Histologic assessment and gene expression analysis of intraoral soft tissue donor sites
Creators: name: Stuhr, Sandra
Publisher: name: University of Iowa
Year: 2023
Subjects: donor site
soft tissue augmentation
public abstract
Connective Tissue
Gene Expression
Histology

description: Introduction: The current gold standard for soft tissue augmentation procedures involving natural teeth and dental implants is the autologous subepithelial connective tissue graft due to its high predictability and effectiveness. The choice of donor site is typically based on the clinician’s preference in terms of quantity, morphology, and extent needed to achieve the therapeutic goal, rather than on the biological properties of the site. Depending on the donor site, diverse patterns of healing have also been observed; however, the molecular understanding behind these variations is limited.
description: Materials and Methods: Full-thickness, standardized tissue punch biopsies (4mm diameter) were collected from 37 subjects, resulting in 50 samples total (13 anterior palate, 13 posterior palate, 12 maxillary tuberosity, and 12 retromolar pad). Each sample was bisected and then one of those portions was subsequently bisected again. The initially bisected portion was stored in formalin to be stained with Hematoxylin/Eosin for morphological analysis and Picrosirius Red for collagen types I and III quantification. The other two sections were included in media for molecular analysis. Two calibrated examiners performed linear measurements of epithelium and lamina propria thickness, and quantified collagen type I and III percentages using a computer software. RNA was isolated and hybridized with reporter and capture probes for a human fibrosis panel. Quantitative data were normalized to house-keeping genes, differential abundance was calculated, and statistical significance was determined.
description: Results: Although epithelial thickness did not differ between donor sites, averaging 0.45mm, lamina propria thickness differed significantly between sites. Lamina propria thickness was higher in the maxillary tuberosity and retromolar pad samples when compared to anterior palate and posterior palate samples. Additionally, there was a higher percentage of collagen type I than collagen type III in all groups. In terms of gene expression, the anterior palate and posterior palate displayed no significant differences. However, gene expression differed significantly between the other sites in terms of collagen biosynthesis, extracellular matrix synthesis, lipogenesis, coagulation, focal adhesion signaling, and cell signaling, with RP samples demonstrating the most differentially abundant genes. RT-PCR analysis validated these results using the posterior palate as the reference site, significantly for the COL1A1, CXCL12, ERO1A, GATA3, and THBS2 genes. For the COL1A1 gene, there was a 5.18, 2.93, and 1.02-fold change difference between MT, RP, and AP sites, respectively. For the CXCL12 gene, there was a 2.19, 1.31, and 1.02-fold change average difference between MT, RP, and AP sites, respectively. For the ERO1A gene, there was a 6.90, 1.86, and 0.80-fold change average difference between RP, AP, and MT sites, respectively. For the GATA3 gene, there was a 14.53, and 12.43-fold change average difference between RP and MT sites, respectively. For the THBS2 gene, there was a 7.21, 2.48, and 2.15-fold change difference between MT, RP, and AP sites, respectively.
description: Conclusion: Tissue samples harvested from the anterior and posterior palatal regions were structurally distinct compared to the maxillary tuberosity and retromolar pad region. Interestingly, each intra-oral donor site demonstrated a unique genetic profile, which may ultimately impact its biological behavior and outcomes in soft tissue augmentation procedures.