A cleft lip and palate gene, Irf6, is involved in osteoblast differentiation of craniofacial bone

Neural crest and periderm-specific requirements of Irf6 during neural tube and craniofacial development

IRF6 is a key genetic determinant of syndromic and non-syndromic cleft lip and palate. The ability to interrogate post-embryonic requirements of Irf6 has been hindered, as global Irf6 ablation in the mouse causes neonatal lethality. Prior work analyzing Irf6 in mouse models defined its role in the embryonic surface epithelium and periderm where it is required to regulate cell proliferation and differentiation. Several reports have also described Irf6 gene expression in other cell types, such as muscle, and neuroectoderm. However, analysis of a functional role in non-epithelial cell lineages has been incomplete due to the severity and lethality of the Irf6 knockout model and the paucity of work with a conditional Irf6 allele. Here we describe the generation and characterization of a new Irf6 floxed mouse model and analysis of Irf6 ablation in periderm and neural crest lineages. This work found that loss of Irf6 in periderm recapitulates a mild Irf6 null phenotype, suggesting that Irf6-mediated signaling in periderm plays a crucial role in regulating embryonic development. Further, conditional ablation of Irf6 in neural crest cells resulted in an anterior neural tube defect of variable penetrance. The generation of this conditional Irf6 allele allows for new insights into craniofacial development and new exploration into the post-natal role of Irf6.

Association between variants around IRF6 and non-syndromic orofacial cleft in Western Han Chinese

OBJECTIVES

Considering limitations of previous studies and differences across populations and subtypes, this study aimed to identify new potential SNPs around IRF6 associated with non-syndromic orofacial cleft (NSOC) in Western Han Chinese.

MATERIALS AND METHODS

We recruited 376 NSOC case-parent trios, including 125 non-syndromic cleft lip only (NSCLO) trios, 151 non-syndromic cleft lip and palate (NSCLP) trios, and 100 non-syndromic cleft palate only (NSCPO) trios. Twenty-two single-nucleotide polymorphisms (SNPs) were genotyped using MassARRAY method. Hardy-Weinberg equilibrium test, allelic transmission disequilibrium test (TDT) analysis, sliding-window haplotype TDT analysis, and tests for parent-of-origin effect were performed using the PLINK software. Pairwise linkage disequilibrium (LD) was computed using the Haploview program.

RESULTS

In TDT analysis, allele A at rs17015217 (p = 0.00011, OR = 0.61 and 95% CI: 0.47-0.78) and allele T at rs12080691 (p = 0.00011, OR = 0.61 and 95% CI: 0.47-0.78) were under-transmitted among NSCLO trios but over-transmitted among NSCPO trios. Haplotypes showing evidence of under-transmission in NSCLO trios were over-transmitted in NSCPO trios. In tests for parent-of-origin effects, T allele at rs12080691 presented paternal under-transmission among NSCLO trios but over-transmission among NSCPO trios.

CONCLUSIONS

Allele A at rs17015217 and allele T at rs12080691 are associated with NSCLO and NSCPO with potential to have opposite effects on two subtypes in this sample from Western Han Chinese.

Consistent downregulation of the cleft lip/palate-associated genes IRF6 and GRHL3 in carcinomas

