Calcium Reservoir Research Articles

Radiographic, computed tomographic, and histologic characteristics of bone for clinically normal laying hens in a free-range housing system.

Laying hens are increasingly being kept in backyard flocks and considered family pets; however, diagnostic imaging characteristics of bone for clinically normal backyard hens are currently limited. This prospective, descriptive study was to describe radiographic, computed tomographic, and histologic characteristics of bone for a group of clinically normal laying hens housed in conditions comparable to those of backyard flocks. Sixteen 60-week-old Lohmann Brown laying hens were included. Hens were housed in a free-range unit with outdoor access at a university research and teaching farm. Hens were defined as clinically normal by the farm manager and a veterinary researcher in laying hen behavior and welfare. Findings from the horizontal beam, left lateral, sternal radiographs (n=16), postmortem, and whole-body CT scans (n=4) were recorded by a veterinary radiologist and a research technician. Histologic findings for sternal, femoral, and tibiotarsal bone samples (n=5) were recorded by a veterinary pathologist. The most frequent radiographic findings for the sternal carina (keel bone) were smoothly marginated concave deviations of the ventral margin and caudal section fractures. Multiple punctate mineral opacities (PMOs) were present in radiographs and CT images for all hens and were involved in the sternal carina and multiple other bones in the axial and appendicular skeleton. No bone abnormalities were identified in any histologic sections where PMOs were radiographically detected. Authors propose that PMOs are normal radiographic and CT findings in the bones of mature, laying hens and may represent temporary calcium reservoirs formed during osteoclastic activities.

Preventing Dental Caries with Calcium-Based Materials: A Concise Review

This concise review provides an update on the use of calcium-based materials for the prevention of dental caries. Some calcium-based materials promote remineralization and neutralize bacterial acids, disrupting cariogenic biofilms and inhibiting bacterial growth. Medical Subject Headings of [Dental Caries] and [Calcium] were adopted to search publications. Information related to the aim of this review was extracted and summarized. Common calcium-based materials are calcium phosphate, hydroxyapatite, calcium carbonate, calcium fluoride and casein phosphopeptide–amorphous calcium phosphate (CPP-ACP). Calcium phosphate is commonly used in toothpaste. It provides calcium and phosphate ions, enhances the incorporation of fluoride into caries lesions and increases mineral density. Hydroxyapatite is a form of calcium phosphate that is chemically similar to the mineral found in teeth. It can be applied on teeth to prevent caries. Calcium carbonate can be found in toothpastes. It neutralizes bacterial acids and acts as a calcium reservoir during remineralization. Calcium fluoride is found in dental products and promotes remineralization as a source of fluoride, which can be incorporated into tooth enamel, forming fluorapatite and increasing resistance to caries. CPP-ACP is derived from milk proteins. It contains calcium and phosphate, which help to remineralize tooth enamel. CPP-ACP inhibits cariogenic bacteria. It also interacts with bacterial biofilms and disrupts their formation. These calcium-based materials can be used to boost the preventive effect of fluorides or, alternatively, as a therapy for caries prevention.

EXPLORING THE IMPACT OF PTH THERAPY ON BONE REMODELING: A MATHEMATICAL INVESTIGATION

The regulatory influence of the parathyroid hormone (PTH) is exerted on bone, which serves as a vital reservoir of calcium within the body. While various aspects of bone growth, turnover, and mechanisms operate independently of gonadal hormones, a crucial role is assumed by sex steroids, particularly estrogen, in maintaining bone equilibrium in adults. In order to unravel the underlying mechanisms of bone remodeling mediated by PTH, a distinguished mathematical model of this intricate process is presented. Subsequently, the temporal effects of Plasma PTH and PTH external dosages are investigated using the proposed mathematical model. Among the limited repertoire of approved and accessible anabolic treatments for severe osteoporosis, daily injections of PTH stand out. This pharmaceutical marvel possesses a unique dual action, capable of acting either anabolically or catabolically, contingent upon the mode of administration. The study aims to accurately predict osteogenic responses to introduced and endogenous PTH, incorporating factors such as [Formula: see text]-[Formula: see text], [Formula: see text], and bisphosphonates in osteoblast–osteoclast signaling, as well as considering PTH’s influence on the gland and the regulatory roles of [Formula: see text], [Formula: see text], and [Formula: see text] in osteoblast apoptosis and bone volume effects. Through diverse methods including illustrative depictions, numerical simulations, sensitivity analysis, and stability analysis, this work seeks to comprehend how PTH therapy impacts bone volume, enhancing its therapeutic relevance.

