Periodontal Ligament Stem Cells: Regenerative Potency in Periodontium

Periodontium is consisted of root cementum, bone lining the tooth socket, gingiva facing the tooth, and periodontal ligament (PDL). Its primary functions are support of the tooth and protection of tooth, nerve, and blood vessels from injury by mechanical loading. Severe periodontitis induces the destruction of periodontium and results in a significant cause of tooth loss among adults. Unfortunately, conventional therapies such as scaling and root planning are often only palliative. Therefore, the ultimate goal of the treatment for periodontitis is to restore disrupted periodontium to its original shape and function. Tissue engineering refers to the process of combining cells, scaffolds, and signaling molecules for the production of functional tissues to restore, maintain, and improve damaged organs. The discovery of periodontal ligament stem cells (PDLSCs) highlighted the possibility for development of tissue engineering technology-based therapeutics for disrupted periodontium. PDLSCs are a kind of somatic stem cells that show potential to differentiate into multiple cell types and undergo robust clonal self-renewal. Therefore, PDLSCs are considered a highly promising stem cell population for regenerative therapy in periodontium; however, their rarity prevents the progression of basic and clinical researches. In this review, we summarize recent research advancement and accumulated information regarding the self-renewal capacity, multipotency, and immunomodulatory effect of PDLSCs, as well as their contribution to repair and regeneration of periodontium and other tissues. We also discuss the possibility of PDLSCs for clinical application of regenerative medicine and provide an outline of the genetic approaches to overcome the issue about the rarity of PDLSCs.

Possible function of GDNF and Schwann cells in wound healing of periodontal tissue

OBJECTIVE

The purpose of this study was to evaluate the function of Schwann cells in wound healing of periodontal tissue.

BACKGROUND

In our previous study, glial cell line-derived neurotrophic factor (GDNF) promoted the migration of human periodontal ligament (PDL) cells and that GDNF expression increased in wounded periodontal tissue. GDNF reportedly induces the migration of Schwann cell precursors. Schwann cells play a crucial role in the regeneration of peripheral tissues, including bone tissue. However, the role of Schwann cells on periodontal tissue regeneration remains unclear.

METHODS

A transwell assay and a WST-1 (water-soluble tetrazolium compound-1) proliferation assay were used to determine whether GDNF promotes the migration and proliferation of Schwann cells, respectively. Quantitative RT-PCR and Alizarin Red S staining were performed to examine the effect of these cells on the differentiation of human preosteoblast (Saos2 cells) using conditioned medium from YST-1 (YST-1-CM). Western blotting analysis was performed to determine whether YST-1-CM activates ERK signaling pathway in Saos2 cells. The expression of Schwann cell markers, S100 calcium-binding protein B (S100-B) and growth associated protein 43 (GAP-43), was determined in normal and wounded periodontal tissue by immunofluorescent staining.

RESULTS

Glial cell line-derived neurotrophic factor promoted the migration of YST-1 cells but did not affect the proliferation of YST-1 cells. Saos2 cells cultured with YST-1-CM increased the expression of osteoblastic markers and mineralization. YST-1-CM also induced phosphorylation of ERK1/2 in Saos2 cells. The number of S100-B-immunoreactive cells which also expressed GAP-43 was increased in rat wounded periodontal tissue during healing process.

CONCLUSION

The accumulation of Schwann cells in wounded periodontal tissue suggests that they play a significant role in wound healing of this tissue, especially alveolar bone tissue.

Expression and function of dopamine in odontoblasts

Dopamine (DA) is produced from tyrosine by tyrosine hydroxylase (TH). A recent study has reported that DA promotes the mineralization of murine preosteoblasts. However, the role of DA in odontoblasts has not been examined. Therefore, in this investigation, we researched the expression of TH and DA in odontoblasts and the effects of DA on the differentiation of preodontoblasts (KN-3 cells). Immunostaining showed that TH and DA were intensely expressed in odontoblasts and preodontoblasts of rat incisors and molars. KN-3 cells expressed D1-like and D2-like receptors for DA. Furthermore, DA promoted odontoblastic differentiation of KN-3 cells, whereas an antagonist of D1-like receptors and a PKA signaling blocker, inhibited such differentiation. However, antagonists of D2-like receptors promoted differentiation. These results suggested that DA in preodontoblasts and odontoblasts might promote odontoblastic differentiation through D1-like receptors, but not D2-like receptors, and PKA signaling in an autocrine or paracrine manner and plays roles in dentinogenesis.

