Human Fetal Development Research Articles

Translating time: Challenges, progress, and future directions.

Mice are the dominant model system to study human health and disease. Yet, there is a pressing need to use diverse model systems to address long-standing issues in biomedical sciences. Mice do not spontaneously recapitulate many of the diseases we seek to study. Accordingly, the relevance of studying mice to understand human disease is limited. We discuss examples associated with limitations of the mouse model, and how the inclusion of a richer array of model systems can help address long standing issues in biomedical sciences. We also discuss a tool called Translating Time, an online resource (www.translatingtime.org) that equates corresponding ages across model systems and humans. The translating time resource can be used to bridge the gap across species and make predictions when data are sparse or unavailable as is the case for human fetal development. Moreover, the Translating Time tool can map findings across species, make inferences about the evolution of shared neuropathologies, and inform the optimal model system for studying human biology in health and in disease. Resources such as these can be utilized to integrate information across diverse model systems to improve the study of human biology in health and disease.

The histological development of the fetal human inferior colliculus during the second trimester.

The inferior colliculus (IC) is an important midbrain station of the auditory pathway, as well as an important hub of multisensory integration. The adult mammalian IC can be subdivided into three nuclei, with distinct cyto- and myeloarchitectonical profiles and distinct calcium binding proteins expression patterns. Despite several studies about its structural and functional development, the knowledge about the human fetal IC is rather limited. In this paper we first systematically describe the histological development of the human fetal IC and its subparts in five stages of the second trimester of pregnancy: 15 gestation weeks (GW), 18 GW, 21 GW, 24 GW, and 27 GW. We 3D reconstruct and calculate the volumetric growth of IC from one stage to another, which increases from 12.85 mm3 at 15 GW to 34.27 mm3 at 27 GW in the left hemisphere. The volumetric changes in the IC were further evaluated at the cellular level using serial Nissl-stained sections, as well as glial fibrillary acidic proteins (GFAP) and calretinin immunohistochemistry. We identify stellate-like and round neurons in the central nucleus of the IC (CNIC) at 24 GW and 27 GW, comparable to the adult human IC. Novel in this study, we investigate the differential calretinin expression patterns in the IC subparts, from 15 GW to 27 GW. CR labeling is identified mainly in the cortical IC rather than in the central nucleus. Furthermore, using GFAP, we describe the radial glial fibers patterns in IC, which are dominant at 18 GW and gradually taper off at later developmental stages. Finally, we describe the development of astroglia in each of the five developmental stages. All these results indicate that the human fetal IC development and cellular maturation occur in two major stages during the second trimester.

Unveiling surfactant protein-A dynamics in human fetal lung development: histological and immunohistochemical insights from Myanmar.

Surfactant protein-A (SP-A) is the most prevalent protein in the pulmonary surfactant system and it is expressed in Type II alveolar epithelial cells. We evaluated SP-A expression in 92 fetal human lungs at various gestational ages in Myanmar (Burma) using hematoxylin and eosin staining and immunohistochemical assays. We detected tubular structures in the fetal lungs during the canalicular stage of development at gestational weeks 22-25. Bronchioles were detected between 26-27 and 28-33 weeks, when primitive alveoli were evident. At 34-40 weeks, clusters of alveolar sacs opened from the alveolar ducts during the saccular development stage. At 40-44 weeks, extremely thin alveolar walls resembled sections of adult lungs. Type II cells secreting surfactant were undetectable at 22-25 weeks, but became detectable from 26 weeks, and the abundance of Type II cells increased after 28 weeks. Surfactant spread throughout the alveoli at 34 weeks. Because the positivity index of these cells significantly correlated with a gestational age of 26-33 weeks, we established a formula to estimate gestational age. Our findings improve understanding of fetal lung development and maturity, and provide valuable insights into the diagnosis and management of respiratory disorders among premature infants in Myanmar.

Human Brain Organoids Model Abnormal Prenatal Neural Development Induced by Thermal Stimulation.

