Biology subjects

Heveran, C. M.

Publications and source records attributed to Heveran, C. M..

14 recordsLinked to original sources

bioRxiv2026

Bone microarchitecture and material properties decline differently across midlife for male and female F344 x BN F1 rats

While bone mineral density (BMD) remains the clinical standard for assessing age-related fracture risk, accumulating evidence indicates that bone quality, including matrix properties and microarchitecture, contributes to fracture susceptibility in ways not captured by BMD alone. As matrix-targeted therapeutics emerge, preclinical models that exhibit translationally relevant bone quality changes are needed. Here, we evaluated the Fischer 344 x Brown Norway (F344xBN) F1 rat, a strain characterized by hybrid vigor and non-pathological aging, as a model for studying matrix-related mechanisms of skeletal aging. Femurs from male and female rats aged 7, 15, and 22 months were analyzed to quantify age- and sex-dependent changes in bone microarchitecture, fracture resistance, and matrix properties. Microcomputed tomography analyses revealed sexually dimorphic aging trajectories. From 7 to 22 months, females exhibited moderate declines in trabecular microarchitecture and no change in cortical porosity, whereas males showed pronounced trabecular deterioration and increased cortical porosity. Whole-bone flexural testing demonstrated age-related declines in material properties that were not attributable to changes in geometry, while females maintained geometry-scaled bone strength. Both sexes exhibited reduced bone toughness with age. Raman spectroscopy identified matrix-level alterations in males by 15 months, whereas systemic markers of bone turnover remained unchanged across age or sex. Together, these findings indicate that males exhibit combined tissue-scale and whole-bone deterioration by midlife, while females exhibit declining fracture resistance preceding substantial cortical bone loss or overt matrix deterioration. These results support the F344xBN F1 rat as a translational model for investigating matrix-driven skeletal aging. Lay summaryF344 x BN F1 hybrid rats provide a healthy, matrix-driven skeletal aging model. This strain exhibits distinct aging trajectories dependent on sex. Strength and toughness decrease in both sexes by midlife. Fracture resistance declines in females prior to substantial bone loss.

physiology↗

bioRxiv2025

Wing Hinge Dynamics Influence Stroke Amplitudes in Flapping Wing Insects: A Frequency Response Approach

Flapping wing insects leverage the dynamics of their compliant flight systems to reduce the energetic costs of flying. However, the extent to which the wing hinge dynamics contribute to the overall system dynamics remains unknown. Therefore, we developed an approach to (1) quantify the passive dynamic properties of the wing hinge, and (2) identify the resonant frequency of the isolated wing/wing hinge system. First, we measured the frequency response relating thorax deformation to wing stroke angle in sacrificed honeybees and army cutworm moths. Using these data, we developed a linear model of the flight system, which we then extended to incorporate nonlinear effects associated with large wing stroke angles. Our findings revealed that both species flap below the linear resonance of the wing hinge. At larger angles, nonlinear aerodynamic damping reduces the resonant frequency, causing both species to flap above wing hinge resonance. We discuss how wing-thorax coupling and muscle dynamics may cause the resonant frequency of the entire flight system to deviate from that of the wing/wing hinge system. Our estimates of wing hinge stiffness and damping provide quantitative parameters that can be incorporated into models of the insect flight system to enable more accurate predictions of resonance behavior.

biophysics↗

bioRxiv2024

High-fat diet exacerbates the loss of bone fracture toughness in aging for C57BL/6JN mice

The elderly are at increased risk of bone fracture and more often consume poor quality diets, such as high-fat diet (HFD). We hypothesized that HFD would exacerbate the loss of bone fracture resistance in aging. To test this hypothesis, we fed 5-month and 22-month C57BL/6JN mice of both sexes HFD or low-fat diet for 8 weeks. Aging and HFD lowered bone fracture toughness, while only aging reduced bone strength. At the tissue-scale, aging increased bone mineral maturity, while HFD altered bone mineralization and maturity as well as collagen structure. Cortical bone metabolism was also dysregulated with aging and HFD. Dysregulated pathways in aging and HFD were related to cellular function and viability, or glucose regulation, respectively. Aging with HFD also impacted osteoclast and adipocyte abundance and osteocyte viability. Together, these data demonstrate that HFD may exacerbate the loss of bone matrix quality and fracture resistance in aging.

