The growth and osteoclastogenic effects of fibroblasts isolated from keratocystic odontogenic tumor

The detection of Gper1 as an important gene promoting jawbone regeneration in the context of estrogen deficiency

Numerous studies have demonstrated that estrogen deficiency inhibit the proliferation and differentiation of pre-osteoblasts in skeleton by affecting osteogenic signaling, lead to decreased bone mass and impaired regeneration. To explore the mechanisms maintaining bone regeneration under estrogen deficiency, we randomly selected 1102 clinical cases, in which female patients aged between 18 and 75 have underwent tooth extraction in Stomatological Hospital of Tongji University, there is little difference in the healing effect of extraction defects, suggesting that to some extent, the regeneration of jawbone is insensitive to the decreased estrogen level. To illuminate the mechanisms promoting jawbone regeneration under estrogen deficiency, a tooth extraction defect model was established in the maxilla of female rats who underwent ovariectomy (OVX) or sham surgery, and jawbone marrow stromal cells (BMSCs) were isolated for single-cell sequencing. Further quantitative PCR, RNA interference, alizarin red staining, immunohistochemistry and western blotting experiments demonstrated that in the context of ovariectomy, maxillary defects promoted G protein-coupled estrogen receptor 1 (Gper1) expression, stimulate downstream cAMP/PKA/pCREB signaling, and facilitate cell proliferation, and thus provided sufficient progenitors for osteogenesis and enhanced the regeneration capacity of the jawbone. Correspondingly, the heterozygous deletion of the Gper1 gene attenuated the phosphorylation of CREB, led to decreased cell proliferation, and impaired the restoration of maxillary defects. This study demonstrates the importance of Gper1 in maintaining jawbone regeneration, especially in the context of estrogen deficiency.

Interactions of Fibroblast Subtypes Influence Osteoclastogenesis and Alveolar Bone Destruction in Periodontitis

Background

To analyze the fibroblasts subtypes in the gingival tissues of healthy controls, gingivitis and periodontitis patients, as well as the effects of interaction between subtypes on alveolar bone destruction.

Methods

Gingival tissues were divided into three groups according to clinical and radiographic examination, and the immunostaining of EDA+FN was assessed. Fibroblasts from gingiva developed colony formation units (CFUs) and induced Trap+MNCs. The expression of osteoclastogenesis-related genes was assessed by real-time PCR. Variances in the gene profiles of CFUs were identified by principal component analysis, and cluster analysis divided CFUs into subtypes. The induction of Trap+MNCs and gene expression were compared among individual or cocultured subtypes. The fibroblast subtypes exerted critical effect on Trap+MNCs formation were selected and edited by CRISPR/Cas to investigate the influence on osteoclastogenesis in the periodontitis in mice.

Results

Most periodontitis samples exhibited intensive EDA+FN staining (P < 0.05), and these fibroblasts also induced most Trap+MNCs among three groups; consistently, fibroblasts from periodontitis highly expressed genes facilitating osteoclastogenesis. According to gene profiles and osteoclastogenic induction, four clusters of CFUs were identified. The proportion of clusters was significantly different (P < 0.05) among three groups, and their interaction influenced osteoclastogenic induction. Although Cluster 4 induced less osteoclasts, it enhanced the effects of Clusters 1 and 3 on Trap+MNCs formation (P < 0.05). EDA knockout in Cluster 4 abrogated this promotion (P < 0.05), and decreased osteoclasts and alveolar bone destruction in experimental periodontitis (P < 0.05).

Conclusion

Heterogeneous fibroblast subtypes affect the switch or development of periodontitis. A subtype (Cluster 4) played important role during alveolar bone destruction, by regulating other subtypes via EDA+FN paracrine.

