Stresses and strains on the human fetal skeleton during development

Pioneering a chick embryo model to explore the intrauterine etiology of developmental dysplasia of the hip in oligohydramnios conditions

OBJECTIVE

To explore the impact of oligohydramnios on fetal movement and hip development, given its association with developmental dysplasia of the hip (DDH) but unclear mechanisms.

METHODS

Chick embryos were divided into four groups based on the severity of oligohydramnios induced by amniotic fluid aspiration (control, 0.2 mL, 0.4 mL, 0.6 mL). Fetal movement was assessed by detection of movement and quantification of residual amniotic fluid volume. Hip joint development was assessed by gross anatomic analysis, micro-computed tomography (micro-CT) for cartilage assessment, and histologic observation at multiple time points. In addition, a subset of embryos from the 0.4 mL aspirated group underwent saline reinfusion and subsequent evaluation.

RESULTS

Increasing volumes of aspirated amniotic fluid resulted in worsening of fetal movement restrictions (e.g., 0.4 mL aspirated and control group at E10: frequency difference -7.765 [95% CI: -9.125, -6.404]; amplitude difference -0.343 [95% CI: -0.588, -0.097]). The 0.4 mL aspirated group had significantly smaller hip measurements compared to controls, with reduced acetabular length (-0.418 [95% CI: -0.575, -0.261]) and width (-0.304 [95% CI: -0.491, -0.117]) at day E14.5. Histological analysis revealed a smaller femoral head (1.084 ± 0.264 cm) and shallower acetabulum (0.380 ± 0.106 cm) in the 0.4 mL group. Micro-CT showed cartilage matrix degeneration (13.6% [95% CI: 0.6%, 26.7%], P = 0.043 on E14.5). Saline reinfusion resulted in significant improvements in the femoral head to greater trochanter (0.578 [95% CI: 0.323, 0.833], P = 0.001).

CONCLUSIONS

Oligohydramnios can cause DDH by restricting fetal movement and disrupting hip morphogenesis in a time-dependent manner. Timely reversal of oligohydramnios during the fetal period may prevent DDH.

Trajectories of brain and behaviour development in the womb, at birth and through infancy

Birth is often seen as the starting point for studying effects of the environment on human development, with much research focused on the capacities of young infants. However, recent imaging advances have revealed that the complex behaviours of the fetus and the uterine environment exert influence. Birth is now viewed as a punctuate event along a developmental pathway of increasing autonomy of the child from their mother. Here we highlight (1) increasing physiological autonomy and perceptual sensitivity in the fetus, (2) physiological and neurochemical processes associated with birth that influence future behaviour, (3) the recalibration of motor and sensory systems in the newborn to adapt to the world outside the womb and (4) the effect of the prenatal environment on later infant behaviours and brain function. Taken together, these lines of evidence move us beyond nature-nurture issues to a developmental human lifespan view beginning within the womb.

A nonsense CC2D1A variant is associated with congenital anomalies, motor delay, hypotonia, and slight deformities

Background

Autosomal recessive intellectual developmental disorder-3 is caused by homozygous or compound heterozygous mutations in the CC2D1A gene. The disorder is characterized by intellectual disability (ID) and autism spectrum disorder (ASD). To date, 39 patients from 17 families with CC2D1A -related disorders have been reported worldwide, in whom only six pathogenic or likely pathogenic loss-of-function variants and three variants of uncertain significance (VUS) in the CC2D1A gene have been identified in these patients.

Methods

We described a patient with ID from a non-consanguineous Chinese family and whole-exome sequencing (WES) was used to identify the causative gene.

Results

The patient presented with severe ID and ASD, speech impairment, motor delay, hypotonia, slight facial anomalies, and finger deformities. Threatened abortion and abnormal fetal movements occurred during pregnancy with the proband but not his older healthy sister. WES analysis identified a homozygous nonsense variant, c.736C > T (p.Gln246Ter), in the CC2D1A gene. In addition, six novel likely pathogenic CC2D1A variants were identified by a retrospective review of the in-house database.

Conclusions

This study expands the genetic and clinical spectra of CC2D1A-associated disorders, and may aid in increasing awareness of this rare condition. Our findings have provided new insights into the clinical heterogeneity of the disease and further phenotype-genotype correlation, which could help to offer scope for more accurate genetic testing and counseling to affected families.

Mechanical stress can regulate temporomandibular joint cavitation via signalling pathways

The temporomandibular joint (TMJ), composed of temporal fossa, mandibular condyle and a fibrocartilage disc with upper and lower cavities, is the biggest synovial joint and biomechanical hinge of the craniomaxillofacial musculoskeletal system. The initial events that give rise to TMJ cavities across diverse species are not fully understood. Most studies focus on the pivotal role of molecules such as Indian hedgehog (Ihh) and hyaluronic acid (HA) in TMJ cavitation. Although biologists have observed that mechanical stress plays an irreplaceable role in the development of biological tissues and organs, few studies have been concerned with how mechanical stress regulates TMJ cavitation. Based on the evidence from human or other animal embryos today, it is implicated that mechanical stress plays an essential role in TMJ cavitation. In this review, we discuss the relationship between mechanical stress and TMJ cavitation from evo-devo perspectives and review the clinical features and potential pathogenesis of TMJ dysplasia.

YAP and TAZ couple osteoblast precursor mobilization to angiogenesis and mechanoregulation in murine bone development

Fetal bone development occurs through the conversion of avascular cartilage to vascularized bone at the growth plate. This requires coordinated mobilization of osteoblast precursors with blood vessels. In adult bone, vessel-adjacent osteoblast precursors are maintained by mechanical stimuli; however, the mechanisms by which these cells mobilize and respond to mechanical cues during embryonic development are unknown. Here, we show that the mechanoresponsive transcriptional regulators Yes-associated protein (YAP) and transcriptional co-activator with PDZ-binding motif (TAZ) spatially couple osteoblast precursor mobilization to angiogenesis, regulate vascular morphogenesis to control cartilage remodeling, and mediate mechanoregulation of embryonic murine osteogenesis. Mechanistically, YAP and TAZ regulate a subset of osteoblast-lineage cells, identified by single-cell RNA sequencing as vessel-associated osteoblast precursors, which regulate transcriptional programs that direct blood vessel invasion through collagen-integrin interactions and Cxcl12. Functionally, in 3D human cell co-culture, CXCL12 treatment rescues angiogenesis impaired by stromal cell YAP/TAZ depletion. Together, these data establish functions of the vessel-associated osteoblast precursors in bone development.