bioengineering↗

bioRxiv2024

Mycelium as a scaffold for biomineralized engineered living materials

Engineered living materials (ELMs) are garnering considerable attention as a promising alternative to traditional building materials because of their potentially lower carbon footprint and additional functionalities conferred by living cells. However, biomineralized ELMs designed for load-bearing purposes are limited in their current design and usage for several reasons, including (1) low microbial viability and (2) limited control of specimen internal microarchitecture. We created third generation biomineralized ELMs from fungal mycelium scaffolds that were mineralized either by the fungus itself or by ureolytic bacteria. Both self-mineralized (i.e. fungally-mineralized) and bacterially-mineralized scaffolds retained high microbial viability for at least four weeks in room temperature or accelerated dehydration storage conditions, without the addition of protectants against desiccation. The microscale modulus of calcium carbonate varied with the different biomineralized scaffold conditions, and moduli were largest and stiffest for bacterial biomineralization of fungal mycelium. As an example of how mycelium scaffolds can enable the design of complex internal geometries of biomineralized materials, osteonal-bone mimetic architectures were patterned from mycelium and mineralized using ureolytic bacteria. These results demonstrate the potential for mycelium scaffolds to enable new frontiers in the design of biomineralized ELMs with improved viability and structural complexity. Progress and PotentialBiomineralized engineered living materials (ELMs) offer new approaches for increasing the sustainability of building materials and processes. However, the design and usage of biomineralized ELMs is constrained by several important limitations, including low microbial viability and limited ability to control internal microarchitecture. Fungal mycelium scaffolds, biomineralized by either fungi or bacteria, achieve much higher viability of ureolytic microorganisms than what has been reported for biomineralized ELMs. Further, mycelium scaffolds permit the manufacturing of complex architectures, such as inspired by the structure of osteonal bone. Mycelium scaffolds have the potential to enable new frontiers in the design and use of biomineralized ELMs. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=71 SRC="FIGDIR/small/592484v1_ufig1.gif" ALT="Figure 1"> View larger version (36K): org.highwire.dtl.DTLVardef@338d98org.highwire.dtl.DTLVardef@94f956org.highwire.dtl.DTLVardef@7d8ed6org.highwire.dtl.DTLVardef@12cb61e_HPS_FORMAT_FIGEXP M_FIG C_FIG

bioengineering↗

bioRxiv2023

Aging decreases osteocyte lacunar-canalicular turnover in female C57BL/6 mice

Osteocytes engage in bone resorption and mineralization surrounding their expansive lacunar-canalicular system (LCS) through LCS turnover. However, fundamental questions persist about where, when, and how often osteocytes engage in LCS turnover and how these processes change with aging. Furthermore, whether LCS turnover depends on tissue strain remains unexplored. To address these questions, we utilized confocal scanning microscopy, immunohistochemistry, and scanning electron microscopy to characterize osteocyte LCS turnover in the cortical (mid-diaphysis) and cancellous (metaphysis) femurs from young (5 mo) and early-old-age (22 mo) female C57BL/6JN mice. LCS bone mineralization was measured by the presence of perilacunar fluorochrome labels. LCS bone resorption was measured by immunohistochemical markers of bone resorption. The dynamics of LCS turnover were estimated from serial fluorochrome labeling, where each mouse was administered two labels between 2 days and 16 days before euthanasia. Osteocyte participation in mineralizing their surroundings is highly abundant in both cortical and cancellous bone of young adult mice but significantly decreases with aging. LCS bone resorption also decreases with aging. Aging has a greater impact on LCS turnover dynamics in cancellous bone than in cortical bone. Lacunae with recent LCS turnover have larger lacunae in both age groups. The impacts of aging on LCS turnover also varies with cortical region of interest and intracortical location, suggesting a dependence on tissue strain. The impact of aging on decreasing LCS turnover may have significant implications for bone quality and mechanosensation. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=88 SRC="FIGDIR/small/571934v1_ufig1.gif" ALT="Figure 1"> View larger version (49K): org.highwire.dtl.DTLVardef@cbb7a9org.highwire.dtl.DTLVardef@86d667org.highwire.dtl.DTLVardef@660eb8org.highwire.dtl.DTLVardef@5062a6_HPS_FORMAT_FIGEXP M_FIG Graphical abstractOsteocyte participation in lacunar-canalicular system (LCS) mineralization is abundant in young mice but decreases with aging in both cortical and cancellous bone. Aging also reduces LCS bone resorption. Aging alters the relationship between LCS turnover and variation in cortical tissue strain. C_FIG

