Fetal Ossification Research Articles

Exposure to environmental contaminants and folic acid supplementation intergenerationally impact fetal skeleton development through the paternal lineage in a rat model.

Persistent organic pollutants (POPs) are ubiquitous in the environment, which is of concern since they are broadly toxic for wildlife and human health. It is generally accepted that maternal prenatal folic acid supplementation (FA) may beneficially impact offspring development, but it has been recently shown that the father's exposures also influence the health of his offspring. Bone is an endocrine organ essential for whole-body homeostasis and is susceptible to toxicants. Herein, we tested the hypotheses that prenatal paternal exposure to POPs induces developmental bone disorders in fetuses across multiple generations and that FA supplementation attenuates these disorders. We used a four-generation rat model, in which F0 founder females were divided into four treatment groups. F0 females were gavaged with corn oil or an environmentally-relevant POPs mixture and fed either a control diet (2 mg FA/kg), or FA supplemented diet (6 mg FA/kg) before mating and until parturition (four treatments in total). After the birth of the F1 litters, all F0 females and subsequent generations received the FA control diet. Staining with alcian blue and alizarin red S of male and female fetal skeletons was performed at Gestational Day 19.5. Paternal direct and ancestral exposure to POPs delayed bone ossification and decreased the length of long limb bones in fetuses. Maternal FA supplementation did not counteract the POPs-associated delayed fetal ossification and reduced long bone length. In conclusion, prenatal paternal POPs exposure causes developmental bone abnormalities over multiple generations, which were not corrected by maternal FA supplementation.

Yenidoğanda İzole Laküner Kafa Deformitesi

The lacunar skull is a fetal ossification disorder first defined in the early 19th century, commonly associated with spina bifida and meningocele, and rarely seen as an isolated defect. It is characterized by defects on the inner table of the skull, in the form of shallow depressions or deep cavitations causes the skull to appear fenestrated because of mesenchymal dysplasia during intramembranous ossification. These bone defects may be present in any part of the calvarium but most frequently occur in the parietal and frontal bones. Clinically, lacunar skull may be suspected, but the diagnosis usually depends on the roentgenographic appearance. We report a newborn diagnosed with severe lacunar skull defect without any congenital malformations however accompanying severe vitamin D deficiency of maternal origin.

Correlations of Maternal Serum Zinc Levels with Cord Blood Procollagen Type 1-N Terminal Propeptide Levels and Anthropometric Measurements of Newborns

Background: Zinc is an important micronutrient that is required for optimal fetal growth and development. Zinc deficiency during pregnancy may interfere with intrauterine fetal ossification. Fetal ossification can be measured with specific bone growth markers, such as procollagen type 1-N terminal propeptide (P1NP). This study aimed to investigate the mean maternal serum zinc levels and assess the correlations of maternal serum zinc levels with cord blood P1NP levels and anthropometric measurements of newborns. Methods: This cross-sectional study was conducted at Universitas Sumatera Utara Hospital and other hospitals in Medan, Indonesia, from April to October 2019. The statistical populations were pregnant mothers and their newborns who met the inclusion criteria. The participants were selected using a consecutive sampling technique. Maternal serum zinc levels and cord blood P1NP levels were measured before delivery; moreover, anthropometric measurements were conducted in this study. Results: A total of 42 subjects were included in this study with a mean maternal serum zinc level of 52.0±9.0 µg/dL. The proportion of pregnant mothers with low serum zinc levels was high (54.8%). According to the results, there was a significant correlation between maternal serum zinc levels and newborn birth weight (r=0.648) and length (r=0.656), as well as head circumference (r=0.578; P=0.001). There was also a significant and positive linear correlation between maternal serum zinc levels and cord blood P1NP levels (r=0.469; P=0.002). Conclusion: The mean maternal serum zinc levels during pregnancy were below normal. There were positive significant correlations between maternal serum zinc levels and cord blood P1NP levels with anthropometric measurements of newborns.

