Reconstructed human keloid models show heterogeneity within keloid scars

Abstract

Keloid scars are often described as having an actively growing peripheral margin with a regressing centre. The aim of this study was to examine the possible heterogeneity within keloids and the involvement of different regions within and around keloid scars in the pathogenesis, using an in vitro keloid scar model. In vitro skin models were constructed from keratinocytes and fibroblasts from normal skin and different regions within and around keloid scars: periphery, centre, and (adjacent) surrounding-normal-skin regions. Additionally, fibroblasts were isolated from the superficial-central and deep-central regions of the keloid and combined with central keratinocytes. All keloid regions showed increased contraction compared to normal skin models, particularly in central regions. Myofibroblasts were present in all keloid regions but were more abundant in models containing central-deep keloid fibroblasts. Secretion of anti-fibrotic HGF and extracellular matrix collagen IV gene expression was reduced in the central deep keloid compared to normal skin. No significant differences between peripheral and central regions within keloids were observed for inflammatory cytokine CCL20, CCL27, CXCL8, IL-6 and IL-18 secretion. Parameters for surrounding-normal-skin showed similarities to both non-lesional normal skin and keloids. In conclusion, a simple but elegant method of culturing keloid-derived keratinocytes and fibroblasts in an organotypic 3D scar model was developed, for the dual purpose of studying the underlying pathology and ultimately testing new therapeutics. In this study, these tissue engineered scar models show that the central keloid region shows a more aggressive keloid scar phenotype than the periphery and that the surrounding-normal-skin also shares certain abnormalities characteristic for keloids.Electronic supplementary materialThe online version of this article (10.1007/s00403-018-1873-1) contains supplementary material, which is available to authorized users.

Hypertrophic and keloid scars fail to progress from the CD 34 − /α‐smooth muscle actin (α‐ SMA ) + immature scar phenotype and show gradient differences in α‐ SMA and p16 expression

“…S3; see Supporting Information). In one keloid sample that was an almost complete circular spheroid, keloidal collagen was very clearly limited to the upper half of the keloid, constituting what we have previously defined as both the periphery and the superficial centre, but this was not observed in the other keloids. Even in the two hypertrophic scar samples with keloidal collagen (3·4% and 28·0% of the total surface area), the abnormally thick collagen bundles were located in less strongly α‐SMA‐stained regions.…”

“…We have previously subdivided keloids into peripheral and central (superficial and deep) regions and found that in our in vitro organotypic scar models, the central deep keloid regions show the most exaggerated keloid phenotype . In native keloid tissue, keloidal collagen was located in the deeper reticular dermis within the CD34 − ‘scar regions’, where α‐SMA staining was reduced (but still positive).…”

“…Having now established that both hypertrophic and keloid scars showed a scar phenotype comprising dermal CD34 − /α‐SMA + /p16 + immunoreactivity, we next sought to determine whether our in vivo findings could translate into our tissue engineered in vitro scar models . CD34 staining was absent in all experimental groups, not just hypertrophic scars and keloid scars (Fig.…”

“…As we had previously observed differences between the peripheral and central keloid regions in vitro , we next evaluated heterogeneity in native keloid tissue. There were no obvious differences between the central and peripheral keloid regions with respect to the markers studied.…”

“…As current research has not yet yielded definitive markers to distinguish hypertrophic scars from keloids, our secondary goal was to compare these two abnormal scar types against each other. Additionally, the different regions within the keloid scars were examined, including the normal skin surrounding the keloid (surrounding‐normal‐skin), as this was previously shown to possess a partial keloid scar phenotype in vitro . Finally, we were interested in determining whether the newly identified abnormal scar parameters also translated to our previous in vitro work, in which we developed organotypic abnormal scar models using scar‐derived keratinocytes and fibroblasts …”