Fibroblast Programmed Cell Death Ligand 1 Promotes Osteoclastogenesis in Odontogenic Keratocysts

Local aggressive growth of odontogenic keratocysts (OKCs) can cause serious bone destruction, even resulting in pathologic fractures of the mandible. The mechanism of osteoclastogenesis in OKCs was explored by investigating the role of programmed cell death ligand 1 (PD-L1), a key immune checkpoint, in OKCs and its relationship with the M2 isoform of pyruvate kinase (PKM2), a key enzyme of glycolysis. The data from immunohistochemistry, real-time quantitative PCR, Western blot, and flow cytometry indicated that the expression level of PD-L1 was significantly increased in the stroma and fibroblasts of OKCs (OKC-Fs) when compared with oral mucosa. Double-labeling staining demonstrated that osteoclasts in OKCs spatially interacted with PD-L1-positive OKC-Fs. Exogenous expression of PD-L1 in OKC-Fs promoted osteoclastogenesis when OKC-Fs were co-cultured with osteoclast precursors (RAW264.7 cells). Because OKC-Fs exhibit energy dependency and acquire energy from PKM2-mediated glycolysis, this study generated stable PKM2 knockdown OKC-Fs using shRNAs against PKM2, and found that PD-L1 expression level was decreased by PKM2 knockdown. Furthermore, Spearman rank correlation analysis showed that there was a positive correlation between the immunostaining of PKM2 and PD-L1 in OKC samples. In addition, double-labeling immunofluorescence showed colocalizations between PKM2 and PD-L1 in the fibrous tissue walls of OKCs. In conclusion, PD-L1 in fibroblasts promotes osteoclastogenesis in OKCs, which is regulated by PKM2.

Increased M2 Isoform of Pyruvate Kinase in Fibroblasts Contributes to the Growth, Aggressiveness, and Osteoclastogenesis of Odontogenic Keratocysts

To investigate the role of glycolysis and the M2 isoform of pyruvate kinase (PKM2) in odontogenic keratocysts (OKCs), the glycolytic flux of primary odontogenic keratocyst fibroblasts (OKC-Fs) and normal oral mucosa fibroblasts (OM-Fs) was determined by glucose uptake, lactate production, and cell proliferation assays. Wound healing assay and Matrigel-coated chamber system were used to investigate the effects of PKM2 on migration and invasion capacities of OKC-Fs. Co-culture of OKC-Fs with osteoclast precursors (RAW264.7 cells) was used to clarify the role of glycolysis in the osteoclastogenic effects of OKC-Fs. In addition, hypoxia-inducible factor 1α and some key enzymes related to glycolysis, including PKM2, 6-phosphofructo-2-kinase/fructose-2, 6-biphosphatase 3, hexokinase 2, and lactate dehydrogenase A, were detected to assess the activation of glycolysis in OKC stroma by immunohistochemistry. Results showed that the glucose uptake and lactate production were significantly higher in OKC-Fs than OM-Fs. PKM2 was elevated in OKC-Fs compared with that in OM-Fs. PKM2 significantly regulated glycolysis, proliferation, migration, invasion, and osteoclastogenic effects of OKC-Fs. Additionally hypoxia-inducible factor 1α, 6-phosphofructo-2-kinase/fructose-2, 6-biphosphatase 3, hexokinase 2, and lactate dehydrogenase A were markedly overexpressed in OKC stroma, and correlated with PKM2. Moreover, the expression of PKM2 was regulated by oxygen concentration in vitro. In sum, PKM2-mediated glycolysis regulated the growth, aggressiveness, and osteoclastogenesis of OKC.

Heterogeneity of fibroblasts from radicular cyst influenced osteoclastogenesis and bone destruction

AIM

To analyze the heterogeneity of fibroblasts isolated from the fibrous capsules of radicular cysts and explore the effects of fibroblast subsets on bone destruction.

METHODOLOGY

Radicular cysts were divided into groups according to varying perilesional sclerosis identified by radiograph. Colony-forming units (CFUs) were isolated from the fibrous capsules of cysts, by which Trap + MNCs were induced, and the expression of osteoclastogenesis-related genes was compared among groups by real-time PCR. The variances in gene profiles of CFUs were identified by principal component analysis, and then, CFUs were divided into subsets using cluster analysis. The induction of Trap + MNCs and related gene expression was compared among subsets, and osteoclastogenic induction was blocked by IST-9 or bevacizumab. The fibroblast subsets in cysts were investigated by retrospective immunostaining with IST-9, VEGF-A, and CD34. A fibroblast subset that underwent gene editing by CRISPR/Cas was injected into the site of bone defects in animal models, and the in vivo effects on osteoclastogenesis were investigated.