The developing human foetal brain is sensitive to thermal stimulation during pregnancy. However, the mechanisms by which heat exposure affects human foetal brain development remain unclear, largely due to the lack of appropriate research models for studying thermal stimulation. To address this, we have developed a periodic heating model based on brain organoids derived from human pluripotent stem cells. The model recapitulated neurodevelopmental disruptions under prenatal heat exposure at the early stages, providing a paradigm for studying the altered neurodevelopment under environmental stimulation. Our study found that periodic heat exposure led to decreased size and impaired neural tube development in the brain organoids. Bulk RNA-seq analysis revealed that the abnormal WNT signalling pathway and the reduction of G2/M progenitor cells might be involved in heat stimulation. Further investigation revealed increased neural differentiation and decreased proliferation under heat stimulation, indicating that periodic heat exposure might lead to abnormal brain development by altering key developmental processes. Hence, our model of periodically heating brain organoids provides a platform for modelling the effects of maternal fever on foetal brain development and could be extended to applications in neurodevelopmental disorders intervention.

Development of nerves and vessels in the penis during the human fetal period.

Although nerves and vessels of the penis play important role in erection, there are few studies on their development in human fetus. Therefore, the objective of the present study is to analyze, quantitatively, in the corpora cavernosa and corpus spongiosum, the development of the nerves and vessels in the fetal penis at different gestational ages. Fifty-six fresh, macroscopically normal human fetuses aged from 13 to 36 weeks post-conception (WPC) were used. Gestational age was determined by the foot length criterion. Penises were immediately fixed in 10% formalin, and routinely processed for paraffin embedding, after which tissue sections from the mid-shaft were obtained. We used immunohistochemical staining to analyze the nerves and vessels in the corpus cavernous and in the corpus spongiosum. These elements were identified and quantified as percentage by using the Image-J software. The quantitative analysis showed that the percentage of nerves varied from 3.03% to 20.35% in the corpora cavernosa and from 1.89% to 23.88% in the corpus spongiosum. The linear regression analysis indicated that nerves growth (incidence) in the corpora cavernosa and corpus spongiosum correlated significantly and positively with fetal age (r2=0.9421, p<0.0001) and (r2=0.9312, p<0.0001), respectively, during the whole fetal period studied. Also, the quantitative analysis showed that the percentage of vessels varies from 2.96% to 12.86% in the corpora cavernosa and from 3.62% to 14.85% in the corpus spongiosum. The linear regression analysis indicated that vessels growth (appearance) in the corpora cavernosa and corpus spongiosum correlated significantly and positively with fetal age (r2=0.8722, p<0.0001) and (r2=0.8218, p<0.0001), respectively, during the whole fetal period studied. In addition, the linear regression analysis demonstrated a more intense growth rate of nerves in the corpus spongiosum during the 2nd trimester of gestation, when compared with nerves in the corpora cavernosa. In addition, the linear regression analysis demonstrated a more intense growth rate of vessels in the corpus spongiosum when compared with the corpora cavernosa, during the whole fetal period studied. In the fetal period, the human penis undergoes major developmental changes, notably in the content and distribution of nerves and vessels. We found strong correlation between nerves and vessels growth (amount) with fetal age, both in the corpora cavernosa and corpus spongiosum. There is significant greater proportional number of nerves than vessels during the whole fetal period studied. Also, nerves and vessels grow in a more intense rate than that of the corpora cavernosa and corpus spongiosum areas.

Light and scanning electron microscope characterization of mandibular symphysis tissue as a functional adaptation in the mandible development of human fetuses.