Interferon Regulatory Factor 6 (IRF6) and Grainyhead Like Transcription Factor 3 (GRHL3) are transcription factors that orchestrate gene regulatory networks required for the balance between keratinocyte differentiation and proliferation. Absence of either protein results in the lack of a normal stratified epidermis with keratinocytes failing to stop proliferating and to terminally differentiate. Numerous pathological variants within IRF6 and GRHL3 have been identified in orofacial cleft-affected individuals and expression of the two transcription factors has been found to be often dysregulated in cancers. However, whether orofacial cleft-associated IRF6 and GRHL3 variants in patients might also affect their cancer risk later in life, is not clear yet. The fact that the role of IRF6 and GRHL3 in cancer remains controversial makes this question even more challenging. Some studies identified IRF6 and GRHL3 as oncogenes, while others could attribute tumor suppressive functions to them. Trying to solve this apparent conundrum, we herein aimed to characterize IRF6 and GRHL3 function in various types of carcinomas. We screened multiple cancer and normal cell lines for their expression, and subsequently proceeded with functional assays in cancer cell lines. Our data uncovered consistent downregulation of IRF6 and GRHL3 in all types of carcinomas analyzed. Reduced levels of IRF6 and GRHL3 were found to be associated with several tumorigenic properties, such as enhanced cell proliferation, epithelial mesenchymal transition, migration and reduced differentiation capacity. Based on our findings, IRF6 and GRHL3 can be considered as tumor suppressor genes in various carcinomas, which makes them potential common etiological factors for cancer and CLP in a fraction of CLP-affected patients.

TWIST1 interacts with β/δ-catenins during neural tube development and regulates fate transition in cranial neural crest cells

Cell fate determination is a necessary and tightly regulated process for producing different cell types and structures during development. Cranial neural crest cells (CNCCs) are unique to vertebrate embryos and emerge from the neural plate borders into multiple cell lineages that differentiate into bone, cartilage, neurons and glial cells. We have previously reported that Irf6 genetically interacts with Twist1 during CNCC-derived tissue formation. Here, we have investigated the mechanistic role of Twist1 and Irf6 at early stages of craniofacial development. Our data indicate that TWIST1 is expressed in endocytic vesicles at the apical surface and interacts with β/δ-catenins during neural tube closure, and Irf6 is involved in defining neural fold borders by restricting AP2α expression. Twist1 suppresses Irf6 and other epithelial genes in CNCCs during the epithelial-to-mesenchymal transition (EMT) process and cell migration. Conversely, a loss of Twist1 leads to a sustained expression of epithelial and cell adhesion markers in migratory CNCCs. Disruption of TWIST1 phosphorylation in vivo leads to epidermal blebbing, edema, neural tube defects and CNCC-derived structural abnormalities. Altogether, this study describes a previously uncharacterized function of mammalian Twist1 and Irf6 in the neural tube and CNCCs, and provides new target genes for Twist1 that are involved in cytoskeletal remodeling.

Embryonic and Early Postnatal Cranial Bone Volume and Tissue Mineral Density Values for C57BL/6J Laboratory Mice

Background

Laboratory mice are routinely used in craniofacial research based on the relatively close genetic relationship and conservation of developmental pathways between humans and mice. Since genetic perturbations and disease states may have localized effects, data from individual cranial bones are valuable for the interpretation of experimental assays. We employ high‐resolution microcomputed tomography to characterize cranial bones of C57BL/6J mice at embryonic day (E) 15.5 and E17.5, day of birth (P0), and postnatal day 7 (P7) and provide estimates of individual bone volume and tissue mineral density (TMD).

Results

Average volume and TMD values are reported for individual bones. Significant differences in volume and TMD during embryonic ages likely reflect early mineralization of cranial neural crest‐derived and intramembranously forming bones. Although bones of the face and vault had higher TMD values during embryonic ages, bones of the braincase floor had significantly higher TMD values by P7.

Conclusions

These ontogenetic data on cranial bone volume and TMD serve as a reference standard for future studies using mice bred on a C57BL/6J genetic background. Our findings also highlight the importance of differentiating “control” data from mice that are presented as “unaffected” littermates, particularly when carrying a single copy of a cre‐recombinase gene.

Higher average volume and density of cranial neural crest‐derived and intramembranously‐forming bones during embryonic development.

Higher average density in bones of the braincase floor during early postnatal development.

Ontogenetic data on cranial bone volume and TMD serve as a reference standard for mice bred on a C57BL/6J genetic background.

