Osteocyte Lacunae Research Articles

Micro-scale vertebral features in postmenopausal women with alcohol-associated and metabolic-associated fatty liver disease: ex vivo bone quality analyses.

Although epidemiological studies indicate increased fracture risk in women with alcohol-associated liver disease (AALD) and metabolic-associated fatty liver disease (MAFLD), data about their micro-scale bone features are still limited. We aimed to characterize bone quality changes in the anterior mid-transverse part of the first lumbar vertebral body collected from 32 adult postmenopausal females. Based on pathohistological assessment of the liver tissue, individuals were divided into AALD (n = 13), MAFLD (n = 9), and control group (n = 10). We analyzed trabecular and cortical micro-architecture (using micro-computed tomography), bone mechanical properties (using Vickers microhardness tester), osteocyte lacunar network and bone marrow adiposity morphology (using optic microscopy). Data were adjusted to elude the covariant effects of advanced age and body mass index on our results. Our data indicated a minor trend toward deteriorated bone quality in MAFLD women, presented in impaired trabecular and cortical micro-architectural integrity, which could be associated with bone marrow adiposity alterations noted in these women. Additionally, we observed a significant decline in micro-architectural, mechanical, and osteocyte lacunar features in lumbar vertebrae collected from the AALD group. Lastly, our data indicated that vertebral bone deterioration was more prominent in the AALD group than in the MAFLD group. Our data suggested that MAFLD and AALD are factors that could play a part in compromised vertebral strength of postmenopausal women. Also, our data contribute to understanding the multifactorial nature of bone fragility in these patients and highlight the necessity for developing more effective patient-specific diagnostic, preventive, and therapeutic strategies.

Bone resorption and formation in the pedicles of European roe deer (Capreolus capreolus) in relation to the antler cycle-A morphological and microanalytical study.

We analyzed pedicle bone from roe bucks that had died around antler casting or shortly before or during the rutting period. Pedicles obtained around antler casting were highly porous and showed signs of intense osteoclastic activity that had caused the formation of an abscission line. Following the detachment of the antler plus a portion of pedicle bone, osteoclastic activity in the pedicles continued for some time, and new bone was deposited onto the separation plane of the pedicle stump, leading to partial pedicle restoration. Pedicles obtained around the rutting period were compact structures. The newly formed, often very large secondary osteons, which had filled the resorption cavities, exhibited a lower mineral density than the persisting older bone. The middle zones of the lamellar infilling frequently showed hypomineralized lamellae and enlarged osteocyte lacunae. This indicates a deficiency in mineral elements during the formation of these zones that occurred along with peak antler mineralization. We suggest that growing antlers and compacting pedicles compete for mineral elements, with the rapidly growing antlers being the more effective sinks. The competition between the two simultaneously mineralizing structures is probably more severe in Capreolus capreolus than in other cervids. This is because roe bucks regrow their antlers during late autumn and winter, a period of limited food and associated mineral supply. The pedicle is a heavily remodeled bone structure with distinct seasonal variation in porosity. Pedicle remodeling differs in several aspects from the normal bone remodeling process in the mammalian skeleton.

Influence of Osteocyte Lacunar-Canalicular Morphology and Network Architecture on Osteocyte Mechanosensitivity.

The goal of this review is to summarize recent findings related to modifications in osteocyte lacunar and canalicular morphology due to physiological and pathological conditions. In addition, this review aims to outline how these modifications may influence the local mechanical environment of osteocytes and their mechanosensitivity. Reduction in lacunar density with age and increasing lacunar size with lactation are confirmed in multiple studies in human and murine bone. There is also evidence of a reduction in canalicular density, length, and branching, as well as increasing sphericity and smaller lacunae with aging and disease. However, while some studies have found modifications in lacunar density, size, shape, and orientation, as well as canalicular density, length, and size due to specific physiological and pathological conditions, others have not observed any differences. Recent finite element models provide insights into how observed modifications in the lacunar-canalicular network (lacunar and canalicular density) and lacunar-canalicular morphology (lacunar area/volume, shape, and orientation as well as canalicular diameter and length) may influence the fluid flow and local strains around the lacunar-canalicular network and modify the local mechanical environment of osteocytes. Modifications in the lacunar-canalicular network morphology may lead to significant changes in the strains received by osteocytes and may influence bone's response to mechanical stimulation as osteocytes are the primary mechanosensing bone cells. Further experimental and computational studies will continue to improve our understanding of the relationship between lacunar-canalicular network morphology and osteocyte mechanosensitivity.

