Function In Adult Mice Research Articles

Prdm16 Is Required for the Maintenance of Brown Adipocyte Identity and Function in Adult Mice

Prdm16 is a transcription factor that regulates the thermogenic gene program in brown and beige adipocytes. However, whether Prdm16 is required for the development or physiological function of brown adipose tissue (BAT) in vivo has been unclear. By analyzing mice that selectively lacked Prdm16 in the brown adipose lineage, we found that Prdm16 was dispensable for embryonic BAT development. However, Prdm16 was required in young mice to suppress the expression of white-fat-selective genes in BAT through recruitment of the histone methyltransferase Ehmt1. Additionally, Prdm16 deficiency caused a severe adult-onset decline in the thermogenic character of interscapular BAT. This resulted in BAT dysfunction and cold sensitivity but did not predispose the animals to obesity. Interestingly, the loss of brown fat identity due to ablation of Prdm16 was accelerated by concurrent deletion of the closely related Prdm3 gene. Together, these results show that Prdm16 and Prdm3 control postnatal BAT identity and function.

In Vivo Delivery of Lenti-Cre or Adeno-Cre into Mice Using Intranasal Instillation

Lung cancer remains the leading cause of cancer deaths among both men and women, with a lower rate of survival than both breast and prostate cancer. Development of the Cre/lox system and improved mouse models have allowed researchers to gain a better understanding of human disease, including lung cancer. Through the viral delivery of Cre, gene function in adult mice can be precisely studied at a specific developmental stage or in a specific cell/tissue type of choice. This protocol describes how to produce adenovirus-Cre precipitate. Using this adeno-Cre (or lentivirus-Cre), Cre can be expressed in mouse lungs. The virus is delivered by intranasal instillation.

The long-term consequences of the exposure to increasing gravity levels on the muscular, vestibular and cognitive functions in adult mice

Adult male mice C57Bl6/J were exposed to gravity levels between 1G and 4G during three weeks, and the long-term consequences on muscular, vestibular, emotional, and cognitive abilities were evaluated at the functional level to test the hypothesis of a continuum in the response to the increasing gravitational force. In agreement with the hypothesis, the growth of body mass slowed down in relation with the gravity level during the centrifugation, and weight recovery was inversely proportional. On the other hand, the long-term consequences on muscular, vestibular, emotional, and cognitive abilities did not fit the hypothesis of a continuum in the response to the gravity level. The hypergravity acted as endurance training on muscle force until 3G, then became deleterious at 4G. The vestibular reactions were not affected until 4G. Persistent emotional reactions appeared at 3G, and particularly 4G. The mice centrifuged at 3G and 4G showed an impaired spatial learning, probably in relation with the increased level of anxiety, but a greater difficulty was also observed in mice exposed at 2G, suggesting another cause for the impairment of spatial memory. The long-term response to the hypergravity was shown to depend on both the level of gravity and the duration of exposition, with different importance depending on the function considered.

MicroRNA-17~92 Is Required for Nephrogenesis and Renal Function

Deletion of all microRNAs (miRNAs) in nephron progenitors leads to premature loss of these cells, but the roles of specific miRNAs in progenitors have not been identified. Deletions in the MIR17HG cluster (miR-17~92 in mice), detected in a subset of patients with Feingold syndrome, represent the first miRNA mutations to be associated with a developmental defect in humans. Although MIR17HG is expressed in the developing kidney, and patients with Feingold syndrome caused by MYCN mutations have renal anomalies, it remains unclear to what extent MIR17HG contributes to renal development and function. To define the role of miR-17~92, we generated mice with a conditional deletion of miR-17~92 in nephron progenitors and their derivatives. The nephron progenitor population was preserved in these mice; however, this deletion impaired progenitor cell proliferation and reduced the number of developing nephrons. Postnatally, mutant mice developed signs of renal disease, including albuminuria by 6 weeks and focal podocyte foot process effacement and glomerulosclerosis at 3 months. Taken together, these data support a role for this miRNA cluster in renal development, specifically in the regulation of nephron development, with subsequent consequences for renal function in adult mice.