Orofacial Cleft and Mandibular Prognathism-Human Genetics and Animal Models

Many complex molecular interactions are involved in the process of craniofacial development. Consequently, the network is sensitive to genetic mutations that may result in congenital malformations of varying severity. The most common birth anomalies within the head and neck are orofacial clefts (OFCs) and prognathism. Orofacial clefts are disorders with a range of phenotypes such as the cleft of the lip with or without cleft palate and isolated form of cleft palate with unilateral and bilateral variations. They may occur as an isolated abnormality (nonsyndromic-NSCLP) or coexist with syndromic disorders. Another cause of malformations, prognathism or skeletal class III malocclusion, is characterized by the disproportionate overgrowth of the mandible with or without the hypoplasia of maxilla. Both syndromes may be caused by the presence of environmental factors, but the majority of them are hereditary. Several mutations are linked to those phenotypes. In this review, we summarize the current knowledge regarding the genetics of those phenotypes and describe genotype-phenotype correlations. We then present the animal models used to study these defects.

Lack of IRF6 Disrupts Human Epithelial Homeostasis by Altering Colony Morphology, Migration Pattern, and Differentiation Potential of Keratinocytes

Variants within the gene encoding for the transcription factor Interferon Regulatory Factor 6 (IRF6) are associated with syndromic and non-syndromic Cleft Lip/Palate (CLP) cases. IRF6 plays a vital role in the regulation of the proliferation/differentiation balance in keratinocytes and is involved in wound healing and migration. Since a fraction of CLP patients undergoing corrective cleft surgery experience wound healing complications, IRF6 represents an interesting candidate gene linking the two processes. However, Irf6 function has been mainly studied in mice and knowledge on IRF6 in human cells remains sparse. Here, we aimed to elucidate the role of IRF6 in human postnatal skin- and oral mucosa-derived keratinocytes. To do so, we applied CRISPR/Cas9 to ablate IRF6 in two TERT-immortalized keratinocyte cultures, which we used as model cell lines. We show that IRF6 controls the appearance of single cells and colonies, with the latter being less cohesive in its absence. Consequently, IRF6 knockout keratinocytes often moved as single cells instead of a collective epithelial sheet migration but maintained their epithelial character. Lack of IRF6 triggered severe keratinocyte differentiation defects, which were already apparent in the stratum spinosum and extended to the stratum corneum in 3D organotypic skin cultures, while it did not alter their growth rate. Finally, proteomics revealed that most of the differentially expressed proteins in the absence of IRF6 could be associated with differentiation, cell-cell adhesion as well as immune response. Our data expand the knowledge on IRF6 in human postnatal keratinocytes, which will help to better understand IRF6-related pathologies.

Alveolar socket healing in 5-lipoxygenase knockout aged female mice treated or not with high dose of zoledronic acid

This study investigated the role 5-lypoxigenase (5-LO) on alveolar socket healing in aged female mice treated with zoledronic acid (ZL). Forty 129/Sv female mice (64–68 weeks old), 20 wild type (WT) and 20 5-LO knockout (5LOKO) were equally distributed according to ZL treatment: WT Control, WT ZL, 5LOKO Control, and 5LOKO ZL. ZL groups were treated with an intraperitoneal injection of 250 µg/Kg of ZL, while controls were treated with saline. Treatments were administered once a week, starting four weeks before surgery for tooth extraction and until 7 and 21 days post-surgery. Mice were euthanized for a comprehensive microscopic analysis (microCT, histomorphometry and immunohistochemistry). WT ZL mice presented intense inflammatory infiltrate (7 days), delayed bone formation (21 days), reduced collagenous matrix quality, and a deficiency in Runx-2 + , TRAP + , and macrophages as compared to controls. 5LOKO ZL animals presented decreased number of Runx-2 + cells in comparison to 5LOKO Control at 7 days, but no major changes in bone healing as compared to WT or 5LOKO mice at 21 days. The knockout of 5LO favored intramembranous bone healing in aged female mice, with a direct impact on inflammatory response and bone metabolism on the development of ONJ-like lesions.