Whole-Bone Toughness Is Linked to Canal and Osteocyte Lacunae Deficits in the ZDSD Type 2 Diabetic Rat Model

Whole-Bone Toughness Is Linked to Canal and Osteocyte Lacunae Deficits in the ZDSD Type 2 Diabetic Rat Model

Bacterial invasion of the submicron osteocyte lacuna-canaliculi network (OLCN); a part of osteomyelitis disease biology.

Two chronic osteomyelitis patients, a diabetic foot osteomyelitis patient and a fracture related infection patient, all with staphylococci positive microbiology, were examined to confirm the clinical relevance of bacterial invasion of the submicron osteocyte lacuna-canaliculi network (OLCN) in bone tissue. Based on immunohistochemistry and light microscopy both Staphylococcus aureus and Staphylococcus epidermidis were identified within the OLCN of all four patients. The findings consolidate that bacterial OLCN invasion is a clinically relevant part of osteomyelitis disease biology, which from experimental porcine infections, seems to be time depending. The microscopy pictures of the four patients significantly adds to visualize the phenomenon of bacterial OLCN invasion.

Microstructural and cellular characterisation of the subchondral trabecular bone in human knee and hip osteoarthritis using synchrotron tomography

It is unclear if different factors influence osteoarthritis (OA) progression and degenerative changes characterising OA disease in hip and knee. We investigated the difference between hip OA and knee OA at the subchondral bone (SCB) tissue and cellular level, relative to the degree of cartilage degeneration. Bone samples were collected from 11 patients (aged 70.4±10.7years) undergoing knee arthroplasty and 8 patients (aged 62.3±13.4years) undergoing hip arthroplasty surgery. Trabecular bone microstructure, osteocyte-lacunar network, and bone matrix vascularity were evaluated using synchrotron micro-CT imaging. Additionally, osteocyte density, viability, and connectivity were determined histologically. The associations between severe cartilage degeneration and increase of bone volume fraction (%) [-8.7, 95% CI (-14.1, -3.4)], trabecular number (#/mm) [-1.5, 95% CI (-0.8, -2.3)], osteocyte lacunar density (#/mm3) [4714.9; 95% CI (2079.1, 7350.6)] and decrease of trabecular separation (mm) [-0.07, 95% CI (0.02, 0.1)] were found in both knee and hip OA. When compared to knee OA, hip OA was characterised by larger (µm3) but less spheric osteocyte lacunae [47.3; 95% CI (11.2, 83.4), -0.04; 95% CI (-0.06, -0.02), respectively], lower vascular canal density (#/mm3) [-22.8; 95% CI (-35.4, -10.3)], lower osteocyte cell density (#/mm2) [-84.2; 95% CI (-102.5, -67.4)], and less senescent (#/mm2) but more apoptotic osteocytes (%) [-2.4; 95% CI (-3.6, -1.2), 24.9; 95% CI (17.7, 32.1)], respectively. SCB from hip OA and knee OA exhibits different characteristics at the tissue and cellular levels, suggesting different mechanisms of OA progression in different joints.

The many facets of micropetrosis - Magnesium whitlockite deposition in bisphosphonate-exposed human alveolar bone with osteolytic metastasis.