When developing, the mandible presents great plasticity and contains condensed mesenchymal cells that develops into Meckel's cartilage, of which the anterior part forms the mandibular symphysis. Mandible human development studies focus on investigating whether the beginning of mandibular fusion in fetal period is related to symphysis ossification and the tensions imposed on it, considering that tongue movements, mouth opening, and closing can be seen in fetuses. This research analyses tissue modifications during human mandibular symphysis growth using light and scanning electron microscopy to relate them to its functional structure. The study sample consisted of 12 human fetuses distributed into two groups: Group I (GI) of 10-14 weeks old and Group II (GII) of 20-24 weeks old. Fragments of mandibular symphysis were removed en bloc together with the surrounding tissues to preserve the relation with adjacent structures. Decalcified specimens were prepared in semi-serial coronal sections 5-μm-thick and stained with hematoxylin and eosin, Masson՚s trichrome, Verhoeff, and Sirius red for histological analysis with light microscopy. Collagen fibers Type I or III and elastic fibers were quantified by volume fraction (Vv). Coronal sections of the GI and GII symphyseal region were submitted to scanning electron microscopy. Comparison between groups used independent t-test. Our study presents the different endochondral ossification stages in the anterior part of Meckel's cartilage in GI. Both groups showed abundantly vascularized mesenchymal tissue with intense cellular activity forming the mandibular symphysis, such as a source of new osteoblasts adjacent to the newly deposited bone matrix. Scanning electron microscopy analysis revealed an invasion of the bony trabecula in the transverse direction from the hemimandible, rectilinear in GI and sinuous in GII due to interdigitating bone process, promoting its ossification. In collagen Vv analysis was verified a prevalence of type I in GII and type III in GI, indicating a proportional relation between maturation and tissue arrangement. Functionally, the collagen and elastic fibers in the mandibular symphysis were arranged in a pantographic network, and the fibrillar interconnectivity clearly contributes to resilience capacity and efficiency of the force transfer. This study inferred the functional significance of the knowledge about the tissue composition of mandibular symphysis, and the importance of this tissue for surrounding structures. The mesenchymal tissue of mandibular symphysis participates in bone growth process, revealing an adaptation mechanism of mandibular symphysis in the fetal period investigated.

Sex differences in human pre-gastrulation embryos.

Human fetuses exhibit notable sex differences in growth rate and response to the intrauterine environment, yet their origins and underlying mechanisms remain uncertain. Here, we conduct a detailed investigation of sex differences in human pre-gastrulation embryos. The lower methylation and incomplete inactivation of the X chromosome in females, as well as the sex-specific cell-cell communication patterns, contribute to sex-differential transcription. Male trophectoderm is more inclined toward syncytiotrophoblast differentiation and exhibits a stronger hormone secretion capacity, while female trophectoderm tends to retain cytotrophoblast program with stronger mitochondrial function as well as higher vasculogenesis and immunotolerance signals. Male primitive endoderm initiates the anterior visceral endoderm transcriptional program earlier than females. The cell cycle activities of the epiblast and primitive endoderm are higher in males compared to females, while the situation is opposite in the trophectoderm. In conclusion, our study provides in-depth insights into the sex differences in human pre-gastrulation embryos and contributes to unraveling the origins of the sex differences in human fetal development.

Mapping the anatomical and transcriptional landscape of early human fetal ovary development

Mapping the anatomical and transcriptional landscape of early human fetal ovary development

A multichannel microfluidic device for revealing the neurotoxic effects of Bisphenol S on cerebral organoids under low-dose constant exposure

Bisphenol S is a widely used plasticizer in manufacturing daily supplies, while little was known about its adverse effect on human health, especially on fetal brain development. Due to the complexity and subtlety of the brain, it remains challenging to reveal the hazardous effects of environmental pollution on human fetal brain development. Taking advantage of stem cell application, cerebral organoids generated from stem cells are becoming powerful tools for understanding brain development and drug toxicity testing models. Here, we developed a microfluidic chip for cerebral organoid culturing to reveal the neurotoxicity of low-dose constant BPS exposure on cerebral organoids. The organoids in our microfluidic system could be continuously cultured for 34 days and expressed all the essential properties of the cerebral organoids. Exposure to BPS was initiated from day 20 for concessive two weeks. The neurotoxic effects were evaluated by immunofluorescence staining and proteomics, and verified by quantitative real-time PCR. Our results indicated BPS exposure would inhibit neuron differentiation, hinder the Wnt signaling pathway, and cause alteration of signaling molecule expressions in brain regionalization. Even exposure to a low dose of BPS constantly might cause neurotoxicity during fetal brain development. Altogether, the multichannel microfluidic chip offers a general platform technique to reveal the effects of different hazardous chemicals on cerebral organoids.