The hidden cross talk between bone and tissues through bone turnover.

Bone is more than a reservoir of calcium and phosphorus. Its lacuno-canalicular arrangement provides an important pathway for exchange with circulation and currently, the skeleton is considered a large endocrine organ with actions that go beyond the control of calcium-phosphorus balance mediated by fibroblastic growth factor 23 (FGF23). Parallel to the modulating effect of adipokines on bone turnover, certain bone proteins, such as osteocalcin and sclerostin, play a counter-regulatory role on energy metabolism, probably in an attempt to ensure its high energy requirement for bone turnover. In this crosstalk between bone and other tissues, especially with adipose tissue, canonical Wnt/β-catenin signaling is involved and therefore, sclerostin, an osteocyte derived protein that inhibits this signalling, emerges as a potential biomarker. Furthermore, its involvement in diverse pathologic conditions supports sclerostin as a therapeutic target, with an anti-sclerostin antibody recently approved in our country for the treatment of osteoporosis. This review addresses the endocrine nature of bone, the role of osteocalcin, and specially, the regulatory and modulatory role of sclerostin on bone turnover and energy homeostasis through its inhibitory effect on canonical Wnt/β-catenin signaling, as well as its potential utility as a biomarker.

SAT229 Symptomatic Hypocalcemia In The Setting Of Crohn’s Disease With Severe Hypomagnesemia

Abstract Disclosure: K. Cuan: None. T. Reisman: None. Introduction: People with Crohn’s Disease (CD) are at risk for various nutritional deficiencies due to decreased oral intake, malabsorption, and increased intestinal losses. CD often causes a negative calcium balance, which does not usually cause hypocalcemia because the bones serve as a reservoir for calcium. However, symptomatic hypocalcemia may occur if a concurrent severe hypomagnesemic state is present. The factors resulting in hypocalcemia in patients with magnesium deficiency are impaired PTH secretion, PTH resistance, and vitamin D deficiency. Clinical Case: A 33-year-old man with CD and rheumatoid arthritis presented following a seizure with additional symptoms of hand cramping and facial twitching. He had previously undergone three small bowel resections and had a history of hypocalcemia due to malabsorption. Although this patient had previously been admitted due to a hypocalcemic seizure, he did not start oral calcium supplements at that time. No issues with magnesium were identified previously. On this encounter, he was found to have a corrected calcium (cCa) of 5.3 mg/dL, undetectably low magnesium at <0.7 mg/dL, normal phosphorus, 25-hydroxyvitamin D at 3.5 ng/mL, and an elevated intact PTH (iPTH) at 169 pg/mL. Aggressive intravenous calcium and magnesium repletion improved cCa to 7.4 mg/dL and magnesium to 2 mg/dL with no further seizure activity. He was discharged on calcium carbonate, calcitriol, and ergocalciferol. A month later, he presented to our endocrinology clinic asymptomatic but with a cCa of 6 mg/dL and magnesium at <0.7 mg/dL. Further biochemical workup revealed normal phosphorus, 25-hydroxyvitamin D at 7.9 ng/mL, and an inappropriately normal iPTH at 49 pg/mL. He was readmitted to the hospital where intravenous repletion improved cCa to 8.1 mg/dL and magnesium to 1.9 mg/dL. His recurrent hypomagnesemia was attributed to malabsorption. An increased dose of calcitriol and oral magnesium were added to his discharge medication regimen, in addition to his ergocalciferol and calcium carbonate. Three days later, he had a cCa level of 7.1 mg/dL as an outpatient. Conclusion: Patients with CD often have nutrient deficiencies, especially if they have had surgical resection within the intestinal tract. Our patient initially developed hypocalcemia from malabsorption, which was then exacerbated by the severely hypomagnesemic state. During his initial hospital encounter, the elevated iPTH level indicated PTH resistance. On his second encounter, the normal iPTH level suggested hypoparathyroidism. Given the relationship between magnesium and calcium homeostasis, addressing the hypomagnesemia eventually aided in achieving stabilization of serum calcium levels. Thus, in patients who are at risk for malabsorption and have recurrent symptomatic hypocalcemia, it is prudent to check magnesium levels as it can affect long term management of hypocalcemia. Presentation: Saturday, June 17, 2023

Current Status of Next-Generation Sequencing in Bone Genetic Diseases.