RESULTS

The fibroblast CFUs isolated from radicular cysts with perilesional unsclerotized cysts induced more Trap + MNCs than those with perilesional sclerotic cysts (p < .05). Most fibroblast CFUs from unsclerotized cysts belonged to Cluster 2, which induced more Trap + MNCs (p < .05) and highly expressed genes facilitating osteoclastogenesis; these results were different from those of Cluster 1 (p < .05), in which most CFUs were isolated from perilesional sclerotic cysts or controls (p < .05). The high expression of EDA + FN and VEGF-A was investigated in both the fibroblasts of Cluster 2 and the fibrous capsules of unsclerotized cysts (p < .05), and the number of Trap + MNCs induced by Cluster 2 was decreased by treatment with IST-9 and bevacizumab (p < .05). Consistently, EDA exon exclusion significantly decreased the osteoclastogenic induction of fibroblasts from Cluster 2 in vivo (p < .05).

CONCLUSION

The fibrous capsules of radicular cysts contain heterogeneous fibroblasts that can form subsets exhibiting different effects on osteoclastogenesis. The subset, which depending on the autocrine effects of EDA + FN on VEGF-A, mainly contributes to the osteoclastogenesis and bone destruction of radicular cysts. The regulation of the proportion of subsets is a possible strategy for artificially interfering with osteoclastogenesis.

The extra domain A of fibronectin facilitates osteoclastogenesis in radicular cysts through vascular endothelial growth factor

AIM

To analyse the effects of the alternatively spliced fibronectin (FN) gene and its isoforms on osteoclastogenesis in radicular cysts.

METHODOLOGY

Specimens of radicular cysts were collected surgically from 22 patients whose radiolucent periapical areas were measured on digital panoramic radiographs before surgery. The associations between the radiolucent areas and FN isoforms, vascular endothelial growth factor (VEGF) expression or micro-vessel density, as well as the relationships amongst them, were analysed by immunohistochemical staining using the antibodies IST-9, BC-1, P1F11, VEGF and CD34. Fibroblasts isolated from those specimens were used to induce Trap + MNCs, and the effects of induction were assessed by blocking FN containing extra domain A (EDA + FN), COX-2 or VEGF in vitro. The effects of EDA exon knockout using CRISPR/Cas system were also assessed. Quantitative PCR was used to analyse relative expression of FN isoforms and osteoclastogenic genes. Data were analysed using linear regression, Spearman's rank correlation analysis, chi-square test and Student's t-test; P < 0.05 was considered significant.

RESULTS

Micro-vessel density and EDA + FN staining were positively associated with the size of radiolucent periapical areas (mm² ; P < 0.05), consistent with a positive association between Trap + MNCs and VEGF expression in fibroblasts (P < 0.05). Blocking the interaction between EDA + FN and fibroblasts inhibited Trap + MNC formation. In addition, EDA exon knockout decreased VEGF expression and inhibited Trap + MNC formation to the extent of blocking VEGF by bevacizumab, but osteoclastogenic induction was restored by recombinant VEGF. Using retrospective clinicopathological data, VEGF staining was shown to be positively associated with EDA + FN staining, micro-vessel density and the size of radiolucent areas (P < 0.05).

CONCLUSION

In fibrous capsules of radicular cysts, the alternatively spliced isoform EDA + FN generated by fibroblasts stimulated VEGF expression via an autocrine effect and then facilitated osteoclastogenesis. Both blockage of VEGF and EDA exon knockout could be used to inhibit bone destruction.

Bevacizumab or fibronectin gene editing inhibits the osteoclastogenic effects of fibroblasts derived from human radicular cysts