Immunoexpression Patterns of Adhesion Molecules (E-cadherin, β-catenin, CD56) and Cytokeratins (CK19, CK20, HMWCK, CAM5.2) During Hair Development in Human Fetuses Compared With Adults.

Abnormalities in the expression of cytokeratins or adhesion molecules have been associated with hair disorders. The expression patterns of these molecules in the hair follicles of developing human fetuses are not obvious. We aimed to investigate the expression patterns of some cytokeratins and adhesion molecules in the hair follicle of human fetuses and compared them with adults. Forty-eight fetuses of >16 gestational weeks and 22 adult cases with total excisions of benign nevi or cysts were enrolled. The skin samples were taken from both the scalp and back of the fetuses. The histopathologically normal skin areas were evaluated in adults. CK19, CK20, CAM5.2, high-molecular-weight cytokeratin, E-cadherin, β-catenin, and CD56 immunohistochemical stainings were performed. In the fetus group, the staining scores declined in the third trimester but elevated and reached the highest level in adults, except for CD56, which did not stain any adult samples. All stainings were mostly observed in the outer root sheath, except CD56 that stained the perifollicular dermal sheath only in fetuses. E-cadherin, β-catenin, and high-molecular-weight cytokeratin strongly and diffusely stained all adult samples. CAM5.2 and CK19 scores were correlated in fetuses (scalp scores: r s = 0.405, P = 0.004; back scores: r s = 0.422, P = 0.003) and adults (back scores: r s = 0.562, P = 0.046). CD56 negativity indicated the immune-privilege feature of adult hair follicles. As CK19, CAM5.2 may be used to find the regions of stem cells or transient amplifying cells.

A human fetal cerebellar map of the late second trimester reveals developmental molecular characteristics and abnormality in trisomy 21

Our understanding of human fetal cerebellum development during the late second trimester, a critical period for the generation of astrocytes, oligodendrocytes, and unipolar brush cells (UBCs), remains limited. Here, we performed single-cell RNA sequencing (scRNA-seq) in human fetal cerebellum samples from gestational weeks (GWs) 18-25. We find that proliferating UBC progenitors distribute in the subventricular zone of the rhombic lip (RLSVZ) near white matter (WM), forming a layer structure. We also delineate two trajectories from astrogenic radial glia (ARGs) to Bergmann glial progenitors (BGPs) and recognize oligodendrogenic radial glia (ORGs) as one source of primitive oligodendrocyte progenitor cells (PriOPCs). Additionally, our scRNA-seq analysis of the trisomy 21 fetal cerebellum at this stage reveals abnormal upregulated genes in pathways such as the cell adhesion pathway and focal adhesion pathway, which potentially promote neuronal differentiation. Overall, our research provides valuable insights into normal and abnormal development of the human fetal cerebellum.

Fluoride-related changes in the fetal cord blood proteome; a pilot study

BackgroundFluoride exposure during pregnancy has been associated with various effects on offspring, including changes in behavior and IQ. To provide clues to possible mechanisms by which fluoride may affect human fetal development, we completed proteomic analyses of cord blood serum collected from second-trimester pregnant women residing in northern California, USA.ObjectiveTo identify changes in cord blood proteins associated with maternal serum fluoride concentration in pregnant women.MethodsThe proteomes of 19 archived second-trimester cord blood samples from women living in northern California, USA, and having varied serum fluoride concentrations, were analyzed by quantitative mass spectrometry. The 327 proteins that were quantified were characterized by their abundance relative to maternal serum fluoride concentration, and subjected to pathway analyses using PANTHER and Ingenuity Pathway Analysis processes.ResultsPathway analyses showed significant increases in process related to reactive oxygen species and cellular oxidant detoxification, associated with increasing maternal serum fluoride concentrations. Pathways showing significant decreases included complement cascade, suggesting alterations in alterations in process associated with inflammation.ConclusionMaternal fluoride exposure, as measured by serum fluoride concentrations in a small, but representative sample of women from northern California, USA, showed significant changes in the second trimester cord blood proteome relative to maternal serum fluoride concentration.