physiology↗

bioRxiv2023

Osteochondral fluid transport in an ex vivo system

ObjectiveAlterations to fluid transport from bone-to-cartilage may contribute to the development of osteoarthritis. However, many questions remain about fluid transport between these tissues. The objectives of this study were to (1) test for diffusion of 3kDa molecular tracers from bone-to-cartilage and (2) assess potential differences in bone-to-cartilage fluid transport between different loading conditions. DesignOsteochondral cores extracted from bovine femurs (N=8 femurs, 10 cores/femur) were subjected to either no-load (i.e., pure diffusion), pre-load only, or cyclic compression (5{+/-}2% or 10{+/-}2% strain) in a two-chamber transport system with the bone compartment filled with a 3kDa tracer. Tracer concentrations in the cartilage compartment were measured every 5 minutes for 120 minutes. Tracer concentrations were analyzed for differences in beginning, peak and equilibrium concentrations, loading effects, and time-to-peak tracer concentration. ResultsPeak tracer concentration in the cartilage compartment was significantly higher compared to beginning and equilibrium tracer concentrations indicating fluid transport from bone to cartilage. Cartilage-compartment tracer concentration was influenced by strain magnitude, but no time-to-peak relationship was found when comparing strain magnitudes. ConclusionThis study shows that osteochondral fluid transport occurs from bone-to-cartilage with 3kDa dextran molecules. These are much larger molecules to move between bone and cartilage than previously reported. Further these results demonstrate the potential for cyclic compression to impact osteochondral fluid transport. Determining the baseline osteochondral fluid transport in healthy tissues is crucial to elucidating the potential mechanisms of progression and onset of osteoarthritis.

bioengineering↗

bioRxiv2022

The gut microbiome has sexually dimorphic effects on bone tissue energy metabolism and multiscale bone quality in C57BL/6J mice

The gut microbiome impacts bone mass, implying a disruption to bone homeostasis, yet significant uncertainty remains regarding the impacts of the gut microbiome on remodeling bone cells. The gut microbiome is thought to be essential for normal biomineralization, but the specific consequences of the absent gut microbiome on tissue mineralization and multiscale bone quality are not determined. We hypothesized that bone homeostasis and tissue-scale metabolism, tissue mineralization, and whole-bone biomechanics are altered in germ-free (GF) C57BL/6J mice. Further, because many characteristics of the gut microbiome are sexually dimorphic, we hypothesized that the gut microbiome would show important sex differences with regards to its impact on bone quality. Differences between GF and conventional mouse bone extended from bone tissue metabolism to whole bone biomechanics. Cortical bone tissue from male mice had a greater signature of amino acid metabolism whereas female cells had a greater signature of lipid metabolism. These sex differences were also present in GF mice and were indeed even more stark. GF increased cortical femur bone formation for both sexes and decreased bone resorption and osteoclast density only in females. GF similarly increased cortical femur tissue mineralization and altered collagen structure for both sexes but led to greater gains in distal femur trabecular microarchitecture for males. Whole femur strength was similarly increased with GF for both sexes, but males had a greater increase in modulus. GF did not impact fracture toughness for either sex. The altered bone quality with GF is multifactorial and is likely contributed to by differences in tissue-scale composition as well as lower cortical porosity. Together, these data demonstrate that the gut microbiome influences bone cells and multiscale bone quality, but that the specific relationships that underlie these effects to bone are different for females and males.