IRF6 Genetic Variation and Maternal Smoking During Pregnancy in Cleft Lip/Palate

The goal of the present work was to revisit published data to test if genetic variation in interferon regulatory factor 6 (IRF6) is associated with children born with cleft lip with or without cleft palate (CL/P) for cases with positive history of maternal smoking. From the 573 individuals originally studied, this reanalysis focused on 57 who had a positive history of maternal smoking during pregnancy (39 born with CL/P and 18 born without CL/P). Seven IRF6 markers (rs4844880, rs2235371, rs2013162, ra861019, rs2073487, rs642961, and rs658860) were tested for over-transmission of alleles and an alpha of 0.05 was considered statistically significant. All individuals born with CL/P were homozygous for the wild type allele of rs2235371 in comparison to just two individuals born without clefts (p = 0.0000001). For rs861019, individuals born with CL/P were more likely to have the variant allele (p = 0.006). A similar trend was seen for rs642961 (p = 0.09). The results suggest that statistical evidence of over-representation of IRF6 alleles in individuals born with CL/P may be unveiled only when maternal smoking during pregnancy is used as the inclusion criterion in the analysis.

The use of glutathione to reduce oxidative stress status and its potential for modifying the extracellular matrix organization in cleft lip

OBJECTIVE

Cleft lip (CL) is a common congenital anomaly that can be syndromic or non-syndromic. It can be triggered by the mutation of gene or environmental factors. The incidence of CL is about 1 out of 700 live births. Facial development is a complex process, and there is no existing therapy to prevent the disease development. One of the characteristics in this facial malformation is the increased presence of reactive oxygen species (ROS). In this study, we hypothesize that the antioxidant glutathione (GSH) could help to attenuate the oxidative stress in this disease.

METHODS

Bioinformatics network pharmacology was applied to determine pharmacological targets and molecular mechanisms of GSH treatment for CL. Moreover, RNA-sequencing of the POLR1C knockdown osteoblast CL model was applied to validate the in silico data of using GSH in CL.

RESULTS

Twenty-two core targets of GSH and CL were identified via various bioinformatics tools. The GO and KEGG analysis indicated that GSH could modulate two major families (matrix metalloproteinase and integrins), which are related to extracellular matrix modification and composition for facial development in CL. The findings from POLR1C knockdown model further supported the rescue response of GSH in CL.

CONCLUSIONS

The study uncovered the possible pharmacological mechanism of GSH for treating CL. The data helps research group to focus on the specific pathways for understanding the biological action of GSH for treating the CL in the future.

Impact of Zika virus on the human type I interferon osteoimmune response

BACKGROUND

The developing field of osteoimmunology supports importance of an interferon (IFN) response pathway in osteoblasts. Clarifying osteoblast-IFN interactions is important because IFN is used as salvage anti-tumor therapy but systemic toxicity is high with variable clinical results. In addition, osteoblast response to systemic bursts and disruptions of IFN pathways induced by viral infection may influence bone remodeling. ZIKA virus (ZIKV) infection impacts bone development in humans and IFN response in vitro. Consistently, initial evidence of permissivity to ZIKV has been reported in human osteoblasts.

HYPOTHESIS

Osteoblast-like Saos-2 cells are permissive to ZIKV and responsive to IFN.

METHODS

Multiple approaches were used to assess whether Saos-2 cells are permissive to ZIKV infection and exhibit IFN-mediated ZIKV suppression. Proteomic methods were used to evaluate impact of ZIKV and IFN on Saos-2 cells.