Immunoexpression Pattern of Autophagy-Related Proteins in Human Congenital Anomalies of the Kidney and Urinary Tract.

The purpose of this study was to evaluate the spatiotemporal immunoexpression pattern of microtubule-associated protein 1 light chain 3 beta (LC3B), glucose-regulated protein 78 (GRP78), heat shock protein 70 (HSP70), and lysosomal-associated membrane protein 2A (LAMP2A) in normal human fetal kidney development (CTRL) and kidneys affected with congenital anomalies of the kidney and urinary tract (CAKUT). Human fetal kidneys (control, horseshoe, dysplastic, duplex, and hypoplastic) from the 18th to the 38th developmental week underwent epifluorescence microscopy analysis after being stained with antibodies. Immunoreactivity was quantified in various kidney structures, and expression dynamics were examined using linear and nonlinear regression modeling. The punctate expression of LC3B was observed mainly in tubules and glomerular cells, with dysplastic kidneys displaying distinct staining patterns. In the control group's glomeruli, LAMP2A showed a sporadic, punctate signal; in contrast to other phenotypes, duplex kidneys showed significantly stronger expression in convoluted tubules. GRP78 had a weaker expression in CAKUT kidneys, especially hypoplastic ones, while normal kidneys exhibited punctate staining of convoluted tubules and glomeruli. HSP70 staining varied among phenotypes, with dysplastic and hypoplastic kidneys exhibiting stronger staining compared to controls. Expression dynamics varied among observed autophagy markers and phenotypes, indicating their potential roles in normal and dysfunctional kidney development.

Single-cell RNA sequencing reveals the gene expression profile and cellular communication in human fetal heart development

The heart is the central organ of the circulatory system, and its proper development is vital to maintain human life. As fetal heart development is complex and poorly understood, we use single-cell RNA sequencing to profile the gene expression landscapes of human fetal hearts from the four-time points: 8, 10, 11, 17 gestational weeks (GW8, GW10, GW11, GW17), and identified 11 major types of cells: erythroid cells, fibroblasts, heart endothelial cells, ventricular cardiomyocytes, atrial cardiomyocytes, macrophage, DCs, smooth muscle, pericytes, neural cells, schwann cells. In addition, we identified a series of differentially expressed genes and signaling pathways in each cell type between different gestational weeks. Notably, we found that ANNEXIN, MIF, PTN, GRN signalling pathways were simple and fewer intercellular connections in GW8, however, they were significantly more complex and had more intercellular communication in GW10, GW11, and GW17. Notably, the interaction strength of OSM signalling pathways was gradually decreased during this period of time (from GW8 to GW17). Together, in this study, we presented a comprehensive and clear description of the differentiation processes of all the main cell types in the human fetal hearts, which may provide information and reference data for heart regeneration and heart disease treatment.

Morphological features of the pons in human fetuses 14-15 weeks of intrauterine development

