https://www.thelancet.com/pdfs/journals/lancet/PIIS0140673604166270.pdf

Investigation of multipotent postnatal stem cells from human periodontal ligament

The first experimental investigation of orthodontic tooth movement was published by Sandstedt in 1904-1905. After 100 years, there is a good understanding of the sequence of events at both tissue and cellular levels and now the current focus of research is at the molecular level. The techniques of reverse transcription-polymerase chain reaction and in situ hybridization to detect mRNAs of interest have revolutionized tooth movement studies and an expanding list of antibodies and enzyme-linked immunosorbent assays directed against human and animal proteins will facilitate their identification in tissue sections and/or culture supernatants. Nevertheless, although this technology has greatly simplified research for the clinical and laboratory investigator, message is not always translated into protein, and the presence of a protein does not necessarily mean it is biologically active. In vivo and in vitro methods have been widely used in tooth movement studies. However, data from in vitro models, in which the mechanical stimulus can be carefully controlled (tension versus compression; intermittent versus continuous), should be correlated with in vivo data from animal models. The current evidence suggests that downstream from the initial mechanotransduction event at focal adhesions which link the extracellular matrix to the cytoskeleton, mechanically induced remodelling is mediated by a complex feedback mechanism involving the synthesis of cytokines such as interleukin-1 (IL-1), IL-6, and receptor activator of nuclear factor k B ligand by cells of the osteoblast and/or fibroblast lineages. These in turn act in an autocrine/paracrine fashion to regulate the expression of transcription factors, cytokines, growth factors, enzymes, and structural molecules involved in the differentiation, proliferation, and function of mesenchymal and other cell types. Contrary to the impression gained from the literature, tooth movement is not confined to events within the periodontal ligament. Orthodontic tooth movement involves two interrelated processes: (1) deflection or bending of the alveolar bone and (2) remodelling of the periodontal tissues.

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The tissue, cellular, and molecular regulation of orthodontic tooth movement: 100 years after Carl Sandstedt.

Periodontitis is an infectious diseaseinvolving periodontal ligament andbone,whichischaracterizedbygingivalinﬂammation and periodontal attach-ment loss, eventually leading to toothloss.Theperiodontalligament(PDL)isan unmineralized connective tissue thatconnects the alveolar bone to teeth.PDL cells consist of heterogeneous cellpopulations with ﬁbroblastic or oste-oblastic properties (1–6). Previousstudies indicate that PDL cells possessthe potential to form mineralized nod-ules in vitro (7), to express bone-relatedmarkers, such as bone sialoprotein andosteocalcin (8), and to express charac-teristic bone regulatory hormone re-sponses (9). Thus, it is very likely thatPDL cells include cell populations atdiﬀerent stages of diﬀerentiation andlineage commitment. The isolation andcharacterization of cell phenotypes thatare eﬀective for periodontal regener-ation in the PDL cell population is def-initely needed. Recently, Seo et al.reported that PDL cells contain stemcells that have the potential to form ce-mentum/PDL-liketissueinvivoandthatthe application of PDL stem cells maybeeﬀectiveforperiodontalregenerativetherapy(10).However,thepropertiesofPDLstemcellsarenotfullyunderstood.A number of studies have shownthat bone marrow-derived mesenchy-mal stem cells (MSCs), which possesscharacteristics of self-renewal andmultilineage diﬀerentiation potential,are suitable for regenerative therapiessuch as the treatment of osteogenesisimperfecta or bone/cartilage defects(11). Kawaguchi et al. reported thatthe transplantation of bone marrow-derived MSCs into partial periodontaldefects was eﬀective for periodontalregeneration (12).MSCs can proliferate rapidly anddiﬀerentiate into osteoblasts, adipo-cytes, chondrocytes, and (possibly)Nagatomo K, Komaki M, Sekiya I, Sakaguchi Y, Noguchi K, Oda S, Muneta T,Ishikawa I. Stem cell properties of human periodontal ligament cells. J Periodont Res2006; 41: 303–310. Blackwell Munksgaard 2006Background and Objective: Stem cells have been used for regenerative therapies invarious ﬁelds. The proportion of cells that possess stem cell properties in humanperiodontal ligament (PDL) cells is not yet well understood. In this study, wequantitatively characterized human PDL cells to clarify their stem cell properties,including self-renewal, multipotency, and stem cell marker expression.Material and Methods: PDL cells were obtained from extracted premolar orwisdom teeth, following which a proliferation assay for self-renewal, a diﬀerenti-ation assay for multipotency, immunostaining for STRO-1, and ﬂuorescence-activated cell sorter (FACS) analysis for stem cell markers (including CD105,CD166, and STRO-1) were performed.Results: Approximately 30% of 400 PDL cells were found to possess replicativepotential and formed single-cell colonies, and 30% of these colonies displayedpositive staining for STRO-1, 20% diﬀerentiated into adipocytes and 30% dif-ferentiated into osteoblasts. FACS analysis revealed that PDL cells, including cellpopulations, expressed the stem cell markers CD105, CD166, and STRO-1.Conclusion: The ﬁndings of this study indicated that PDL cells possess crucialstem cell properties, such as self-renewal and multipotency, and express themesenchymal stem cell markers CD105, CD166, and STRO-1 on their cell surface,although there were some variations. Thus, PDL cells can be used for periodontalregenerative procedures.

