Fibroblast inflammatory priming determines regenerative versus fibrotic skin repair in reindeer.

Adult mammalian skin wounds heal by forming fibrotic scars. We report that full-thickness injuries of reindeer antler skin (velvet) regenerate, whereas back skin forms fibrotic scar. Single-cell multi-omics reveal that uninjured velvet fibroblasts resemble human fetal fibroblasts, whereas back skin fibroblasts express inflammatory mediators mimicking pro-fibrotic adult human and rodent fibroblasts. Consequently, injury elicits site-specific immune responses: back skin fibroblasts amplify myeloid infiltration and maturation during repair, whereas velvet fibroblasts adopt an immunosuppressive phenotype that restricts leukocyte recruitment and hastens immune resolution. Ectopic transplantation of velvet to scar-forming back skin is initially regenerative, but progressively transitions to a fibrotic phenotype akin to the scarless fetal-to-scar-forming transition reported in humans. Skin regeneration is diminished by intensifying, or enhanced by neutralizing, these pathologic fibroblast-immune interactions. Reindeer represent a powerful comparative model for interrogating divergent wound healing outcomes, and our results nominate decoupling of fibroblast-immune interactions as a promising approach to mitigate scar.

Embryogenesis and Adult Life in the Absence of Intrinsic Apoptosis Effectors BAX, BAK, and BOK.

Intrinsic apoptosis, reliant on BAX and BAK, has been postulated to be fundamental for morphogenesis, but its precise contribution to this process has not been fully explored in mammals. Our structural analysis of BOK suggests close resemblance to BAX and BAK structures. Notably, Bok-/-Bax-/-Bak-/- animals exhibited more severe defects and died earlier than Bax-/-Bak-/- mice, implying that BOK has overlapping roles with BAX and BAK during developmental cell death. By analyzing Bok-/-Bax-/-Bak-/- triple-knockout mice whose cells are incapable of undergoing intrinsic apoptosis, we identified tissues that formed well without this process. We provide evidence that necroptosis, pyroptosis, or autophagy does not substantially substitute for the loss of apoptosis. Albeit very rare, unexpected attainment of adult Bok-/-Bax-/-Bak-/- mice suggests that morphogenesis can proceed entirely without apoptosis mediated by these proteins and possibly without cell death in general.

Coexpression networks implicate human midfetal deep cortical projection neurons in the pathogenesis of autism.

Autism spectrum disorder (ASD) is a complex developmental syndrome of unknown etiology. Recent studies employing exome- and genome-wide sequencing have identified nine high-confidence ASD (hcASD) genes. Working from the hypothesis that ASD-associated mutations in these biologically pleiotropic genes will disrupt intersecting developmental processes to contribute to a common phenotype, we have attempted to identify time periods, brain regions, and cell types in which these genes converge. We have constructed coexpression networks based on the hcASD "seed" genes, leveraging a rich expression data set encompassing multiple human brain regions across human development and into adulthood. By assessing enrichment of an independent set of probable ASD (pASD) genes, derived from the same sequencing studies, we demonstrate a key point of convergence in midfetal layer 5/6 cortical projection neurons. This approach informs when, where, and in what cell types mutations in these specific genes may be productively studied to clarify ASD pathophysiology.

Human fetal cerebellar cell atlas informs medulloblastoma origin and oncogenesis.

