Dental and craniofacial characteristics in a patient with Hutchinson-Gilford progeria syndrome

From the Matrix to the Nucleus and Back: Mechanobiology in the Light of Health, Pathologies, and Regeneration of Oral Periodontal Tissues

Among oral tissues, the periodontium is permanently subjected to mechanical forces resulting from chewing, mastication, or orthodontic appliances. Molecularly, these movements induce a series of subsequent signaling processes, which are embedded in the biological concept of cellular mechanotransduction (MT). Cell and tissue structures, ranging from the extracellular matrix (ECM) to the plasma membrane, the cytosol and the nucleus, are involved in MT. Dysregulation of the diverse, fine-tuned interaction of molecular players responsible for transmitting biophysical environmental information into the cell's inner milieu can lead to and promote serious diseases, such as periodontitis or oral squamous cell carcinoma (OSCC). Therefore, periodontal integrity and regeneration is highly dependent on the proper integration and regulation of mechanobiological signals in the context of cell behavior. Recent experimental findings have increased the understanding of classical cellular mechanosensing mechanisms by both integrating exogenic factors such as bacterial gingipain proteases and newly discovered cell-inherent functions of mechanoresponsive co-transcriptional regulators such as the Yes-associated protein 1 (YAP1) or the nuclear cytoskeleton. Regarding periodontal MT research, this review offers insights into the current trends and open aspects. Concerning oral regenerative medicine or weakening of periodontal tissue diseases, perspectives on future applications of mechanobiological principles are discussed.

Role of Mechanotransduction in Periodontal Homeostasis and Disease

Novel findings broaden the concept of mechanotransduction (MT) in biophysically stimulated tissues such as the periodontium by considering nuclear MT, convergence of intracellular MT pathways, and mechanoresponsive cotranscription factors such as Yes-associated protein 1 (YAP1). Regarding periodontal disease, recent studies have elucidated the role of bacterial gingipain proteases in disturbing the barrier function of cadherins, thereby promoting periodontal inflammation. This leads to dysregulation of extracellular matrix homeostasis via proteases and changes the cell's biophysical environment, which leads to alterations in MT-induced cell behavior and loss of periodontal integrity. Newest experimental evidence from periodontal ligament cells suggests that the Hippo signaling protein YAP1, in addition to integrin-FAK (focal adhesion kinase) mechanosignaling, also regulates cell stemness. By addressing mechanosignaling-dependent transcription factors, YAP1 is involved in osteogenic and myofibroblast differentiation and influences core steps of autophagy. Recent in vivo evidence elucidates the decisive role of YAP1 in epithelial homeostasis and underlines its impact on oral pathologies, such as periodontitis-linked oral squamous cell carcinogenesis. Here, new insights reveal that YAP1 contributes to carcinogenesis via overexpression rather than mutation; promotes processes such as apoptosis resistance, epithelial-mesenchymal transition, or metastasis; and correlates with poor prognosis in oral squamous cell carcinoma. Furthermore, YAP1 has been shown to contribute to periodontitis-induced bone loss. Mechanistically, molecules identified to regulate YAP1-related periodontal homeostasis and disease include cellular key players such as MAPK (mitogen-activated protein kinase), JNK (c-Jun N-terminal kinase), Rho (Ras homologue) and ROCK (Rho kinase), Bcl-2 (B-cell lymphoma 2), AP-1 (activator protein 1), and c-myc (cellular myelocytomatosis). These findings qualify YAP1 as a master regulator of mechanobiology and cell behavior in human periodontal tissues. This review summarizes the most recent developments in MT-related periodontal research, thereby offering insights into outstanding research questions and potential applications of molecular or biophysical strategies aiming at periodontal disease mitigation or prevention.

Microbiome at sites of gingival recession in children with Hutchinson-Gilford progeria syndrome

BACKGROUND

Hutchinson-Gilford progeria syndrome (HGPS) is a rare premature aging disorder with significant oral and dental abnormalities. Clinical symptoms include various features of accelerated aging such as alopecia, loss of subcutaneous fat, bone abnormalities, and premature cardiovascular disease. In addition, children with HGPS have been observed to suffer from generalized gingival recession. Whether periodontal manifestations associated with this syndrome are the results of changes in the oral flora is unknown. The present study aimed to identify the microbial composition of subgingival sites with gingival recession in children with HGPS.

METHODS

Nine children with HGPS were enrolled in this study. Plaque samples were collected from teeth with gingival recession. DNA samples were analyzed using the Human Oral Microbe Identification Microarray (HOMIM). Microbial profiles from HGPS children were compared with microbial profiles of controls from healthy individuals (n = 9) and patients with periodontal disease (n = 9).

RESULTS

Comparison of microbial compositions of HGPS samples with periodontal health samples demonstrated significant differences for two bacterial taxa; Porphyromonas catoniae and Prevotella oulora were present in children with HGPS, but not normal controls. There were statistically significant differences of 20 bacterial taxa between HGPS and periodontal disease groups.

CONCLUSIONS

Typical periodontal pathogens were not present at sites with gingival recession in HGPS children. The microbial compositions of sites of gingival recession and attachment loss in HGPS were generally more similar to those of periodontal health than periodontal disease. Species other than typical periodontal pathogens may be involved in this recession.

Orofacial signs and dental abnormalities in patients with Mulvihill-Smith syndrome: A literature review on this rare progeroid pathology

BACKGROUND

Mulvihill-Smith syndrome is a rare sporadic condition that was first recognized in 1975. A total of 11 cases have been described in the literature. The aim of this study was to describe the orofacial signs and dental anomalies, their frequency, and the relationship between Mulvihill-Smith syndrome and other progeroid syndromes via a review of the literature.

METHODS

A systematic PubMed search was performed to retrieve articles published between 1975 and the present day that described patients affected by Mulvihill-Smith syndrome. The search identified 14 articles, and data on 11 patients were extracted from the selected articles.

RESULTS

A total of 7 patients (63.6%) affected by Mulvihill-Smith syndrome were described as having a typical "bird" face. Dental abnormalities, including irregular shape, enamel defects, hypodontia, and taurodontism, were described in 6 patients (54.5%). All patients (100%) had multiple pigmented nevi on the face and a lack or thinning of subcutaneous tissue around the neck and face. Three patients with Mulvihill-Smith syndrome exhibited early onset of tumors of the gastrointestinal tract, including the tongue.

CONCLUSION

Mulvihill-Smith syndrome is a clinically complex disease that may be caused by a single gene mutation. Numerous different tissues of the body are affected. This analysis of the orofacial signs may help clinicians to diagnose this rare pathology.