microbiology↗

bioRxiv2022

Ensemble Clustering Combined with Clustering Optimization: A Novel Workflow for Analyzing Metabolomics Data

Modern biological research often leverages clustering to elucidate disease endotypes and underlying mechanisms. Mono-cluster solutions remain the predominant method; however, this approach has concerning pitfalls, motivating the need for ensemble clustering methods. We present Ensemble Clustering Combined with Cluster Optimization (ECCO), an open-source Python UI that provides a fast, scalable framework for ensemble clustering of large-scale data. It includes zero-code integration of novel ensemble clustering methods and many pre- and post-processing functionalities, enabling researchers to efficiently integrate advanced clustering methodologies into their analysis pipelines.

bioinformatics↗

bioRxiv2022

Subchondral bone and synovial fluid metabolomic profiles are altered in injured and contralateral limbs 7 days after non-invasive joint injury in skeletally-mature C57BL/6 mice

ObjectivePost-traumatic osteoarthritis (PTOA) is a common long-term outcome following ACL injury. However, early changes to bone and synovial fluid after ACL injury are not sufficiently understood. The objectives of this study were to (1) evaluate whether acute bone loss one week after ACL injury is accompanied by altered subchondral bone plate modulus, (2) determine if bone changes are localized to the injured limb or extend to the contralateral-to-injured limb compared with sham-loaded controls, and (3) identify shifts in synovial fluid metabolism unique to injured limbs. DesignFemale C57Bl\6N mice (19 weeks at injury) were subjected to either a single tibial compression overload to simulate ACL injury (n=8) or a small pre-load (n=8). Mice were euthanized 7 days after injury, and synovial fluid was immediately harvested for metabolomic profiling. Bone microarchitecture, bone formation, and subchondral bone modulus at the proximal tibia were studied using microCT, histomorphometry, and nanoindentation, respectively. Osteoclast number density was assessed at the distal femur. For each bone measure a mixed model ANOVA was generated to determine the effects of injury and loaded side. ResultsEpiphyseal and subchondral bone microarchitecture decreased while subchondral bone tissue modulus was unchanged after ACL injuries. Bone resorption increased but bone formation was not changed. Loss of bone microarchitecture also occurred for the contralateral-to-injured limb, demonstrating that the early response to ACL injury extended beyond the injured joint. While the metabolomic profiles of the injured and contralateral-to-injured limbs had many similarities, there were also distinct metabolic shifts present in only the injured limbs. The most prominent of the pathways was cysteine and methionine metabolism, which is associated with osteoclast activity. ConclusionThese results add to the understanding of early bone changes following ACL injury. Confirming prior reports, we observe a decline in epiphyseal and subchondral bone microarchitecture. We add the finding that subchondral bone modulus remains unchanged at one week after ACL injury. A potential biomarker of this initial bone catabolic response may be synovial fluid cysteine and methionine metabolism, which was only dysregulated in injured knees. Our results implicate a rapidly changing biological and mechanical environment within both the injured and contralateral joints that has the potential for influencing the progression to PTOA.

bioengineering↗

bioRxiv2021

Experimental Studies of Carpenter Bee (Xylocopa: Apidae) Thorax Mechanics During Defensive Buzzing