Medulloblastoma (MB) is the most common malignant childhood brain tumour1,2, yet the origin of the most aggressive subgroup-3 form remains elusive, impeding development of effective targeted treatments. Previous analyses of mouse cerebella3-5 have not fully defined the compositional heterogeneity of MBs. Here we undertook single-cell profiling of freshly isolated human fetal cerebella to establish a reference map delineating hierarchical cellular states in MBs. We identified a unique transitional cerebellar progenitor connecting neural stem cells to neuronal lineages in developing fetal cerebella. Intersectional analysis revealed that the transitional progenitors were enriched in aggressive MB subgroups, including group 3 and metastatic tumours. Single-cell multi-omics revealed underlying regulatory networks in the transitional progenitor populations, including transcriptional determinants HNRNPH1 and SOX11, which are correlated with clinical prognosis in group 3 MBs. Genomic and Hi-C profiling identified de novo long-range chromatin loops juxtaposing HNRNPH1/SOX11-targeted super-enhancers to cis-regulatory elements of MYC, an oncogenic driver for group 3 MBs. Targeting the transitional progenitor regulators inhibited MYC expression and MYC-driven group 3 MB growth. Our integrated single-cell atlases of human fetal cerebella and MBs show potential cell populations predisposed to transformation and regulatory circuitries underlying tumour cell states and oncogenesis, highlighting hitherto unrecognized transitional progenitor intermediates predictive of disease prognosis and potential therapeutic vulnerabilities.

RANK links thymic regulatory T cells to fetal loss and gestational diabetes in pregnancy.

Successful pregnancies rely on adaptations within the mother1, including marked changes within the immune system2. It has long been known that the thymus, the central lymphoid organ, changes markedly during pregnancy3. However, the molecular basis and importance of this process remain largely obscure. Here we show that the osteoclast differentiation receptor RANK4,5 couples female sex hormones to the rewiring of the thymus during pregnancy. Genetic deletion of Rank (also known as Tnfrsf11a) in thymic epithelial cells results in impaired thymic involution and blunted expansion of natural regulatory T (Treg) cells in pregnant female mice. Sex hormones, in particular progesterone, drive the development of thymic Treg cells through RANK in a manner that depends on AIRE+ medullary thymic epithelial cells. The depletion of Rank in the mouse thymic epithelium results in reduced accumulation of natural Treg cells in the placenta, and an increase in the number of miscarriages. Thymic deletion of Rank also results in impaired accumulation of Treg cells in visceral adipose tissue, and is associated with enlarged adipocyte size, tissue inflammation, enhanced maternal glucose intolerance, fetal macrosomia, and a long-lasting transgenerational alteration in glucose homeostasis, which are all key hallmarks of gestational diabetes. Transplantation of Treg cells rescued fetal loss, maternal glucose intolerance and fetal macrosomia. In human pregnancies, we found that gestational diabetes also correlates with a reduced number of Treg cells in the placenta. Our findings show that RANK promotes the hormone-mediated development of thymic Treg cells during pregnancy, and expand the functional role of maternal Treg cells to the development of gestational diabetes and the transgenerational metabolic rewiring of glucose homeostasis.

Clinical and molecular characteristics of 26 fetuses with lethal multiple congenital contractures.

Multiple congenital contractures (MCC) due to fetal akinesia manifest across a broad spectrum of diseases, ranging from mild distal arthrogryposis to lethal fetal akinesia deformation sequence. We hereby present a series of 26 fetuses displaying severe MCC phenotypes from 18 families and describe detailed prenatal ultrasound findings, postmortem clinical evaluations, and genetic investigations. Most common prenatal findings were abnormal facial profile (65%), central nervous system abnormalities (62%), polyhydramnios (50%), increased nuchal translucency (50%), and fetal hydrops (35%). Postmortem examinations unveiled additional anomalies including facial dysmorphisms, dysplastic skeletal changes, ichthyosis, multiple pterygia, and myopathy, allowing preliminary diagnosis of particular Mendelian disorders in multiple patients. Evaluation of the parents revealed maternal grip myotonia in one family. By exome sequencing and targeted testing, we identified causative variants in ACTC1, CHST14, COG6, DMPK, DOK7, HSPG2, KLHL7, KLHL40, KIAA1109, NEB, PSAT1, RAPSN, USP14, and WASHC5 in 15 families, and one patient with a plausible diagnosis associated with biallelic NEB variants. Three patients received a dual diagnosis. Pathogenic alterations in newly discovered genes or in previously known genes recently linked to new MCC phenotypes were observed in 44% of the cohort. Our results provide new insights into the clinical and molecular landscape of lethal MCC phenotypes.