The developing juvenile talus: Radiographic identification of distinct ontogenetic phases and structural trajectories

Trabecular bone architecture in the developing skeleton is a widely researched area of bone biomechanics; however, despite its significance in weight-bearing locomotion, the developing talus has received limited examination. This study investigates the talus with the purpose of identifying ontogenetic phases and developmental patterns that contribute to the growing understanding of the developing juvenile skeleton. Colour gradient mapping and radiographic absorptiometry were utilised to investigate 62 human tali from 38 individuals, ranging in age-at-death from 28 weeks intrauterine to 20 years of age. The perinatal talus exhibited a rudimentary pattern comparable to the structural organisation observed within the late adolescent talus. This early internal organisation is hypothesised to be related to the vascular pattern of the talus. After 2 years of age, the talus demonstrated refinement, where radiographic trajectories progressively developed into patterns consistent with adult trabecular organisation, which are linked to the forces associated with the bipedal gait, suggesting a strong influence of biomechanical forces on the development of the talus.

Unlocking the Role of sMyBP-C: A Key Player in Skeletal Muscle Development and Growth

Skeletal muscle is the largest organ in the body, responsible for gross movement and metabolic regulation. Recently, variants in the MYBPC1 gene have been implicated in a variety of developmental muscle diseases, such as distal arthrogryposis. How MYBPC1 variants cause disease is not well understood. Here, through a collection of novel gene-edited mouse models, we define a critical role for slow myosin binding protein-C (sMyBP-C), encoded by MYBPC1, across muscle development, growth, and maintenance during prenatal, perinatal, postnatal and adult stages. Specifically, Mybpc1 knockout mice exhibited early postnatal lethality and impaired skeletal muscle formation and structure, skeletal deformity, and respiratory failure. Moreover, a conditional knockout of Mybpc1 in perinatal, postnatal and adult stages demonstrates impaired postnatal muscle growth and function secondary to disrupted actomyosin interaction and sarcomere structural integrity. These findings confirm the essential role of sMyBP-C in skeletal muscle and reveal specific functions in both prenatal embryonic musculoskeletal development and postnatal muscle growth and function.

Lack of skeletal muscle contraction disrupts fibrous tissue morphogenesis in the developing murine knee

Externally applied forces, such as those generated through skeletal muscle contraction, are important to embryonic joint formation, and their loss can result in gross morphologic defects including joint fusion. While the absence of muscle contraction in the developing chick embryo leads to dissociation of dense connective tissue structures of the knee and ultimately joint fusion, the central knee joint cavitates whereas the patellofemoral joint does not in murine models lacking skeletal muscle contraction, suggesting a milder phenotype. These differential results suggest that muscle contraction may not have as prominent of a role in the growth and development of dense connective tissues of the knee. To explore this question, we investigated the formation of the menisci, tendon, and ligaments of the developing knee in two murine models that lack muscle contraction. We found that while the knee joint does cavitate, there were multiple abnormalities in the menisci, patellar tendon, and cruciate ligaments. The initial cellular condensation of the menisci was disrupted and dissociation was observed at later embryonic stages. The initial cell condensation of the tendon and ligaments were less affected than the meniscus, but these tissues contained cells with hyper-elongated nuclei and displayed diminished growth. Interestingly, lack of muscle contraction led to the formation of an ectopic ligamentous structure in the anterior region of the joint as well. These results indicate that muscle forces are essential for the continued growth and maturation of these structures during this embryonic period.

Non-Contact Monitoring of Fetal Movement Using Abdominal Video Recording

Fetal movement (FM) is an important indicator of fetal health. However, the current methods of FM detection are unsuitable for ambulatory or long-term observation. This paper proposes a non-contact method for monitoring FM. We recorded abdominal videos from pregnant women and then detected the maternal abdominal region within each frame. FM signals were acquired by optical flow color-coding, ensemble empirical mode decomposition, energy ratio, and correlation analysis. FM spikes, indicating the occurrence of FMs, were recognized using the differential threshold method. FM parameters including number, interval, duration, and percentage were calculated, and good agreement was found with the manual labeling performed by the professionals, achieving true detection rate, positive predictive value, sensitivity, accuracy, and F1_score of 95.75%, 95.26%, 95.75%, 91.40%, and 95.50%, respectively. The changes in FM parameters with gestational week were consistent with pregnancy progress. In general, this study provides a novel contactless FM monitoring technology for use at home.

Mechanoregulatory role of TRPV4 in prenatal skeletal development

Biophysical cues are essential for guiding skeletal development, but the mechanisms underlying the mechanical regulation of cartilage and bone formation are unknown. TRPV4 is a mechanically sensitive ion channel involved in cartilage and bone cell mechanosensing, mutations of which lead to skeletal developmental pathologies. We tested the hypothesis that loading-driven prenatal skeletal development is dependent on TRPV4 activity. We first establish that mechanically stimulating mouse embryo hindlimbs cultured ex vivo stimulates knee cartilage growth, morphogenesis, and expression of TRPV4, which localizes to areas of high biophysical stimuli. We then demonstrate that loading-driven joint cartilage growth and shape are dependent on TRPV4 activity, mediated via control of cell proliferation and matrix biosynthesis, indicating a mechanism by which mechanical loading could direct growth and morphogenesis during joint formation. We conclude that mechanoregulatory pathways initiated by TRPV4 guide skeletal development; therefore, TRPV4 is a valuable target for the development of skeletal regenerative and repair strategies.

The Lower Limb Movements of the Fetus in Uterus: A Narrative Review

The fetus movements play an important role in fetal well-being. With the continuous advancement of real-time scanning machines, it is feasible to observe the fetus movement in detail. The characteristics of fetal lower limb movements in prenatal examination have not been systematically investigated. This review proposes the patterns of fetal lower limb movements, the maternal influence on fetal lower limb movements, and the application of fetal lower limb movements for the diagnosis of prenatal diseases. A systematic search of literature on the lower limb movements of the fetus in uterus was performed in the databases, namely, Web of Science and Scopus. Thirty-four publications were selected. This review demonstrates that isolated fetal lower limb movements are rare and always accompanied with the movements of other body segments. Detection of the presence of fetal leg movements seems to be of no diagnostic value for fetuses with prenatal diseases. The isolated lower limb movement was statistically significant different between fetuses of low- and high-risk pregnant women. The coordinated movements of the fetal lower limbs and other parts should be considered when analyzing fetal movements in the future study.

YAP and TAZ couple osteoblast precursor mobilization to angiogenesis and mechanoregulated bone development

Endochondral ossification requires coordinated mobilization of osteoblast precursors with blood vessels. During adult bone homeostasis, vessel adjacent osteoblast precursors respond to and are maintained by mechanical stimuli; however, the mechanisms by which these cells mobilize and respond to mechanical cues during embryonic development are unknown. Previously, we found that deletion of the mechanoresponsive transcriptional regulators, YAP and TAZ, from Osterix-expressing osteoblast precursors and their progeny caused perinatal lethality. Here, we show that embryonic YAP/TAZ signaling couples vessel-associated osteoblast precursor mobilization to angiogenesis in developing long bones. Osterix-conditional YAP/TAZ deletion impaired endochondral ossification in the primary ossification center but not intramembranous osteogenesis in the bone collar. Single-cell RNA sequencing revealed YAP/TAZ regulation of the angiogenic chemokine, Cxcl12, which was expressed uniquely in vessel-associated osteoblast precursors. YAP/TAZ signaling spatially coupled osteoblast precursors to blood vessels and regulated vascular morphogenesis and vessel barrier function. Further, YAP/TAZ signaling regulated vascular loop morphogenesis at the chondro-osseous junction to control hypertrophic growth plate remodeling. In human cells, mesenchymal stromal cell co-culture promoted 3D vascular network formation, which was impaired by stromal cell YAP/TAZ depletion, but rescued by recombinant CXCL12 treatment. Lastly, YAP and TAZ mediated mechanotransduction for load-induced osteogenesis in embryonic bone.