Leaf ethanolic extract of Etlingera hemesphaerica Blume mitigates defects in fetal anatomy and endochondral ossification due to mercuric chloride during the post-implantation period in Mus musculus.

This study aimed to investigate the effectiveness of leaf ethanolic extract of Etlingera hemisphaerica (LE3H) in reducing defects in fetal anatomy and endochondral ossification in mice induced by HgCl2 during the post-implantation period. Pregnant mice were divided into four groups, each consisting of 10 dams, and received drink and food ad libitum. The first group was administered LE3H (E1), the second one HgCl2 (E2), the third one HgCl2+LE3H (E3), and the fourth was control (E0), administered double-distilled water only. HgCl2 (5 mg/kg bw) was administrated by injection intraperitoneally on gestation day (GD)9 and LE3H (0.39 mg/g bw) was administered by gavage on GD10. The treated and control animals were killed by cervical dislocation on GD18, dissected, and the morphologically normal living fetuses (MNLF) were collected. The MNLF of E0, E1, E2, and E3 from 5 dams were fixed with Bouin solution, and observed using the free hand razor blade technique for soft tissue examination. The remaining MNLF were fixed with 96% ethanol, and then stained with Alizarin Red S and Alcian Blue for ossification examination. Index of length of ossified part (ILOP) of humerus, index of width of ossified part (IWOP) of humerus, ILOP of femur, and IWOP of femur were calculated. E2 had higher cases of anatomical defects (74,6%) than E3 (48.9%), E1 (15.0%), and E0 (0%). E2 had humerus IWOP of 0.82±0.03, which was significantly lower than that of E0 (0.89±0.04) and E1 (0.89±0.03), while that of E1 and E0 was not significantly different from each other. Meanwhile, IWOP in E3 (0.88±0.03) was significantly higher than that in E2, but not different from that in E1 and E0. Thus, LE3H mitigated defects in fetal anatomy and endochondral ossification induced by HgCl2 in mice.

Effects of benzo(a)pyrene at environmentally relevant doses on embryo-fetal development in rats.

Studies have demonstrated that Benzo(a)Pyrene (BaP), a polycyclic aromatic hydrocarbon ubiquituous in the environment, can cause teratogenic effects. Since the majority of studies used in vitro models or high doses of BaP, this study evaluated the teratogenicity, reproductive and developmental performance of low doses of BaP through maternal and fetus examination after daily oral administration of BaP (0; 0.1; 1.0 or 10 μg/kg) to pregnant Wistar rats from Gestational day (GD) 6 to GD 15 (the organogenesis period). Pregnant rats did not exhibit clinical signs of toxicity during the exposure period. However, dams exposed to the lowest dose of BaP showed a reduction in the erythrocytes number and in the creatinine levels. The groups exposed to 0.1 and 1.0 μg/kg presented a decrease in placental efficiency, as well as an increase in placental weight. After fetal examination, the treated group with the lowest dose showed a reduced relative anogenital distance, while the curve of normal distribution of weight was changed in the highest dose group. In addition, anomalies evidenced by changes in the renal size and degree of fetal ossification were observed in treated-fetus. In conclusion, treatment with BaP during organogenesis at this dose level is detrimental to the normal development of fetuses.

Ultrasonographic assessment of fetal thyroid in Japan: thyroid circumference and distal femoral and proximal tibial ossification.