A review of the literature on the efficacy of mineral trioxide aggregate in conservative dentistry

The aim of this literature review was to assess the clinical performance of MTA to establish the evidence level for its effectiveness in vital pulp therapy, perforation repair, and retrograde root canal filling. A comprehensive literature survey was performed via electronic databases of PubMed/MEDLINE. A total of 58 papers were reviewed in this study, of which 2 were systematic reviews/meta-analysis, 9 were randomized controlled trials (RCTs), and the rest were fallen into other categories. Mineral trioxide aggregate (MTA) provided better pulp protection as a direct capping material when compared with calcium hydroxide. As perforation repair materials, MTA demonstrated an excellent sealing ability in vitro. For periodontal tissues around a perforation, MTA provided normal healing processes in clinical trials. It is therefore concluded that MTA has a high potential in repairing perforations. MTA is the most promising material when used for retrograde root canal filling demonstrating normal healing in short/long term clinical outcomes.

R-spondin 2 promotes osteoblastic differentiation of immature human periodontal ligament cells through the Wnt/β-catenin signaling pathway

OBJECTIVE

In this study, we measured the expression of R-spondin 2 (RSPO2) in periodontal ligament (PDL) tissue and cells. Further, we examined the effects of RSPO2 on osteoblastic differentiation of immature human PDL cells (HPDLCs).

BACKGROUND

R-spondin (RSPO) family proteins are secreted glycoproteins that play important roles in embryonic development and tissue homeostasis through activation of the Wnt/β-catenin signaling pathway. RSPO2, a member of the RSPO family, has been reported to enhance osteogenesis in mice. However, little is known regarding the roles of RSPO2 in PDL tissues.

METHODS

Expression of RSPO2 in rat PDL tissue and primary HPDLCs was examined by immunohistochemical and immunofluorescence staining, as well as by semiquantitative RT-PCR. The effects of stretch loading on the expression of RSPO2 and Dickkopf-related protein 1 (DKK1) were assessed by quantitative RT-PCR. Expression of receptors for RSPOs, such as Leucine-rich repeat-containing G-protein-coupled receptors (LGRs) 4, 5, and 6 in immature human PDL cells (cell line 2-14, or 2-14 cells), was investigated by semiquantitative RT-PCR. Mineralized nodule formation in 2-14 cells treated with RSPO2 under osteoblastic inductive condition was examined by Alizarin Red S and von Kossa stainings. Nuclear translocation of β-catenin and expression of active β-catenin in 2-14 cells treated with RSPO2 were assessed by immunofluorescence staining and Western blotting analysis, respectively. In addition, the effect of Dickkopf-related protein 1 (DKK1), an inhibitor of Wnt/β-catenin signaling, was also examined.

RESULTS

Rat PDL tissue and HPDLCs expressed RSPO2, and HPDLCs also expressed RSPO2, while little was found in 2-14 cells. Expression of RSPO2 as well as DKK1 in HPDLCs was significantly upregulated by exposure to stretch loading. LGR4 was predominantly expressed in 2-14 cells, which expressed low levels of LGR5 and LGR6. RSPO2 enhanced the Alizarin Red S and von Kossa-positive reactions in 2-14 cells. In addition, DKK1 suppressed nuclear translocation of β-catenin, activation of β-catenin, and increases of Alizarin Red S and von Kossa-positive reactions in 2-14 cells, all of which were induced by RSPO2 treatment.

CONCLUSION

RSPO2, which is expressed in PDL tissue and cells, might play an important role in regulating the osteoblastic differentiation of immature human PDL cells through the Wnt/β-catenin signaling pathway.

Abstract P1-07-13: Obesity is associated with poor prognosis of Japanese breast cancer, especially in ER positive/HER2 negative subtype, which tendency is prominent

Introduction: Body mass index (BMI) is defined as a poor prognostic factor in breast cancer patients in western countries. Since the percentage of the overweight differs between Asian and western breast cancer patients, we do not know if breast cancer prognosis in Asia is related to obesity, the same as in western countries. Therefore, we have investigated the association between BMI and the prognosis of Japanese breast cancer patients.