Multiple pregnancy with complete hydatidiform mole and coexisting normal fetus in a retrospective cohort of 141 patients.

BACKGROUND: Multiple pregnancy with a complete hydatidiform mole and a normal fetus is prone to severe obstetrical complications and malignant transformation after birth. Prognostic information is limited for this rare form of gestational trophoblastic disease. OBJECTIVE: This study aimed to determine obstetrical outcomes and the risk of gestational trophoblastic neoplasia in women with multiple pregnancy with complete hydatidiform mole and coexisting normal fetus, and to identify risk factors for poor obstetrical and oncological outcomes to improve patient information and management. STUDY DESIGN: This was a retrospective national cohort study of 11,411 records from the French National Center for Trophoblastic Disease registered between January 2001 and January 2022. RESULTS: Among 11,411 molar pregnancies, 141 involved histologically confirmed multiple pregnancy with complete hydatidiform mole and coexisting normal fetus. Roughly a quarter of women (23%; 33/141) decided to terminate pregnancy because of presumed poor prognosis or by choice. Among the 77% of women (108/141) who continued their pregnancy, 16% of pregnancies (17/108) were terminated because of maternal complications, and 37% (40/108) ended in spontaneous miscarriage before 24 weeks' gestation. The median gestational age at delivery in the remaining 47% of pregnancies (51/108) was 32 weeks. The overall neonatal survival rate at day 8 was 36% (39/108; 95% confidence interval, 27-46) after excluding elective pregnancy terminations. Patients with free beta human chorionic gonadotropin levels <10 multiples of the median were significantly more likely to reach 24 weeks' gestation compared with those with free beta human chorionic gonadotropin levels >10 multiples of the median (odds ratio, 7.0; 95% confidence interval, 1.3-36.5; P=.022). A lower free beta human chorionic gonadotropin level was also associated with better early neonatal survival (the median free beta human chorionic gonadotropin level was 9.4 multiples of the median in patients whose child was alive at day 8 vs 20.0 multiples of the median in those whose child was deceased; P=.02). The overall rate of gestational trophoblastic neoplasia after a multiple pregnancy with complete hydatidiform mole and a normal fetus was 26% (35/136; 95% confidence interval, 19-34). All 35 patients had low-risk International Federation of Gynecology and Obstetrics scores, and the cure rate was 100%. Termination of pregnancy on patient request was not associated with lower risk of gestational trophoblastic neoplasia. Maternal complications such as preeclampsia and postpartum hemorrhage were not associated with higher risk of gestational trophoblastic neoplasia, and neither were high human chorionic gonadotropin levels or newborn survival at day 8. CONCLUSION: Multiple pregnancy with complete hydatidiform mole and coexisting fetus carries a high risk of obstetrical complications. In patients who continued their pregnancy, approximately one-third of neonates were alive at day 8, and roughly 1 in 4 patients developed gestational trophoblastic neoplasia. Therefore, the risk of malignant transformation appears to be higher compared with singleton complete moles. Low levels of free beta human chorionic gonadotropin may be indicative of better early neonatal survival, and this relationship warrants further study.

Skeletal Growth Arrest Lines in Fetal Remains: Histopathology and Correlative Placental Pathology.

INTRODUCTION: Skeletal growth arrest lines (GAL) are transverse lines of metaphyseal radiodensity accompanying episodic severe physiological stress. They are poorly described in fetal remains. MATERIALS AND METHODS: We searched our autopsy practice for instances of fetal GAL in post mortem radiology, and correlated them with long bone histology and placental pathology. We describe the appearance, distribution, and pathology of GAL in a cohort of fetal autopsies, and compare the placental pathology accompanying GAL to the placental pathology of asymmetrical growth restriction (AGR) in the same time period. RESULTS: In 2108 consecutive fetal post mortems, we found 20 cases with GAL. About 16 were in singletons with AGR. In these 16, the distribution of placental pathologies was similar to a contemporaneous cohort of 113 cases with AGR. Of the remaining 4, two twins out of 9 sets of monochorionic twins with AGR demonstrated GAL. One case of GAL had symmetrical growth restriction with cytomegalovirus infection, and one case had no AGR and an old, unexplained retroplacental hemorrhage. On histology, GAL are characterized by a region of mineralized chondroid, which is variably incorporated into irregular trabecular bone. DISCUSSION: GALs accompany a variety of placental pathologies and twin-twin transfusion, suggesting episodic disease progression.

