Objective- Investigating of the isolation, culture, differentiation potential and electronic microscopic characterization of canine periodontal ligament stem cells (PDLSCs). Design- Experimental in vitro study Animals- Four intact, male, mongrel dogs, 8-10 months-old were selected to collect PDLSCs from their teeth. Procedures- The dogs were anesthetized and the first maxillary and mandibular premolars were extracted for the isolation of periodontal ligament cells (PDLCs). Canine PDLCs were plated and culture expanded through 3 successive subcultures. The resultant cells were then plated at differentiating conditions into bone and adipose cell lineages in order to confirm their mesenchymal stem cell character. Furthermore for the first time we studied PDLSCs ultrastructural morphology by scanning and transmission electron microscopy (SEM and TEM). Results- based to our observations, isolated canine PDLSCs exhibited mesenchymal stem cells (MSCs) characteristics such as fibroblastic appearance, clonogenicity, high proliferation and easily differentiation into osteocyte and adipocyte. This study determined morphologically by electron microscopy a secreted extracellular matrix (ECM) around the PDLSCs and also they contained abundant organelles, such as mitochondria, ribosome, rough endoplasm and collagen fiber as assessed by transmission electron microscopy. Conclusion- Fibroblastic cells from canine PDLCs are capable to be expanded and proliferated in vitro and have differentiation potential into two skeletal lineages; hence they are MSCs that are suitable for cell therapy experimentations.

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