Patients and Methods: This study is a retrospective analysis of the 1,924 primary Japanese female breast cancer patients with clinical stage I through III disease to have undergone surgery between January 2004 and December 2013 at the Hokkaido Cancer Center. The data of BMI were at the time of diagnosis, and stratified into 2 groups as non-Obese (BMI < 25 kg/m2), Obese (BMI ≥ 25 kg/m2). The overall survival (OS) and disease-free survival (DFS) were compared between two BMI groups using the Kaplan-Meier method and Cox hazards model.

Results: The number of non-Obese group was 1,353 (70.3%) and Obese group was 571 (29.7%) of the 1,924 patients. Six hundred and thirty two patients were in premenopausal (32.8%), 1,289 were in postmenopausal (67.0%) and 3 were unknown. The median follow-up period was 73 months. Breast cancer recurred in 239 patients (12.2%), and 204 patients died. There were 110 cases of breast cancer-related death, 48 cases of non-breast cancer death, and 46 cases of unknown as the cause of death. Patients in Obese group had shown significantly poorer OS (adjusted hazard ratio (HR) = 1.68, 95% confidence interval (CI) = 0.45 to 0.79) and DFS (HR = 1.46, 95% CI = 1.16 to 1.82). As investigating by subtype analysis, a high BMI in ER positive/HER2 negative patients was associated with a significantly worse OS (HR = 2.04, 95% CI = 1.42 to 2.92) and significantly worse DFS (HR = 1.61, 95% CI = 1.23 to 2.11). On the other hand, there was no significant interaction found between the BMI and OS or DFS in ER negative/HER2 negative patients and HER2 positive patients. Subsequently, when analysis was limited to ER positive HER2 negative, there was a difference in the degree of association between obesity and prognosis due to the difference in menopause status. In premenopausal patients with ER positive/HER2 negative cancer, Obese group had significantly poorer OS (HR = 2.83, 95%CI = 1.32 to 5.88) and significantly poorer DFS (HR = 2.41, 95%CI = 1.41 to 3.99). In postmenopausal patients, Obese group patients had significantly poorer OS (HR = 1.71, 95%CI = 1.11 to 2.58) and poorer DFS (HR = 1.35, 95%CI = 0.98 to 1.86), however. The relevance was not so large compared with that in premenopausal patients.

Conclusion: Among Japanese breast cancer patients, Obese (BMI ≥ 25 kg/m2) was one of poor prognostic factors. Specifically, obesity was associated as an extremely strong prognostic factor in ER positive/HER2 negative premenopausal patients. Since hormone therapy has been practiced in almost all ER positive breast cancers, the relationship between hormonal therapy susceptibility and obesity is noticed not only in western patients but also in Asian patients.

Citation Format: Sato M, Terai S, Tachikawa H, Maeda H, Yamamoto M, Tomioka N, Watanabe K, Takahashi M. Obesity is associated with poor prognosis of Japanese breast cancer, especially in ER positive/HER2 negative subtype, which tendency is prominent [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P1-07-13.

Abstract P5-20-11: Comparative effectiveness of neoadjuvant therapy for HER2-Positive breast cancer: Addition of new clinical evidence to network meta-analysis and data update after 5 years

Background: It is becoming more popular to perform neoadjuvant chemotherapy including anti-HER2 agents to operable HER2-positive breast cancer patients. Increasing HER2-targeted treatment options urge us to define the best neoadjuvant therapy. In 2014, we reported the systematical assessment of the efficacy and safety of neoadjuvant therapy for HER2-positive breast cancer, using network meta-analysis based on Bayesian model (Nagayama et al., JNCI 2014). Network meta-analysis synthesizes information from a network of trials, which helps interpret the randomized evidence and can rank treatments from different trials. After five years from our first literature search, we decided to update our analysis due to accumulation of new clinical evidence.

Methods: We assessed odds ratio for pathological complete response (pCR), completion, and safety in seven treatment arms utilizing pooling effect sizes. The treatment arms included the combinations of chemotherapy (CT), trastzumab (tzmb), lapatinib (lpnb) and pertzumab (pzmb). All statistical tests were two-sided, and we followed Preferred Reporting Items for Systematic Reviews and MetaAnalyses (PRISMA) guidelines.