The lacuno-canalicular space of apoptotic osteocytes eventually becomes mineralised in vivo. This condition is known as micropetrosis and is a fundamental characteristic of ageing bone. Increased prevalence of such hypermineralised osteocyte lacunae is viewed as a structural marker of impaired bone function - both mechanical and biological. Within the lacuno-canalicular space, mineralised apoptotic debris typically occurs as micrometre-sized, spherical nodules of magnesium-rich, carbonated apatite. Moreover, characteristically facetted, rhomboidal nodules of magnesium whitlockite [Mg-whitlockite; Ca18Mg2(HPO4)2(PO4)12] have been reported in human alveolar bone exposed to the bisphosphonate alendronate. This work provides supporting evidence for Mg-whitlockite formation in the alveolar bone of a 70-year-old male exposed to the bisphosphonate zoledronic acid to suppress osteolytic changes in skeletal metastasis. Backscattered electron scanning electron microscopy (BSE-SEM) revealed spherical and rhomboidal nodules within the lacuno-canalicular space. A variant of spherical nodules exhibited a fuzzy surface layer comprising radially extending acicular crystallites. The rhomboidal nodules ranged between ∼200nm to ∼2.4µm across the widest dimension (652±331nm). Micro-Raman spectroscopy and energy dispersive X-ray spectroscopy confirmed that rhomboidal nodules are compositionally distinct from spherical nodules, exhibiting higher Mg content and lower Ca/P ratio. Formation of Mg-whitlockite within osteocyte lacunae is multifactorial in nature and suggests altered bone biomineralisation. Nevertheless, the underlying mechanism(s) and sequence of events remain poorly understood and warrant further investigation. The possibility to discriminate between carbonated apatite and Mg-whitlockite nodules within osteocyte lacunae, based on particle morphology, attests to the diagnostic potential of BSE-SEM with or without additional analyses of material composition.

Osteocyte apoptosis and cellular micropetrosis signify skeletal aging in type 1 diabetes.

Bone fragility is a profound complication of type 1 diabetes mellitus (T1DM), increasing patient morbidity. Within the mineralized bone matrix, osteocytes build a mechanosensitive network that orchestrates bone remodeling; thus, osteocyte viability is crucial for maintaining bone homeostasis. In human cortical bone specimens from individuals with T1DM, we found signs of accelerated osteocyte apoptosis and local mineralization of osteocyte lacunae (micropetrosis) compared with samples from age-matched controls. Such morphological changes were seen in the relatively young osteonal bone matrix on the periosteal side, and micropetrosis coincided with microdamage accumulation, implying that T1DM drives local skeletal aging and thereby impairs the biomechanical competence of the bone tissue. The consequent dysfunction of the osteocyte network hampers bone remodeling and decreases bone repair mechanisms, potentially contributing to the enhanced fracture risk seen in individuals with T1DM. STATEMENT OF SIGNIFICANCE: Type 1 diabetes mellitus (T1DM) is a chronic autoimmune disease that causes hyperglycemia. Increased bone fragility is one of the complications associated with T1DM. Our latest study on T1DM-affected human cortical bone identified the viability of osteocytes, the primary bone cells, as a potentially critical factor in T1DM-bone disease. We linked T1DM with increased osteocyte apoptosis and local accumulation of mineralized lacunar spaces and microdamage. Such structural changes in bone tissue suggest that T1DM speeds up the adverse effects of aging, leading to the premature death of osteocytes and potentially contributing to diabetes-related bone fragility.

High-energy synchrotron-radiation-based X-ray micro-tomography enables non-destructive and micro-scale palaeohistological assessment of macro-scale fossil dinosaur bones.