The present study established a nomogram of fetal thyroid circumference (FTC) and the appearance timing of fetal distal femoral and proximal tibial ossification to assess fetal thyroid function in Japan. Between April 2015 and July 2019, normal pregnant women at our hospital were recruited for the study. FTC was measured by the automatic ellipse outline and plotted against gestational age (GA). Fetal distal femoral and proximal tibial ossification measurements were obtained with standard electronic calipers from outer-to-outer margins (> 1mm as the presence of ossification). A total of 199 pregnant women were examined. FTC increased logarithmically to GA. A nomogram of FTC was expressed by a logarithmic formula: [Formula: see text]. The respective 5-95th percentiles of FTC at each GA were 20.2-36.2mm at 22weeks, 25.0-44.8mm at 26weeks, 29.2-52.3mm at 30weeks, and 32.9-59.0mm at 34weeks. The fetal distal femoral epiphysis was not visualized before 30weeks, but was visualized in 100% of fetuses after 35weeks of gestation. The fetal proximal tibial epiphysis was not visualized before 33weeks, but was visualized in 73.7% of fetuses at 37weeks of gestation. We generated a GA-dependent FTC nomogram for Japanese fetuses. We also confirmed the appearance timing of fetal distal femoral and proximal tibial ossification to assess bone maturation. These assessments may be very useful for evaluating fetal thyroid function in Japan.

Developmental origin, functional maintenance and genetic rescue of osteoclasts

Osteoclasts are multinucleated giant cells that resorb bone, ensuring development and continuous remodelling of the skeleton and the bone marrow haematopoietic niche. Defective osteoclast activity leads to osteopetrosis and bone marrow failure1–9, whereas excess activity can contribute to bone loss and osteoporosis10. Osteopetrosis can be partially treated by bone marrow transplantation in humans and mice11–18, consistent with a haematopoietic origin of osteoclasts13,16,19 and studies that suggest that they develop by fusion of monocytic precursors derived from haematopoietic stem cells in the presence of CSF1 and RANK ligand1,20. However, the developmental origin and lifespan of osteoclasts, and the mechanisms that ensure maintenance of osteoclast function throughout life in vivo remain largely unexplored. Here we report that osteoclasts that colonize fetal ossification centres originate from embryonic erythro-myeloid progenitors21,22. These erythro-myeloid progenitor-derived osteoclasts are required for normal bone development and tooth eruption. Yet, timely transfusion of haematopoietic-stem-cell-derived monocytic cells in newborn mice is sufficient to rescue bone development in early-onset autosomal recessive osteopetrosis. We also found that the postnatal maintenance of osteoclasts, bone mass and the bone marrow cavity involve iterative fusion of circulating blood monocytic cells with long-lived osteoclast syncytia. As a consequence, parabiosis or transfusion of monocytic cells results in long-term gene transfer in osteoclasts in the absence of haematopoietic-stem-cell chimerism, and can rescue an adult-onset osteopetrotic phenotype caused by cathepsin K deficiency23,24. In sum, our results identify the developmental origin of osteoclasts and a mechanism that controls their maintenance in bones after birth. These data suggest strategies to rescue osteoclast deficiency in osteopetrosis and to modulate osteoclast activity in vivo. Multinucleated osteoclasts required for normal bone development and tooth eruption in the mouse originate from embryonic erythro-myeloid progenitors and are maintained after birth by fusion with circulating monocytes.

Developmental origin, functional maintenance and genetic rescue of osteoclasts.

Osteoclasts are multinucleated giant cells that resorb bone, ensuring development and continuous remodelling of the skeleton and the bone marrow haematopoietic niche. Defective osteoclast activity leads to osteopetrosis and bone marrow failure1-9, whereas excess activity can contribute to bone loss and osteoporosis10. Osteopetrosis can be partially treated by bone marrow transplantation in humans and mice11-18, consistent with a haematopoietic origin of osteoclasts13,16,19 and studies thatsuggest that they develop by fusion of monocytic precursors derived from haematopoietic stem cells in the presence of CSF1 and RANK ligand1,20. However, the developmental origin and lifespan of osteoclasts, and the mechanisms that ensure maintenance of osteoclast function throughout life in vivo remain largely unexplored. Here we report that osteoclasts that colonize fetal ossification centres originate from embryonic erythro-myeloid progenitors21,22. These erythro-myeloid progenitor-derived osteoclasts are required for normal bone development and tooth eruption. Yet, timely transfusion of haematopoietic-stem-cell-derived monocytic cells in newborn mice is sufficient to rescue bone development in early-onset autosomal recessive osteopetrosis. We also found that the postnatal maintenance of osteoclasts, bone mass and the bone marrow cavity involve iterative fusion of circulating blood monocytic cells with long-lived osteoclast syncytia. As a consequence, parabiosis or transfusion of monocytic cells results in long-term gene transfer in osteoclasts in the absence of haematopoietic-stem-cell chimerism, and can rescue an adult-onset osteopetrotic phenotype caused by cathepsin K deficiency23,24. In sum, our results identify the developmental origin of osteoclasts and a mechanism that controls their maintenance in bones after birth. These data suggest strategies to rescue osteoclast deficiency in osteopetrosis and to modulate osteoclast activity in vivo.