Early Life Stress (ELS) Effects on Fetal and Adult Bone Development

Early life stress (ELS) refers to harmful environmental events (i.e., poor maternal health, metabolic restraint, childhood trauma) occurring during the prenatal and/or postnatal period, which may cause the 'epigenetic corruption' of cellular and molecular signaling of mental and physical development. While the impact of ELS in a wide range of human diseases has been confirmed, the ELS susceptibility to bone diseases has been poorly explored. In this review, to understand the potential mediating pathways of ELS in bone diseases, PRISMA criteria were used to analyze different stress protocols in mammal models and the effects elicited in dams and their progeny. Data collected, despite the methodological heterogeneity, show that ELS interferes with fetal bone formation, also revealing that the stress type and affected developmental phase may influence the variety and severity of bone anomalies. Interestingly, these findings highlight the maternal and fetal ability to buffer stress, establishing a new role for the placenta in minimizing ELS perturbations. The functional link between ELS and bone impairments will boost future investigations on maternal stress transmission to the fetus and, parallelly, help the assessment of catch-up mechanisms of skeleton adaptations from the cascading ELS effects.

Endostructural and periosteal growth of the human humerus

The growth and development of long bones are of considerable interests in the fields of comparative anatomy and palaeoanthropology, as evolutionary changes and adaptations to specific physical activity patterns are expected to be revealed during bone ontogeny. Traditionally, the cross-sectional geometry of long bones has been examined at discrete locations usually placed at set intervals or fixed percentage distances along the midline axis of the bone shaft. More recently, the technique of morphometric mapping has enabled the continuous analysis of shape variation along the shaft. Here we extend this technique to the full sequence of late fetal and postnatal development of the humeral shaft in a modern human population sample, with the aim of establishing the shape changes during growth and their relationship with the development of the arm musculature and activity patterns. A sample of modern human humeri from individuals of age ranging from 24 weeks in utero to 18 years was imaged using microtomography at multiple resolutions and custom Matlab scripts. Standard biomechanical properties, cortical thickness, surface curvature, and pseudo-landmarks were extracted along radial vectors spaced at intervals of 1° at each 0.5% longitudinal increment measured along the shaft axis. Heat maps were also generated for cortical thickness and surface curvature. The results demonstrate that a whole bone approach to analysis of cross-sectional geometry is more desirable where possible, as there is a continuous pattern of variation along the shaft. It is also possible to discriminate very young individuals and adolescents from other groups by relative cortical thickness, and also by periosteal surface curvature.

From mesenchymal niches to engineered in vitro model systems: Exploring and exploiting biomechanical regulation of vertebrate hedgehog signalling

Tissue patterning is the result of complex interactions between transcriptional programs and various mechanical cues that modulate cell behaviour and drive morphogenesis. Vertebrate Hedgehog signalling plays key roles in embryogenesis and adult tissue homeostasis, and is central to skeletal development and the osteogenic differentiation of mesenchymal stem cells. The expression of several components of the Hedgehog signalling pathway have been reported to be mechanically regulated in mesodermal tissue patterning and osteogenic differentiation in response to external stimulation. Since a number of bone developmental defects and skeletal diseases, such as osteoporosis, are directly linked to aberrant Hedgehog signalling, a better knowledge of the regulation of Hedgehog signalling in the mechanosensitive bone marrow-residing mesenchymal stromal cells will present novel avenues for modelling these diseases and uncover novel opportunities for extracellular matrix-targeted therapies. In this review, we present a brief overview of the key molecular players involved in Hedgehog signalling and the basic concepts of mechanobiology, with a focus on bone development and regeneration. We also highlight the correlation between the activation of the Hedgehog signalling pathway in response to mechanical cues and osteogenesis in bone marrow-derived mesenchymal stromal cells. Finally, we propose different tissue engineering strategies to apply the expanding knowledge of 3D material-cell interactions in the modulation of Hedgehog signalling in vitro for fundamental and translational research applications.

Three-dimensional visualization and quantitative analysis of embryonic and fetal thigh muscles using magnetic resonance and phase-contrast X-ray imaging

The musculoskeletal system around the human hip joint has acquired a suitable structure for erect bipedal walking. However, little is known about the process of separation and maturation of individual muscles during the prenatal period, when muscle composition is acquired. Understanding the maturation process of the normal musculoskeletal system contributes to elucidating the acquisition of bipedal walking in humans and to predicting normal growth and detecting congenital muscle disorders and anomalies. In this study, we clarify the process of thigh muscle maturation from the embryonic stage to the mid-fetal stage using serial sections, phase-contrast X-ray computed tomography, and magnetic resonance imaging. We also provide a 4D atlas of human thigh muscles between 8 and 23 weeks of gestation. As a result, we first show that muscle separation in the lower thigh tends to progress from the superficial to the deep layers and that all musculoskeletal components are formed by Carnegie Stage 22. Next, we show that femur and muscle volume grow in correlation with crown-rump length. Finally, we show that the anterior, abductor, and posterior muscle groups in the thigh contain a high percentage of monoarticular muscle volume by the end of the embryonic period. This ratio approaches that of adult muscle composition during normal early fetal development and is typical of bipedal walking. This study of fetal muscle composition suggests that preparation for postnatal walking may begin in early fetal period.

Clinical Assessment of Fetal Well-Being and Fetal Safety Indicators

Delivering safe clinical trials of novel therapeutics is central to enable pregnant women and their babies to access medicines for better outcomes. This review describes clinical monitoring of fetal well-being and safety. Current pregnancy surveillance includes regular antenatal checks of blood pressure and urine for signs of gestational hypertension. Fetal and placental development is assessed routinely using the first-trimester "dating" and mid-trimester "anomaly" ultrasound scans, but the detection of fetal anomalies can continue throughout pregnancy using targeted sonography or magnetic resonance imaging (MRI). Serial sonography can be used to assess fetal size, well-being, and placental function. Carefully defined reproducible imaging parameters, such as the head circumference (HC), abdominal circumference (AC), and femur length (FL), are combined to calculate an estimate of the fetal weight. Doppler analysis of maternal uterine blood flow predicts placental insufficiency, which is associated with poor fetal growth. Fetal doppler analysis can indicate circulatory decompensation and fetal hypoxia, requiring delivery to be expedited. Novel ways to assess fetal well-being and placental function using MRI, computerized cardiotocography (CTG), serum circulating fetoplacental proteins, and mRNA may improve the assessment of the safety and efficacy of maternal and fetal interventions. Progress has been made in how to define and grade clinical trial safety in pregnant women, the fetus, and neonate. A new system for improved safety monitoring for clinical trials in pregnancy, Maternal and Fetal Adverse Event Terminology (MFAET), describes 12 maternal and 18 fetal adverse event (AE) definitions and severity grading criteria developed through an international modified Delphi consensus process. This fills a vital gap in maternal and fetal translational medicine research.