Palaeohistological analysis has numerous applications in understanding the palaeobiology of extinct dinosaurs. Recent developments of synchrotron-radiation-based X-ray micro-tomography (SXMT) have allowed the non-destructive assessment of palaeohistological features in fossil skeletons. Yet, the application of the technique has been limited to specimens on the millimetre to micrometre scale because its high-resolution capacity has been obtained at the expense of a small field of view and low X-ray energy. Here, SXMT analyses of dinosaur bones with widths measuring ∼3 cm under a voxel size of ∼4 µm at beamline BL28B2 at SPring-8 (Hyogo, Japan) are reported, and the advantages of virtual-palaeohistological analyses with large field of view and high X-ray energy are explored. The analyses provide virtual thin-sections visualizing palaeohistological features comparable with those obtained by traditional palaeohistology. Namely, vascular canals, secondary osteons and lines of arrested growth are visible in the tomography images, while osteocyte lacunae are unobservable due to their micrometre-scale diameter. Virtual palaeohistology at BL28B2 is advantageous in being non-destructive, allowing multiple sampling within and across skeletal elements to exhaustively test the skeletal maturity of an animal. Continued SXMT experiments at SPring-8 should facilitate the development of SXMT experimental procedures and aid in understanding the paleobiology of extinct dinosaurs.

NRF2 DEFICIENCY CONTRIBUTES TO AGE-DEPENDENT PROGRESSION OF FEMALE OSTEOPOROSIS

Nuclear factor erythroid 2–related factor 2 (Nrf2) is a crucial transcription factor to maintain cellular redox homeostasis, but is also affecting bone metabolism. As the association between Nrf2 and osteoporosis in elderly females is not fully elucidated, our aim was to shed light on the potential contribution of Nrf2 to the development of age-dependent osteoporosis using a mouse model.Female wild-type (WT, n=18) and Nrf2-knockout (KO, n=12) mice were sacrificed at different ages (12 weeks=young mature adult, and 90 weeks=old), morphological cortical and trabecular properties of femoral bone analyzed by micro-computed tomography (µCT), and compared to histochemistry. Mechanical properties were derived from quasi-static compression tests and digital image correlation (DIC) used to analyze full-field strain distribution. Bone resorbing cells and aromatase expression by osteocytes were evaluated immunohistochemically and empty osteocyte lacunae counted in cortical bone. Wilcoxon rank sum test was used for data comparison and differences considered statistically significant at p<0.05.When compared to old WT mice, old Nrf2-KO mice revealed a significantly reduced trabecular bone mineral density (BMD), cortical thickness (Ct.Th), cortical area (Ct.Ar), and cortical bone fraction (Ct.Ar/Tt.Ar). Surprisingly, these parameters were not different in skeletally mature young adult mice. Metaphyseal trabeculae were thin but present in all old WT mice, while no trabecular bone was detectable in 60% of old KO mice. Occurrence of empty osteocyte lacunae did not differ between both groups, but a significantly higher number of osteoclast-like cells and fewer aromatase-positive osteocytes were found in old KO mice. Furthermore, female Nrf2-KO mice showed an age-dependently reduced fracture resilience when compared to age-matched WT mice.Our results confirmed lower bone quantity and quality as well as an increased number of bone resorbing cells in old female Nrf2-KO mice. Additionally, aromatase expression in osteocytes of old Nrf2-KO mice was compromised, which may indicate a chronic lack of estrogen in bones of old Nrf2-deficient mice. Thus, chronic Nrf2 loss seems to contribute to age-dependent progression of female osteoporosis.

Bone Tissue Evaluation Indicates Abnormal Mineralization in Patients with Autoimmune Polyendocrine Syndrome Type I: Report on Three Cases

Autoimmune polyendocrine syndrome type-1 (APS1) is characterized by autoimmune manifestations affecting different organs from early childhood on. Immunological abnormalities, the resulting endocrinopathies, and their treatments may compromise bone health. For the first time in APS1, we analyzed transiliac bone biopsy samples by bone histomorphometry and quantitative backscattered electron imaging in three adult patients (female P1, 38 years; male P2, 47 years; male P3, 25 years). All had biallelic mutations in the autoimmune regulator gene and in addition to endocrinopathies, also significant bone fragility. Histomorphometry showed bone volume in the lower normal range for P1 (BV/TV, − 0.98 SD) and P3 (− 1.34 SD), mainly due to reduced trabecular thickness (TbTh, − 3.63 and − 2.87 SD). In P1, osteoid surface was low (OS/BS, − 0.96 SD); active osteoblasts and double labeling were seen only on cortical bone. P3 showed a largely increased bone turnover rate (BFR/BV, + 4.53 SD) and increased mineralization lag time (Mlt, + 3.40 SD). Increased osteoid surface (OS/BS, + 2.03 and + 4.71 SD for P2 and P3) together with a large proportion of lowly mineralized bone area (Trab CaLow, + 2.22 and + 9.81 SD for P2 and P3) and focal mineralization defects were consistent with abnormal mineralization. In all patients, the density and area of osteocyte lacunae in cortical and trabecular bone were similar to healthy adults. The bone tissue characteristics were variable and included decreased trabecular thickness, increased amount of osteoid, and abnormal mineralization which are likely to contribute to bone fragility in patients with APS1.