Stem cell properties of human periodontal ligament cells

The management of periodontal tissue defects that result from periodontitis represents a medical and socioeconomic challenge. Concerted efforts have been and still are being made to accelerate and augment periodontal tissue and bone regeneration, including a range of regenerative surgical procedures, the development of a variety of grafting materials, and the use of recombinant growth factors. More recently, tissue-engineering strategies, including new cell- and/or matrix-based dimensions, are also being developed, analyzed, and employed for periodontal regenerative therapies. Tissue engineering in periodontology applies the principles of engineering and life sciences toward the development of biological techniques that can restore lost alveolar bone, periodontal ligament, and root cementum. It is based on an understanding of the role of periodontal formation and aims to grow new functional tissues rather than to build new replacements of periodontium. Although tissue engineering has merged to create more opportunities for predictable and optimal periodontal tissue regeneration, the technique and design for preclinical and clinical studies remain in their early stages. To date, the reconstruction of small- to moderate-sized periodontal bone defects using engineered cell-scaffold constructs is technically feasible, and some of the currently developed concepts may represent alternatives for certain ideal clinical scenarios. However, the predictable reconstruction of the normal structure and functionality of a tooth-supporting apparatus remains challenging. This review summarizes current regenerative procedures for periodontal healing and regeneration and explores their progress and difficulties in clinical practice, with particular emphasis placed upon current challenges and future possibilities associated with tissue-engineering strategies in periodontal regenerative medicine.

Periodontal Tissue Engineering and Regeneration: Current Approaches and Expanding Opportunities

The efficacy of the local application of recombinant human fibroblast growth factor-2 (FGF-2) in periodontal regeneration has been investigated. In this study, a randomized, double-blind, placebo-controlled clinical trial was conducted in 253 adult patients with periodontitis. Modified Widman periodontal surgery was performed, during which 200 µL of the investigational formulation containing 0% (vehicle alone), 0.2%, 0.3%, or 0.4% FGF-2 was administered to 2- or 3-walled vertical bone defects. Each dose of FGF-2 showed significant superiority over vehicle alone (p < 0.01) for the percentage of bone fill at 36 wks after administration, and the percentage peaked in the 0.3% FGF-2 group. No significant differences among groups were observed in clinical attachment regained, scoring approximately 2 mm. No clinical safety problems, including an abnormal increase in alveolar bone or ankylosis, were identified. These results strongly suggest that topical application of FGF-2 can be efficacious in the regeneration of human periodontal tissue that has been destroyed by periodontitis.

FGF-2 Stimulates Periodontal Regeneration Results of a Multi-center Randomized Clinical Trial

Background: Periodontal ligament fibroblasts (PDLFs) are the cells essential for periodontal regeneration. PDLFs comprise a heterogeneous cell population and consist of several cell subsets that differ in their function. It is known that PDLFs produce osteoblast-related extracellular matrix proteins and show higher alkaline phosphatase (ALP) activity compared with gingival fibroblasts (GFs), implying that PDLFs have osteogenic characterisitics. The aim of the present study was to isolate the osteogenic population of PDLFs according to their expression of ALP. Methods: PDLFs and gingival fibroblasts were separated into two populations, ALP-positive and ALP-negative, with an immunomagnetic method using a monoclonal antibody against human bone type ALP and magnetic beads conjugated with a secondary antibody. Expression of basic fibroblast growth factor (bFGF) receptor and transforming growth factor (TGF)-β receptor was investigated in these two populations. Osteoblastrelated molecules, osteocalcin, and bone ...

Yuya Murakami

Papers

Novel isolation of alkaline phosphatase-positive subpopulation from periodontal ligament fibroblasts.