Implications of cultured periodontal ligament cells for the clinical and experimental setting: a review

Abstract

The periodontal ligament (PDL) is a key contributor to the process of regeneration of the periodontium. The heterogeneous nature of the PDL tissue, its development during early adulthood, and the different conditions to which the PDL tissue is exposed to in vivo impart on the PDL unique characteristics that may be of consequence during its cultivation in vitro. Several factors affecting the in vivo setting influence the behaviour of PDL fibroblasts in culture. The purpose of this review is to address distinct factors that influence the behaviour of PDL fibroblasts in culture -in vivo-in vitro transitions, cell identification/isolation markers, primary PDL cultures and cell lines, tooth-specific factors, and donor-specific factors. Based on the reviewed studies, the authors recommendations include the use of several identification markers to confirm cell identity, use of primary cultures at early passage to maintain unique PDL heterogeneic characteristics, and noting donor conditions such as age, systemic health status, and tooth health status. Continued efforts will expand our understanding of the in vitro and in vivo behaviour of cells, with the goal of orchestrating optimal periodontal regeneration. This understanding will lead to improved evidence-based rationales for more individualized and predictable periodontal regenerative therapies.

Figure 1

Schematic view of the rich and complex nature of the periodontal tissue, including the cellular, vascular and extracellular matrix elements. The different components are depicted with different colors: osteoblasts in orange and osteoclasts in pink in proximity to the bone; fibroblasts in green following collagen fiber orientation; stem cells in purple, differentiating into a fibroblast-like or osteoblast-like cell; cementoblasts in blue and epithelial cells rest of Malassez (ERM) in aqua in proximity to the cementum; blood vessels emerge from the alveolar bone, along with nerve fibers.

Figure 2

Microvasculature of the periodontium in a premolar tooth of a beagle dog prepared using the resin cast model (10). A and B) Vascular network under light microscope of the gingival (G) and periodontal ligament (PDL) tissues; alveolar bone (AB) is also depicted; C) Rich vascular network of the PDL tissue emerging from the bone observed by scanning electron microscopy under 12X; inferior alveolar nerve (IAA) is also depicted; D) Volkmann’s canals (VC) observed at 50X, and E) AB and PDL observed at 150X, with a double arrow depicting the thickness of the PDL vascularization.

Figure 3

Transitions that can occur when periodontal ligament fibroblasts are used for regenerative purposes. Transition 1 happens when the healthy donor tooth is taken to the cell culture environment. Transition 2 happens when the cells are taken from the culture environment to the in vivo setting, the latter compromised by periodontal disease.

Figure 4

Schematic figure showing the zone of destruction created by the periodontal biofilm. The safe zone for tissue collection of periodontal ligament is represented as a distance of 1 to 2mm in the immediate vicinity of the infectious biofilm.