Fibronectin (FN) is a main component of extracellular matrix (ECM) in most adult tissues. Under pathological conditions, particularly inflammation, wound healing and tumors, an alternatively spliced exon extra domain A (EDA) is included in the FN protein (EDA⁺FN), which facilitates cellular proliferation, motility, and aggressiveness in different lesions. In this study we investigated the effects of EDA⁺FN on bone destruction in human radicular cysts and explored the possibility of editing FN gene or blocking the related paracrine signaling pathway to inhibit the osteoclastogenesis. The specimens of radicular cysts were obtained from 20 patients. We showed that the vessel density was positively associated with both the lesion size (R = 0.49, P = 0.001) and EDA⁺FN staining (R = 0.26, P = 0.022) in the specimens. We isolated fibroblasts from surgical specimens, and used the CRISPR/Cas system to knockout the EDA exon, or used IST-9 antibody and bevacizumab to block EDA⁺FN and VEGF, respectively. Compared to control fibroblasts, the fibroblasts from radicular cysts exhibited significantly more Trap⁺MNCs, the relative expression level of VEGF was positively associated with both the ratio of EDA⁺FN/total FN (R = 0.271, P = 0.019) and with the number of Trap⁺MNCs (R = 0.331, P = 0.008). The knockout of the EDA exon significantly decreased VEGF expression in the fibroblasts derived from radicular cysts, leading to significantly decreased osteoclastogenesis; similar results were observed using bevacizumab to block VEGF, but block of EDA⁺FN with IST-9 antibody had no effect. Furthermore, the inhibitory effects of gene editing on Trap⁺MNC development were restored by exogenous VEGF. These results suggest that EDA⁺FN facilitates osteoclastogenesis in the fibrous capsule of radicular cysts, through a mechanism mediated by VEGF via an autocrine effect on the fibroblasts. Bevacizumab inhibits osteoclastogenesis in radicular cysts as effectively as the exclusion of the EDA exon by gene editing.

Bone marrow mesenchymal stem cell-derived exosomes enhance osteoclastogenesis during alveolar bone deterioration in rats

BMMSC-derived exosomes from rats with bone deterioration increased the osteoclastogenesis of the Raw264.7 cells, which suggests that BMMSC-derived exosomes could accelerate osteoclastogenesis in alveolar bone deterioration.

Treatment of Keratocystic Odontogenic Tumours: A Prospective Study of 30 Cases

AIM

This prospective study aimed at presenting different treatment modalities and its association with the recurrence rate of KCOT.

MATERIAL AND METHOD

The study was conducted on 30 patients diagnosed with KCOT between March 2009 and 2012. The patients were followed up for a period of at least 1 year. The clinical, radiographic and demographic data were recorded and four different treatment modalities were followed to assess the recurrence of the tumour.

RESULTS

In the study, KCOT showed male predominance with a male: female ratio of 23:7. Of the total cases, 26 (86.67 %) patients had parakeratinised KCOT and the rest 4 (13.3 %) patients had orthokeratnised KCOT. Nine (30 %) patients were reported with recurrence of the tumour within 1-2 years of surgery-all these patients had parakeratinised cyst. Recurrence was observed in four (50 %) out of eight cases of marsupialisation and four (44.44 %) out of nine cases of treatment using the enucleation process. No recurrence was seen in patients treated with resection; however only one out of three patients treated with enucleation, followed by fixation with Carnoy's solution showed signs of recurrence. The histopathological examination determined the aggressive nature of KCOT and its association with the recurrence rate as well. The findings of our study indicate that more aggressive treatment can aid in reducing the chances of recurrence.

Osteoclastogenesis in Local Alveolar Bone in Early Decortication-Facilitated Orthodontic Tooth Movement

Objective

In the current study, we aimed to investigate the effects of alveolar decortication on local bone remodeling, and to explore the possible mechanism by which decortication facilitates tooth movement.

Materials and Methods

Forty rabbits were included in the experiment. The left mandible was subjected to decortication-facilitated orthodontics, and the right mandible underwent traditional orthodontics as a control. The animals were sacrificed on the days 1, 3, 5, 7 and 14, after undergoing orthodontic procedures. Tooth movement was measured by Micro-CT, and the local periodontal tissues were investigated using H&E, Masson's trichrome and tartrate-resistant acid phosphatase (TRAP) staining. The mRNA levels of genes related to bone remodeling in the alveolar bone were analyzed using real-time PCR.

Result

On days 3, 5, 7 and 14, tooth movement was statistically accelerated by decortication (P < 0.05) and was accompanied by increased hyperemia. Despite the lack of new bone formation in both groups, more osteoclasts were noted in the decorticated group, with two peak counts (P < 0.05). The first peak count was consistent with the maximum values of ctsk and TRAP expression, and the second peak counts accompanied the maximum nfatc1 and jdp2 expression. The increased fra2 expression and the ratio of rankl/opg also accompanied the second peak counts.