Knowledge of human embryonic development is essential to improve our understanding of human fetal anatomy and for better understanding the etiology of congenital malformations. Currently, the structures of the posterior cranial fossa and the brain stem are of great interest to researchers, because of a large number of nuclei are located in the pons area, which play an important role in ensuring vital functions. The aim of the scientific work is to establish the morphological features of the pons of human fetuses at 14-15 weeks of gestation, the size and area of the nuclei of cranial nerves and neurons which are located in the area of the pons. Anatomical and histological research was carried out on 6 human fetuses aged 14-15 weeks of gestation. The cadaver material for research was obtained as a result of late abortions which were conducted according to medical indications in Vinnytsia maternity hospitals. Preparations were fixed in a 10 % solution of neutral formalin, stained with hematoxylin-eosin, toluidine blue modified by Nissl. Computer histometry (Toup View) was used for morphometric research. Statistical digital data were processed on a personal computer using Microsoft Excel 2016 and “Statistica 6.1” software. We established that in human fetuses at 14-15 weeks of intrauterine development, the nuclei of the trigeminal, abductor and vestibulocochlear nerves were detected. The nucleus of the facial nerve on 14-15 weeks of gestation is represented by single polygonal nerve cells with eosinophilic cytoplasm. The nucleus of the abductor nerve had the largest area, the cochlear nucleus of the vestibulocochlear nerve had the smallest area. The largest area of neurons was in the nuclei of the VIII pair of cranial nerve, the smallest – in the nucleus of the abductor and facial nerves. At 14-15 weeks of intrauterine development of human fetuses, the area of the cell nucleus could be determined only in the nuclei of the vestibulocochlear nerve, while the cell nuclei of the trigeminal, facial, and abductor nerves were represented by nerve cells of a spherical shape with a nucleus in which a basophilic nucleolus and a homogeneous eosinophilic cytoplasm were noted. Thus, in human fetuses of 14-15 weeks of intrauterine development, differences in the sizes and areas of the nuclei of cranial nerves and neurons that form nuclei in the pons area were found.

Developmentally dynamic changes in DNA methylation in the human pancreas

Development of the human pancreas requires the precise temporal control of gene expression via epigenetic mechanisms and the binding of key transcription factors. We quantified genome-wide patterns of DNA methylation in human fetal pancreatic samples from donors aged 6 to 21 post-conception weeks. We found dramatic changes in DNA methylation across pancreas development, with > 21% of sites characterized as developmental differentially methylated positions (dDMPs) including many annotated to genes associated with monogenic diabetes. An analysis of DNA methylation in postnatal pancreas tissue showed that the dramatic temporal changes in DNA methylation occurring in the developing pancreas are largely limited to the prenatal period. Significant differences in DNA methylation were observed between males and females at a number of autosomal sites, with a small proportion of sites showing sex-specific DNA methylation trajectories across pancreas development. Pancreas dDMPs were not distributed equally across the genome and were depleted in regulatory domains characterized by open chromatin and the binding of known pancreatic development transcription factors. Finally, we compared our pancreas dDMPs to previous findings from the human brain, identifying evidence for tissue-specific developmental changes in DNA methylation. This study represents the first systematic exploration of DNA methylation patterns during human fetal pancreas development and confirms the prenatal period as a time of major epigenomic plasticity.

Palmitic acid impairs human and mouse placental function by inhibiting trophoblast autophagy through induction of acyl-coenzyme A-binding protein (ACBP) upregulation.

