Assessment of cell sheet constructs with periodontal ligament stem cells and endothelial cells for periodontal regeneration

Abstract

Periodontitis is an infectious and inflammatory oral disease, which damages the tooth supporting structures and is one of the major causes of tooth loss in adults. Thus, periodontal diseases hinder the patient’s quality of life in terms of oral health and functions leading to significant socio-economic outbreak worldwide. Since the periodontium has extremely limited and restricted capability for self-renewal, conventional treatments have not been influential in creating significant outcomes. These limitations have opened pathways for searching new approaches for periodontal regeneration. In recent years, periodontal ligament stem cells (PDLSCs) have been considered to be the promising cell source for periodontal regeneration in cell-based tissue engineering approaches. PDLSCs have been experimentally used for the regeneration of periodontal tissues and eventually demonstrated significant results in general. Cell sheet technology steps into tissue engineering and regenerative medicine as a novel approach by overcoming many drawbacks coupled with traditional tissue engineering methods. Using this approach, cells could be harvested as an intact cell sheet by adjusting the dish surface temperature. In this study, PDLSCs and human umbilical vein endothelial cells (HUVECs) were used to create three-dimensional (3-D) cell sheet constructs to assess the periodontal regeneration potential in vitro and in vivo. PDLSCs were characterized for their “stemness” and multilineage differentiation potentials. PDLSCs and HUVECs were used to create 3-D cell sheet constructs and unraveled the synergistic effects in different ratios of these cells. The present study suggested that co-culture groups exhibited higher level of osteo/odontogenic gene expressions compared to monoculture cell sheet groups. Moreover, vessel-like structures were observed in a cell sheet assembly in vitro. Further studies would be necessary to evaluate the exact parameters required for the development of such vessel-like structures and angiogenesis in 3-D cell sheet constructs in vitro. In vivo assessment of tooth-root coated with three different combinations of triple-layered cell sheet groups (PDLSCs-PDLSCs-PDLSCs, PDLSCs-HUVECs-PDLSCs and Co-culture group) showed periodontal ligament like tissue regeneration around implanted roots compared with control groups. Positive immunohistochemical staining for periostin and bone sialoprotein further confirmed periodontal regeneration, cementogenesis, and osteogenesis in cell sheet groups. Immunohistochemistry for human mitochondrial antibody was used to verify the cells of human origin. Vessel-like structures were observed in periodontal compartment of transplanted cell sheet groups (PDLSCs-HUVECs-PDLSCs and co-culture) facilitating the successful integration of host vasculature with transplanted cell sheet constructs. In summary, the results suggested that HUVECs enhanced the osteo/odontogenic potentials of PDLSCs in 3-D cell sheet model with formation of rudimentary vessel-like structures in vitro. Furthermore, following the transplantation of these cell sheet constructs with tooth roots into the subcutaneous space of immunodeficient mice, periodontal ligament like tissues were observed around transplanted constructs with the positive sign of cementogenesis and osteogenesis. In translational terms, current accumulated data would be a preliminary foundation for future studies and this novel 3-D PDLSCs-HUVECs cell sheet-based approach may be potentially beneficial and thus encourage for future periodontal regenerative therapy. It is evidently proven that the use of above approach might unleash the potential beyond the stipulated and conventional frameworks of dentistry.