Results: A database search identified 993 articles with 13 studies meeting the eligibility criteria, adding three studies (a trial of CT + tzmb vs CT + lpnb, and two trials of CT + tzmb vs CT + lpnb vs CT + tzmb + lpnb) to previous analysis. In direct comparison, CT + tzmb significantly achieved more pCR than CT + lpnb (OR=0.68, 95% CI = 0.52 to 0.89, p=.005) despite no statistical difference was found previously. In indirect comparison, treatment arms of dual anti-HER2 agents with CT achieved more pCR than other arms, reducing their credibility intervals against all other arms. This trend was stronger in CT + tzmb + lpnb arm (CT + tzmb + lpnb vs CT + tzmb, OR = 1.62, 95% CrI = 1.19 to 2.22, p = .003), which we added sufficient clinical evidence. Moreover, it exposed the need for additional clinical data for pzmb relative arms. Values of surface under the cumulative ranking (SUCRA) suggested that CT + tzmb + pzmb had the highest probability of being the best treatment arm for pCR (SUCRA = 0.95), followed by CT + tzmb + lpnb (SUCRA = 0.87), and CT + tzmb (SUCRA = 0.62), widening the gap and differentiating the top two dual blockade arms which were close in our previous report. All outcomes from our present analysis were consistent with our previous report and strengthened data solidity by reducing confidence or credibility intervals.

Conclusion: Consistent results in not only in pCR but also in completion rates and adverse events indicate that we are looking at the results which are close to the truth. Additional trials of lpnb relative regimens are not probable to change the results, but pzmb relative trials are required to improve evidence solidity. New clinical data established stronger evidence in network meta-analysis that combining two anti-HER2 agents with CT is most effective in the neoadjuvant setting for HER2-positive breast cancer.

Citation Format: Nakashoji A, Hayashida T, Yokoe T, Maeda H, Watanuki R, Kikuchi M, Seki T, Takahashi M, Abe T, Kitagawa Y. Comparative effectiveness of neoadjuvant therapy for HER2-Positive breast cancer: Addition of new clinical evidence to network meta-analysis and data update after 5 years [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P5-20-11.

Solitary pulmonary nodules due to non-tuberculous mycobacteriosis among 28 resected cases

BACKGROUND

In some patients, non-tuberculous mycobacteria (NTM) infections manifest in solitary nodules (solitary nodular [SN] type) generally caused by Mycobacterium avium complex (MAC). In patients treated using surgical resection, the American Thoracic Society guidelines state that postoperative chemotherapy is not necessary in the absence of lesions, although there have been a few reports of such cases.

METHODS

Twenty-eight patients diagnosed with NTM who underwent solitary pulmonary nodule resection at Toneyama Hospital, Osaka, Japan, between January 2000 and October 2012 were enrolled. We evaluated the influence of the surgical procedure and chemotherapy on outcomes in this retrospective study.

RESULTS

Of the 28 patients, 12 were males and 16 were females; the mean age was 58.6 ± 13.2 years. Twenty-five patients were asymptomatic and bronchoscopy was performed in 18; only 2 had a definitive diagnosis of NTM. The pathogen responsible was MAC in 27 patients and M. kansasii in 1. The surgical procedure used was wedge resection in 22 patients, segmentectomy in 1 and lobectomy in 5. Postoperative chemotherapy was administered to 9 patients. Twenty-six patients had no recurrence.

CONCLUSION

We believe that wedge resection is a valid surgical intervention for SN type NTM; additional postoperative chemotherapy is unnecessary in cases with no residual lesions in the operated lung lobe.

Psychiatric comorbidities in patients with Atypical Odontalgia

OBJECTIVE

Atypical Odontalgia (AO) is a condition characterized by tooth pain with no apparent cause. Although psychiatric comorbidity seems to be very common, it has rarely been studied. To clarify the influence of psychiatric comorbidity on the clinical features in patients with AO, we retrospectively evaluated their examination records.

METHODS

Clinical features and psychiatric diagnoses of 383 patients with AO were investigated by reviewing patients' medical records and referral letters. Psychiatric diagnoses were categorized according to the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5). We also analyzed visual analogue scale (VAS), self-rating depression scale (SDS), and the short-form McGill pain questionnaire (SF-MPQ) scores.