Assessment of Right Ventricular Structure and Function in Mouse Model of Pulmonary Artery Constriction by Transthoracic Echocardiography

Emerging clinical data support the notion that RV dysfunction is critical to the pathogenesis of cardiovascular disease and heart failure(1-3). Moreover, the RV is significantly affected in pulmonary diseases such as pulmonary artery hypertension (PAH). In addition, the RV is remarkably sensitive to cardiac pathologies, including left ventricular (LV) dysfunction, valvular disease or RV infarction(4). To understand the role of RV in the pathogenesis of cardiac diseases, a reliable and noninvasive method to access the RV structurally and functionally is essential. A noninvasive trans-thoracic echocardiography (TTE) based methodology was established and validated for monitoring dynamic changes in RV structure and function in adult mice. To impose RV stress, we employed a surgical model of pulmonary artery constriction (PAC) and measured the RV response over a 7-day period using a high-frequency ultrasound microimaging system. Sham operated mice were used as controls. Images were acquired in lightly anesthetized mice at baseline (before surgery), day 0 (immediately post-surgery), day 3, and day 7 (post-surgery). Data was analyzed offline using software. Several acoustic windows (B, M, and Color Doppler modes), which can be consistently obtained in mice, allowed for reliable and reproducible measurement of RV structure (including RV wall thickness, end-diastolic and end-systolic dimensions), and function (fractional area change, fractional shortening, PA peak velocity, and peak pressure gradient) in normal mice and following PAC. Using this method, the pressure-gradient resulting from PAC was accurately measured in real-time using Color Doppler mode and was comparable to direct pressure measurements performed with a Millar high-fidelity microtip catheter. Taken together, these data demonstrate that RV measurements obtained from various complimentary views using echocardiography are reliable, reproducible and can provide insights regarding RV structure and function. This method will enable a better understanding of the role of RV cardiac dysfunction.

The effect of brief neonatal cryoanesthesia on physical development and adult cognitive function in mice

Deep hypothermia (cryoanesthesia) is often used as general anesthesia during surgery in neonatal rodents. Neonatal cryoanesthesia has been used recently to generate somatic brain transgenic (SBT) mouse models via intracerebral ventricular injection of rAAV vectors into both non-transgenic mice and numerous transgenic mouse models. Since, the evaluation of cognition is one of the main experimental endpoints in many of these studies, we examined the consequences of brief neonatal cryoanesthesia on the physical development and mnemonic function of adult mice. Two groups of 129FVBF1 pups from reciprocal breeding crosses underwent cryoanesthesia for 6min (Cryo6) or 12min (Cryo12), respectively, within the first hours (<12h) of postnatal life. A group of pups separated from the nest and kept in ambient temperature of 33°C for 6min served as a control. Our results revealed that lowering the temperature of pups to ∼8°C (Cryo6) or ∼5°C (Cryo12) did not affect their body weight at pre-weaning stage and in the adulthood. The evaluation of cognitive function in adult mice revealed strong and comparable to control spatial reference, and context and tone fear memories of neonatally cryoanesthetized mice. Also, the experimental and control groups had comparable brain weight at the end of the study. Our results demonstrate that neonatal cryoanesthesia, lasting up to 12min, has no adverse effects on the body weight of mice during development, and on their cognition in the adulthood.

Met signaling in cardiomyocytes is required for normal cardiac function in adult mice

Hepatocyte growth factor (HGF) and its receptor, Met, are key determinants of distinct developmental processes. Although HGF exerts cardio-protective effects in a number of cardiac pathologies, it remains unknown whether HGF/Met signaling is essential for myocardial development and/or physiological function in adulthood. We therefore investigated the requirement of HGF/Met signaling in cardiomyocyte for embryonic and postnatal heart development and function by conditional inactivation of the Met receptor in cardiomyocytes using the Cre-α-MHC mouse line (referred to as α-MHCMet-KO). Although α-MHCMet-KO mice showed normal heart development and were viable and fertile, by 6months of age, males developed cardiomyocyte hypertrophy, associated with interstitial fibrosis. A significant upregulation in markers of myocardial damage, such as β-MHC and ANF, was also observed. By the age of 9months, α-MHCMet-KO males displayed systolic cardiac dysfunction. Mechanistically, we provide evidence of a severe imbalance in the antioxidant defenses in α-MHCMet-KO hearts involving a reduced expression and activity of catalase and superoxide dismutase, with consequent reactive oxygen species accumulation. Similar anomalies were observed in females, although with a slower kinetics. We also found that Met signaling down-regulation leads to an increase in TGF-β production and a decrease in p38MAPK activation, which may contribute to phenotypic alterations displayed in α-MHCMet-KO mice. Consistently, we show that HGF acts through p38α to upregulate antioxidant enzymes in cardiomyocytes. Our results highlight that HGF/Met signaling in cardiomyocytes plays a physiological cardio-protective role in adult mice by acting as an endogenous regulator of heart function through oxidative stress control.

