Periodontitis is a globally prevalent inflammatory disease that causes destruction of the tooth-supporting periodontal tissues. In the past 4 decades, a variety of procedures, including bone grafting, guided tissue regeneration, and the use of growth factors （GFs） have been performed either alone or in combination to accomplish periodontal regeneration. More recently, tissue engineering technologies using scaffolds, GFs and cells have been developed for regenerative medicine. However, all current approaches have been shown to have variable outcomes and limitations. To obtain favorable periodontal healing, there is an ongoing need to develop more reasonable therapeutics based on self-repair capacity in injured periodontal defect where the progenitor/stem cells from neighboring tissues can be recruited for ｉｎ　ｓｉｔｕ periodontal regeneration. In this review, the emerging various challenges for periodontal regenerative therapy using an “ｉｎ　ｓｉｔｕ tissue engineering approach” that avoid the ex vivo culture of cells are addressed for future clinical management of periodontal intrabony defects.

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Cells connect to each other and are supported by extracellular matrix （ECM） formed structure in organism of a living body. ECM proteins such as collagen, elastin and laminin supports cell to cell interaction. The receptors on cell surface, especially integrins family, interacts with ECM, which determine how to respond to the surrounding environment. The conventional two dimentional cultures on cell plate do not reproduce the tissue architecture in vivo. Spheroids, spherical clusters of cells formed by self-assembly, comprise one of the useful models for three dimentional culture. Three dimentional spheroid culture is superior to two dimentional culture in terms of cellular heterogeneity, nutrient and oxygen gradients, cell-cell interactions, matrix deposition, and gene expression profiles. Spheroid formation is also required to maintain multipotency of stem cells in vitro culture. Thus, spheroids have recently emerged as a novel application for regenerative medicine. This review summarizes the characteristics of spheroid and methods for preparation of spheroids, and explores the possibility of periodontal regeneration by cell spheroids.

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