Evaluierung eines neuen Ansatzes für die Weichteilgeweberekonstruktion mittels externer Gewebeexpansion
Zellbiologie
Zusammenfassung der Projektergebnisse
The adequate reconstruction of soft tissue defects, e.g. after trauma or severe burns has been a challenge in plastic and reconstructive surgery. Autologous fat tissue grafting represents a potential solution, but current approaches have been hampered by numerous limitations such as inferior vascularization of the graft and low long-term graft volumes. We surmised that the external expansion of adipose tissue (external volume expansion; EVE) through mechanical vacuum stress could constitute a promising solution. Although such a procedure is already principally clinically established in breast augmentation, at the outset of our project, little was known about the underlying mechanisms of adipose tissue expansion, effects of vacuum-/mechanical stress on adipose-derived stem cell (ASC) behavior, and the trophic properties of ASCs as well as their interplay with other cell types in the tissue before and after grafting such as adipose tissue macrophages (ATMs) and keratinocytes (HKs). We established a cyclic stretch protocol that simulates vacuum/mechanical stress procedures as they occur during lipoaspiration (LA) or EVE and studied the impact of cyclic stretching stress on human ASCs obtained from healthy donors who underwent elective operations (e.g. abdominoplasties or flap thinning procedures). The gene expression profile of ASCs was found to be significantly, time-dependently, and reversibly altered by the mechanical stress with pathways related to extracellular matrix organization, vascular remodeling, and cell stress most prominently changed. The monooxygenase CYP1B1, an enzyme involved in lipid oxidation, was identified as the major upregulated gene. Surprisingly, cyclic stretching led to an attenuation of both ASC differentiation and proliferation. This suggested that ASCs respond to EVE stress not by altered differentiation or proliferation, but by metabolic reprogramming and alteration of their trophic program to shape the adipose tissue environment. Following up on this notion, we opted to study growth factors and cytokines produced by human ASCs as well as the effects of ASCs and inflamed adipose tissue on other cells in the adipose tissue environment in a clinical setting rather in an in vivo mouse model of grafting as initially planned. ASCs obtained from surgical lipoaspirates (LAs) were found to upregulate different growth factors and enhance the proliferation rate and migration of keratinocytes more favorably than those from non-stressed en bloc adipose tissue (Eb-AT), confirming the influence of vacuum stress on ASC trophism in human ASCs in a clinical setting. We also studied the interplay between ASCs and ATMs in inflamed adipose tissue. We found that inflammation promoted the polarization of ATMs toward an M1-type, which in turn was accompanied by an impairment in stem cell characteristics of ASCs, suggesting that adipose tissue-based grafting procedures should implement conditions facilitating M2-skewing and upregulation of stem cell markers. Further work also showed that macrophage migration inhibitory factor (MIF), a pleiotropic macrophage cytokine that has emerged as a major regulator of adipose tissue inflammation, is upregulated by ASCs and represents a trophic factor. MIF but not MIF-2/D-DT was found to be a mediator of monocyte recruitment into inflamed adipose tissue as demonstrated by expression analysis in clinical tissue specimens and functional studies in an Mif gene knockout mouse model. The MIF receptors CXCR2 and 4 were found to mediate this effect. Finally, one practical aspect of clinical translation of ASC-based procedures was studied. In tissue expansion procedures, where fat grafts and/or ASCs are harvested and transferred in a surgical setting that necessitates a sterile donor/harvest site environment, the interaction with antiseptic agents needs to be considered. We found that certain antiseptics have a substantial adverse influence on the viability, proliferation, differentiation, and stem cell marker expression of ASCs. While Mafenide acetate may be regarded as a feasible antiseptic in surgical procedures with exposed adipose tissue due to its low ASC toxicity, the concentrations of several other antiseptics should be carefully selected.
Projektbezogene Publikationen (Auswahl)
- Macrophage migration inhibitory factor in acute adipose tissue inflammation. PLoS One. 2015;10:e0137366
Kim BS, Rongisch R, Hager S, Grieb G, Nourbakhsh M, Rennekampff HO, Bucala R, Bernhagen J, Pallua N
(Siehe online unter https://doi.org/10.1371/journal.pone.0137366) - The macrophage migration inhibitory factor protein superfamily in obesity and wound repair. Exp Mol Med. 2015;47:e161
Kim BS, Pallua N, Bernhagen J, Bucala R
(Siehe online unter https://doi.org/10.1038/emm.2015.26) - The effect of lipoaspirates on human keratinocytes. Aesthet Surg J. 2016;36:941-951
Kim BS, Gaul C, Paul NE, Dewor M, Stromps JP, Hwang SS, Nourbakhsh M, Bernhagen J, Rennekampff HO, Pallua N
(Siehe online unter https://doi.org/10.1093/asj/sjw049) - Characterization of adipose tissue macrophages and adipose-derived stem cells in critical wounds. PeerJ. 2017;5:e2824
Kim BS, Tilstam PV, Springenberg-Jung K, Boecker AH, Schmitz C, Heinrichs D, Hwang SS, Stromps JP, Ganse B, Kopp R, Knobe M, Bernhagen J, Pallua N, Bucala R
(Siehe online unter https://doi.org/10.7717/peerj.2824) - D-dopachrome tautomerase in adipose tissue inflammation and wound repair. J Cell Mol Med. 2017; 21:35-45
Kim BS, Tilstam PV, Hwang SS, Simons D, Schulte W, Leng L, Sauler M, Ganse B, Averdunk L, Kopp R, Stoppe C, Bernhagen J, Pallua N, Bucala R
(Siehe online unter https://doi.org/10.1111/jcmm.12936) - The Effect of antiseptics on adipose-derived stem cells. Plast Reconstr Surg. 2017; 139:625-637
Kim BS, Ott V, Boecker AH, Stromps JP, Paul NE, Alharbi Z, Cakmak E, Bernhagen J, Bucala R, Pallua N
(Siehe online unter https://doi.org/10.1097/PRS.0000000000003125) - The effect of mechanical stress on the proliferation, adipogenic differentiation and gene expression of human adipose-derived stem cells. J Tissue Eng Regen Med. 2018; 12:276-284
Paul NE, Denecke B, Kim BS, Dreser A, Bernhagen J, Pallua N
(Siehe online unter https://doi.org/10.1002/term.2411)
