicate that a prolonged inflammatory context can be deleterious to the capillary network featured by in vitro engineered tissues. Strategies aiming at preserving the integrity of the vascular network will help develop substitutes that are better suited to face inflammatory conditions upon grafting.
ABSTRACT
Promotion of skin repair for acute or chronic wounds through the use of tissue-engineered products is an active field of research. This study evaluates the effects mediated by tissue-engineered biological dressings containing human in vitro-differentiated adipocytes and adipose-derived stromal cells (ASCs). Re-epithelialization, granulation tissue formation and neovascularization of full-thickness cutaneous wounds were specifically assessed using a murine model featuring a fluorescent epidermis. In comparison with wounds that did not receive an adipocyte-containing biological dressing, treated wounds displayed a slight but significantly faster wound closure based on macroscopic observations over 18 days. Non-invasive imaging of GFP-expressing keratinocytes determined that the kinetics of re-epithelialization were similar for both groups. Treated wounds featured thicker granulation tissues (1.7-fold, P < 0.0001) enriched in collagens (1.3-fold, P < 0.0104). In addition, wound cryosections labeled for detection of CD31-expressing cells indicated a 2.2-fold (P < 0.0002) increased neovascularization for the treated wounds at the time of terminal biopsy. This is in accordance with the secretion of pro-angiogenic factors detected in media conditioned by the dressings. Taken together, these results establish that a new type of engineered substitutes featuring a mixture of adipocytes and ASCs can promote cutaneous healing when applied as temporary dressings, suggesting their potential relevance for chronic wound management studies.