The development of next-generation sequencing (NGS) has dramatically increased the speed and volume of genetic analysis. Furthermore, the range of applications of NGS is rapidly expanding to include genome, epigenome (such as DNA methylation), metagenome, and transcriptome analyses (such as RNA sequencing and single-cell RNA sequencing). NGS enables genetic research by offering various sequencing methods as well as combinations of methods. Bone tissue is the most important unit supporting the body and is a reservoir of calcium and phosphate ions, which are important for physical activity. Many genetic diseases affect bone tissues, possibly because metabolic mechanisms in bone tissue are complex. For instance, the presence of specialized immune cells called osteoclasts in the bone tissue, which absorb bone tissue and interact with osteoblasts in complex ways to support normal vital functions. Moreover, the many cell types in bones exhibit cell-specific proteins for their respective activities. Mutations in the genes encoding these proteins cause a variety of genetic disorders. The relationship between age-related bone tissue fragility (also called frailty) and genetic factors has recently attracted attention. Herein, we discuss the use of genomic, epigenomic, transcriptomic, and metagenomic analyses in bone genetic disorders.

Advanced Skeletal Ossification Is Associated with Genetic Variants in Chronologically Young Beef Heifers.

Osteogenesis is a developmental process critical for structural support and the establishment of a dynamic reservoir for calcium and phosphorus. Changes in livestock breeding over the past 100 years have resulted in earlier bone development and increased physical size of cattle. Advanced skeletal maturity is now commonly observed at harvest, with heifers displaying more mature bone than is expected at 30 months of age (MOA). We surmise that selection for growth traits and earlier reproductive maturity resulted in co-selection for accelerated skeletal ossification. This study examines the relationship of single nucleotide polymorphisms (SNPs) in 793 beef heifers under 30 MOA with USDA-graded skeletal maturity phenotypes (A-, B-, C- skeletal maturity). Further, the estrogen content of FDA-approved hormonal implants provided to heifers prior to harvest was evaluated in association with the identified SNPs and maturities. Association tests were performed, and the impact of the implants were evaluated as covariates against genotypes using a logistic regression model. SNPs from the ESR1, ALPL, PPARGC1B, SORCS1 genes, and SNPs near KLF14, ANKRD61, USP42, H1C1, OVCA2, microRNA mir-29a were determined to be associated with the advanced skeletal ossification phenotype in heifers. Higher dosage estrogen implants increased skeletal maturity in heifers with certain SNP genotypes.

Osteology as a Forum for Research on the ‘Living Mineral’: Bone

About 400 million years ago, the first bone-like material, aspidin, was developed for external protection for the body of invertebrate marine creatures; this mineral shell is now believed to function as a reservoir for phosphorous and calcium [...]

Crosstalk between bone and other organs.

Bone has long been considered as a silent organ that provides a reservoir of calcium and phosphorus, traditionally. Recently, further study of bone has revealed additional functions as an endocrine organ connecting systemic organs of the whole body. Communication between bone and other organs participates in most physiological and pathological events and is responsible for the maintenance of homeostasis. Here, we present an overview of the crosstalk between bone and other organs. Furthermore, we describe the factors mediating the crosstalk and review the mechanisms in the development of potential associated diseases. These connections shed new light on the pathogenesis of systemic diseases and provide novel potential targets for the treatment of systemic diseases.

Structural and Metabolic Changes in Bone.

Simple SummaryBone is an extremely metabolically active tissue that is regenerated and repaired over its lifetime by bone remodeling. Most bone diseases are caused by abnormal restructure processes that undermine bone structure and mechanical strength and trigger clinical symptoms, such as pain, deformity, fracture, and abnormalities of calcium and phosphate homoeostasis. The article examines the main aspects of bone development, anatomy, structure, and the mechanisms of cell and molecular regulation of bone remodeling.As an essential component of the skeleton, bone tissue provides solid support for the body and protects vital organs. Bone tissue is a reservoir of calcium, phosphate, and other ions that can be released or stored in a controlled manner to provide constant concentration in body fluids. Normally, bone development or osteogenesis occurs through two ossification processes (intra-articular and intra-chondral), but the first produces woven bone, which is quickly replaced by stronger lamellar bone. Contrary to commonly held misconceptions, bone is a relatively dynamic organ that undergoes significant turnover compared to other organs in the body. Bone metabolism is a dynamic process that involves simultaneous bone formation and resorption, controlled by numerous factors. Bone metabolism comprises the key actions. Skeletal mass, structure, and quality are accrued and maintained throughout life, and the anabolic and catabolic actions are mostly balanced due to the tight regulation of the activity of osteoblasts and osteoclasts. This activity is also provided by circulating hormones and cytokines. Bone tissue remodeling processes are regulated by various biologically active substances secreted by bone tissue cells, namely RANK, RANKL, MMP-1, MMP-9, or type 1 collagen. Bone-derived factors (BDF) influence bone function and metabolism, and pathophysiological conditions lead to bone dysfunction. This work aims to analyze and evaluate the current literature on various local and systemic factors or immune system interactions that can affect bone metabolism and its impairments.