Approximately 10% of flowering plant species conceal their pollen within tube-like poricidal anthers. Bees extract pollen from poricidal anthers via floral buzzing, a behavior during which they apply cyclic forces by biting the anther and rapidly contracting their flight muscles. The success of pollen extraction during floral buzzing relies on the direction and magnitude of the forces applied by the bees, yet these forces and forcing directions have not been previously quantified. In this work, we developed an experiment to simultaneously measure the directional forces and thorax kinematics produced by carpenter bees (Xylocopa californica) during defensive buzzing, a behavior regulated by similar physiological mechanisms as floral buzzing. We found that the buzzing frequencies averaged about 130 Hz and were highly variable within individuals. Force amplitudes were on average 170 mN, but at times reached nearly 500 mN. These forces were 30 - 80 times greater than the weight of the bees tested. The two largest forces occurred within a plane formed by the bees flight muscles. Force amplitudes were moderately correlated with thorax displacement, velocity and acceleration amplitudes but only weakly correlated with buzzing frequency. Linear models developed through this work provide a mechanism to estimate forces produced during non-flight behaviors based on thorax kinematic measurements in carpenter bees. Based on the buzzing frequencies, individual bees capacity to vary buzz frequency and predominant forcing directions, we hypothesize that carpenter bees leverage vibration amplification to increase the deformation of poricidal anthers, and hence the amount of pollen ejected.

biophysics↗

bioRxiv2021

Perilacunar bone tissue exhibits sub-micrometer modulus gradation which depends on the recency of osteocyte bone formation

Osteocytes are capable of resorbing and replacing bone local to the lacunar-canalicular system (LCS remodeling). However, the impacts of these processes on perilacunar bone quality are not understood. It is well established that aging is associated with reduced whole-bone fracture resistance, reduced osteocyte viability, and truncated LCS geometries, but it remains unclear if aging changes perilacunar bone quality. In this study, we employed atomic force microscopy (AFM) to quantify sub-micrometer gradations from 2D maps surrounding osteocyte lacunae in young (5 mo) and aged (22 mo) female mice. AFM-mapped lacunae were also imaged with confocal laser scanning microscopy to determine which osteocytes had recently deposited bone as determined by the presence of fluorochrome labels. These assays allowed us to quantify gradations in nanoscale mechanical properties of bone-forming/non-bone-forming osteocytes in young and aged mice. This study reports for the first time that there are sub-micrometer gradations in modulus surrounding lacunae and that these gradations are dependent upon recent osteocyte bone formation. Perilacunar bone adjacent to bone-forming osteocytes demonstrated lower peak and bulk modulus values when compared to bone near non-bone-forming osteocytes from the same mouse. Bone-forming osteocytes also showed increased perilacunar modulus variability. Age reduced lacunar size but did not significant effect modulus gradation or variability. In general, lacunar morphology was not a strong predictor of modulus gradation patterns. These findings support the idea that lacunar-canalicular remodeling activity changes the material properties of surrounding bone tissue on a sub-micrometer scale. Therefore, conditions that affect osteocyte health have the potential to impact bone quality. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=62 SRC="FIGDIR/small/461298v1_ufig1.gif" ALT="Figure 1"> View larger version (29K): org.highwire.dtl.DTLVardef@1fe5a68org.highwire.dtl.DTLVardef@1e17e90org.highwire.dtl.DTLVardef@13c2e3corg.highwire.dtl.DTLVardef@1ff9f38_HPS_FORMAT_FIGEXP M_FIG C_FIG

physiology↗

bioRxiv2021

The mouse bone metabolome is sexually dimorphic and is associated with whole bone strength

Cortical bone quality, which is sexually dimorphic, depends on bone turnover and therefore the activities of remodeling bone cells. However, sex differences in cortical bone metabolism are not yet defined. Adding to the uncertainty about cortical bone metabolism, the metabolomes of whole bone, isolated cortical bone without marrow, and bone marrow have not been compared. We hypothesized that the metabolome of isolated cortical bone would be distinct from that of bone marrow and would reveal sex differences. Metabolite profiles from LC-MS of whole bone, isolated cortical bone, and bone marrow were generated from humeri from 20-week-old female C57Bl/6J mice. The cortical bone metabolomes were then compared for 20-week-old female and male C57Bl/6J mice. Femurs from male and female mice were evaluated for flexural material properties and were then categorized into bone strength groups. The metabolome of isolated cortical bone was distinct from both whole bone and bone marrow. We also found sex differences in the isolated cortical bone metabolome. Based on metabolite pathway analysis, females had higher lipid metabolism, and males had higher amino acid metabolism. High-strength bones, regardless of sex, had greater tryptophan and purine metabolism. For males, high strength bones had upregulated nucleotide metabolism, whereas lower strength bones had greater pentose phosphate pathway metabolism. Since the higher strength groups (females compared with males, high strength males compared with lower strength males) had higher serum CTX1/P1NP, we estimate that the metabolomic signature of bone strength in our study at least partially reflects differences in bone turnover. These data provide novel insight into bone bioenergetics and the sexual dimorphic nature of bone material properties in C57Bl/6 mice.