BET acetyl-lysine binding proteins control pathological cardiac hypertrophy

Cardiac hypertrophy is an independent predictor of adverse outcomes in patients with heart failure, and thus represents an attractive target for novel therapeutic intervention. JQ1, a small molecule inhibitor of bromodomain and extraterminal (BET) acetyl-lysine reader proteins, was identified in a high throughput screen designed to discover novel small molecule regulators of cardiomyocyte hypertrophy. JQ1 dose-dependently blocked agonist-dependent hypertrophy of cultured neonatal rat ventricular myocytes (NRVMs) and reversed the prototypical gene program associated with pathological cardiac hypertrophy. JQ1 also blocked left ventricular hypertrophy (LVH) and improved cardiac function in adult mice subjected to transverse aortic constriction (TAC). The BET family consists of BRD2, BRD3, BRD4 and BRDT. BRD4 protein expression was increased during cardiac hypertrophy, and hypertrophic stimuli promoted recruitment of BRD4 to the transcriptional start site (TSS) of the gene encoding atrial natriuretic factor (ANF). Binding of BRD4 to the ANF TSS was associated with increased phosphorylation of local RNA polymerase II. These findings define a novel function for BET proteins as signal-responsive regulators of cardiac hypertrophy, and suggest that small molecule inhibitors of these epigenetic reader proteins have potential as therapeutics for heart failure.

Resveratrol - an ingredient of red wine abrogates the reproductive capacity in male mice

Resveratrol has been considered as an antioxidant in biological system. However, its role in male reproductive biology has not yet been evaluated in much detail. Present study analysed its effect on male reproductive function in adult mouse, after its intraperitoneal administration (2, 8 and 20 mg kg b.wt.(-1) per day) for 2 weeks. The generation of reactive oxygen species and lipid peroxidation in testis increased with concomitant decrease in sperm count and motility following resveratrol treatment as compared with the control group. Resveratrol had a negative impact on the activities of antioxidant enzymes namely catalase and superoxide dismutase and on the level of reduced glutathione. Increase in the level of oxidised glutathione by resveratrol lead to a shift in the redox ratio. Additionally, a significant loss of Leydig cells and alterations in testicular histomorphology (excessive vacuolisation and shrinkage of seminiferous tubules) was also observed. In conclusion, the deleterious effects of resveratrol on germ cells could be attributed to its pro-oxidant ability leading to testicular tissue damage.

Persistent effects of neonatal hyperoxia on bronchioles and lung function in adult mice: additional effects of concomitant growth restriction

Persistent effects of neonatal hyperoxia on bronchioles and lung function in adult mice: additional effects of concomitant growth restriction

Impairment of mitochondria in adult mouse brain overexpressing predominantly full-length, N-terminally acetylated human α-synuclein.

While most forms of Parkinson’s Disease (PD) are sporadic in nature, a small percentage of PD have genetic causes as first described for dominant, single base pair changes as well as duplication and triplication in the α-synuclein gene. The α-synuclein gene encodes a 140 amino acid residue protein that interacts with a variety of organelles including synaptic vesicles, lysosomes, endoplasmic reticulum/Golgi vesicles and, reported more recently, mitochondria. Here we examined the structural and functional interactions of human α-synuclein with brain mitochondria obtained from an early, pre-manifest mouse model for PD over-expressing human α-synuclein (ASOTg). The membrane potential in ASOTg brain mitochondria was decreased relative to wildtype (WT) mitochondria, while reactive oxygen species (ROS) were elevated in ASOTg brain mitochondria. No selective interaction of human α-synuclein with mitochondrial electron transport complexes cI-cV was detected. Monomeric human α-synuclein plus carboxyl terminally truncated forms were the predominant isoforms detected in ASOTg brain mitochondria by 2-dimensional PAGE (Native/SDS) and immunoblotting. Oligomers or fibrils were not detected with amyloid conformational antibodies. Mass spectrometry of human α-synuclein in both ASOTg brain mitochondria and homogenates from surgically resected human cortex demonstrated that the protein was full-length and postranslationally modified by N-terminal acetylation. Overall the study showed that accumulation of full-length, N-terminally acetylated human α-synuclein was sufficient to disrupt brain mitochondrial function in adult mice.