Wnt/β-Catenin Signaling in Craniomaxillofacial Osteocytes.

There is a growing appreciation within the scientific community that cells exhibit regional variation. Whether the variation is attributable to differences in embryonic origin or anatomical location and mechanical loading has not been elucidated; what is clear, however, is that adult cells carry positional information that ultimately affects their functions. The purpose of this review is to highlight the functions of osteocytes in the craniomaxillofacial (CMF) skeleton as opposed to elsewhere in the body, and in doing so gain mechanistic insights into genetic conditions and chemically-induced diseases that particularly affect this region of our anatomy. In the CMF skeleton, elevated Wnt/β-catenin signaling affects not only bone mass and volume, but also mineralization of the canalicular network and osteocyte lacunae. Aberrant elevation in the Wnt/β-catenin pathway can also produce micropetrosis and osteonecrosis of CMF bone, presumably due to a disruption in the signaling network that connects osteocytes to one another, and to osteoblasts on the bone surface.

Assessing the extent of bone bioerosion in short timescales – A novel approach for quantifying microstructural loss

The evaluation of bone diagenetic phenomena in archaeological timescales is well established, but little is known about the extent of bone diagenesis in short forensic timescales. In particular, the use of the Oxford Histological Index (OHI) has become synonymous with assessing bioerosion in archaeological bone samples, but it may not be ideal for use on samples with shorter, forensic post-depositional timescales. Here, we present a novel method of quantifying the extent of bioerosion occurring on samples with short post-depositional periods by counting the number of normal and diagenetic osteocyte lacunae observed within the microstructure of the bone, which enables calculation of the percentage of destroyed bone within the sample. Due to the potential for condition of the remains, or depositional environment to affect bone diagenesis, this study investigated multiple conditions; whole rat carcasses, defleshed rat long bones, and excised fleshed rat limbs that were either placed in soil in plastic boxes or exposed on a clean plastic surface, and left to decompose from four to 28 weeks, to allow bone bioerosion to occur. Statistically significant differences in the number of average diagenetic lacunae observed were found between the three conditions, while a statistically significant difference was observed between OHI scores of samples in the two deposition environments. The number of diagenetic osteocyte lacunae increased in all conditions, showing statistically significant increase in the percentage of destroyed bone over time. Diagenetic changes were seen as early as 4-weeks post-deposition. Comparisons between the OHI scores and the lacunae counts showed that, while the use of OHI could not distinguish between samples with discrete microstructural deterioration, counting the normal and diagenetic lacunae could distinguish such diagenetic changes.