RESULTS

Evidence is presented confirming Saos-2 cells are permissive to ZIKV and support IFN-mediated suppression of ZIKV. ZIKV and IFN differentially impact the Saos-2 proteome, exemplified by HELZ2 protein which is upregulated by IFN but non responsive to ZIKV. Both ZIKV and IFN suppress proteins associated with microcephaly/pseudo-TORCH syndrome (BI1, KI20A and UBP18), and ZIKV induces potential entry factor PLVAP.

CONCLUSIONS

Transient ZIKV infection influences osteoimmune state, and IFN and ZIKV activate distinct proteomes in Saos-2 cells, which could inform therapeutic, engineered, disruptions.

IRF6, MSX1, TGFA, dental anomalies, and skeletal malocclusion

OBJECTIVE

Verify the presence of association between four variables-transforming growth factor α (TGFA; C/T rs1523305), interferon regulatory factor 6 (IRF6; A/C rs2013162), muscle segment homeobox 1 (MSX1; A/G rs12532), and dental anomalies-with skeletal malocclusion by comparing these four variables with Angle Classes I, II, and III, and normal, hyperdivergent, and hypodivergent growth patterns.

METHODS

A total of 505 orthodontic records of patients older than 8 years were evaluated. The sample consisted of 285 (56.4 per cent) females, 220 (43.6 per cent) males, 304 (60.2 per cent) Whites (the rest were mixed Blacks with Whites), with a mean age of 20.28 (±10.35) years (ranging from 8 to 25 years). Eight cephalometric points, which served as the anatomical framework for obtaining angles and cephalometric measurements, were used for skeletal characterization using the Dolphin Software. Samples of saliva were collected and the DNA was extracted, diluted and quantified. Markers in TGFA, IRF6, and MSX1 were used and genotypes were obtained using TaqMan chemistry. Odds ratio (OR) and 95 per cent confidence interval (CI) calculations, chi-square, Fisher's Exact, Mann-Whitney, and correlation coefficient tests (significance level: 95 per cent) were performed. Bonferroni correction was applied and an alpha of 0.0006 was considered statistically significant.

RESULTS

There was no statistically significant associations between markers in TGFA or IRF6 with skeletal malocclusions. Tooth agenesis was associated with facial convexity (P < 0.001). MSX1 was associated with Class II skeletal malocclusion (P = 0.0001, OR = 0.6, CI = 0.46-0.78).

CONCLUSION

Individuals with tooth agenesis were more likely to have a convex face. MSX1 was associated with Class II skeletal malocclusion.

A Novel IRF6 Variant Detected in a Family With Nonsyndromic Cleft Lip and Palate by Whole Exome Sequencing

ABSTRACT

Nonsyndromic cleft lip with or without cleft palate (NSCL/P) is the most common congenital craniofacial malformation, and its harmful effects on affected individuals and families are apparent. The causative genes and their mechanisms are not completely clear, although several studies have been conducted. Accordingly, in the present study, we recruited a Han Chinese family with hereditary NSCL/P to explore the possible causative variants of this disease using whole exome sequencing. Bioinformatics screening and analysis, mutation function prediction, species conservation analysis, and homology protein modeling were used to identify the variants and evaluate their influence. A mutation in the interferon regulatory factor 6 (IRF6) gene (c.961C>T; p.Val321Met) was detected as a candidate causative variant and predicted to be deleterious. The codon was found to be conserved in many species, and the residue change caused by this mutation changed the structure of IRF6 to a certain degree. The findings suggest that this IRF6 variant is probably the pathogenic cause of NSCL/P in this family. Our results further provide evidence that IRF6 variants play a role in the etiology of NSCL/P.