A Pipeline for Natural Small Molecule Inhibitors of Endoplasmic Reticulum Stress.

The homeostasis of eukaryotic cells is inseverable of that of the endoplasmic reticulum (ER). The main function of this organelle is the synthesis and folding of a significant portion of cellular proteins, while it is also the major calcium reservoir of the cell. Upon unresolved ER stress, a set of stress response signaling pathways that are collectively labeled as the unfolded protein response (UPR) is activated. Prolonged or intense activation of this molecular machinery may be deleterious. It is known that compromised ER homeostasis, and consequent UPR activation, characterizes the pathogenesis of neurodegenerative diseases. In an effort to discover new small molecules capable of countering ER stress, we subjected a panel of over 100 natural molecules to a battery of assays designed to evaluate several hallmarks of ER stress. The protective potential of these compounds against ER stress was evaluated at the levels of calcium homeostasis, key gene and protein expression, and levels of protein aggregation in fibroblasts. The most promising compounds were subsequently tested in neuronal cells. This framework resulted in the identification of several bioactive molecules capable of countering ER stress and deleterious events associated to it. Delphinidin stands out as the most promising candidate against neurodegeneration. This compound significantly inhibited the expression of UPR biomarkers, and displayed a strong potential to inhibit protein aggregation in the two aforementioned cell models. Our results indicate that natural products may be a valuable resource in the development of an effective therapeutic strategy against ER stress-related diseases.

Osteoderms as calcium reservoirs: Insights from the lizard Ouroborus cataphractus.

The functional significance of osteoderms-bony elements embedded in the dermis-remains a topic of much debate. Although many hypotheses have been put forward in the past, the idea that osteoderms can serve as calcium reservoirs has received little experimental attention thus far. In this study, we use micro-computed tomography to investigate inter- and intrasexual variation in osteoderm density in the viviparous lizard Ouroborus cataphractus and conduct histochemical analyses to unravel the potential mechanism involved in mineral resorption from the osteoderms. Our results show that females have denser, more compact osteoderms than males of similar body sizes, regardless of the season during which they were collected and their reproductive state. Furthermore, a histochemical study demonstrates the presence of mononucleated TRAP-positive cells in the vascular canals of the osteoderms. Based on the findings of this study, we suggest that the mineral storage hypothesis merits further attention as a candidate explanation for osteoderm evolution.

Molecular Mechanisms Involved in Hypoxia-Induced Alterations in Bone Remodeling.

Bone is crucial for the support of muscles and the protection of vital organs, and as a reservoir of calcium and phosphorus. Bone is one of the most metabolically active tissues and is continuously renewed to adapt to the changes required for healthy functioning. To maintain normal cellular and physiological bone functions sufficient oxygen is required, as evidence has shown that hypoxia may influence bone health. In this scenario, this review aimed to analyze the molecular mechanisms involved in hypoxia-induced bone remodeling alterations and their possible clinical consequences. Hypoxia has been associated with reduced bone formation and reduced osteoblast matrix mineralization due to the hypoxia environment inhibiting osteoblast differentiation. A hypoxic environment is involved with increased osteoclastogenesis and increased bone resorptive capacity of the osteoclasts. Clinical studies, although with contradictory results, have shown that hypoxia can modify bone remodeling.

Gellan gum/alginate-based Ca-enriched acellular bilayer hydrogel with robust interface bonding for effective osteochondral repair

The treatment of osteochondral (OC) defects remains challenging because of the lack of economical and feasible therapeutic strategies for OC repair and reconstruction. In this study, we report an integrated bilayer hydrogel with robust interface binding force (40 kPa) by facilitating the diffusion of calcium ions to the secondary crosslink of the bilayer hydrogel, in which gellan gum and sodium alginate acted as the chondral layer, gellan gum and hydroxyapatite acted as subchondral layer. This integrated construct has high cytocompatibility, and can seed with mesenchymal stem cells (MSCs) related to different functional protein expression for cartilage and bone formation, respectively. Furthermore, in the rabbit critical-sized osteochondral defect model (4.0 mm in diameter and 8.0 mm in depth), the calcium enriched hydrogel act as a calcium reservoir, promote neovascularization at week 4, and repair the critical defect at week 8, demonstrating the feasible preparation of an acellular hydrogel for OC repair.