The histone deacetylase, SIRT1, contributes to the resistance of young mice to ischemia/reperfusion-induced acute kidney injury

Acute kidney injury (AKI) is a critical condition with a mortality rate as high as 50% and significantly contributes to the burden of end-stage renal disease (ESRD) requiring renal replacement therapy. The incidence and prognosis of AKI have been shown to vary with patient age, with younger individuals being more resistant to AKI. In mice, clamping the renal artery for 45 min causes substantial kidney damage in 4-month-old animals but only mild renal injury in 2-month-old animals. Here, younger mice were found to express higher levels of the NAD(+)-dependent histone deacetylase SIRT1 in the kidney. A small molecule SIRT1 activator, SRT-1720, markedly improved renal tubular pathology and overall renal function in adult mice following ischemia/reperfusion. Genetic ablation of one allele (SIRT1(+/-)) significantly enhanced the level of kidney damage relative to that in wild-type (SIRT1(+/+)) mice. The mechanisms underlying the protective effect of SIRT1 included the suppression of cell apoptosis. Hence, our results suggest that SIRT1 might be a novel therapeutic target for ischemia/reperfusion-induced kidney damage.

Quercetin Exerts Deleterious Effects on the Reproductive Potential of Male Mice

Oxidative stress is a leading cause of male infertility. To combat this, germ cells and spermatozoa are endowed with various enzymes, vitamins and proteins. Certain other components of food, including bioflavonoids also provide protection against free radicals. Present study analyzed the effect of quercetin, a bioflavonoid, on male reproductive function in adult mouse, after intra-peritoneal treatment with varying concentrations of quercetin (2, 8 and 20mg/kg b.wt.) for two weeks. Quercetin increased the generation of reactive oxygen species and lipid peroxidation in the testis with concomitant decrease in sperm count and motility in a dose dependent manner. Activities of antioxidant enzymes catalase, superoxide dismutase and levels of reduced glutathione were found to be decreased in a dose dependent manner. Also, the levels of oxidized glutathione were increased leading to a shift in redox ratio. The testicular histomorphology was also altered dose dependently. Germ cell kinetic study revealed significant loss of various germ cell populations with increasing dose of quercetin. Interestingly, there was a reduction in germinal epithelium thickness concomitant with an increase in seminiferous tubule lumen diameter. In conclusion, the deleterious effects of quercetin on germ cells could be attributed to its pro-oxidant ability which might affect the sertoli cell functions.

The CB1Cannabinoid Receptor Drives Corticospinal Motor Neuron Differentiation through the Ctip2/Satb2 Transcriptional Regulation Axis

The generation and specification of pyramidal neuron subpopulations during development relies on a complex network of transcription factors. The CB(1) cannabinoid receptor is the major molecular target of endocannabinoids and marijuana active compounds. This receptor has been shown to influence neural progenitor proliferation and axonal growth, but its involvement in neuronal differentiation and the functional impact in the adulthood caused by altering its signaling during brain development are not known. Here we show that the CB(1) receptor, by preventing Satb2 (special AT-rich binding protein 2)-mediated repression, increased Ctip2 (COUP-TF interacting protein 2) promoter activity, and Ctip2-positive neuron generation. Unbalanced neurogenic fate determination found in complete CB(1)(-/-) mice and in glutamatergic neuron-specific Nex-CB(1)(-/-) mice induced overt alterations in corticospinal motor neuron generation and subcerebral connectivity, thereby resulting in an impairment of skilled motor function in adult mice. Likewise, genetic deletion of CB(1) receptors in Thy1-YFP-H mice elicited alterations in corticospinal tract development. Altogether, these data demonstrate that the CB(1) receptor contributes to the generation of deep-layer cortical neurons by coupling endocannabinoid signals from the neurogenic niche to the intrinsic proneurogenic Ctip2/Satb2 axis, thus influencing appropriate subcerebral projection neuron specification and corticospinal motor function in the adulthood.