Computation of Fetal Kicking in Various Fetal Health Examinations: A Systematic Review

Fetal movement has always been considered an essential indicator to evaluate the health of the unborn fetus. Many factors affect fetal movement. The frequency of fetal kicking is an important measurement of whether fetal development is progressing and healthy. Various instruments and methods of detecting fetal movement have been used and each method has its advantages and disadvantages. Although limited by the fetal environment in utero, the finite element method and musculoskeletal model can be used to calculate fetal lower limb movement. This review aims to summarize the current detection techniques for fetal movement, especially in the lower limbs. These will be outlined by describing the different measurements of fetal movement, and the related biomechanical analyses of fetal lower limb skeletogenesis and the associated muscular development to better evaluate and calculate the movements of the fetus in the womb.

A Review on the Vagus Nerve and Autonomic Nervous System During Fetal Development: Searching for Critical Windows

The autonomic nervous system (ANS) is one of the main biological systems that regulates the body's physiology. Autonomic nervous system regulatory capacity begins before birth as the sympathetic and parasympathetic activity contributes significantly to the fetus' development. In particular, several studies have shown how vagus nerve is involved in many vital processes during fetal, perinatal, and postnatal life: from the regulation of inflammation through the anti-inflammatory cholinergic pathway, which may affect the functioning of each organ, to the production of hormones involved in bioenergetic metabolism. In addition, the vagus nerve has been recognized as the primary afferent pathway capable of transmitting information to the brain from every organ of the body. Therefore, this hypothesis paper aims to review the development of ANS during fetal and perinatal life, focusing particularly on the vagus nerve, to identify possible "critical windows" that could impact its maturation. These "critical windows" could help clinicians know when to monitor fetuses to effectively assess the developmental status of both ANS and specifically the vagus nerve. In addition, this paper will focus on which factors-i.e., fetal characteristics and behaviors, maternal lifestyle and pathologies, placental health and dysfunction, labor, incubator conditions, and drug exposure-may have an impact on the development of the vagus during the above-mentioned "critical window" and how. This analysis could help clinicians and stakeholders define precise guidelines for improving the management of fetuses and newborns, particularly to reduce the potential adverse environmental impacts on ANS development that may lead to persistent long-term consequences. Since the development of ANS and the vagus influence have been shown to be reflected in cardiac variability, this paper will rely in particular on studies using fetal heart rate variability (fHRV) to monitor the continued growth and health of both animal and human fetuses. In fact, fHRV is a non-invasive marker whose changes have been associated with ANS development, vagal modulation, systemic and neurological inflammatory reactions, and even fetal distress during labor.

A review of strategies for development of tissue engineered meniscal implants

The meniscus is a key stabilizing tissue of the knee that facilitates proper tracking and movement of the knee joint and absorbs stresses related to physical activity. This review article describes the biology, structure, and functions of the human knee meniscus, common tears and repair approaches, and current research and development approaches using modern methods to fabricate a scaffold or tissue engineered meniscal replacement. Meniscal tears are quite common, often resulting from sports or physical training, though injury can result without specific contact during normal physical activity such as bending or squatting. Meniscal injuries often require surgical intervention to repair, restore basic functionality and relieve pain, and severe damage may warrant reconstruction using allograft transplants or commercial implant devices. Ongoing research is attempting to develop alternative scaffold and tissue engineered devices using modern fabrication techniques including three-dimensional (3D) printing which can fabricate a patient-specific meniscus replacement. An ideal meniscal substitute should have mechanical properties that are close to that of natural human meniscus, and also be easily adapted for surgical procedures and fixation. A better understanding of the organization and structure of the meniscus as well as its potential points of failure will lead to improved design approaches to generate a suitable and functional replacement.

Effects of chondrogenic priming duration on mechanoregulation of engineered cartilage

Chondrocyte maturation during cartilage development occurs under diverse and dynamic mechanical environments. Mechanical stimulation through bioreactor culture may mimic these conditions to direct cartilage tissue engineering in vitro. Mechanical cues can promote chondrocyte homeostasis or hypertrophy and mineralization, depending potentially on the timing of load application. Here, we tested the effects of chondrogenic priming duration on the response of engineered human cartilage constructs to dynamic mechanical compression. We cultured human bone marrow stromal cells (hMSCs) in fibrin hydrogels under chondrogenic priming conditions for periods of 0, 2, 4, or 6 weeks prior to two weeks of either static culture or dynamic compression. We measured construct mechanical properties, cartilage matrix composition, and gene expression. Dynamic compression increased the equilibrium and dynamic modulus of the engineered tissue, depending on the duration of chondrogenic priming. For priming times of 2 weeks or greater, dynamic compression enhanced COL2A1 and AGGRECAN mRNA expression at the end of the loading period, but did not alter total collagen or glycosaminoglycan matrix deposition. Load initiation at priming times of 4 weeks or less repressed transient osteogenic signaling (RUNX2, OPN) and expression of CYR61, a YAP/TAZ-TEAD-target gene. No suppression of osteogenic gene expression was observed if loading was initiated after 6 weeks of in vitro priming, when mechanical stimulation was observed to increase the expression of type X collagen. Taken together, these data demonstrate that the duration of in vitro chondrogenic priming regulates the cell response to dynamic mechanical compression and suggests that early loading may preserve chondrocyte homeostasis while delayed loading may support cartilage maturation.

Joint development recovery on resumption of embryonic movement following paralysis

Fetal activity in utero is a normal part of pregnancy and reduced or absent movement can lead to long-term skeletal defects, such as Fetal Akinesia Deformation Sequence, joint dysplasia and arthrogryposis. A variety of animal models with decreased or absent embryonic movements show a consistent set of developmental defects, providing insight into the aetiology of congenital skeletal abnormalities. At developing joints, defects include reduced joint interzones with frequent fusion of cartilaginous skeletal rudiments across the joint. At the spine, defects include shortening and a spectrum of curvature deformations. An important question, with relevance to possible therapeutic interventions for human conditions, is the capacity for recovery with resumption of movement following short-term immobilisation. Here, we use the well-established chick model to compare the effects of sustained immobilisation from embryonic day (E)4-10 to two different recovery scenarios: (1) natural recovery from E6 until E10 and (2) the addition of hyperactive movement stimulation during the recovery period. We demonstrate partial recovery of movement and partial recovery of joint development under both recovery conditions, but no improvement in spine defects. The joints examined (elbow, hip and knee) showed better recovery in hindlimb than forelimb, with hyperactive mobility leading to greater recovery in the knee and hip. The hip joint showed the best recovery with improved rudiment separation, tissue organisation and commencement of cavitation. This work demonstrates that movement post paralysis can partially recover specific aspects of joint development, which could inform therapeutic approaches to ameliorate the effects of human fetal immobility. This article has an associated First Person interview with the first author of the paper.