Conclusions

Following alveolar decortication, osteoclastogenesis was initially induced to a greater degree than the new bone formation which was thought to have caused a regional acceleratory phenomenon (RAP). The amount of steoclastogenesis in the decorticated alveolar bone was found to have two peaks, perhaps due to attenuated local resistance. The first peak count in osteoclasts may have been due to previously existing osteoclast precursors, whereas the second may represent the differentiation of peripheral blood mononuclear cells which came from circulation as the result of hyperemia.

Disruption of Smad4 in odontoblasts and dental epithelial cells influences the phenotype of multiple keratocystic odontogenic tumors

Keratocystic odontogenic tumors (KCOTs) are cystic epithelial neoplasms with a high recurrence rate. The molecular mechanisms underlying the initiation and progression of KCOTs are still largely unknown. Previous research showed that specific ablation of Smad4 in odontoblasts and dental epithelia resulted in spontaneous KCOTs in mice, and that constitutively activated Hedgehog (Hh) signaling was detected in the cyst epithelia of both Smad4(Co/Co) OC-Cre and Smad4(Co/Co) K5-Cre mice. Here, we ablated Smad4 in mouse odontoblasts and dental epithelia and compared the sizes and numbers of KCOTs. Both the number and size of KCOTs in Smad4(Co/Co) OC-Cre mice were larger than those in Smad4(Co/Co) K5-Cre mice, suggesting that paracrine signals from root odontoblasts play a more important role than those from Hertwig's epithelial root sheath (HERS) cells.

Fibroblasts regulate variable aggressiveness of syndromic keratocystic and non-syndromic odontogenic tumors

Keratocystic odontogenic tumors (KCOTs) are jaw lesions that can be either sporadic or associated with nevoid basal cell carcinoma syndrome, which typically occurs as multiple, aggressive lesions that can lead to large areas of bone destruction and resorption and cause major impairment and even jaw fracture. To clarify the role of fibroblasts in the aggressivness of syndromic (S-) as compared with non-syndromic (NS-) KCOTs, we assessed fibroblasts derived from 16 S- and NS-KCOTs for differences in cell proliferation, multilineage differentiation potential, alkaline phosphatase activity, and osteoclastogenic potential. S-KCOT fibroblasts had proliferative and osteoclastogenic capacity higher than those from NS-KCOTs, as evidenced by higher numbers of tartrate-resistant acid-phosphatase-positive multinuclear cells, expression of cyclooxygenase 2, and ratio of receptor activator of nuclear factor-kappa B ligand to osteoprotegerin. The osteogenic potential was higher for S- than for NS-KCOT fibroblasts and was associated with lower mRNA expression of runt-related transcription factor 2, collagen type I α1, osteocalcin, and osteopontin as well as reduced alkaline phosphatase activity. These results suggest that the distinct characteristics of fibroblasts in KCOTs are responsible for the greater aggressiveness observed in the syndromic subtype.

ABBREVIATIONS

AP, alkaline phosphatase; CK, cytokeratin; COL1A1, collagen type I α1; COX-2, cyclooxygenase-2; GM-CSF, granulocyte-macrophage colony-stimulating factor; IL-1α, interleukin 1α; KCOT, keratocystic odontogenic tumor; NBCCS, nevoid basal cell carcinoma syndrome; NS-KCOT, non-syndrome-associated KCOT; OCN, osteocalcin; OPG, osteoprotegerin; OPN, osteopontin; RANKL, receptor activator of nuclear factor-kappa B ligand; Runx2, runt-related transcription factor 2; S-KCOT, syndrome-associated KCOT; TAF, tumor-associated fibroblast; and TRAP, tartrate-resistant acid phosphatase.

Fibroblasts isolated from a keratocystic odontogenic tumor promote osteoclastogenesis in vitro via interaction with epithelial cells

OBJECTIVES

Investigate the role of the epithelial-mesenchymal interaction of keratocystic odontogenic tumor (KCOT) in influencing osteoclastogenesis.