Embryo–fetal toxicity assessment of vonoprazan in rats and rabbits

Vonoprazan is a new potassium-competitive acid blocker to treat acid-related diseases. However, its safety during pregnancy is unclear. The aim of the study was to investigate the potential reproductive toxicity on the embryo-fetal development of vonoprazan. Vonoprazan acetate was administered by intravenous injection to pregnant rats (0, 2, 6 and 20mgkg-1 day-1 ) and rabbits (0, 1.2, 3.6 and 12mgkg-1 day-1 ) during the organogenetic period (gestation day 6-15 [rats] and 6-18 [rabbits]). Maternal reproductive endpoints were evaluated, together with effects on fetal growth and morphological development. In rats, no treatment-related effects were found in the highest dose group (20mgkg-1 ) and the maternal plasma exposure was ≥50-fold the expected clinical human exposure. However, in rabbits, dose-related clinical signs (soft or liquid feces) occurred in the 12mgkg-1 group, which was regarded as a maternal toxicity. Besides, decreased maternal weight gain also was considered as a minimal maternal toxicity. At 12mgkg-1 , delayed fetal ossification was found as evidence of embryo-fetal growth retardation, which was related to decreased fetal and placental weights. There was no maternal and developmental toxicity in the 1.2 and 3.6mgkg-1 groups. Thus, the no-observed-adverse-effect levels of vonoprazan acetate in rabbits are considered 3.6mgkg-1 day-1 , which produced plasma exposure that was about 18-fold human clinical exposure.

An embryo-fetal development toxicity study with dimethylaminoethyl ginkgolide B in rats and rabbits.

Ginkgo biloba (a herbal product) has long been used in traditional Chinese medicine to treat cerebrovascular and cardiovascular diseases. Ginkgolide B is one of the important pharmacologically active components of Ginkgo biloba. Dimethylaminoethyl ginkgolide B (a novel ginkgolide B derivative) has been developed to overcome the poor water-solubility of natural drugs and to achieve higher bioavailability. This study investigated the potential effects of dimethylaminoethyl ginkgolide B on pregnant dams and embryo-fetal development in Sprague-Dawley rats and New Zealand white rabbits following maternal exposure on gestational day (GD) 6-15 and GD 6-18, respectively. Dimethylaminoethyl ginkgolide B was administered by intravenous injection to pregnant rats (0, 10, 30 and 100 mg kg-1 d-1) and rabbits (0, 6, 18 and 60 mg kg-1 d-1). Maternal toxicity signs, such as lower maternal body weight gain and food consumption, were observed at 100 mg kg-1 d-1 in rats and 60 mg kg-1 d-1 in rabbits. The developmental toxic effects included a decrease in fetal and placental weights, increased incidences of skeletal variations and delay in fetal ossification. Fetal growth and development were affected by dimethylaminoethyl ginkgolide B in the high-dose group in rabbits. The no-observed-adverse-effect level of dimethylaminoethyl ginkgolide B is considered to be 30 mg kg-1 d-1 for rats and 18 mg kg-1 d-1 for rabbits.