Fetal Movement Counting Using Optical Fibre Sensors

Daily fetal movement counting based on maternal perception is widely deployed to monitor fetal wellbeing. However, the counting performed by the mother is prone to errors for various reasons. There are limited devices on the market that can provide reliable and automatic counting. This paper presents a prototype of a novel fetal movement monitoring device based on fibre Bragg grating sensors. Deformation of the skin caused by a fetal movement can lead to a change of the strain and stress on the optical fibre sensors, therefore can induce distortions to the breathing pattern of the mother. In the study data was gathered by the sensors through strain measurement and was post-processed using independent component analysis (ICA) and high-pass filtering to show the instances of the fetal movements. Information gathered during user trials with the prototype suggests that the system detects significantly higher numbers of fetus movements than that observed based on the mother's perception. Among the various techniques available for fetal movement monitoring, fibre optic sensing provides many advantages including multiplex capability, flexibility and minimal size, making the concept an attractive solution for reliable monitoring of antenatal fetal movements.

A systematic scoping review to identify the design and assess the performance of devices for antenatal continuous fetal monitoring

BACKGROUND

Antepartum fetal monitoring aims to assess fetal development and wellbeing throughout pregnancy. Current methods utilised in clinical practice are intermittent and only provide a 'snapshot' of fetal wellbeing, thus key signs of fetal demise could be missed. Continuous fetal monitoring (CFM) offers the potential to alleviate these issues by providing an objective and longitudinal overview of fetal status. Various CFM devices exist within literature; this review planned to provide a systematic overview of these devices, and specifically aimed to map the devices' design, performance and factors which affect this, whilst determining any gaps in development.

METHODS

A systematic search was conducted using MEDLINE, EMBASE, CINAHL, EMCARE, BNI, Cochrane Library, Web of Science and Pubmed databases. Following the deletion of duplicates, the articles' titles and abstracts were screened and suitable papers underwent a full-text assessment prior to inclusion in the review by two independent assessors.

RESULTS

The literature searches generated 4,885 hits from which 43 studies were included in the review. Twenty-four different devices were identified utilising four suitable CFM technologies: fetal electrocardiography, fetal phonocardiography, accelerometry and fetal vectorcardiography. The devices adopted various designs and signal processing methods. There was no common means of device performance assessment between different devices, which limited comparison. The device performance of fetal electrocardiography was reduced between 28 to 36 weeks' gestation and during high levels of maternal movement, and increased during night-time rest. Other factors, including maternal body mass index, fetal position, recording location, uterine activity, amniotic fluid index, number of fetuses and smoking status, as well as factors which affected alternative technologies had equivocal effects and require further investigation.

CONCLUSIONS

A variety of CFM devices have been developed, however no specific approach or design appears to be advantageous due to high levels of inter-device and intra-device variability.

A Novel Fetal Movement Simulator for the Performance Evaluation of Vibration Sensors for Wearable Fetal Movement Monitors

Fetal movements (FM) are an important factor in the assessment of fetal health. However, there is currently no reliable way to monitor FM outside clinical environs. While extensive research has been carried out using accelerometer-based systems to monitor FM, the desired accuracy of detection is yet to be achieved. A major challenge has been the difficulty of testing and calibrating sensors at the pre-clinical stage. Little is known about fetal movement features, and clinical trials involving pregnant women can be expensive and ethically stringent. To address these issues, we introduce a novel FM simulator, which can be used to test responses of sensor arrays in a laboratory environment. The design uses a silicon-based membrane with material properties similar to that of a gravid abdomen to mimic the vibrations due to fetal kicks. The simulator incorporates mechanisms to pre-stretch the membrane and to produce kicks similar to that of a fetus. As a case study, we present results from a comparative study of an acoustic sensor, an accelerometer, and a piezoelectric diaphragm as candidate vibration sensors for a wearable FM monitor. We find that the acoustic sensor and the piezoelectric diaphragm are better equipped than the accelerometer to determine durations, intensities, and locations of kicks, as they have a significantly greater response to changes in these conditions than the accelerometer. Additionally, we demonstrate that the acoustic sensor and the piezoelectric diaphragm can detect weaker fetal movements (threshold wall displacements are less than 0.5 mm) compared to the accelerometer (threshold wall displacement is 1.5 mm) with a trade-off of higher power signal artefacts. Finally, we find that the piezoelectric diaphragm produces better signal-to-noise ratios compared to the other two sensors in most of the cases, making it a promising new candidate sensor for wearable FM monitors. We believe that the FM simulator represents a key development towards enabling the eventual translation of wearable FM monitoring garments.

The influence of musculoskeletal forces on the growth of the prenatal cortex in the ilium: a finite element study

Remodelling and adaptation of bone within the pelvis is believed to be influenced by the mechanical strains generated during locomotion. Variation in the cortical bone thickness observed in the prenatal ilium has been linked to the musculoskeletal loading associated with in utero movements; for example the development of a thicker gluteal cortex is a possible response to contractions of the gluteal muscles. This study examines if the strains generated in the prenatal iliac cortex due to musculoskeletal loading in utero are capable of initiating bone remodelling to either maintain homeostasis or form new bone. Computational modelling techniques were used firstly to predict the muscle forces and resultant joint reaction force acting on the pelvis during a range of in utero movements. Finite element analyses were subsequently performed to calculate the von Mises strains induced in the prenatal ilium. The results demonstrated that strains generated in the iliac cortex were above the thresholds suggested to regulate bone remodelling to either maintain homeostasis or form new bone. Further simulations are required to investigate the extent to which the heterogeneous cortex forms in response to these strains (i.e., remodelling) or if developmental bone modelling plays a more pivotal role.

Associations between prenatal indicators of mechanical loading and proximal femur shape: findings from a population-based study in ALSPAC offspring

OBJECTIVES

Hip development is influenced by mechanical loading, but associations between prenatal loading and hip shape in later life remain unexplored.

METHODS

We examined associations between prenatal loading indicators (gestation length, oligohydramnios (OH) and breech) obtained from obstetric records and hip shape modes (HSMs) generated using dual-energy X-ray absorptiometry images taken at age 14- and 18-years in participants from the UK Avon Longitudinal Study of Parents and Children (ALSPAC). These associations were examined in 2453 (30 OH, 105 breech) and 2330 (27 OH, 95 breech) participants with complete data at age 14- and 18-years respectively using confounder-adjusted models.