Arsenic (III) and/or Antimony (III) induced disruption of calcium homeostasis and endoplasmic reticulum stress resulting in apoptosis in mice heart

Arsenic (As) and antimony (Sb) are known as an environmental contaminant with cardiotoxicity properties. The endoplasmic reticulum (ER) is the largest calcium reservoir in the cell, and its calcium homeostasis disorder plays a vital role in endoplasmic reticulum stress (ERS) and apoptosis. The objective of this study was to investigate whether As and Sb induced apoptosis via endoplasmic reticulum stress (ERS) linked to calcium homeostasis disturbance. In this study, thirty-two adult mice were gavage-fed daily with As2O3 (4 mg/kg), SbCl3 (15 mg/kg) and co-treat with SbCl3 (15 mg/kg) and As2O3 (4 mg/kg) daily for 60 days. It was observed that As or/and Sb caused histopathological lesions and ER expansion of the heart. Meanwhile, the gene expression of ER Ca2+ release channels (RyR2 and IP3R) and calmodulin-dependent protein kinase II (CaMKII) increased while the levels of mRNA and protein of ER Ca2+ uptake channel (SERCA2) downregulated significantly compared to the controls. Then, As or/and Sb induced ERS and triggered the ER apoptotic pathway by activating unfolded protein response (UPR)-associated genes ((PERK, ATF6, IRE1, XBP1, JNK, GRP78), and apoptosis-related genes (Caspase12, Caspase3, p53, CHOP). Above indicators in As + Sb group became more severe than that of As group and Sb group. Overall, our results proved that the cardiotoxicity caused by As or/and Sb might be concerning disturbing calcium homeostasis, which induced apoptosis through the ERS pathway.

Endoplasmic reticulum stress, cell death and tumor: Association between endoplasmic reticulum stress and the apoptosis pathway in tumors (Review).

External and internal stimuli are often involved in the pathogenesis of tumors, and the deterioration of endoplasmic reticulum (ER) function within cells is also an important etiological factor of tumorigenesis resulting in the impairment of the endoplasmic reticulum, which is termed ER stress. The ER is an organelle that serves a crucial role in the process of protein synthesis and maturation, and also acts as a reservoir of calcium to maintain intracellular Ca2+ homeostasis. ER stress has been revealed to serve a critical role in tumorigenesis. In the present review, the association between ER stress-related pathways and tumor cell apoptosis is examined. Primarily, the role of ER stress in tumor cell apoptosis is discussed, and it is stipulated that ER stress, induced by drugs both directly and indirectly, promotes tumor cell apoptosis.

In vitro SEM analysis of desensitizing agents and experimental hydroxyapatite-based composition effectiveness in occluding dentin tubules.

Novel materials used for dentin hypersensitivity (DH) treatment, including hydroxyapatite-based desensitizers, are not only effective in occluding dentinal tubules, but are also biocompatible and non-toxic. A newly formulated desensitizer containing hydroxyapatite was evaluated in comparison to commercially available desensitizers. To compare the occluding efficacy and durability of 3 commercially available desensitizing agents with a pharmaceutical composition developed by the authors based on hydroxyapatite (HAp). For the experiment, 40 disc-shaped dentin specimens (5 mm thick) were obtained from extracted human teeth. Each disc was divided into 4 sections, so that each desensitizing agent could be applied to each specimen and prepared for further evaluation in most homogenous conditions. The chemical composition of the dentin surfaces was analyzed using scanning electron microscopy (SEM) equipped with an energy-dispersive X-ray spectroscope (EDS), Fourier-transform infrared (FTIR) and Raman spectra techniques. The specimens were immersed in an artificial saliva solution for 24 h, 48 h and 7 days to assess the durability of the layers and the tubule-obliteration effectiveness. Data analysis was performed using Student's t-test with an average value of normal distribution at an unknown variance with a standard deviation (SD) of σ-0.4. All the test groups showed some degree of dentinal tubule occlusion or a covering layer, but the HAp-based composition proved to be the longest-lasting. It was concluded that the developed pharmaceutical composition creates a coating on the dentin surface built of hydroxyapatite crystals sized 10-20 μm, which are likely to constitute a reservoir of calcium and phosphate ions, as well as smaller crystals (0.2-0.3 μm) that occlude dentinal tubules. The composition containing biocompatible hydroxyapatite effectively occluded dentinal tubules and therefore exhibits a potential for reducing the pain and discomfort caused by dentin hypersensitivity.