Novel Method to Study Mouse Bone Marrow Endothelial Cells in Vivo and in Vitro

Abstract 617Self-renewal, differentiation, and proliferation of hematopoietic stem cells (HSCs) and leukemia stem cells (LSCs) are maintained in a complex microenvironment of the adult bone marrow (BM). BM endothelial cells (ECs) have been proposed to be a key component of HSC and LSC niche. However, in contrast to the well-developed culture system of human ECs, current work of murine BM endothelial cells is hindered by a lack of mouse bone marrow endothelial cell primary culture and suitable assay methods to clearly define murine BMEC functionality in vivo and in vitro, which limits genetic and mechanistic studies by using mouse models. To establish an in vivo approach to study the EC function in adult mice, a strain of Tie2-CreER transgenic mice was generated to allow conditional and inducible manipulation of BMECs by Cre recombinase expression under the Tie2 promoter. In vivo lineage tracing was achieved in a Tie2-CreER/TD-tomato or -EGFP reporter mouse strain. Upon a four day Tamoxifen injection regimen, TD-tomato or EGFP reporter was readily visualized in bone marrow vasculature that colocalizes with CD31+ ECs as determined by immunostaining. FACS analysis of Tie2-CreER/EGFP reporter mice showed that the EGFP+ cells in the BM were exclusively in the CD45- VEGFR2+ and CD31+ cell fraction, with no EGFP+ cells being detectable in the CD45+ hematopoietic lineages or osteoblast/stroma cell fractions, suggesting that the Tie2-driven CreER expression is limited to the endothelial lineage in the adult BM. Next, we developed an in vitro method to culture and assay the mouse BMECs functionally. An in vitro selection process allowed us to establish a primary BM cell culture condition that permitted functional expansion and maintenance of mouse BMECs in long-term tissue culture, yielding homogenous CD45- cells expressing endothelial markers CD31, CD34 and VEGFR2. These cells formed capillary-like structures in 2-demensional and 3-demensional tubes/capillaries, and showed TD-tomato reporter color when derived from the Tamoxifen induced Tie2-CreER/TD-tomato mouse BM. They showed expected adhesion and migration activities and morphology of ECs. Lineage chasing assays using isolated CD45+ and CD45- BM cells from the Tie2-CreER/Td-tomato mice demonstrated that the BMECs in our culture system, bearing the Tie2-promoter driven TD-tomato color and CD31+ marker, were exclusively derived from CD45- non-hematopoietic lineage. Taken together, we have established a faithful assay method for studying murine BM EC functions in vivo and in vitro, allowing the tracking and genetic manipulation of adult BM ECs in mice and in culture. The method can be useful for delineating molecular and cellular mechanisms of BMEC regulation and EC-mediated BM niche function, and may have value in testing anti-angiogenic activities of anticancer drugs in animal models. Disclosures:No relevant conflicts of interest to declare.

Regulatory roles of the NMDA receptor GluN3A subunit in locomotion, pain perception and cognitive functions in adult mice

Since the discovery of the glutamate NMDA receptor subunit 3A (GluN3A), the functional role of this unique inhibitory subunit has been largely obscure. GluN3A expression is high in the neonatal brain but declines to a low level in the adult brain; it is thus commonly believed that GluN3A does not have a major functional impact in adulthood. Using wild-type (WT) and GluN3A knockout (KO) mice, we show here that deletion of GluN3A affected multiple behavioural functions in adult animals. GluN3A KO mice showed impaired locomotor activity on a variety of motor function tests, and increased sensitivity to acute and sub-acute inflammatory pain. GluN3A KO mice also showed enhanced recognition and spatial learning and memory functions. Hippocampal slices from juvenile and adult GluN3A KO mice showed greater long-term potentiation (LTP) compared with WT slices. GluN3A deletion resulted in increased expression of Ca(2+)/calmodulin-dependent kinase II (CaMKII) in the forebrain, and the phosphorylated CaMKII level upon LTP induction was significantly higher in the GluN3A KO hippocampus compared with WT controls. CaMKII inhibition abrogated the enhanced LTP in GluN3A KO slices. These data reveal for the first time that the presence of GluN3A may have profound impacts on several functional/behavioural activities in adult animals, and could be a therapeutic target for neurological disorders associated with NMDA receptor functions.

