title: Cell death, cavitation and spontaneous multi-differentiation of dental pulp stem cells-derived spheroids in vitro: a journey to survival and organogenesis.
abstract: BACKGROUND
  During embryonic development, cell death transforms the solid embryonic cell mass into a hollow structure (cavitation), which allows the surviving cells to differentiate into varied tissues and organs around the cavity. This process can be partly reproduced with embryonic stem cells. However, it is unknown if adult stem cell masses have the same ability to cavitate and then differentiate into organs. In this study, we assessed the capacity of human dental pulp stem cells (DPSCs)-derived spheroids to mimic the above-mentioned cavitation and spontaneous differentiation in vitro.
  
  
  RESULTS
  DPSCs were able to form large-sized spheroids on matrigel in osteogenic medium. Inside the spheroids, cells in the centre showed positive stain to stem cell markers, alkaline phosphatase and STRO-1. Hypoxia and massive cell death were observed in the core of the spheroids. Cavities were formed when the spheroids were cultivated in the osteogenic medium for about 14 days. After 28 days of cultivation, the surviving cells around the cavity spontaneously differentiated into neuronal (28.8%), vascular (33.3%), osteogenic (46.7%) and cartilaginous (72.0%) tissues under the osteogenic medium only. In contrast, when DPSCs-formed cell sheets were folded into giant-sized lumps and cultivated under the same conditions, the folded cell sheets became an entire lumenal structure and failed to differentiate into neuronal, osteogenic and cartilaginous cells. Marker analysis showed that cavitation-related molecules BMP7 and FGF3 expressed on the wall of the cavity in the spheroids, suggesting that the cavitation was functional, whereas cavitation-related molecules were absent in the folded cell sheets.
  
  
  CONCLUSIONS
  DPSC-derived spheroids can mimic the developmental process of cell survival, cavitation and spontaneous multi-differentiation on matrigel under certain conditions. This work allows for functional studies to investigate organ regeneration with human DPSCs in vitro.
authors.affiliation: Department of Pharmacology, School of Life Dentistry at Tokyo, The Nippon Dental University, Chiyoda-ku, Tokyo, 102-0071, Japan.
authors.forename: Li
authors.initials: L
authors.lastname: Xiao
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Kumazawa
authors.forename: Hisashi
authors.initials: H
authors.lastname: Okamura
mesh_terms: D000293:Adolescent; D000328:Adult; D053687:Adult Stem Cells / Q000166:cytology* / Q000378:metabolism; D000943:Antigens, Differentiation / Q000032:analysis; D002113:Calcification, Physiologic; D018929:Cell Culture Techniques; D002454:Cell Differentiation; D015687:Cell Hypoxia; D019070:Cell Lineage; D002470:Cell Survival; D003094:Collagen; D003470:Culture Media / Q000494:pharmacology; D003782:Dental Pulp / Q000166:cytology* / Q000196:embryology; D004338:Drug Combinations; D020869:Gene Expression Profiling; D006801:Humans; D019394:Ki-67 Antigen / Q000032:analysis; D007797:Laminin; D008964:Molar, Third / Q000166:cytology; D018919:Neovascularization, Physiologic; D038081:Organogenesis / Q000502:physiology*; D039904:Pluripotent Stem Cells / Q000166:cytology / Q000378:metabolism; D011509:Proteoglycans; D018874:Spheroids, Cellular / Q000166:cytology* / Q000378:metabolism; D055815:Young Adult
chemical_list: D000943:Antigens, Differentiation; D003470:Culture Media; D004338:Drug Combinations; D019394:Ki-67 Antigen; D007797:Laminin; D011509:Proteoglycans; C059485:matrigel; D003094:Collagen
keywords: Cartilage; Cavitation; Neurogenesis; Osteogenesis; Spheroid