RESULTS

At 14 years HSM2 was 0.59SD lower in OH males, and HSM5 (-0.31SD) and HSM9 (-0.32SD) were lower in OH in both sexes. At 18 years HSM1 (-0.44SD) and HSM2 (-0.71SD) were lower and HSM6 (0.61SD) and HSM8 (1.06SD) were higher in OH males, whilst HSM5 was lower in OH in both sexes. OH appeared to be associated with a wider femoral neck and head, and larger lesser/greater trochanters. Only weak associations were observed between gestation length/breech and HSMs.

CONCLUSIONS

These results suggest that prenatal skeletal loading, in particular oligohydramnios, may influence adolescent joint shape with associations generally stronger in males.

Rotational Malalignment of the Knee Extensor Mechanism: Defining Rotation of the Quadriceps and Its Role in the Spectrum of Patellofemoral Joint Instability

Osseous rotational malalignment of the lower limb is widely accepted as a factor contributing to patellofemoral instability, particularly in pediatric patients. Patellar instability occurs when the lateral force vector generated by the quadriceps exceeds the restraints provided by osseous and soft-tissue anatomy. The anatomy and activation of the quadriceps are responsible for the force applied across the patellofemoral joint, which has previously been measured using the quadriceps (Q)-angle. To our knowledge, the contribution of the quadriceps anatomy in generating a force vector in the axial plane has not previously been assessed. The primary aim of this study was to introduce the quadriceps torsion angle, a measure of quadriceps rotational alignment in the juvenile population. The secondary aims of this study were to determine the inter-assessor and intra-assessor reliability of the quadriceps torsion angle in the juvenile population and to investigate whether a large quadriceps torsion angle is a classifier of patellar dislocator group membership in a mixed cohort of patellar dislocators and typically developing controls.

Mechanics of cervical remodelling: insights from rodent models of pregnancy

The uterine cervix undergoes a complex remodelling process during pregnancy, characterized by dramatic changes in both extracellular matrix (ECM) structure and mechanical properties. Understanding the cervical remodelling process in a term or preterm birth will aid efforts for the prevention of preterm births (PTBs), which currently affect 14.8 million babies annually worldwide. Animal models of pregnancy, particularly rodents, continue to provide valuable insights into the cervical remodelling process, through the study of changes in ECM structure and mechanical properties at defined gestation time points. Currently, there is a lack of a collective, quantitative framework to relate the complex, nonlinear mechanical behaviour of the rodent cervix to changes in ECM structure. This review aims to fill this gap in knowledge by outlining the current understanding of cervical remodelling during pregnancy in rodent models in the context of solid biomechanics. Here we highlight the collective contribution of multiple mechanical studies which give evidence that cervical softening coincides with known ECM changes throughout pregnancy. Taken together, mechanical tests on tissue from pregnant rodents reveal the cervix's remarkable ability to soften dramatically during gestation to allow for a compliant tissue that can withstand damage and can dissipate mechanical loads.

Word-object and action-object association learning across early development

Successful communication often involves comprehension of both spoken language and observed actions with and without objects. Even very young infants can learn associations between actions and objects as well as between words and objects. However, in daily life, children are usually confronted with both kinds of input simultaneously. Choosing the critical information to attend to in such situations might help children structure the input, and thereby, allow for successful learning. In the current study, we therefore, investigated the developmental time course of children's and adults' word and action learning when given the opportunity to learn both word-object and action-object associations for the same object. All participants went through a learning phase and a test phase. In the learning phase, they were presented with two novel objects which were associated with a distinct novel name (e.g., "Look, a Tanu") and a distinct novel action (e.g., moving up and down while tilting sideways). In the test phase, participants were presented with both objects on screen in a baseline phase, then either heard one of the two labels or saw one of the two actions in a prime phase, and then saw the two objects again on screen in a recognition phase. Throughout the trial, participants' target looking was recorded to investigate whether participants looked at the target object upon hearing its label or seeing its action, and thus, would show learning of the word-object and action-object associations. Growth curve analyses revealed that 12-month-olds showed modest learning of action-object associations, 36-month-olds learned word-object associations, and adults learned word-object and action-object associations. These results highlight how children attend to the different information types from the two modalities through which communication is addressed to them. Over time, with increased exposure to systematic word-object mappings, children attend less to action-object mappings, with the latter potentially being mediated by word-object learning even in adulthood. Thus, choosing between different kinds of input that may be more relevant in their rich environment encompassing different modalities might help learning at different points in development.

Combinatorial morphogenetic and mechanical cues to mimic bone development for defect repair

Endochondral ossification during long bone development and natural fracture healing initiates by mesenchymal cell condensation, directed by local morphogen signals and mechanical cues. Here, we aimed to mimic development for regeneration of large bone defects. We hypothesized that engineered human mesenchymal condensations presenting transforming growth factor-β1 (TGF-β1) and/or bone morphogenetic protein-2 (BMP-2) from encapsulated microparticles promotes endochondral defect regeneration contingent on in vivo mechanical cues. Mesenchymal condensations induced bone formation dependent on morphogen presentation, with BMP-2 + TGF-β1 fully restoring mechanical function. Delayed in vivo ambulatory loading significantly enhanced the bone formation rate in the dual morphogen group. In vitro, BMP-2 or BMP-2 + TGF-β1 initiated robust endochondral lineage commitment. In vivo, however, extensive cartilage formation was evident predominantly in the BMP-2 + TGF-β1 group, enhanced by mechanical loading. Together, this study demonstrates a biomimetic template for recapitulating developmental morphogenic and mechanical cues in vivo for tissue engineering.

Breech presentation is associated with lower adolescent tibial bone strength

We compared bone outcomes in adolescents with breech and cephalic presentation. Tibia bone mineral content, density, periosteal circumference, and cross-sectional moment of inertia were lower in breech presentation, and females with breech presentation had lower hip CSA. These findings suggest that prenatal loading may exert long-lasting influences on skeletal development.

INTRODUCTION

Breech position during pregnancy is associated with reduced range of fetal movement, and with lower limb joint stresses. Breech presentation at birth is associated with lower neonatal bone mineral content (BMC) and area, but it is unknown whether these associations persist into later life.

METHODS

We examined associations between presentation at onset of labor, and tibia and hip bone outcomes at age 17 years in 1971 participants (1062 females) from a UK prospective birth cohort that recruited > 15,000 pregnant women in 1991-1992. Cortical BMC, cross-sectional area (CSA) and bone mineral density (BMD), periosteal circumference, and cross-sectional moment of inertia (CSMI) were measured by peripheral quantitative computed tomography (pQCT) at 50% tibia length. Total hip BMC, bone area, BMD, and CSMI were measured by dual-energy X-ray absorptiometry (DXA).

RESULTS

In models adjusted for sex, age, maternal education, smoking, parity, and age, singleton/multiple births, breech presentation (n = 102) was associated with lower tibial cortical BMC (- 0.14SD, 95% CI - 0.29 to 0.00), CSA (- 0.12SD, - 0.26 to 0.02), BMD (- 0.16SD, - 0.31 to - 0.01), periosteal circumference (- 0.14SD, - 0.27 to - 0.01), and CSMI (- 0.11SD, - 0.24 to 0.01). In females only, breech presentation was associated with lower hip CSA (- 0.24SD, - 0.43 to 0.00) but not with other hip outcomes. Additional adjustment for potential mediators (delivery method, birthweight, gestational age, childhood motor competence and adolescent height and body composition) did not substantially affect associations with either tibia or hip outcomes.