Metastatic Lymphomas of the Placenta: A Literature Review With an Illustrative Case.

Lymphoma is the fourth most common tumor to display placental metastasis. This study aimed to report a case of high-grade lymphoma involving the placenta and review the literature on lymphomas metastatic to the placenta. A systematic review was performed following the PRISMA guidelines, using the keywords "lymphoma" AND "placenta." All case reports and case series on lymphoma infiltrating the placenta were collected. Eight cases from 7 studies, including the present case, were synthesized. The mean patient age is 29.5 years. The clinical presentation is non-specific. Hematologic derangements included cytopenias or cytoses, and elevated prothrombin time. The mean gestational age (GA) when a diagnosis of lymphoma was rendered is 27 weeks. Five cases presented with either lymphadenopathy or visceral masses on imaging. Four of these cases eventually led to maternal demise. The mean GA when the fetus was delivered is 31 3/4 weeks. Grossly, most placentas had non-specific findings. Leukemic infiltrates were mostly seen within intervillous spaces. Intravillous infiltrates were associated with high-grade lymphomas, resulting in either maternal demise or stillborn fetuses. This study suggests that the placenta has mechanisms to guard against malignancies; however, these defense mechanisms are not foolproof and may be breached by tumor cells.

Late gestation fetal hypothyroidism alters cell cycle regulation across multiple organ systems.

BACKGROUND: Hypothyroidism is a common endocrine disruption observed in utero that adversely affects fetal growth and maturation leading to long-term impacts on health; however, the exact molecular mechanisms by which these deleterious effects occur are unknown. We hypothesize that fetal hypothyroidism during late gestation will disrupt cell cycle regulation in a tissue-specific manner. To evaluate this, eight pregnant gilts were dosed with either methimazole or an equivalent negative control during days 85-106 out of 114 days of gestation (n = 4/group). Following treatment, the gilts were humanely euthanized, and tissue samples of fetal heart, ileum, kidney, lung, liver, muscle, spleen, and thymus taken from two male and two female fetuses (n = 32) from each gilt. RESULTS: The relative expression of three cell cycle promoters (CDK1, CDK2, and CDK4), and one cell cycle inhibitor (CDKN1A) was compared in each tissue to determine the effect of hypothyroidism on the developing fetus. All of the eight tissues examined experienced at least one significant up- or downregulation in the expression of the aforementioned genes as a result of treatment with methimazole. Substantial changes were observed in the liver and muscle, with the latter experiencing significant downregulations of CDK1, CDK2, and CDK4 as a result of treatment. In addition, all tissues were examined for changes in protein content, which further elucidated the impact of hypothyroidism on the fetal liver by the observation of a marked increase in protein content in the methimazole-treated group. Finally, the heart and liver were histologically examined for evidence of cellular hyperplasia and hypertrophy by measuring average nuclei density and size in each tissue, with the results showing a significant decrease in average nuclei size in the liver of hypothyroid fetuses. CONCLUSIONS: Collectively, these findings indicate the occurrence of organ-specific disruptions in cell cycle progression as a result of in utero hypothyroidism, which may explain the long term and widespread effects of hypothyroidism on fetal development.

Prenatal diagnosis and appearance of nasal chondromesenchymal hamartoma in a fetus: A case report.