Secondary Genome-Wide Association Study Using Novel Analytical Strategies Disentangle Genetic Components of Cleft Lip and/or Cleft Palate in 1q32.2

Orofacial cleft (OFC) is one of the most prevalent birth defects, leading to substantial and long-term burdens in a newborn's quality of life. Although studies revealed several genetic variants associated with the birth defect, novel approaches may provide additional clues about its etiology. Using the Center for Craniofacial and Dental Genetics project data (n = 10,542), we performed linear mixed-model analyses to study the genetic compositions of OFC and investigated the dependence among identified loci using conditional analyses. To identify genes associated with OFC, we conducted a transcriptome-wide association study (TWAS) based on predicted expression levels. In addition to confirming the previous findings at four loci, 1q32.2, 8q24, 2p24.2 and 17p13.1, we untwined two independent loci at 1q32.2, TRAF3IP3 and IRF6. The sentinel SNP in TRAF3IP3 (rs2235370, p-value = 5.15 × 10^-9) was independent of the sentinel SNP at IRF6 (rs2235373, r² < 0.3). We found that the IRF6 effect became nonsignificant once the 8q24 effect was conditioned, while the TRAF3IP3 effect remained significant. Furthermore, we identified nine genes associated with OFC in TWAS, implicating a glutathione synthesis and drug detoxification pathway. We identified some meaningful additions to the OFC etiology using novel statistical methods in the existing data.

New Surgical Model for Bone-Muscle Injury Reveals Age and Gender-Related Healing Patterns in the 5 Lipoxygenase (5LO) Knockout Mouse

Signaling lipid mediators released from 5 lipoxygenase (5LO) pathways influence both bone and muscle cells, interfering in their proliferation and differentiation capacities. A major limitation to studying inflammatory signaling pathways in bone and muscle healing is the inadequacy of available animal models. We developed a surgical injury model in the vastus lateralis (VL) muscle and femur in 129/SvEv littermates mice to study simultaneous musculoskeletal (MSK) healing in male and female, young (3 months) and aged (18 months) WT mice compared to mice lacking 5LO (5LOKO). MSK defects were surgically created using a 1-mm punch device in the VA muscle followed by a 0.5-mm round defect in the femur. After days 7 and 14 post-surgery, the specimens were removed for microtomography (microCT), histopathology, and immunohistochemistry analyses. In addition, non-injured control skeletal muscles along with femur and L5 vertebrae were analyzed. Bones were microCT phenotyped, revealing that aged female WT mice presented reduced BV/TV and trabecular parameters compared to aged males and aged female 5LOKO mice. Skeletal muscles underwent a customized targeted lipidomics investigation for profiling and quantification of lipid signaling mediators (LMs), evidencing age, and gender related-differences in aged female 5LOKO mice compared to matched WT. Histological analysis revealed a suitable bone-healing process with osteoid deposition at day 7 post-surgery, followed by woven bone at day 14 post-surgery, observed in all young mice. Aged WT females displayed increased inflammatory response at day 7 post-surgery, delayed bone matrix maturation, and increased TRAP immunolabeling at day 14 post-surgery compared to 5LOKO females. Skeletal muscles of aged animals showed higher levels of inflammation in comparison to young controls at day 14 post-surgery; however, inflammatory process was attenuated in aged 5LOKO mice compared to aged WT. In conclusion, this new model shows that MSK healing is influenced by age, gender, and the 5LO pathway, which might serve as a potential target to investigate therapeutic interventions and age-related MSK diseases. Our new model is suitable for bone-muscle crosstalk studies.

Extracellular Matrix Composition and Remodeling: Current Perspectives on Secondary Palate Formation, Cleft Lip/Palate, and Palatal Reconstruction