A woolly mammoth (Mammuthus primigenius) carcass from Maly Lyakhovsky Island (New Siberian Islands, Russian Federation)

A partial carcass of an adult woolly mammoth (Mammuthus primigenius) found in 2012 on Maly Lyakhovsky Island presents a new opportunity to retrieve associated anatomical, morphological, and life history data on this important component of Pleistocene biotas. In addition, we address hematological, histological, and microbiological issues that relate directly to quality of preservation. Recovered by staff from North-Eastern Federal University in Yakutsk, this individual is a relatively old female preserving soft tissue of the anteroventral portion of the head, most of both fore-quarters, and the ventral aspect of much of the rest of the body. Both tusks were recovered and subjected to computed tomographic analysis in which annual dentin increments were revealed as cycles of variation in X-ray attenuation. Measurements of annual increment areas (in longitudinal section) display a pulsed pattern of tusk growth showing cycles of growth rate variation over periods of 3–5 years. These intervals are interpreted as calving cycles reflecting regular shifts in calcium and phosphate demand for tusk growth vs. fetal ossification and lactation. Brown liquid associated with the frozen carcass turned out to include remains of hemolyzed blood, and blood samples examined microscopically included white blood cells with preserved nuclei. Muscle tissue from the trunk was unusually well preserved, even at the histological level. Intestinal contents and tissue samples were investigated microbiologically, and several strains of lactic-acid bacteria (e.g., Enterococcus faecium, Enterococcus hirae) that are widely distributed as commensal organisms in the intestines of herbivores were isolated.

Endochondral Ossification Is Accelerated in Cholinesterase-Deficient Mice and in Avian Mesenchymal Micromass Cultures.

Most components of the cholinergic system are detected in skeletogenic cell types in vitro, yet the function of this system in skeletogenesis remains unclear. Here, we analyzed endochondral ossification in mutant murine fetuses, in which genes of the rate-limiting cholinergic enzymes acetyl- (AChE), or butyrylcholinesterase (BChE), or both were deleted (called here A-B+, A+B-, A-B-, respectively). In all mutant embryos bone growth and cartilage remodeling into mineralizing bone were accelerated, as revealed by Alcian blue (A-blu) and Alizarin red (A-red) staining. In A+B- and A-B- onset of mineralization was observed before E13.5, about 2 days earlier than in wild type and A-B+ mice. In all mutants between E18.5 to birth A-blu staining disappeared from epiphyses prematurely. Instead, A-blu+ cells were dislocated into diaphyses, most pronounced so in A-B- mutants, indicating additive effects of both missing ChEs in A-B- mutant mice. The remodeling effects were supported by in situ hybridization (ISH) experiments performed on cryosections from A-B- mice, in which Ihh, Runx2, MMP-13, ALP, Col-II and Col-X were considerably decreased, or had disappeared between E18.5 and P0. With a second approach, we applied an improved in vitro micromass model from chicken limb buds that allowed histological distinction between areas of cartilage, apoptosis and mineralization. When treated with the AChE inhibitor BW284c51, or with nicotine, there was decrease in cartilage and accelerated mineralization, suggesting that these effects were mediated through nicotinic receptors (α7-nAChR). We conclude that due to absence of either one or both cholinesterases in KO mice, or inhibition of AChE in chicken micromass cultures, there is increase in cholinergic signalling, which leads to increased chondroblast production and premature mineralization, at the expense of incomplete chondrogenic differentiation. This emphasizes the importance of cholinergic signalling in cartilage and bone formation.