Osteocyte lacunae in transiliac bone biopsy samples across life span

Osteocytes act as bone mechanosensors, regulators of osteoblast/osteoclast activity and mineral homeostasis, however, knowledge about their functional/morphological changes throughout life is limited. We used quantitative backscattered electron imaging (qBEI) to investigate osteocyte lacunae sections (OLS) as a 2D-surrogate characterizing the osteocytes. OLS characteristics, the density of mineralized osteocyte lacunae (i.e., micropetrotic osteocytes, md.OLS-Density in nb/mm2) and the average degree of mineralization (CaMean in weight% calcium) of cortex and spongiosa were analyzed in transiliac biopsy samples from healthy individuals under 30 (n=59) and over 30 years (n=50) (i.e., before and after the age of peak bone mass, respectively). We found several differences in OLS-characteristics: 1). Inter-individually between the age groups: OLS-Density and OLS-Porosity were reduced by about 20% in older individuals in spongiosa and in cortex versus younger probands (both, p<0.001). 2). Intra-individually between bone compartments: OLS-Density was higher in the cortex, +18.4%, p<0.001 for younger and +7.6%, p<0.05 for older individuals. Strikingly, the most frequent OLS nearest-neighbor distance was about 30 µm in both age groups and at both bone sites revealing a preferential organization of osteocytes in clusters. OLS-Density was negatively correlated with CaMean in both spongiosa and cortex (both, p<0.001). Few mineralized OLS were found in young individuals along with an increase of md.OLS-Density with age. In summary, this transiliac bone sample analysis of 200000 OLS from 109 healthy individuals throughout lifespan reveals several age-related differences in OLS characteristics. Moreover, our study provides reference data from healthy individuals for different ages to be used for diagnosis of bone abnormalities in diseases. STATEMENT OF SIGNIFICANCE: Osteocytes are bone cells embedded in lacunae within the mineralized bone matrix and have a key role in the bone metabolism and the mineral homeostasis. Not easily accessible, we used quantitative backscattered electron imaging to determine precisely number and shape descriptors of the osteocyte lacunae in 2D. We analyzed transiliac biopsy samples from 109 individuals with age distributed from 2 to 95 years. Compact cortical bone showed constantly higher lacunar density than cancellous bone but the lacunar density in both bone tissue decreased with age before the peak bone mass age at 30 years and stabilized or even increased after this age. This extensive study provides osteocyte lacunae reference data from healthy individuals usable for bone pathology diagnosis.

Evocalcet Rescues Secondary Hyperparathyroidism-driven Cortical Porosity in CKD Male Rats.

To elucidate the effect of evocalcet, a new oral calcimimetic to bone of secondary hyperparathyroidism (SHPT) with chronic kidney disease (CKD), the rats were 5/6 nephrectomized and fed on a high-phosphate diet. The treated rats were then divided into vehicle groups and evocalcet administered groups. The rats in the vehicle groups exhibited increased levels of serum PTH and inorganic phosphate (Pi) levels, high bone turnover, and severe cortical porosity, mimicking SHPT (CKD-SHPT rats). The cortical bone of the CKD-SHPT rats showed broad demineralization around the osteocytes, suppression of Phex/small integrin-binding ligand N-linked glycoprotein-mediated mineralization in the periphery of the osteocytic lacunae, and increased levels of osteocytic cell death, all of which were considered as the first steps of cortical porosity. In contrast, evocalcet ameliorated the increased serum PTH levels, the enlarged osteocytic lacunae, and the cortical porosity of the CKD-SHPT rats. Osteocytes of CKD-SHPT rats strongly expressed PTH receptor and Pit1/Pit2, which sense extracellular Pi, indicating that PTH and Pi affected these osteocytes. Cell death of cultured osteocytes increased in a Pi concentration-dependent manner, and PTH administration rapidly elevated Pit1 expression and enhanced osteocytic death, indicating the possibility that the highly concentrated serum PTH and Pi cause severe perilacunar osteolysis and osteocytic cell death. It is likely therefore that evocalcet not only decreases serum PTH but also reduces the exacerbation combined with PTH and Pi to the demineralization of osteocytic lacunae and osteocytic cell death, thereby protecting cortical porosity in CKD-SHPT rats.

Abnormal morphological features of osteocyte lacunae in adolescent idiopathic scoliosis: A large-scale assessment by ultra-high-resolution micro-computed tomography.