cell biology↗

bioRxiv2021

The flying insect thoracic cuticle is heterogenous in structure and in thickness-dependent modulus gradation

The thorax is a specialized structure central to an insects ability to fly. In the thorax, flight muscles are surrounded by a thin layer of cuticle. The structure, composition, and material properties of this chitinous structure may influence the efficiency of the thorax in flight. However, these properties, as well as their variation throughout anatomical regions of the thorax or between insect taxa, are not known. In this work, we provide a multi-faceted assessment of thorax cuticle for fliers with asynchronous (honey bee; Apis mellifera) and synchronous (hawkmoth; Manduca sexta) muscles. We investigated cuticle structure using histology, material composition through confocal laser scanning microscopy, and modulus gradation with nanoindentation. Our results suggest that cuticle properties of the thorax are highly dependent on anatomical region and species. Modulus gradation, but not mean modulus, differed between the two types of fliers. In some regions, A. mellifera had a positive linear modulus gradient from cuticle interior to exterior of about 2 GPa. In M. sexta, the modulus gradients were variable and were not well represented by linear fits with respect to cuticle thickness. We utilized finite element modeling to assess how measured modulus gradients influenced maximum stress in cuticle. Stress was reduced when cuticle with a linear gradient was compressed from the high modulus side. These results support the protective role of the A. mellifera thorax cuticle. Our multi-faceted assessment advances our understanding of thorax cuticle structural and material heterogeneity and the potential benefit of material gradation to flying insects. Graphical Abstract O_FIG_DISPLAY_L [Figure 1] M_FIG_DISPLAY C_FIG_DISPLAY Statement of SignificanceThe insect thorax is essential for efficient flight but questions remain about the contribution of exoskeletal cuticle. We assessed the thorax cuticle using a high resolution multi-faceted approach to determine how cuticle properties vary within thorax anatomical regions and between fliers with asynchronous (honey bee; Apis mellifera) and synchronous (hawkmoth; Manduca sexta) muscles. We examined structure using histological staining, modulus using nanoindentation, and material composition using confocal scanning light microscopy. We further utilized finite element modeling to understand the effect of the modulus gradations observed experimentally on stress accumulation. Cuticle properties vary through cuticle thickness, by thorax region, and between flight lineages.

biophysics↗

bioRxiv2020

Development and analytical validation of a finite element model of fluid transport through osteochondral tissue

Fluid transport between cartilage and bone is critical to joint health. The objective of this study was to develop and analytically validate a finite element model of osteochondral tissue capable of modeling cartilage-bone fluid transport. A biphasic viscoelastic model using an ellipsoidal fiber distribution was created with three distinct layers of cartilage (superficial zone, middle zone, and deep zone) along with a layer of subchondral bone. For stress-relaxation in unconfined compression, our results for compressive stress, radial stress, effective fluid pressure, and elastic recoil were compared with established biphasic analytical solutions. Our model also shows the development of fluid pressure gradients at the cartilage-bone interface during loading. Fluid pressure gradients developed at the cartilage-bone interface with consistently higher pressures in cartilage following initial loading to 10% strain, followed by convergence towards equal pressures in cartilage and bone during the 400s relaxation period. These results provide additional evidence that fluid is transported between cartilage and bone during loading and improves upon estimates of the magnitude of this effect through incorporating a realistic distribution and estimate of the collagen ultrastructure. Understanding fluid transport between cartilage and bone may be key to new insights about the mechanical and biological environment of both tissues in health and disease.

bioengineering↗