MATERIALS AND METHODS

Fibroblasts isolated from KCOT fibrous capsule and normal gingival mucosa were, respectively, co-cultured with human immortalized oral epithelial cells (HIOECs), and the supernatant was collected to make conditioned medium, in which the osteoclastogenesis of osteoclast precursor cell line Raw 264.7 was observed. Genes related to bone resorption (RANKL, OPG, COX-2, and M-CSF) were analyzed by real-time PCR. Antibodies against human sRANKL and inhibitor of COX-2: NS398 were added to conditioned medium to investigate the inhibitory effect on osteoclastogenesis.

RESULTS

Compared with co-cultured gingival fibroblasts and HIOECs (GE-CM), the conditioned medium from co-cultured KCOT fibroblasts and HIOECs (KE-CM) induced more osteoclast-like cell formation and increased NFATC1 mRNA in Raw264.7 cells (P < 0.05). Co-cultured KCOT fibroblasts (KF) and HIOECs, respectively, expressed more COX-2 mRNA than the co-cultured gingival fibroblasts (GF) and HIOECs (P < 0.05). While the ratio of RANKL/OPG in HIOECs co-cultured with KF was also significantly higher than that co-cultured with GF (P < 0.05). The anti-human sRANKL antibody in KE-CM inhibited osteoclastogenesis of Raw264.7 cells; however, NS398 displayed little inhibition.

CONCLUSION

An interesting phenomenon of osteoclastogenic effect of KE-CM in vitro was investigated, which suggested an indispensable role of epithelial-mesenchymal interaction of KCOT in its bone destruction. It could be at least partly attributed to the up-regulated ratio of RANKL/OPG in epithelium induced by KCOT fibroblasts, the aggressiveness of tumor as result of epithelial-mesenchymal interaction deserves exploration further.

Identification of the involvement of LOXL4 in generation of keratocystic odontogenic tumors by RNA-Seq analysis

Keratocystic odontogenic tumors (KCOT) are benign, locally aggressive intraosseous tumors of odontogenic origin. KCOT have a higher stromal microvessel density (MVD) than dentigerous cysts (DC) and normal oral mucosa. To identify genes in the stroma of KCOT involved in tumor development and progression, RNA sequencing (RNA-Seq) was performed using samples from KCOT and primary stromal fibroblasts isolated from gingival tissues. Seven candidate genes that possess a function potentially related to KCOT progression were selected and their expression levels were confirmed by quantitative PCR, immunohistochemistry and enzyme-linked immunosorbent assay. Expression of lysyl oxidase-like 4 (LOXL4), the only candidate gene that encodes a secreted protein, was enhanced at both the mRNA and protein levels in KCOT stromal tissues and primary KCOT stromal fibroblasts compared to control tissues and primary fibroblasts (P<0.05). In vitro, high expression of LOXL4 could enhance proliferation and migration of the human umbilical vein endothelial cells (HUVECs). There was a significant, positive correlation between LOXL4 protein expression and MVD in stroma of KCOT and control tissues (r=0.882). These data suggest that abnormal expression of LOXL4 of KCOT may enhance angiogenesis in KCOT, which may help to promote the locally aggressive biological behavior of KCOT.

Keratocystic odontogenic tumor: a retrospective analysis of genetic, immunohistochemical and therapeutic features. Proposal of a multicenter clinical survey tool

OBJECTIVE

In 2005, the World Health Organization reclassified the parakeratinizing odontogenic keratocyst as a neoplasm. This article reviews the research leading to this reclassification, and validates a new survey tool that can be easily used to pool surgical and recurrence data from multiple offices.

STUDY DESIGN

All odontogenic lesions accessioned in the Iowa Surgical Oral Pathology Laboratory between 1949 and 2010 were identified from the database. A survey tool to assess treatment and follow-up was created. A total of 46 surgeons agreed to participate.

RESULTS

A total of 70 keratocystic odontogenic tumors (KOTs) had documented recurrences at follow-up intervals ranging from 6 months to 5 years. Primary tumors that recurred ranged in size as measured by greatest radiographic diameter from 0.7 to 6 cm.

CONCLUSIONS

This survey tool is recommended as standard allowing treatment of cases by multiple practitioners to be compared retrospectively or prospectively.