Can exposure to palmitic acid (PA), a common saturated fatty acid, modulate autophagy in both human and mouse trophoblast cells through the regulation of acyl-coenzyme A-binding protein (ACBP)? PA exposure before and during pregnancy impairs placental development through mechanisms involving placental autophagy and ACBP expression. High-fat diets, including PA, have been implicated in adverse effects on human placental and fetal development. Despite this recognition, the precise molecular mechanisms underlying these effects are not fully understood. Extravillous trophoblast (EVT) cell line HTR-8/SVneo and human trophoblast stem cell (hTSC)-derived EVT (hTSCs-EVT) were exposed to PA or vehicle control for 24 h. Female wild-type C57BL/6 mice were divided into PA and control groups (n = 10 per group) and subjected to a 12-week dietary intervention. Afterward, they were mated with male wild-type C57BL/6 mice and euthanized on Day 14 of gestation. Female ACBPflox/flox mice were also randomly assigned to control and PA-exposed groups (each with 10 mice), undergoing the same dietary intervention and mating with ACBPflox/floxELF5-Cre male mice, followed by euthanasia on Day 14 of gestation. The study assessed the effects of PA on mouse embryonic development and placental autophagy. Additionally, the role of ACBP in the pathogenesis of PA-induced placental toxicity was investigated. The findings were validated using real-time PCR, Western blot, immunofluorescence, transmission electron microscopy, and shRNA knockdown approaches. Exposure to PA-upregulated ACBP expression in both human HTR-8/SVneo cells and hTSCs-EVT, as well as in mouse placenta. PA exposure also induced autophagic dysfunction in HTR-8/SVneo cells, hTSCs-EVT, and mouse placenta. Through studies on ACBP placental conditional knockout mice and ACBP knockdown human trophoblast cells, it was revealed that reduced ACBP expression led to trophoblast malfunction and affected the expression of autophagy-related proteins LC3B-II and P62, thereby impacting embryonic development. Conversely, ACBP knockdown partially mitigated PA-induced impairment of placental trophoblast autophagy, observed both in vitro in human trophoblast cells and in vivo in mice. N/A. Primary EVT cells from early pregnancy are fragile, limiting research use. Maintaining their viability is tough, affecting data reliability. The study lacks depth to explore PA diet cessation effects after 12 weeks. Without follow-up, understanding postdiet impacts on pregnancy stages is incomplete. Placental abnormalities linked to elevated PA diet in embryos lack confirmation due to absence of control groups. Clarifying if issues stem solely from PA exposure is difficult without proper controls. Consuming a high-fat diet before and during pregnancy may result in complications or challenges in successfully carrying the pregnancy to term. It suggests that such dietary habits can have detrimental effects on the health of both the mother and the developing fetus. This work was supported in part by the National Natural Science Foundation of China (82171664, 82301909) and the Natural Science Foundation of Chongqing Municipality of China (CSTB2022NS·CQ-LZX0062, cstc2019jcyj-msxmX0749, and cstc2021jcyj-msxmX0236). The authors declare that they have no conflict of interest. N/A.

The effect of VEGF-A isoforms on capillary endothelial cell differentiation in human fetal lung development

Rationale: Single-cell RNA-sequencing has revealed two distinct capillary cell populations in the lung - general capillary cells (gCap) and alveolar capillary cells (aCap). Studies in mouse have demonstrated that VEGF-A188 promotes the formation of aCaps in vitro. Our study investigates the role of VEGF-A in endothelial cell (EC) differentiation into functional pulmonary capillaries during human lung development. We hypothesize that VEGFA-189, the human equivalent of murine VEGFA-188, promotes the formation of aCaps in the developing human lung. Methods: We examined the expression of the different VEGF-A isoforms ( VEGF-A121, 145, 165 and 189) on human fetal lungs aged 10-20 weeks gestation. RT-qPCR was performed to correlate the expression of VEGF-A isoforms to the expression of aCap makers ( CA4, EDNRB, SOSTDC1, HPGD, TBX2 and IL1RL1). In parallel to these analyses, we examined the effects of VEGF-A isoforms by culturing human fetal lung explants (13-20 weeks gestation) for either 2 or 7 days in the presence or absence of either recombinant human protein VEGF-A165 (20 ng/mL) or VEGF-A189 (80 ng/mL) (n=8). To verify this hypothesis of VEGF-A189, we selected VEGF-A165 which has one exon less (exon 6) than VEGF-A189. Explants were collected and analyzed for gCap ( EDN1) and aCap ( TBX2, EDNRB, SOSTDC1, HPGD, and CA4) markers expression by RT-qPCR. Immunofluorescence (IF) staining was also performed on explants to analyze the effect of VEGF-A isoforms on the proliferation of endothelial cell. Results: In native human fetal lung, we demonstrated a simultaneous expression of VEGF-A-121, 145 and 189 isoforms with several aCap markers ( SOSTDC1, EDNRB, HPGD), that peaked at around 18 weeks of gestation. Based on this, we decided to culture human fetal lung explants within this same developmental stage in the presence or absence of either VEGF-A165 or -189. Following 2 days treatment with VEGF-A165, RT-qPCR demonstrated that human fetal lung explants exhibited a significant increase in the expression of EDN1 (p&lt;0.005), accompanied by a significant decrease in expression of CA4 (p&lt;0.005). Interestingly, whereas VEGF-A189 also demonstrated decreased expression of several aCap markers ( CA4, EDNRB, SOSTDC1, and HPGD (p&lt;0.01)) it also showed increased expression of TBX2 and EDN1 (p&lt;0.05). Furthermore, IF staining displayed decreased Ki67/CD31 double positive cells on explants treated with VEGF-A189 with a more elongated and flattened morphology, much like what is observed in aCaps. Prolonging the treatment to 7 days yielded comparable results to the 2 days treatment, with VEGF-A165 and VEGF-A189 downregulating several aCap markers. Conclusion: Our study revealed that the VEGF-A189 isoform does not have the same effect on human lung capillary differentiation as observed in mouse. We noted a contrasting impact of VEGF-A isoforms on the expression of gCap and aCap markers and highlighted the significance of specific VEGF isoforms in capillary EC differentiation. Additional investigations are required to elucidate the underlying mechanisms. California Institute for Regenerative Medicine-CIRM. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Autophagy and Exocytosis of Lipofuscin Into the Basolateral Extracellular Space of Human Retinal Pigment Epithelium From Fetal Development to Adolescence.