We report a case of fetal nasal chondromesenchymal hamartoma (NCMH) first noted on prenatal ultrasound at 34 weeks. A solid-cystic mass which predominantly hyperechoicgenic and relatively clear margin, was located on the left nasal cavity and pharynx, with anterior extension and moderate blood flow. Further follow-up ultrasound examination depicted an enlargement of the tumor. Fetal magnetic resonance imaging (MRI) showed an inhomogeneous signal lesion involving the ethmoid sinuses, nasal cavity, and pharynx. The infant, delivered via cesarean section at 37 + 5 weeks, required urgent neonatology intervention due to respiratory difficulties. Neonatal MRI and computer tomography were subsequently performed at 1 day after birth. Surgical excision occurred at 7 days, confirming NCMH via histological examination. Awareness of this entity, is essential to avoid potentially harmful therapies, especially in prenatal period. Considered NCMH in diagnosis when fetal nasal masses presenting with predominantly high-level echo, well-defined margins and moderate vascularity.

Clinical outcomes of fetuses with cardiac rhabdomyoma: A case series from a tertiary center.

AIMS: The study aims to evaluate the genetic and clinical outcomes of fetal cardiac rhabdomyoma in our tertiary center. METHODS: Data of cases with cardiac rhabdomyoma detected by fetal echocardiography during antenatal follow-up were analyzed retrospectively. RESULTS: Nine cases were included in the study. The incidence of cardiac rhabdomyoma was 0.003%. The median fetal diagnosis time was 26th weeks, the most common location was the LV. There was no hemodynamic disorder requiring cardiovascular intervention in any of the cases. Of the eight genetically tested cases, four were tuberous sclerosis complex (TSC) gene-negative, one hereditary TSC2, one de novo TSC1, and two de novo TSC2 gene mutants. Postnatal first-year survival rate of the cases was 88.8%. CONCLUSIONS: Cardiac rhabdomyoma is a rare fetal and pediatric pathology that generally is a remarkable finding in the clinical process of TSC. Therefore, cases should be evaluated multisystemically and genetic counseling should be given to the family.

Neuroimaging Findings in Fetal Hemimegalencephaly: Case Study and Review.

BACKGROUND: Limited information exists in the prenatal literature regarding the neuroimaging features of fetal hemimegalencephaly. SUMMARY: This report describes ultrasound and magnetic resonance imaging (MRI) findings in a second-trimester fetus with an isolated, severe form of hemimegalencephaly. The most prominent imaging findings included unilateral enlarged cerebral hemisphere and ipsilateral ventriculomegaly causing cerebral asymmetry, midline shift, and macrocephaly. Abnormal cortical development imaging signs were also evident. A literature review encompassing 23 reports describing 36 cases, including ours, is presented. KEY MESSAGES: Characteristic ultrasound findings for the diagnosis of hemimegalencephaly are not always apparent prenatally. Asymmetric ventriculomegaly emerges as the most common but nonspecific presenting feature during routine second- or third-trimester ultrasound scans. Subsequent high-resolution prenatal neurosonography and fetal MRI facilitate definitive prenatal diagnosis, showcasting associated features primarily related to cortical migration, differentiation, and maturation. Postnatally, the prognosis is poor due to intractable seizures, hemiplegia, and progressive neurodevelopmental delay.

The Auditory Pathway in Congenitally Cytomegalovirus-Infected Human Fetuses.

Congenital cytomegalovirus (CMV) infection is the main cause of non-hereditary sensorineural hearing loss (SNHL). In order to shed light on SNHL pathophysiology, we examined the auditory pathway in CMV-infected fetuses; the temporal lobe, in particular the auditory cortex, and the inner ear. We investigated both inner ears and temporal lobes of 20 human CMV-infected fetuses at 21 weeks of gestation. As a negative group, five fetuses from spontaneous miscarriages without CMV infection were studied. Inner ears and temporal lobes were histologically examined, immunohistochemistry for CMV and CMV-PCR were performed. On the auditory cortex, we evaluated the local microglial reaction to the infection. CMV-positive cells were found in 14/20 brains and the damage was classified as severe, moderate, or mild, according to histological features. Fetuses with severe brain damage had a statistically higher temporal lobe viral load and a higher number of activated microglial cells in the auditory cortex compared to fetuses with mild brain damage (p: 0.01; p: 0.01). In the inner ears, the marginal cells of the stria vascularis were the most CMV positive. In our study, CMV affected the auditory pathway, suggesting a tropism for this route. In addition, in the auditory cortex, microglial activation may favor further tissue damage contributing to hearing loss.

