Using co-culture system to differentiate periodontal ligament-derived stem cell to ductal salivary gland cells

Introduction
Irreversible harm to salivary glands is a complication that is treated using symptomatic treatment only. Stem cell therapy provides a new approach in treating irreversible harm to the salivary glands. Salivary gland’s ductal cells transport saliva and change its’ composition. Co-culture is a regulatory cell culture technique, in which two or more different cell populations grow with various degrees of interaction.

Objective
Given the role of salivary glands ductal cells in their final saliva production, this study aimed to examine the differentiation of periodontal ligament stem cells (PDL-SCs) in salivary glands ductal cells using the co-culture technique.

Material and methods
PDL-SCs were isolated from adult human PDL tissue and co-cultured with rat parotid ductal cells using an indirect co-culture system. Trans-differentiation of PDL-SCs was evaluated by polymerase chain reaction (PCR) analysis of kallikrein 1 and keratin 19 genes, with unique functional expression in ductal cells.

Results
Expression of CD90, CD73, CD44, and CD105 mesenchymal markers were proved that the obtained PDL-SCs were mesenchymal stromal cells (MSCs). Positive oil red and alizarin red staining showed differentiation of stem cells into fat and bone cells. Expression of kallikrein 1 and keratin 19 demonstrated successful trans-differentiation of PDL-SCs into salivary ductal cells after co-culturing for three weeks.

Conclusions
These findings highlight the potential usefulness of the co-culture system in the differentiation of PDL-SCs-derived mesenchymal stem cells into salivary gland ductal cells. The proximity of mesenchymal stem cells to salivary acinar cells and the expression of acinar cells’ specific markers lead to differentiation.