Effects of Melamine and Cyanuric Acid on Embryo‐Fetal Development in Rats

After the outbreak of acute renal failure associated with melamine-contaminated pet food, melamine and melamine-related compounds have become of great interest from a toxicologic perspective. We investigated the potential effects of melamine in combination with cyanuric acid (M + CA, 1:1) on pregnant dams and embryo-fetal development in rats. M + CA was orally administered to pregnant rats from gestational days 6 through 19 at doses of 0, 3, 10, and 30 mg/kg/day of both melamine and cyanuric acid. Maternal toxicity of rats administered 30 mg/kg/day M + CA was manifested as increased incidences of clinical signs and death; gross pathologic findings; higher blood urea nitrogen and creatinine levels; lower body weight gain and food intake; decreased thymus weight; and increased heart, lung, and kidney weights. Histopathological examinations revealed an increase in the incidence of congestion, tubular necrosis/degeneration, crystals, casts, mineralization, inflammatory cells in tubules, tubular dilation, and atrophy of glomeruli in maternal kidneys, whereas fetal kidneys did not show any histopathological changes. Developmental toxicity included a decrease in fetal (28%) and placental weights and a delay in fetal ossification (n = 7). Increased incidence of gross and histopathological changes in the maternal kidney was also found in the middle dose group (n = 12). No treatment-related maternal or developmental effects were observed in the low dose group (n = 12). Under these experimental conditions, M + CA is embryotoxic at an overt maternotoxic dose in rats and the no-observed-adverse-effect level of M + CA is considered to be 3 mg/kg/day for pregnant dams and 10 mg/kg/day for embryo-fetal development.

THU0011 Three Different Protein Products are Codified by Human MMP-13 Gene

BackgroundCollagenase-3 (MMP-13) is a human matrix metalloproteinase highly overexpressed in diseases where tissue repair and remodelling is needed, such as rheumatoid arthritis (RA), osteoarthritis (OA) and some cancers. However, its...

Verification of three different MMP-13 isoforms expression in human osteoarthritic cartilage

Verification of three different MMP-13 isoforms expression in human osteoarthritic cartilage

Ex vivo and in vivo magnetic resonance imaging of cartilage canals in swine at predilection sites of osteochondrosis

Ex vivo and in vivo magnetic resonance imaging of cartilage canals in swine at predilection sites of osteochondrosis

Coronal Vertebral Clefts: A Radiological Indicator for Chromosomal Aberrations

Coronal clefts-a radiolucent band running through at least one vertebral body, visualized in the lateral spinal radiograph and discussed as a physiological variation of the fetal vertebral ossification pattern-are often found in fetal autopsies with trisomies. Published studies are missing concerning the question of whether this finding could serve as a diagnostic radiological or even ultrasonographic sign. We studied the incidence of radiological coronal clefts and their association with chromosomal aberrations in 443 fetuses (mostly medically induced abortions). In 42 of the 443 fetuses (9.5%), coronal clefts were visualized. The majority (71%) were localized in the lumbar spine. No cervical or singular sacral clefts were detected. Twenty-five of the 42 fetuses (60%) displaying coronal clefts had chromosomal aberrations, either as a trisomy (13 or 21) or as monosomy X. Histologically, coronal clefts showed a missing central ossification of the vertebral body. Remnants of the notochord could be excluded. Hence, coronal clefts represent a variant ossification of vertebral bodies in fetal development that is found almost exclusively in fetuses with chromosomal aberrations or severe congenital malformations. This finding could be a helpful supplement to prenatal diagnostics and fetal autopsy. On the other hand, the genetic diagnosis of chromosomal aberration, especially trisomy, does not automatically imply the presence of coronal clefts.

Dose–Response Effects of Diphenylhydantoin on Pregnant Dams and Embryo‐Fetal Development in Rats