Craniofacial development comprises a complex process in humans in which failures or disturbances frequently lead to congenital anomalies. Cleft lip with/without palate (CL/P) is a common congenital anomaly that occurs due to variations in craniofacial development genes, and may occur as part of a syndrome, or more commonly in isolated forms (non-syndromic). The etiology of CL/P is multifactorial with genes, environmental factors, and their potential interactions contributing to the condition. Rehabilitation of CL/P patients requires a multidisciplinary team to perform the multiple surgical, dental, and psychological interventions required throughout the patient's life. Despite progress, lip/palatal reconstruction is still a major treatment challenge. Genetic mutations and polymorphisms in several genes, including extracellular matrix (ECM) genes, soluble factors, and enzymes responsible for ECM remodeling (e.g., metalloproteinases), have been suggested to play a role in the etiology of CL/P; hence, these may be considered likely targets for the development of new preventive and/or therapeutic strategies. In this context, investigations are being conducted on new therapeutic approaches based on tissue bioengineering, associating stem cells with biomaterials, signaling molecules, and innovative technologies. In this review, we discuss the role of genes involved in ECM composition and remodeling during secondary palate formation and pathogenesis and genetic etiology of CL/P. We also discuss potential therapeutic approaches using bioactive molecules and principles of tissue bioengineering for state-of-the-art CL/P repair and palatal reconstruction.

Interferon regulatory factor 6 is required for proper wound healing in vivo

BACKGROUND

Van der Woude syndrome (VWS) is the most common form of syndromic orofacial cleft caused predominantly by mutations in Interferon Regulatory Factor 6 (IRF6). We previously reported that individuals with VWS have increased risk of wound healing complications following cleft repair compared with individuals with nonsyndromic orofacial clefts (nonsyndromic cleft lip and palate-NSCLP). In vitro, absence of IRF6 leads to impaired keratinocyte migration and embryonic wound healing. However, there is currently no data on tissue repair in adult animals and cells with reduced levels of IRF6 like in VWS.

RESULTS

Excisional wounds of Irf6^+/- and wild-type animals were analyzed 4 and 7 days post-wounding. Although all wounds were reepithelialized after 7 days, the epidermal and wound volume of repaired wounds was larger in Irf6^+/- . These data were supported by increased keratinocyte proliferation in the neoformed epidermis and a less mature granulation tissue with increased cytokine levels. This effect was not cell autonomous, as Irf6^+/- neonatal keratinocytes in vitro did not exhibit defects in scratch wound closure or proliferation. Keratinocytes from individuals with VWS also migrated similarly to keratinocytes from NSCLP individuals.

CONCLUSIONS

These data support a role for IRF6 in wound healing by regulating keratinocyte proliferation, granulation tissue maturation, and cytokine levels.

Medication-related osteonecrosis of the jaws after tooth extraction in senescent female mice treated with zoledronic acid: Microtomographic, histological and immunohistochemical characterization

Treatment with cumulative dosages of zoledronic acid (ZA) in elderly patients is a risk factor for the development of medication-related osteonecrosis of the jaws (MRONJ), mainly related to surgical triggers such as tooth extraction. However, animal models for the investigation and understanding of MRONJ pathophysiology in senescent and postmenopausal stages remains to be developed and characterized. The aim of this study was to analyze MRONJ development in senescent female mice treated with cumulative dosages of ZA. For this purpose, twenty 129/Sv female mice, 64 weeks old, were treated with 0.9% saline solution as control group (n = 10), and with ZA at 250μg/Kg (n = 10), once a week, starting 4 weeks before the upper right incisor extraction and until the end of the experimental time points (7 days and 21 days). At 7 and 21 days post-surgery, specimens were harvested for microCT, histological, birefringence and immunohistochemical analysis. Clinically, an incomplete epithelialization was observed in ZA group at 7 days and a delayed bone matrix mineralization and collagen maturation at 7 and 21 days compared to the controls. Controls revealed sockets filled with mature bone at 21 days as observed by microCT and birefringence, while ZA group presented delayed bone deposition at 7 and 21 days, as well increased leukocyte infiltration and blood clot at 7 days, and increased bone sequestrum and empty osteocyte lacunae at 21 days (p<0.05). Also, ZA group presented decreased quantity of TGFb+ and Runx-2+ cells at 7 days, and decreased quantity of TRAP+ osteoclasts compared to the control at 21 days (p<0.05). Altogether, these data demonstrate the usefulness of this model to understanding the pathophysiology of MRONJ.