Selenoprotein N is an endoplasmic reticulum calcium sensor that links luminal calcium levels to a redox activity

The endoplasmic reticulum (ER) is the reservoir for calcium in cells. Luminal calcium levels are determined by calcium-sensing proteins that trigger calcium dynamics in response to calcium fluctuations. Here we report that Selenoprotein N (SEPN1) is a type II transmembrane protein that senses ER calcium fluctuations by binding this ion through a luminal EF-hand domain. In vitro and in vivo experiments show that via this domain, SEPN1 responds to diminished luminal calcium levels, dynamically changing its oligomeric state and enhancing its redox-dependent interaction with cellular partners, including the ER calcium pump sarcoplasmic/endoplasmic reticulum calcium ATPase (SERCA). Importantly, single amino acid substitutions in the EF-hand domain of SEPN1 identified as clinical variations are shown to impair its calcium-binding and calcium-dependent structural changes, suggesting a key role of the EF-hand domain in SEPN1 function. In conclusion, SEPN1 is a ER calcium sensor that responds to luminal calcium depletion, changing its oligomeric state and acting as a reductase to refill ER calcium stores.

Estimation and correlation of salivary calcium, phosphorous, alkaline phosphatase, pH, white spot lesions, and oral hygiene status among orthodontic patients.

Introduction:The initial carious lesions are the so-called “white spot” lesions (WSLs), which implies that there is a subsurface area with most of the mineral loss beneath a relatively intact enamel surface. It is common in patients who are taking orthodontic treatment. Salivary reservoir of calcium and phosphorous counteracts the demineralization and encourages re-mineralization providing protection against caries challenge. This study was aimed to estimate and correlate the oral hygiene status, WSLs and salivary calcium, phosphorus, alkaline phosphatase (ALP), and pH in patients undergoing fixed orthodontic therapy.Materials and Methods:All clinical and biochemical parameters were recorded in 27 patients before starting orthodontic treatment and at 6 months of orthodontic treatment. The salivary calcium, phosphorous, ALP, and pH were determined by Arsenazo III method, Molybdate – UV and the International Federation of Clinical Chemistry method, respectively. International caries detection and assessment system index for WSL, orthodontic plaque index, bleeding on probing, and gingival index were recorded. Shapiro–Wilk's test and Wilcoxon test were applied to the data collected for statistical analysis.Results:There was a statistically significant increase with ALP levels, orthodontic plaque index score, gingival index score, and bleeding on probing index score. A statistically significant reduction was seen with respect to levels of calcium and pH.Conclusion:Maxillary canines and lateral incisors were the most affected teeth with WSLs (78.84%). There is a need for more stringent prevention programs and oral hygiene practices prior to initiation of orthodontic treatment and also during orthodontic treatment.

The development of cephalic armor in the tokay gecko (Squamata: Gekkonidae: Gekko gecko).

Armored skin resulting from the presence of bony dermal structures, osteoderms, is an exceptional phenotype in gekkotans (geckos and flap-footed lizards) only known to occur in three genera: Geckolepis, Gekko, and Tarentola. The Tokay gecko (Gekko gecko LINNAEUS 1758) is among the best-studied geckos due to its large size and wide range of occurrence, and although cranial dermal bone development has previously been investigated, details of osteoderm development along a size gradient remain less well-known. Likewise, a comparative survey of additional species within the broader Gekko clade to determine the uniqueness of this trait has not yet been completed. Here, we studied a large sample of gekkotans (38 spp.), including 18 specimens of G. gecko, using X-rays and high-resolution computed tomography for visualizing and quantifying the dermal armor in situ. Results from this survey confirm the presence of osteoderms in a second species within this genus, Gekko reevesii GRAY 1831, which exhibits discordance in timing and pattern of osteoderm development when compared with its sister taxon, G. gecko. We discuss the developmental sequence of osteoderms in these two species and explore in detail the formation and functionality of these enigmatic dermal ossifications. Finally, we conducted a comparative analysis of endolymphatic sacs in a wide array of gekkotans to explore previous ideas regarding the role of osteoderms as calcium reservoirs. We found that G. gecko and other gecko species with osteoderms have highly enlarged endolymphatic sacs relative to their body size, when compared to species without osteoderms, which implies that these membranous structures might fulfill a major role of calcium storage even in species with osteoderms.