Evaluation of the Nature of Collagen Fibers in KCOT, Dentigerous Cyst and Ameloblastoma using Picrosirius Red Stain - A Comparative Study

Single-cell analysis reveals immune cellular components in odontogenic keratocysts

OBJECTIVES

Various types of cells comprising a complex and diverse cell population are required for the biological activities of odontogenic keratocyst (OKC). Immune and non-immune cells collaborate via cytokine- or chemokine-mediated communication and direct cell-cell interactions. This study aimed to characterize the immune ecosystem and understand the potential chemotactic role of OKC fibroblasts in immune cell migration.

MATERIALS AND METHODS

Mass cytometry of 41 markers was employed for the classification of OKC cells from six OKC samples. Immunofluorescence staining and single-cell RNA sequencing (GSE176351) were used for the detection of fibroblast subpopulations. Enzyme-linked immunosorbent assay and immunofluorescence staining were employed for chemokine detection in hypoxia- and/or HIF-1α inhibitor-treated OKC fibroblasts and tissues. Chemotaxis assay was employed to determine the chemotactic effect of fibroblasts via co-culture with peripheral blood mononuclear cells. A cell communication network was constructed based on the single-cell RNA sequencing data.

RESULTS

The characterization of the immune cell types of OKC evidenced the enrichment of macrophages, neutrophils and B cells. The majority (41.5%) of fibroblast subsets consisted of chemokine ligand-enriched myofibroblasts. The activation of the HIF-1α signaling pathway in fibroblasts was associated with chemokine release. The chemokines released by OKC fibroblasts remarkably promoted the migration of peripheral blood mononuclear cells in the co-culture system. Close interactions between myofibroblasts and immune cells were validated by cell-cell interaction analysis. Increased RANKL expression was detected in OKC fibroblasts in the co-culture system with peripheral blood mononuclear cells.

CONCLUSIONS

Our results provided deep insights into the immune ecosystem and highlighted the potential chemotactic effects of chemokine-enriched myofibroblasts within OKCs. The close interaction between immune cells and fibroblasts demonstrated in this study may be responsible for the osteoclastogenic effects of OKC fibroblasts.

Identification of Immune Infiltration in Odontogenic Keratocyst by Integrated Bioinformatics Analysis

BACKGROUND

Odontogenic keratocyst (OKC) is a relatively common odontogenic lesion characterized by local invasion in the maxillary and mandibular bones. In the pathological tissue slices of OKC, immune cell infiltrations are frequently observed. However, the immune cell profile and the molecular mechanism for immune cell infiltration of OKC are still unclear. We aimed to explore the immune cell profile of OKC and to explore the potential pathogenesis for immune cell infiltration in OKC.

METHODS

The microarray dataset GSE38494 including OKC and oral mucosa (OM) samples were obtained from the Gene Expression Omnibus (GEO) database. The differentially expressed genes (DEGs) in OKC were analyzed by R software. The hub genes of OKC were performed by protein-protein interaction (PPI) network. The differential immune cell infiltration and the potential relationship between immune cell infiltration and the hub genes were performed by single-sample gene set enrichment analysis (ssGSEA). The expression of COL1A1 and COL1A3 were confirmed by immunofluorescence and immunohistochemistry in 17 OKC and 8 OM samples.

RESULTS

We detected a total of 402 differentially expressed genes (DEGs), of which 247 were upregulated and 155 were downregulated. DEGs were mainly involved in collagen-containing extracellular matrix pathways, external encapsulating structure organization, and extracellular structure organization. We identified ten hub genes, namely FN1, COL1A1, COL3A1, COL1A2, BGN, POSTN, SPARC, FBN1, COL5A1, and COL5A2. A significant difference was observed in the abundances of eight types of infiltrating immune cells between the OM and OKC groups. Both COL1A1 and COL3A1 exhibited a significant positive correlation with natural killer T cells and memory B cells. Simultaneously, they demonstrated a significant negative correlation with CD56dim natural killer cells, neutrophils, immature dendritic cells, and activated dendritic cells. Immunohistochemistry analysis showed that COL1A1 (P = 0.0131) and COL1A3 (P < 0.001) were significantly elevated in OKC compared with OM.

CONCLUSIONS

Our findings provide insights into the pathogenesis of OKC and illuminate the immune microenvironment within these lesions. The key genes, including COL1A1 and COL1A3, may significantly impact the biological processes associated with OKC.

Collagen during odontogenesis and in ameloblastoma: A polarizing microscopic study

Background:

Odontogenesis is a highly coordinated and complex process which depends on cell–cell interactions that result in initiation and generation of tooth. Tissue remnants of developing tooth can form odontogenic tumors possibly, reflecting different developmental stages in tooth formation. In both odontogenesis and odontogenic tumors, stroma plays a prominent role in maintaining epithelial tissues with continuous molecular interactions. As the collagen forms an integral part of connective tissue stroma, in the present study, polarization colors and thickness of the collagen fibers were assessed in both tooth germ papillae and ameloblastoma using picrosirius red (PSR) stain.

Materials and Methods:

Collagen fibers in 20 cases of ameloblastoma and 10 tooth germs from the human fetus were evaluated with PSR stain and examined under polarizing microscopy.

Results:

Polarization colors of red-colored collagen fibers with greater diameter were more in ameloblastoma when compared to tooth germ papillae in which green-colored collagen fibers with smaller diameter being more.

Conclusion:

The absence of hard tissue formation in ameloblastoma might be due to the presence of significantly more number and greater thickness of red-colored collagen fibers. Thus, the nature of collagen fibers can predict the nature in terms of biologic behavior and prognosis.

Collagen and Its Role in predicting the Biological Behavior of Odontogenic Lesions

INTRODUCTION

Odontogenic cysts and tumors have variable recurrence rates. Recurrence rate is mainly due to the activity of the epithelium. The epithelium of these lesions has been investigated extensively in regard to their role in proliferative and aggressive behavior of the lesions. However, the role of the connective tissue wall in their behavior has not been studied as extensively. Collagen is an essential part of the connective tissue as a whole and fibrous wall of cystic lesions especially. It is demonstrated by picrosirius red dye staining combined with polarization microscopy. This method permits the evaluation of the nature of the collagen fibers in addition to their thickness.

MATERIALS AND METHODS

A total of 56 histopathologically diagnosed cases comprising odontogenic follicle, dentigerous cyst, unicystic ameloblastoma, keratocystic odontogenic tumor (KCOT), multicystic/solid ameloblastoma, and ameloblastic carcinoma were taken and stained using picrosirius red stain and evaluated using a polarizing microscope.

RESULTS

Collagen fibers in odontogenic follicles and dentiger-ous cysts showed predominant orange-red birefringence; fibers in unicystic ameloblastoma and KCOT showed both orange red and greenish-yellow birefringence; and fibers of multicystic/ solid ameloblastoma showed predominant greenish-yellow birefringence and ameloblastic carcinoma that showed almost complete greenish birefringence. As the biological behavior of the lesions in the spectrum studied progress toward aggressive nature, increase in immature collagen fibers is noticed.

CONCLUSION

This study suggests that the nature of collagen fibers plays a pivotal role in predicting the biological behavior of odontogenic lesions.

CLINICAL SIGNIFICANCE

Aggressive nature of the odontogenic lesions is determined by both the epithelium and the connective tissue components (collagen). Studying the nature and type of collagen helps in predicting its biological behavior.