The interplay of fibroblasts, the extracellular matrix, and inflammation in scar formation.

Various forms of fibrosis, comprising tissue thickening and scarring, are involved in 40% of deaths across the world. Since the discovery of scarless functional healing in fetuses prior to a certain stage of development, scientists have attempted to replicate scarless wound healing in adults with little success. While the extracellular matrix (ECM), fibroblasts, and inflammatory mediators have been historically investigated as separate branches of biology, it has become increasingly necessary to consider them as parts of a complex and tightly regulated system that becomes dysregulated in fibrosis. With this new paradigm, revisiting fetal scarless wound healing provides a unique opportunity to better understand how this highly regulated system operates mechanistically. In the following review, we navigate the four stages of wound healing (hemostasis, inflammation, repair, and remodeling) against the backdrop of adult versus fetal wound healing, while also exploring the relationships between the ECM, effector cells, and signaling molecules. We conclude by singling out recent findings that offer promising leads to alter the dynamics between the ECM, fibroblasts, and inflammation to promote scarless healing. One factor that promises to be significant is fibroblast heterogeneity and how certain fibroblast subpopulations might be predisposed to scarless healing. Altogether, reconsidering fetal wound healing by examining the interplay of the various factors contributing to fibrosis provides new research directions that will hopefully help us better understand and address fibroproliferative diseases, such as idiopathic pulmonary fibrosis, liver cirrhosis, systemic sclerosis, progressive kidney disease, and cardiovascular fibrosis.

Congenital Mpox Syndrome (Clade I) in Stillborn Fetus after Placental Infection and Intrauterine Transmission, Democratic Republic of the Congo, 2008.

We report the autopsy pathology findings of a 21-week stillborn fetus with congenital mpox syndrome that occurred in the Democratic Republic of the Congo in 2008. The fetus acquired mpox from the mother after intrauterine transplacental monkeypox virus transmission. We confirmed monkeypox virus infection in the mother, fetus, and placenta by using a monkeypox virus-specific quantitative PCR. Subtyping of the virus was not performed, but the mother and fetus were almost certainly infected with the clade I variant that was endemic in the Democratic Republic of the Congo at the time. Risk for intrauterine infection appears to differ between virus clades, but clinicians should be aware of potential for intrauterine monkeypox virus transmission among pregnant persons during ongoing and future mpox outbreaks.

TrkA mediates effect of novel KIDINS220 mutation in human brain ventriculomegaly.

Congenital hydrocephalus is a potentially devastating, highly heterogeneous condition whose genetic subset remains incompletely known. We here report a consanguineous family where three fetuses presented with brain ventriculomegaly and limb contractures and shared a very rare homozygous variant of KIDINS220, consisting of an in-frame deletion of three amino acids adjacent to the fourth transmembrane domain. Fetal brain imaging and autopsy showed major ventriculomegaly, reduced brain mass, and with no histomorphologic abnormalities. We demonstrate that the binding of KIDINS220 to TrkA is diminished by the deletion mutation. This family is the second that associates a KIDINS220 genetic variant with human ventriculomegaly and limb contractures, validating causality of the gene and indicating TrkA as a likely mediator of the phenotype.

A fetal wound healing program after intrauterine bile duct injury may contribute to biliary atresia.

