Molecular Insights Into the Effects of PLLA-SCA on Gene Expression and Collagen Synthesis in Human 3D Skin Models Containing Macrophages

April 2024 | Volume 23 | Issue 4 | 285 | Copyright © April 2024


Published online March 7, 2024

Sebastian Huth PhDa, Laura Huth PhDa, Yvonne Marquardt a, Manuela Jansen a, Cheng Lin MDb, Matthias Bartneck PhDb, Jens Malte Baron MDa

aDepartment of Dermatology and Allergology, Medical Faculty, RWTH Aachen University, Aachen, Germany
bDepartment of Internal Medicine III, Medical Faculty, RWTH Aachen University, Aachen, Germany

DISCUSSION

Although several human and animal studies demonstrated the volume-enhancing effects of PLLA-SCA injections, the molecular biological effects of PLLA-SCA are only partially understood. The few in vitro studies to date on the efficacy of PLLA-SCA have used only monolayer cell cultures.12 In our previous in vitro study, we found a stimulatory effect on epidermal thickness at day 5 after PLLA-SCA injection in full-thickness 3D skin models comprising fibroblasts and keratinocytes.7 Gene expression profiling in these models revealed a PLLA-SCA-induced upregulation of integrins, laminins, and growth factors, among other genes.7 Now, to investigate more deeply the biostimulatory effects of PLLA-SCA on collagen synthesis, we developed a new 3D skin model with incorporated macrophages, since it was shown that PLLA-SCA-dependent collagen production in fibroblasts occurs only in co-culture with macrophages.12 In contrast to a previous in vitro study claiming a potentially unfavorable effect of PLLA-SCA fillers on fibroblast phenotype,13 we did not observe any adverse effects of PLLA-SCA injection in our 3D skin models.

On days 5 and 14 after injection of PLLA-SCA into macrophage-containing skin models, we found an increased epidermal thickness at the histological level, consistent with our previous findings in 3D skin models without macrophages.7 
 
On day 14 after PLLA-SCA injection, a gene expression profiling revealed an upregulation of genes expressing essential components of the dermal-epidermal junction (e.g. integrins such as ITGA6, laminins such as LAMA3, and desmogleins such as DSG2). These data support the stimulatory effects of PLLA-SCA on the volume and integrity of the epidermis and especially the basement membrane. In this regard, it is interesting to note that a new study suggests a potential benefit of PLLA-SCA in the treatment of melasma where disorders of the basement membrane are involved.14 Our data would support this potential use of PLLA-SCA in the treatment of melasma, especially by restoring basement membrane damage and upregulation of TGFb1 expression, which is known to decrease melanin synthesis via delayed extracellular signal-regulated kinase activation.15 Further studies are needed to clarify this in detail.

Interestingly, immunohistochemical analyses exhibited a stimulatory effect of PLLA-SCA injection on collagen I production in our macrophage-containing skin models, which correlates to previous clinical findings.16 This is the first time that these PLLA-SCA-dependent effects on collagen synthesis have been demonstrated in an in vitro 3D skin model. We assume that these effects could be attributed, at least in part, to the upregulation of IL1B and CXCL6 that we found in our gene expression analysis. In this context, previous studies indicated that CXCL6, which appears to be mainly induced by IL1B,17 stimulates collagen synthesis in lung fibroblasts.18 To substantiate our assumption, we have now shown for the first time that CXCL6 can also stimulate the synthesis of collagen I in dermal fibroblasts. 

In summary, our data provide for the first time deeper molecular insights into the biostimulatory mode of operation of PLLA-SCA injections by performing a comprehensive in vitro study using 3D skin models containing macrophages.

DISCLOSURES

The authors have no conflicts of interest to declare.

ACKNOWLEDGMENT

This work was supported by a grant from Galderma.

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AUTHOR CORRESPONDENCE

Sebastian Huth PhD shuth@ukaachen.de
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