Despite the widespread use of diphenylhydantoin (DPH), there is a lack of reliable information on the teratogenic effects, correlation with maternal and developmental toxicity, and dose-response relationship of DPH. This study investigated the dose-response effects of DPH on pregnant dams and embryo-fetal development as well as the relationship between maternal and developmental toxicity. DPH was orally administered to pregnant rats from gestational days 6 through 15 at 0, 50, 150, and 300 mg/kg/day. At 300 mg/kg, maternal toxicity including increased clinical signs, suppressed body weight, decreased food intake, and increased weights of adrenal glands, liver, kidneys, and brain were observed in dams. Developmental toxicity, including a decrease in fetal and placental weights, increased incidence of morphological alterations, and a delay in fetal ossification delay also occurred. At 150 mg/kg, maternal toxicity manifested as an increased incidence of clinical signs, reduced body weight gain and food intake, and increased weights of adrenal glands and brain. Only minimal developmental toxicity, including decreased placental weight and an increased incidence of visceral and skeletal variations, was observed. No treatment-related maternal or developmental effects were observed at 50 mg/kg. These results show that DPH is minimally embryotoxic at a minimal maternotoxic dose (150 mg/kg/day) but is embryotoxic and teratogenic at an overt maternotoxic dose (300 mg/kg/day). Under these experimental conditions, the no-observed-adverse-effect level of DPH for pregnant dams and embryo-fetal development is considered to be 50 mg/kg/day. These data indicate that DPH is not a selective developmental toxicant in the rat.

Morphological and morphometric study on sphenoid and basioccipital ossification in normal human fetuses

Congenital anomalies of the brain frequently correspond to cranial base anomalies, and a detailed description of morphology and individual variations in the developing cranial base is of clinical importance for diagnosing anomalies. Development of the human cranial base has been studied using dissection, computed tomography, and magnetic resonance imaging, each of which has advantages and disadvantages. We here examined development of the normal human fetal cranial base using bone staining, which allows for direct observation of the ossification centers and precise three-dimensional measurements. We observed alizarin red S-stained sphenoids and basiocciputs of 22 normal formalin-fixed human fetuses with crown-rump lengths (CRL) of 115-175 mm. We defined landmarks and measured sphenoids and basiocciputs using a fine caliper. Growth patterns of these ossifying bones were obtained, and we found similarities and differences among the growth patterns. We also observed individual variations in the ossification patterns, in particular, single- or double-ossification center patterns for the basisphenoid. The orbitosphenoid and basisphenoid widths and ratios of the widths to the total cranial base width were significantly different between the two pattern groups, whereas the other measurements and their ratios to the total cranial base did not differ between the groups. We measured the cerebrum and pons in different sets of 22 human fetuses with CRLs of 105-186 mm and found close relationships with the development of corresponding parts of the cranial base. The results contribute to the quantitative and qualitative information about the growth patterns and variations during human fetal cranial base development.

Effects of melamine on pregnant dams and embryo‐fetal development in rats

There are worldwide concerns regarding the potential adverse effect of melamine. This study investigated the potential effects of melamine on pregnant dams and embryo-fetal development in Sprague-Dawley rats following maternal exposure on gestational days (GD) 6-20. Melamine was administered to pregnant rats by gavage at doses of 0, 200, 400 and 800 mg kg⁻¹ per day (n = 8-10 for each group). All dams were subjected to a Caesarean section on GD 21 and their fetuses were examined for morphological abnormalities. With administration of melamine at 800 mg kg⁻¹ per day, maternal toxicity manifested as increased incidences of clinical signs and death, lower body weight gain and food intake, and increases in heart, adrenal gland and kidney weights. Histopathological examinations revealed an increase in incidences of congestion, tubular necrosis/degeneration, crystals, casts, inflammatory cells in tubules, tubular dilation and tubular hyaline droplets in the maternal kidneys, while fetal kidneys (one fetus/litter) did not show any histopathological changes. Developmental toxic effects included a decrease in fetal weight, an increase in the incidence of skeletal variations and a delay in fetal ossification. No treatment-related maternal or developmental effects were observed at doses ≤ 400 mg kg⁻¹ per day. These results show that 15-day repeated oral dosing of melamine is embryo-/fetotoxic at a maternotoxic dose, but not teratogenic in rats. The no-observed-adverse-effect level of melamine for pregnant dams and embryo-fetal development is considered to be 400 mg kg⁻¹ per day.