Abnormal osteocyte lacunar morphology in adolescent idiopathic scoliosis (AIS) has been reported while the results were limited by the number of osteocyte lacunae being quantified. The present study aimed to validate previous findings through (a) comparing morphological features of osteocyte lacunae between AIS patients and controls in spine and ilium using a large-scale assessment, and (b) investigating whether there is an association between the acquired morphological features of osteocyte lacunae and disease severity in AIS. Trabecular bone tissue of the facet joint of human vertebrae on both concave and convex sides at the apex of the scoliotic curve were collected from 4 AIS and 5 congenital scoliosis (CS) patients, and also at the same anatomic site from 3 non-scoliosis (NS) subjects intraoperatively. Trabecular bone tissue from ilium was obtained from 12 AIS vs 9 NS subjects during surgery. Osteocyte lacunae were assessed using ultra-high-resolution micro-computed tomography. Clinical information such as age, body mass index (BMI) and radiological Cobb angle of the major curve were collected. There was no significant difference between density of osteocyte lacuna and bone volume fraction (BV/TV) between groups. A total of 230,076 and 78,758 osteocyte lacunae from facet joints of apical vertebra of scoliotic curve and iliac bone were included in the analysis, respectively. In facet joint bone biopsies, lacunar stretch (Lc.St) was higher, and lacunar equancy (Lc.Eq), lacunar oblateness (Lc.Ob), and lacunar sphericity (Lc.Sr) were lower in AIS and CS groups when compared with NS group. CA side was associated with higher Lc.St when compared with CX side. In iliac bone biopsies, Lc.Ob was higher and lacunar surface area (Lc.S) was lower in AIS group than NS group. Median values of Lc.St, Lc.Eq and Lc.Sr were significantly associated with radiological Cobb angle with adjustment for age and BMI (R-squared: 0.576, 0.558 and 0.543, respectively). This large-scale assessment of osteocyte lacunae confirms that AIS osteocyte lacunae are more oblate in iliac bone that is less influenced by asymmetric loading of the deformed spine than the vertebrae. Shape of osteocyte lacunae in iliac bone is associated with radiological Cobb angle of the major curve in AIS patients, suggesting the likelihood of systemic abnormal osteocyte morphology in AIS. Osteocyte lacunae from concave side of scoliotic curves were more stretched in both AIS and CS groups, which is likely secondary to asymmetric mechanical loading.

Morphometric Changes of Osteocyte Lacunar in Diabetic Pig Mandibular Cancellous Bone.

Osteocytes play an important role in bone metabolism. The interactions of osteocytes with the surrounding microenvironment can alter cellular and lacunar morphological changes. However, objective quantification of osteocyte lacunae is challenging due to their deep location in the bone matrix. This project established a novel method for the analytical study of osteocytes/lacunae, which was then used to evaluate the osteocyte morphological changes in diabetic pig mandibular bone. Eight miniature pigs were sourced, and diabetes was randomly induced in four animals using streptozotocin (STZ) administration. The mandibular tissues were collected and processed. The jawbone density was evaluated with micro-CT. Osteocyte lacunae were effectively acquired and identified using backscattered electron scanning microscopy (BSE). A significantly decreased osteocyte lacunae size was found in the diabetic group. Using the acid etching method, it was demonstrated that the area of osteocyte and lacunae, and the pericellular areas were both significantly reduced in the diabetes group. In conclusion, a standard and relatively reliable method for analyzing osteocyte/lacunae morphological changes under compromised conditions has been successfully established. This method demonstrates that diabetes can significantly decrease osteocyte/lacunae size in a pig's mandibular cancellous bone.

An insight into cancer palaeobiology: does the Mesozoic neoplasm support tissue organization field theory of tumorigenesis?

