Effect of total sonicated Aggregatibacter actinomycetemcomitans fragments on gingival stem/progenitor cells

Thymoquinone-Mediated Modulation of Toll-like Receptors and Pluripotency Factors in Gingival Mesenchymal Stem/Progenitor Cells

Thymoquinone (TQ), the key active component of Nigella sativa (NS), demonstrates very promising biomedical anti-inflammatory, antioxidant, antimicrobial and anticancer properties. Several investigations have inspected the modulative activities of TQ on different stem/progenitor cell types, but its possible role in the regulation of gingival mesenchymal stem/progenitor cells (G-MSCs) has not yet been characterized. For the first time, this study investigates the effects of TQ on G-MSCs’ stemness and Toll-like receptor expression profiles. G-MSCs (n = 5) were isolated, sorted via anti-STRO-1 antibodies and then disseminated on cell culture dishes to create colony-forming units (CFUs), and their stem/progenitor cell attributes were characterized. TQ stimulation of the G-MSCs was performed, followed by an examination of the expression of pluripotency-related factors using RT-PCR and the expression profiles of TLRs 1−10 using flowcytometry, and they were compared to a non-stimulated control group. The G-MSCs presented all the predefined stem/progenitor cells’ features. The TQ-activated G-MSCs displayed significantly higher expressions of TLR3 and NANOG with a significantly reduced expression of TLR1 (p < 0.05, Wilcoxon signed-rank test). TQ-mediated stimulation preserves G-MSCs’ pluripotency and facilitates a cellular shift into an immunocompetent-differentiating phenotype through increased TLR3 expression. This characteristic modulation might impact the potential therapeutic applications of G-MSCs.

Mesenchymal Stem/Progenitor Cells: The Prospect of Human Clinical Translation

Mesenchymal stem/progenitor cells (MSCs) are key players in regenerative medicine, relying principally on their differentiation/regeneration potential, immunomodulatory properties, paracrine effects, and potent homing ability with minimal if any ethical concerns. Even though multiple preclinical and clinical studies have demonstrated remarkable properties for MSCs, the clinical applicability of MSC-based therapies is still questionable. Several challenges exist that critically hinder a successful clinical translation of MSC-based therapies, including but not limited to heterogeneity of their populations, variability in their quality and quantity, donor-related factors, discrepancies in protocols for isolation, in vitro expansion and premodification, and variability in methods of cell delivery, dosing, and cell homing. Alterations of MSC viability, proliferation, properties, and/or function are also affected by various drugs and chemicals. Moreover, significant safety concerns exist due to possible teratogenic/neoplastic potential and transmission of infectious diseases. Through the current review, we aim to highlight the major challenges facing MSCs' human clinical translation and shed light on the undergoing strategies to overcome them.

Effect of Inflammation on Gingival Mesenchymal Stem/Progenitor Cells' Proliferation and Migration through Microperforated Membranes: An In Vitro Study

Background

In the field of periodontal guided tissue regeneration, microperforated membranes have recently proved to be very promising periodontal regenerative tissue engineering tools. Regenerative periodontal approaches, employing gingival mesenchymal stem/progenitor cells in combination with these novel membranes, would occur mostly in inflamed microenvironmental conditions intraorally. This in turn entails the investigation into how inflammation would affect the proliferation as well as the migration dynamics of gingival mesenchymal stem/progenitor cells. Materials and Methods. Clones of human gingival mesenchymal stem/progenitor cells (GMSCs) from inflamed gingival tissues were characterized for stem/progenitor cells' characteristics and compared to clones of healthy human GMSCs (n = 3), to be subsequently seeded on perforated collagen-coated poly-tetra-floro-ethylene (PTFE) membranes with a pore size 0.4 and 3 microns and polycarbonic acid membranes of 8 microns pore size in Transwell systems. The population doubling time and the MTT test of both populations were determined. Fetal bovine serum (FBS) was used as a chemoattractant in the culturing systems, and both groups were compared to their negative controls without FBS. Following 24 hours of incubation period, migrating cells were determined on the undersurface of microperforated membranes and the membrane-seeded cells were examined by scanning electron microscopy.

Results

GMSCs demonstrated all predefined stem/progenitor cell characteristics. GMSCs from inflamed gingival tissues showed significantly shorter population doubling times. GMSCs of inflamed and healthy tissues did not show significant differences in their migration abilities towards the chemoattractant, with no cellular migration observed in the absence of FBS. GMSCs from healthy gingival tissue migrated significantly better through larger micropores (8 microns). Scanning electron microscopic images proved the migratory activity of the cells through the membrane pores.

Conclusions

Inflammation appears to boost the proliferative abilities of GMSCs. In terms of migration through membrane pores, GMSCs from healthy as well as inflamed gingival tissues do not demonstrate a difference in their migration abilities through smaller pore sizes, whereas GMSCs from healthy gingival tissues appear to migrate significantly better through larger micropores.

Dental Stem Cell-Derived Secretome/Conditioned Medium: The Future for Regenerative Therapeutic Applications

Regenerative medicine literature has proposed mesenchymal stem/progenitor cell- (MSC-) mediated therapeutic approaches for their great potential in managing various diseases and tissue defects. Dental MSCs represent promising alternatives to nondental MSCs, owing to their ease of harvesting with minimally invasive procedures. Their mechanism of action has been attributed to their cell-to-cell contacts as well as to the paracrine effect of their secreted factors, namely, secretome. In this context, dental MSC-derived secretome/conditioned medium could represent a unique cell-free regenerative and therapeutic approach, with fascinating advantages over parent cells. This article reviews the application of different populations of dental MSC secretome/conditioned medium in in vitro and in vivo animal models, highlights their significant implementation in treating different tissue' diseases, and clarifies the significant bioactive molecules involved in their regenerative potential. The analysis of these recent studies clearly indicate that dental MSCs' secretome/conditioned medium could be effective in treating neural injuries, for dental tissue regeneration, in repairing bone defects, and in managing cardiovascular diseases, diabetes mellitus, hepatic regeneration, and skin injuries, through regulating anti-inflammatory, antiapoptotic, angiogenic, osteogenic, and neurogenic mediators.