RESULTS

Of the 383 patients with AO, 177 (46.2%) had comorbid psychiatric disorders. The most common were depressive disorders (15.4%) and anxiety disorders (10.1%). Serious psychotic disorders such as bipolar disorder (3.0%) and schizophrenia (1.8%) were rare. Dental trigger of AO was reported in 217 (56.7%) patients. There were no significant correlations between psychiatric comorbidities and most of the demographic features. Higher VAS and SDS scores, higher frequency of sleep disturbance, and higher ratings of "Fearful" and "Punishing-cruel" descriptors of the SF-MPQ were found in patients with psychiatric comorbidity.

CONCLUSIONS

About half of AO patients had comorbid psychiatric disorders. Dental procedures are not necessarily causative factors of AO. In AO patients with comorbid psychiatric disorders, pain might have a larger emotional component than a sensory one. VAS, SDS, and SF-MPQ scores might aid in the noticing of underlying comorbid psychiatric disorders in AO patients.

Extracellular Matrix from Periodontal Ligament Cells Could Induce the Differentiation of Induced Pluripotent Stem Cells to Periodontal Ligament Stem Cell-Like Cells

The periodontal ligament (PDL) plays an important role in anchoring teeth in the bone socket. Damage to the PDL, such as after severe inflammation, can be treated with a therapeutic strategy that uses stem cells derived from PDL tissue (PDLSCs), a strategy that has received intense scrutiny over the past decade. However, there is an insufficient number of PDLSCs within the PDL for treating such damage. Therefore, we sought to induce the differentiation of induced pluripotent stem (iPS) cells into PDLSCs as an initial step toward PDL therapy. To this end, we first induced iPS cells into neural crest (NC)-like cells. We then captured the p75 neurotrophic receptor-positive cells (iPS-NC cells) and cultured them on an extracellular matrix (ECM) produced by human PDL cells (iPS-NC-PDL cells). These iPS-NC-PDL cells showed reduced expression of embryonic stem cell and NC cell markers as compared with iPS and iPS-NC cells, and enrichment of mesenchymal stem cell markers. The cells also had a higher proliferative capacity, multipotency, and elevated expression of PDL-related markers than iPS-NC cells cultured on fibronectin and laminin (iPS-NC-FL cells) or ECM produced by human skin fibroblast cells (iPS-NC-SF cells). Overall, we present a culture method to produce high number of PDLSC-like cells from iPS cells as a first step toward a strategy for PDL regeneration.

The Dlx5-FGF10 signaling cascade controls cranial neural crest and myoblast interaction during oropharyngeal patterning and development

Craniofacial development depends on cell-cell interactions, coordinated cellular movement and differentiation under the control of regulatory gene networks, which include the distal-less (Dlx) gene family. However, the functional significance of Dlx5 in patterning the oropharyngeal region has remained unknown. Here, we show that loss of Dlx5 leads to a shortened soft palate and an absence of the levator veli palatini, palatopharyngeus and palatoglossus muscles that are derived from the 4th pharyngeal arch (PA); however, the tensor veli palatini, derived from the 1st PA, is unaffected. Dlx5-positive cranial neural crest (CNC) cells are in direct contact with myoblasts derived from the pharyngeal mesoderm, and Dlx5 disruption leads to altered proliferation and apoptosis of CNC and muscle progenitor cells. Moreover, the FGF10 pathway is downregulated in Dlx5^-/- mice, and activation of FGF10 signaling rescues CNC cell proliferation and myogenic differentiation in these mutant mice. Collectively, our results indicate that Dlx5 plays crucial roles in the patterning of the oropharyngeal region and development of muscles derived from the 4th PA mesoderm in the soft palate, likely via interactions between CNC-derived and myogenic progenitor cells.

Rabi oscillations in the spatial profiles of superfluorescent pulses from rubidium vapor

In this study, we investigate 420-nm yoked superfluorescence (YSF) emitted from the atomic vapor of rubidium (Rb) by driving the Rb 5S - 5D two-photon transition with an ultrashort pulsed laser. When the pump pulse is close to its transform limit (~ 100 fs) or down-chirped up to around 200 fs, the 420-nm YSF appears as a low-divergence beam with a ring-shaped radial profile. Although such a beam profile is less sensitive to the vapor pressure of Rb in a cell, its diameter rigorously varies as a function of the pump-pulse power. By numerically solving a time-dependent Schrödinger equation for a single-Rb atom, we well reproduce our experimental observation, indicating that a single-atom Rabi oscillation is responsible for the spatial beam profile of the 420-nm emission.