BACKGROUND & AIMS: Biliary atresia (BA) is an obstructive cholangiopathy that initially affects the extrahepatic bile ducts (EHBDs) of neonates. The etiology is uncertain, but evidence points to a prenatal cause. Fetal tissues have increased levels of hyaluronic acid (HA), which plays an integral role in fetal wound healing. The objective of this study was to determine whether a program of fetal wound healing is part of the response to fetal EHBD injury. METHODS: Mouse, rat, sheep, and human EHBD samples were studied at different developmental time points. Models included a fetal sheep model of prenatal hypoxia, human BA EHBD remnants and liver samples taken at the time of the Kasai procedure, EHBDs isolated from neonatal rats and mice, and spheroids and other models generated from primary neonatal mouse cholangiocytes. RESULTS: A wide layer of high molecular weight HA encircling the lumen was characteristic of the normal perinatal but not adult EHBD. This layer, which was surrounded by collagen, expanded in injured ducts in parallel with extensive peribiliary gland hyperplasia, increased mucus production and elevated serum bilirubin levels. BA EHBD remnants similarly showed increased HA centered around ductular structures compared with age-appropriate controls. High molecular weight HA typical of the fetal/neonatal ducts caused increased cholangiocyte spheroid growth, whereas low molecular weight HA induced abnormal epithelial morphology; low molecular weight HA caused matrix swelling in a bile duct-on-a-chip device. CONCLUSION: The fetal/neonatal EHBD, including in human EHBD remnants from Kasai surgeries, demonstrated an injury response with prolonged high levels of HA typical of fetal wound healing. The expanded peri-luminal HA layer may swell and lead to elevated bilirubin levels and obstruction of the EHBD. IMPACT AND IMPLICATIONS: Biliary atresia is a pediatric cholangiopathy associated with high morbidity and mortality rates; although multiple etiologies have been proposed, the fetal response to bile duct damage is largely unknown. This study explores the fetal pathogenesis after extrahepatic bile duct damage, thereby opening a completely new avenue to study therapeutic targets in the context of biliary atresia.

The visible skeleton 2.0: phenotyping of cartilage and bone in fixed vertebrate embryos and foetuses based on X-ray microCT.

For decades, clearing and staining with Alcian Blue and Alizarin Red has been the gold standard to image vertebrate skeletal development. Here, we present an alternate approach to visualise bone and cartilage based on X-ray microCT imaging, which allows the collection of genuine 3D data of the entire developing skeleton at micron resolution. Our novel protocol is based on ethanol fixation and staining with Ruthenium Red, and efficiently contrasts cartilage matrix, as demonstrated in whole E16.5 mouse foetuses and limbs of E14 chicken embryos. Bone mineral is well preserved during staining, thus the entire embryonic skeleton can be imaged at high contrast. Differences in X-ray attenuation of ruthenium and calcium enable the spectral separation of cartilage matrix and bone by dual energy microCT (microDECT). Clearing of specimens is not required. The protocol is simple and reproducible. We demonstrate that cartilage contrast in E16.5 mouse foetuses is adequate for fast visual phenotyping. Morphometric skeletal parameters are easily extracted. We consider the presented workflow to be a powerful and versatile extension to the toolkit currently available for qualitative and quantitative phenotyping of vertebrate skeletal development.

Severe thrombocytopenia is sufficient for fetal and neonatal intracerebral hemorrhage to occur.

Intracerebral hemorrhage (ICH) has a devastating impact on the neonatal population. Whether thrombocytopenia is sufficient to cause ICH in neonates is still being debated. In this study, we comprehensively investigated the consequences of severe thrombocytopenia on the integrity of the cerebral vasculature by using 2 orthogonal approaches: by studying embryogenesis in the Nfe2-/- mouse line and by using biologics (anti-GP1Bα antibodies) to induce severe thrombocytopenia at defined times during development. By using a mouse model, we acquired data demonstrating that platelets are required throughout fetal development and into neonatal life for maintaining the integrity of the cerebral vasculature to prevent hemorrhage and that the location of cerebral hemorrhage is dependent on when thrombocytopenia occurs during development. Importantly, this study demonstrates that fetal and neonatal thrombocytopenia-associated ICH occurs within regions of the brain which, in humans, could lead to neurologic damage.