CONCLUSIONS

These findings suggest that prenatal skeletal loading may exert long-lasting influences on skeletal size and strength but require replication.

Strategic research agenda for biomedical imaging

This Strategic Research Agenda identifies current challenges and needs in healthcare, illustrates how biomedical imaging and derived data can help to address these, and aims to stimulate dedicated research funding efforts.Medicine is currently moving towards a more tailored, patient-centric approach by providing personalised solutions for the individual patient. Innovation in biomedical imaging plays a key role in this process as it addresses the current needs for individualised prevention, treatment, therapy response monitoring, and image-guided surgery.The use of non-invasive biomarkers facilitates better therapy prediction and monitoring, leading to improved patient outcomes. Innovative diagnostic imaging technologies provide information about disease characteristics which, coupled with biological, genetic and -omics data, will contribute to an individualised diagnosis and therapy approach.In the emerging field of theranostics, imaging tools together with therapeutic agents enable the selection of best treatments and allow tailored therapeutic interventions.For prenatal monitoring, the use of innovative imaging technologies can ensure an early detection of malfunctions or disease.The application of biomedical imaging for diagnosis and management of lifestyle-induced diseases will help to avoid disease development through lifestyle changes.Artificial intelligence and machine learning in imaging will facilitate the improvement of image interpretation and lead to better disease prediction and therapy planning.As biomedical imaging technologies and analysis of existing imaging data provide solutions to current challenges and needs in healthcare, appropriate funding for dedicated research is needed to implement the innovative approaches for the wellbeing of citizens and patients.

Bone physiology as inspiration for tissue regenerative therapies

The development, maintenance of healthy bone and regeneration of injured tissue in the human body comprise a set of intricate and finely coordinated processes. However, an analysis of current bone regeneration strategies shows that only a small fraction of well-reported bone biology aspects has been used as inspiration and transposed into the development of therapeutic products. Specific topics that include inter-scale bone structural organization, developmental aspects of bone morphogenesis, bone repair mechanisms, role of specific cells and heterotypic cell contact in the bone niche (including vascularization networks and immune system cells), cell-cell direct and soluble-mediated contact, extracellular matrix composition (with particular focus on the non-soluble fraction of proteins), as well as mechanical aspects of native bone will be the main reviewed topics. In this Review we suggest a systematic parallelization of (i) fundamental well-established biology of bone, (ii) updated and recent advances on the understanding of biological phenomena occurring in native and injured tissue, and (iii) critical discussion of how those individual aspects have been translated into tissue regeneration strategies using biomaterials and other tissue engineering approaches. We aim at presenting a perspective on unexplored aspects of bone physiology and how they could be translated into innovative regeneration-driven concepts.

Breech presentation is associated with lower bone mass and area: findings from the Southampton Women's Survey

We compared bone outcomes in children with breech and cephalic presentation at delivery. Neonatal whole-body bone mineral content (BMC) and area were lower in children with breech presentation. At 4 years, no differences in whole-body or spine measures were found, but hip BMC and area were lower after breech presentation.

INTRODUCTION

Breech presentation is associated with altered joint shape and hip dysplasias, but effects on bone mineral content (BMC), area (BA) and density (BMD) are unknown.

METHODS

In the prospective Southampton Women's Survey mother-offspring cohort, whole-body bone outcomes were measured using dual-energy X-ray absorptiometry (DXA) in 1430 offspring, as neonates (mean age 6 days, n = 965, 39 with a breech presentation at birth) and/or at age 4.1 years (n = 999, 39 breech). Hip and spine bone outcomes were also measured at age 4 years.

RESULTS

Neonates with breech presentation had 4.2 g lower whole-body BMC (95% CI -7.4 to - 0.9 g, P = 0.012) and 5.9 cm² lower BA (- 10.8 to - 1.0 cm², P = 0.019), but BMD was similar between groups (mean difference - 0.007, - 0.016 to 0.002 g/cm², P = 0.146) adjusting for sex, maternal smoking, gestational diabetes, mode of delivery, social class, parity, ethnicity, age at scan, birthweight, gestational age and crown-heel length. There were no associations between breech presentation and whole-body outcomes at age 4 years, but, in similarly adjusted models, regional DXA (not available in infants) showed that breech presentation was associated with lower hip BMC (- 0.51, - 0.98 to - 0.04 g, P = 0.034) and BA (- 0.67, - 1.28 to - 0.07 cm², P = 0.03) but not with BMD (- 0.009, - 0.029 to 0.012 g, P = 0.408), or spine outcomes.

CONCLUSIONS

These results suggest that breech presentation is associated with lower neonatal whole-body BMC and BA, which may relate to altered prenatal loading in babies occupying a breech position; these differences did not persist into later childhood. Modest differences in 4-year hip BMC and BA require further investigation.

The mechanical impact of col11a2 loss on joints; col11a2 mutant zebrafish show changes to joint development and function, which leads to early-onset osteoarthritis

Collagen is the major structural component of cartilage, and mutations in the genes encoding type XI collagen are associated with severe skeletal dysplasias (fibrochondrogenesis and Stickler syndrome) and early-onset osteoarthritis (OA). The impact of the lack of type XI collagen on cell behaviour and mechanical performance during skeleton development is unknown. We studied a zebrafish mutant for col11a2 and evaluated cartilage, bone development and mechanical properties to address this. We show that in col11a2 mutants, type II collagen is made but is prematurely degraded in maturing cartilage and ectopically expressed in the joint. These changes are correlated with increased stiffness of both bone and cartilage; quantified using atomic force microscopy. In the mutants, the skeletal rudiment terminal region in the jaw joint is broader and the interzone smaller. These differences in shape and material properties impact on joint function and mechanical performance, which we modelled using finite element analyses. Finally, we show that col11a2 heterozygous carriers reach adulthood but show signs of severe early-onset OA. Taken together, our data demonstrate a key role for type XI collagen in maintaining the properties of cartilage matrix; which when lost leads to alterations to cell behaviour that give rise to joint pathologies.This article is part of the Theo Murphy meeting issue 'Mechanics of development'.

Embryo movements regulate tendon mechanical property development

Tendons transmit forces from muscles to bones to enable skeletal motility. During development, tendons begin to bear load at the onset of embryo movements. Using the chick embryo model, this study showed that altered embryo movement frequency led to changes in elastic modulus of calcaneal tendon. In particular, paralysis led to decreased modulus, whereas hypermotility led to increased modulus. Paralysis also led to reductions in activity levels of lysyl oxidase (LOX), an enzyme that we previously showed is required for cross-linking-mediated elaboration of tendon mechanical properties. Additionally, inhibition of LOX activity abrogated hypermotility-induced increases in modulus. Taken together, our findings suggest embryo movements are critical for tendon mechanical property development and implicate LOX in this process. These exciting findings expand current knowledge of how functional tendons form during development and could guide future clinical approaches to treat tendon defects associated with abnormal mechanical loading in utero.