Activin Signaling Regulates Sertoli Cell Differentiation and Function

Throughout development, activin A signaling stimulates proliferation and inhibits differentiation of testicular Sertoli cells. A decline in activin levels at puberty corresponds with the differentiation of Sertoli cells that is required to sustain spermatogenesis. In this study, we consider whether terminally differentiated Sertoli cells can revert to a functionally immature phenotype in response to activin A. To increase systemic activin levels, the right tibialis anterior muscle of 7-wk-old C57BL/6J mice was transduced with an adeno-associated virus (rAAV6) expressing activin A. We show that chronic activin signaling reduces testis mass by 23.5% compared with control animals and induces a hypospermatogenic phenotype, consistent with a failure of Sertoli cells to support spermatogenesis. We use permeability tracers and transepithelial electrical resistance measurements to demonstrate that activin potently disrupts blood-testis-barrier function in adult mice and ablates tight junction formation in differentiated primary Sertoli cells, respectively. Furthermore, increased activin signaling reinitiates a program of cellular proliferation in primary Sertoli cells as determined by 5-ethynyl-2'-deoxyuridine incorporation. Proliferative cells reexpress juvenile markers, including cytokeratin-18, and suppress mature markers, including claudin-11. Thus, activin A is the first identified factor capable of reprogramming Sertoli cells to an immature, dedifferentiated phenotype. This study indicates that activin signaling must be strictly controlled in the adult in order to maintain Sertoli cell function in spermatogenesis.

Development of Interleukin-17-Producing γδ T Cells Is Restricted to a Functional Embryonic Wave

γδ Tcells are an important innate source of interleukin-17 (IL-17). In contrast to T helper 17 (Th17) cell differentiation, which occurs in the periphery, IL-17-producing γδ Tcells (γδT17 cells) are probably committed during thymic development. To study when γδT17 cells arise during ontogeny, we used TcrdH2BeGFP reporter mice to monitor Tcell receptor (TCR) rearrangement and IL-17 production in the embryonic thymus. We observed that several populations such as innate lymphoid cells and early Tcell precursors were able to produce IL-17 prior to (and thus independent of) TCR recombination. γδT17 cells were absent after transplantation of IL-17-sufficient bone marrow into mice lacking both Il17a and Il17f. Also, γδT17 cells were not generated after genetic restoration of defective Rag1 function in adult mice. Together, these data suggested that these cells developed exclusively before birth and subsequently persisted in adult mice as self-renewing, long-lived cells.

Postnatal inactivation reveals enhanced requirement for MeCP2 at distinct age windows

Rett Syndrome is a neurological disorder caused by mutations in the X-linked MECP2 gene. Mouse models where Mecp2 is inactivated or mutated recapitulate several features of the disorder and have demonstrated a requirement for the protein to ensure brain function in adult mice. We deleted the Mecp2 gene in ~80% of brain cells at three postnatal ages to determine whether the need for MeCP2 varies with age. Inactivation at all three time points induced Rett-like phenotypes and caused premature death of the animals. We find two threshold ages beyond which the requirement for MeCP2 markedly increases in stringency. The earlier threshold (8-14 weeks), when inactivated mice develop symptoms, represents early adulthood in the mouse and coincides with the period when Mecp2-null mice exhibit terminal symptoms. Unexpectedly, we identified a later age threshold (30-45 weeks) beyond which an 80% reduction in MeCP2 is incompatible with life. This finding suggests an enhanced role for MeCP2 in the aging brain.

Quercetin impairs the reproductive potential of male mice

Oxidative stress is a leading cause of male infertility. To combat this, germ cells and spermatozoa are endowed with various enzymes, vitamins and proteins. Certain other components of food, including bioflavonoids, also provide protection against free radicals. This study analysed the effect of quercetin, a bioflavonoid, on male reproductive function in adult mice, after intraperitoneal treatment with varying concentrations of quercetin (2, 8 and 20mgkg(-1) b.wt.) for 2weeks. Quercetin increased the generation of reactive oxygen species and lipid peroxidation in the testis with concomitant decrease in sperm count and motility in a dose-dependent manner. Activities of antioxidant enzymes catalase, superoxide dismutase and levels of reduced glutathione were found to be decreased in a dose-dependent manner. Also, the levels of oxidised glutathione were increased leading to a shift in redox ratio. The testicular histomorphology was also altered dose dependently. Germ cell kinetic study revealed significant loss of various germ cell populations with increasing dose of quercetin. Interestingly, there was a reduction in germinal epithelium thickness concomitant with an increase in seminiferous tubule lumen diameter. In conclusion, the deleterious effects of quercetin on germ cells could be attributed to its pro-oxidant ability that might affect the Sertoli cell functions.