To undertake the first ultrastructural characterization of human retinal pigment epithelial (RPE) differentiation from fetal development to adolescence. Ten fetal eyes and three eyes aged six, nine, and 17 years were examined in the temporal retina adjacent to the optic nerve head by transmission electron microscopy. The area, number, and distribution of RPE organelles were quantified and interpreted within the context of adjacent photoreceptors, Bruch's membrane, and choriocapillaris maturation. Between eight to 12 weeks' gestation (WG), pseudostratified columnar epithelia with apical tight junctions differentiate to a simple cuboidal epithelium with random distribution of melanosomes and mitochondria. Between 12 to 26 WG, cells enlarge and show long apical microvilli and apicolateral junctional complexes. Coinciding with eye opening at 26 WG, melanosomes migrate apically whereas mitochondria distribute to perinuclear regions, with the first appearance of phagosomes, complex granules, and basolateral extracellular space (BES) formation. Significantly, autophagy and heterophagy, as evidenced by organelle recycling, and the gold standard of ultrastructural evidence for autophagy of double-membrane autophagosomes and mitophagosomes were evident from 32 WG, followed by basal infoldings of RPE cell membrane at 36 WG. Lipofuscin formation and deposition into the BES evident at six years increased at 17 years. We provide compelling ultrastructural evidence that heterophagy and autophagy begins in the third trimester of human fetal development and that deposition of cellular byproducts into the extracellular space of RPE takes place via exocytosis. Transplanted RPE cells must also demonstrate the capacity to subserve autophagic and heterophagic functions for effective disease mitigation.

The gonadal niche safeguards human fetal germline cell development following maternal SARS-CoV-2 infection

During pregnancy, germline development is vital for maintaining the continuation of species. Recent studies have shown increased pregnancy risks in COVID-19 patients at the perinatal stage. However, the potential consequence of infection for reproductive quality in developing fetuses remains unclear. Here, we analyze the transcriptome and DNA methylome of the fetal germline following maternal severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. We find that infection at early gestational age, a critical period of human primordial germ cell specification and epigenetic reprogramming, trivially affects fetal germ cell (FGC) development. Additionally, FGC-niche communications are not compromised by maternal infection. Strikingly, both general and SARS-CoV-2-specific immune pathways are greatly activated in gonadal niche cells to protect FGCs from maternal infection. Notably, there occurs an "in advance" development tendency in FGCs after maternal infection. Our study provides insights into the impacts of maternal SARS-CoV-2 infection on fetal germline development and serves as potential clinical guidance for future pandemics.