This article is part of the Theo Murphy meeting issue ‘Mechanics of development’.

The mechanical response of the mouse cervix to tensile cyclic loading in term and preterm pregnancy

A well-timed modification of both the collagen and elastic fiber network in the cervix during pregnancy accompanies the evolution of tissue mechanical parameters that are key to a successful pregnancy. Understanding of the cervical mechanical behaviour along normal and abnormal pregnancy is crucial to define the molecular events that regulate remodeling in term and preterm birth (PTB). In this study, we measured the mechanical response of mouse cervical tissue to a history of cyclic loading and quantified the tissue's ability to recover from small and large deformations. Assessments were made in nonpregnant, pregnant (gestation days 6, 12, 15 and 18) and mouse models of infection mediated PTB treated with lipopolysaccharide on gestation d15 (LPS treated) and hormone withdrawal mediated PTB on gestation d15 (RU486 treated). The current study uncovers the contributions of collagen and elastic fiber networks to the progressive change in mechanical function of the cervix through pregnancy. Premature cervical remodeling induced on gestation day 15 in the LPS infection model is characterized by distinct mechanical properties that are similar but not identical to mechanical properties at term ripening on day 18. Remodeling in the LPS infection model results in a weaker cervix, unable to withstand high loads. In contrast, the RU486 preterm model resembles the cyclic mechanical behaviour seen for term d18 cervix, where the extremely compliant tissue is able to withstand multiple cycles under large deformations without breaking. The distinct material responses to load-unload cycles in the two PTB models matches the differing microstructural changes in collagen and elastic fibers in these two models of preterm birth. Improved understanding of the impact of microstructural changes to mechanical performance of the cervix will provide insights to aid in the development of therapies for prevention of preterm birth.

STATEMENT OF SIGNIFICANCE

Preterm Birth (PTB) still represents a serious challenge to be overcome, considering its implications on infant mortality and lifelong health consequences. While the causes and etiologies of PTB are diverse and yet to be fully elucidated, a common pathway leading to a preterm delivery is premature cervical remodeling. Throughout pregnancy, the cervix remodels through changes of its microstructure, thus altering its mechanical properties. An appropriate timing for these transformations is critical for a healthy pregnancy and avoidance of PTB. Hence, this study aims at understanding how the mechanical function of the cervix evolves during a normal and preterm pregnancy. By performing cyclic mechanical testing on cervix samples from animal models, we assess the cervix's ability to recover from moderate and severe loading. The developed methodology links mechanical parameters to specific microstructural components. This work identifies a distinct biomechanical signature associated with inflammation mediated PTB that differs from PTB induced by hormone withdrawal and from normal term remodeling.

Altered biomechanical stimulation of the developing hip joint in presence of hip dysplasia risk factors

Fetal kicking and movements generate biomechanical stimulation in the fetal skeleton, which is important for prenatal musculoskeletal development, particularly joint shape. Developmental dysplasia of the hip (DDH) is the most common joint shape abnormality at birth, with many risk factors for the condition being associated with restricted fetal movement. In this study, we investigate the biomechanics of fetal movements in such situations, namely fetal breech position, oligohydramnios and primiparity (firstborn pregnancy). We also investigate twin pregnancies, which are not at greater risk of DDH incidence, despite the more restricted intra-uterine environment. We track fetal movements for each of these situations using cine-MRI technology, quantify the kick and muscle forces, and characterise the resulting stress and strain in the hip joint, testing the hypothesis that altered biomechanical stimuli may explain the link between certain intra-uterine conditions and risk of DDH. Kick force, stress and strain were found to be significantly lower in cases of breech position and oligohydramnios. Similarly, firstborn fetuses were found to generate significantly lower kick forces than non-firstborns. Interestingly, no significant difference was observed in twins compared to singletons. This research represents the first evidence of a link between the biomechanics of fetal movements and the risk of DDH, potentially informing the development of future preventative measures and enhanced diagnosis. Our results emphasise the importance of ultrasound screening for breech position and oligohydramnios, particularly later in pregnancy, and suggest that earlier intervention to correct breech position through external cephalic version could reduce the risk of hip dysplasia.

Quantitative anatomy of the ilium's primary ossification center in the human fetus

Purpose

An understanding of the development of the ilium’s primary ossification center may be useful in both determining the fetal stage and maturity, and for detecting congenital disorders. This study was performed to quantitatively examine the ilium’s primary ossification center with respect to its linear, planar and volumetric parameters.

Materials and methods

Using methods of CT, digital-image analysis and statistics, the size of the ilium’s primary ossification center in 42 spontaneously aborted human fetuses of crown–rump length (CRL) ranged from 130 to 265 mm (aged 18–30 weeks) was studied.

Results

With no sex and laterality differences, the best fit growth dynamics for the ilium’s primary ossification center was modelled by the following functions: y = − 63.138 + 33.413 × ln(CRL) ± 1.609 for its vertical diameter, y = − 59.220 + 31.353 × ln(CRL) ± 1.736 for its transverse diameter, y = − 105.681 + 1.137 × CRL ± 16.035 for its projection surface area, and y = 478.588 + 4.035 × CRL ± 14.332 for its volume. The shape of the ilium’s primary ossification center did not change over the study period, because its transverse -to- vertical diameter ratio was stable at the level of 0.94 ± 0.07.

Conclusions

The size of the ilium’s primary ossification center displays neither sex nor laterality differences. The ilium’s primary ossification center grows logarithmically with respect to its vertical and transverse diameters, and linearly with respect to its projection surface area and volume. The shape of the ilium’s primary ossification center does not change throughout the examined period. The obtained quantitative data of the ilium’s primary ossification center is considered normative for respective prenatal weeks and may contribute to the prenatal ultrasound diagnostics of congenital defects.

Responsiveness of rat fetuses to sibling motor activity: Communication in utero?

Previous research has revealed that fetuses detect and respond to extrauterine stimuli such as maternal movement and speech, but little attention has been cast on how fetuses may directly influence and respond to each other in the womb. This study investigated whether motor activity of E20 rat fetuses influenced the behavior of siblings in utero. Three experiments showed that; (a) contiguous siblings expressed a higher frequency of synchronized movement than noncontiguous siblings; (b) fetuses that lay between two siblings immobilized with curare showed less movement relative to fetuses between saline or uninjected controls; and (c) fetuses between two siblings behaviorally activated by the opioid agonist U50,488 also showed less activity and specific behavioral changes compared to controls. Our findings suggest that rat fetuses are directly impacted by sibling motor activity, and thus that a rudimentary form of communication between siblings may influence the development of fetuses in utero.