Dermal Fibroblasts from Different Layers of Pig Skin Exhibit Different Profibrotic and Morphological Characteristics

Abstract

In vitro studies of human dermal fibroblast (DF) heterogeneity have long been reported, yet in vivo studies and related research on animals are rare. The objectives of the study were to determine whether the DFs of pigs exhibit heterogeneity and to identify an animal model for the in vivo study of DF heterogeneity. The skin of three female red Duroc pigs (FRDPs) was separated into six layers, and the second and fifth layers (i.e., the superficial and deep dermis) were used in the establishment of wound models and cell cultures. To create the wound models, 54 tongue-shaped flaps were created on one side of the dorsum, and the underlying dermis was then fully replaced with the superficial or deep dermis (the superficial and deep groups, respectively). Skin samples were harvested at postoperative weeks 1, 2, and 3 for measurements of the normal and wounded skin thicknesses. Cells cultured from the superficial and deep dermis (i.e., superficial and deep DFs) were subjected to quantitative estimation of collagen and electron microscopy. The wounded skin thickness in the deep group was significantly greater than that in the superficial group. In contrast with the long deep DFs, the superficial DFs were short and exhibited microvilli-like cell surface projections. Compared with the superficial DFs, the deep DFs exhibited a greater density of rough endoplasmic reticulum and produced significantly more collagen. Similar to humans, FRDPs exhibit DF heterogeneity and should thus be a good animal model for in vivo studies of DF heterogeneity. Anat Rec, 299:1585-1599, 2016. © 2016 Wiley Periodicals, Inc.

Dermis, acellular dermal matrix, and fibroblasts from different layers of pig skin exhibit different profibrotic characteristics: evidence fromin vivostudy

“…Because the normal skin thickness of the FRDPs showed great discrepancy [6, 7], and the normal skin thickness was crucial for the subsequent establishment of the wound models, the thickness of the normal skin from seven anatomical locations (site A to site G) was carefully measured. It was observed that the normal skin thicknesses of the FRDPs were 2.073±0.386 mm(site A), 2.495±0.167 mm(site B), 2.313±0.311 mm(site C), 1.820±0.079 mm(site D), 2.183±0.225 mm(site E), 1.910±0.161 mm(site F), 2.383±0.264 mm(site G), respectively.…”

“…It was reported that the thickness of the healed wounds was an important parameter of cutaneous fibrosis [6, 7], so the wounded skin thickness in the deep/superficial dermis group and the superficial/deep ADM group was measured. It was observed that the wounded skin thicknesses in the deep dermis group were significantly greater than those in the superficial dermis group at 2(2.510±0.138 mm, 2.173±0.219 mm, P=0.040), 4(2.334±0.147 mm, 1.997±0.184 mm, P= 0.028), and 8(2.640±0.156 mm, 2.390±0.080 mm, P= 0.029) weeks post-wounding (Figure 3).…”

“…To resolve this issue, we separated the skin of three FRDPs into six layers and autografted the second and fifth layers. It was observed that the skin thickness of the wound models autografted with the fifth layer was significantly greater than that of the second layer at postoperative weeks 2 and 3 [7]. However, in sharp contrast with the long-term process of cutaneous fibrosis, the research period of this study was relatively short.…”

“…Based on these observations, we hypothesized that ADM derived from the deep dermis (termed the deep ADM) exhibited fewer profibrotic characteristics than that from the superficial dermis (termed the superficial ADM). On the other hand, a large number of in vitro studies have shown that cells cultured from the deep dermis (termed the deep DF) produced significantly more collagen and exhibited more profibrotic characteristics than those from the superficial dermis (termed the superficial DF) in humans and pigs, yet in vivo studies have been rare [7, 13]. Based on these observations, we hypothesized that autologous implantation of the deep DF showed more profibrotic characteristics than that of the superficial DF.…”

“…Because ❶experiments using pigs are less restricted by ethical restrictions than clinical trials, ❷ the similarities of pig and human skin have long been reported [14–16], and the FRDP has been proposed to be a good animal for in vivo studies of wound healing, HTS, and DF heterogeneity [6, 7, 17, 18], ❸ skin of rodents, the common laboratory species, is sufficiently different from human skin in histology, anatomy, and immunology, as well, compared with pig skin, rodent skin is more difficult to be separated into several layers using a dermatome [19–21], we designed the following experiment on 7 FRDPs. To the best of our knowledge, this was the first in vivo study to explore the profibrotic characteristics of ADM and DF from different layers of pig skin.…”