BackgroundNeoplasms are common across the animal kingdom and seem to be a feature plesiomorphic for metazoans, related with an increase in somatic complexity. The fossil record of cancer complements our knowledge of the origin of neoplasms and vulnerability of various vertebrate taxa. Here, we document the first undoubted record of primary malignant bone tumour in a Mesozoic non-amniote. The diagnosed osteosarcoma developed in the vertebral intercentrum of a temnospondyl amphibian, Metoposaurus krasiejowensis from the Krasiejów locality, southern Poland.ResultsA wide array of data collected from gross anatomy, histology, and microstructure of the affected intercentrum reveals the tumour growth dynamics and pathophysiological aspects of the neoplasm formation on the histological level. The pathological process almost exclusively pertains to the periosteal part of the bone composed from a highly vascularised tissue with lamellar matrix. The unorganised arrangement of osteocyte lacunae observed in the tissue is characteristic for bone tissue types connected with static osteogenesis, and not for lamellar bone. The neoplastic bone mimics on the structural level the fast growing fibrolamellar bone, but on the histological level develops through a novel ossification type. The physiological process of bone remodelling inside the endochondral domain continued uninterrupted across the pathology of the periosteal part.ConclusionsBased on the results, we discuss our case study’s consistence with the Tissue Organization Field Theory of tumorigenesis, which locates the causes of neoplastic transformations in disorders of tissue architecture.

Nuclear factor erythroid 2–related factor 2 (Nrf2) deficiency causes age-dependent progression of female osteoporosis

BackgroundNuclear factor erythroid 2–related factor 2 (Nrf2) is a crucial transcription factor for cellular redox homeostasis. The association of Nrf2 with elderly female osteoporotic has yet to be fully described. The aim was to elucidate a potential age-dependent Nrf2 contribution to female osteoporosis in mice.MethodsEighteen female wild type (WT) and 16 Nrf2-knockout (KO) mice were sacrificed at different ages (12 weeks = young mature adult and 90 weeks = old) to analyze their femurs. The morphological properties (trabecular and cortical) were evaluated by micro-computed tomography (μCT) and compared to gold standard histochemistry analysis. The quasi-static compression tests were performed to calculate the mechanical properties of bones. Additionally, the population of bone resorbing cells and aromatase expression by osteocytes was immunohistochemically evaluated and empty osteocyte lacunae was counted in cortical bone.ResultsOld Nrf2-KO mice revealed a significantly reduced trabecular bone mineral density (BMD), cortical thickness, cortical area, and bone fraction compared to old WT mice, regardless of no significant difference in skeletally mature young adult mice between WT and KO. Specifically, while all old WT mice showed thin metaphyseal trabeculae, trabecular bone was completely absent in 60% of old KO mice. Additionally, old KO mice showed significantly more osteoclast-like cells and fewer aromatase-positive osteocytes than WT mice, whereas the occurrence of empty osteocyte lacunae did not differ between both groups. Nrf2-KO mice further showed an age-dependently reduced fracture resilience compared to age-matched WT mice.ConclusionOur results suggest that chronic Nrf2 loss can lead to age-dependent progression of female osteoporosis.

The petrous bone contains high concentrations of osteocytes: One possible reason why ancient DNA is better preserved in this bone.

The characterization of ancient DNA in fossil bones is providing invaluable information on the genetics of past human and other animal populations. These studies have been aided enormously by the discovery that ancient DNA is relatively well preserved in the petrous bone compared to most other bones. The reasons for this better preservation are however not well understood. Here we examine the hypothesis that one reason for better DNA preservation in the petrous bone is that fresh petrous bone contains more DNA than other bones. We therefore determined the concentrations of osteocyte cells occluded inside lacunae within the petrous bone and compared these concentrations to other bones from the domestic pig using high resolution microCT. We show that the concentrations of osteocyte lacunae in the inner layer of the pig petrous bone adjacent to the otic chamber are about three times higher (around 95,000 lacunae per mm3) than in the mastoid of the temporal bone (around 28,000 lacunae per mm3), as well as the cortical bone of the femur (around 27,000 lacunae per mm3). The sizes and shapes of the lacuna in the inner layer of the petrous bone are similar to those in the femur. We also show that the pig petrous bone lacunae do contain osteocytes using a histological stain for DNA. We therefore confirm and significantly expand upon previous observations of osteocytic lacuna concentrations in the petrous bone, supporting the notion that one possible reason for better preservation of ancient DNA in the petrous bone is that this bone initially contains at least three times more DNA than other bones. Thus during diagenesis more DNA is likely to be preserved in the petrous bone compared to other bones.