Ontogeny of Skin Stem Cells and Molecular Underpinnings.

Skin stem cells (SCs) play a pivotal role in supporting tissue homeostasis. Several types of SCs are responsible for maintaining and regenerating skin tissue. These include bulge SCs and others residing in the interfollicular epidermis, infundibulum, isthmus, sebaceous glands, and sweat glands. The emergence of skin SCs commences during embryogenesis, where multipotent SCs arise from various precursor populations. These early events set the foundation for the diverse pool of SCs that will reside in the adult skin, ready to respond to tissue repair and regeneration demands. A network of molecular cues regulates skin SC behavior, balancing quiescence, self-renewal, and differentiation. The disruption of this delicate equilibrium can lead to SC exhaustion, impaired wound healing, and pathological conditions such as skin cancer. The present review explores the intricate mechanisms governing the development, activation, and differentiation of skin SCs, shedding light on the molecular signaling pathways that drive their fate decisions and skin homeostasis. Unraveling the complexities of these molecular drivers not only enhances our fundamental knowledge of skin biology but also holds promise for developing novel strategies to modulate skin SC fate for regenerative medicine applications, ultimately benefiting patients with skin disorders and injuries.

Skin Development and Disease: A Molecular Perspective.

Skin, the largest organ in the human body, is a crucial protective barrier that plays essential roles in thermoregulation, sensation, and immune defence. This complex organ undergoes intricate processes of development. Skin development initiates during the embryonic stage, orchestrated by molecular cues that control epidermal specification, commitment, stratification, terminal differentiation, and appendage growth. Key signalling pathways are integral in coordinating the development of the epidermis, hair follicles, and sweat glands. The complex interplay among these pathways is vital for the appropriate formation and functionality of the skin. Disruptions in multiple molecular pathways can give rise to a spectrum of skin diseases, from congenital skin disorders to cancers. By delving into the molecular mechanisms implicated in developmental processes, as well as in the pathogenesis of diseases, this narrative review aims to present a comprehensive understanding of these aspects. Such knowledge paves the way for developing innovative targeted therapies and personalised treatment approaches for various skin conditions.

Fatal misdiagnosis of progressive disseminated histoplasmosis.

Disseminated histoplasmosis is the form of a mycosis caused by the fungus Histoplasma capsulatum that mainly occurs in immunosuppressed hosts, usually with non-specific symptoms. In non-endemic areas, where the disease is rarely involved in the differential diagnosis, a delay in treatment may lead to severe medical complications. Due to the rising prevalence of disseminated histoplasmosis in these areas, a thorough medical history is regarded as the decisive factor in prompt diagnosis of the disease. We, herein, report the case of an immunocompetent Greek farmer with disseminated histoplasmosis whose condition was initially misdiagnosed, and the consequential inadequate treatment led to his death.

Genetic Identity of Neural Crest Cell Differentiation in Tissue and Organ Development.

The neural crest (NC), also known as the "fourth germ layer", is an embryonic structure with important contributions to multiple tissue and organ systems. Neural crest cells (NCCs) are subjected to epithelial to mesenchymal transition and migrate throughout the embryo until they reach their destinations, where they differentiate into discrete cell types. Specific gene expression enables this precise NCCs delamination and colonization potency in distinct and diverse locations therein. This review aims to summarize the current experimental evidence from multiple species into the NCCs specifier genes that drive this embryo body axes segmentation. Additionally, it attempts to filter further into the genetic background that produces these individual cell subpopulations. Understanding the multifaceted genetic makeup that shapes NC-related embryonic structures will offer valuable insights to researchers studying organogenesis and disease phenotypes arising from dysmorphogenesis.

The Impact of Lifestyle on the Secondary Sex Ratio: A Review.

The secondary sex ratio (SSR), indicating the ratio of male to female live births, has garnered considerable attention within the realms of reproductive biology and public health. Numerous factors have been posited as potential trendsetters of the SSR. Given the extensive research on the impact of daily behaviors and habits on individuals' reproductive health, there is a plausible suggestion that lifestyle choices may also influence the SSR. By synthesizing the existing literature on the current research field, this comprehensive review indicates that an elevated SSR has been associated with an increased intake of fatty acids and monosaccharides, proper nutrition, higher educational levels, financial prosperity, and favorable housing conditions. On the other hand, a decreased SSR may be linked to undernutrition, socioeconomic disparities, and psychological distress, aligning with the Trivers-Willard hypothesis. Occupational factors, smoking habits, and cultural beliefs could also contribute to trends in the SSR. Our review underscores the significance of considering the aforementioned factors in studies examining the SSR and emphasizes the necessity for further research to unravel the mechanisms underpinning these connections. A more profound comprehension of SSR alterations due to lifestyle holds the potential to adequately develop public health interventions and healthcare strategies to enhance reproductive health and overall well-being.

Effects of hazardous chemicals on secondary sex ratio: A comprehensive review.

The secondary sex ratio (SSR), defined as the ratio of male to female offspring at birth, has garnered significant scientific interest due to its potential impact on population dynamics and evolution. In recent years, there has been a growing concern regarding the potential consequences of environmental chemicals on the SSR, given their widespread exposure and potential enduring ramifications on the reproductive system. While SSR serves as an indicator of health, ongoing research and scientific inquiry are being conducted to explore the potential relationship between chemicals and offspring ratio. Although some studies have suggested a possible correlation, others have yielded inconclusive results, indicating that the topic is intricate and still needs to be elucidated. The precise mechanism by which chemical agents exert their influence on the SSR remains ambiguous, with disruption of the endocrine system being a prominent justification. In light of the complex interplay between chemical exposure and SSR, the present review aims to comprehensively examine and synthesize existing scientific literature to gain a deeper understanding of how specific chemical exposures may impact SSR. Insights into chemical hazards that shift SSR patterns or trends could guide prevention strategies, including legislative bans of certain chemicals, to minimize environmental and public health risks.

Clinical and Genetic Correlation in Neurocristopathies: Bridging a Precision Medicine Gap.

Neurocristopathies (NCPs) encompass a spectrum of disorders arising from issues during the formation and migration of neural crest cells (NCCs). NCCs undergo epithelial-mesenchymal transition (EMT) and upon key developmental gene deregulation, fetuses and neonates are prone to exhibit diverse manifestations depending on the affected area. These conditions are generally rare and often have a genetic basis, with many following Mendelian inheritance patterns, thus making them perfect candidates for precision medicine. Examples include cranial NCPs, like Goldenhar syndrome and Axenfeld-Rieger syndrome; cardiac-vagal NCPs, such as DiGeorge syndrome; truncal NCPs, like congenital central hypoventilation syndrome and Waardenburg syndrome; and enteric NCPs, such as Hirschsprung disease. Additionally, NCCs' migratory and differentiating nature makes their derivatives prone to tumors, with various cancer types categorized based on their NCC origin. Representative examples include schwannomas and pheochromocytomas. This review summarizes current knowledge of diseases arising from defects in NCCs' specification and highlights the potential of precision medicine to remedy a clinical phenotype by targeting the genotype, particularly important given that those affected are primarily infants and young children.

Detecting Apoptotic Human Lens Epithelial Cells With Transmission Electron Microscopy.

Introduction Cataract formation is a prevalent issue worldwide, and understanding the cellular processes involved is crucial to advancing treatment options. The scope of the study was to explore the presence of apoptotic cells in the lens epithelium of Greek patients with senile cataracts using transmission electron microscopy (TEM). Methods Twenty-one patients with senile cataracts were included in this cross-sectional study, and their anterior lens capsules were thoroughly examined. The presence of apoptosis was ultrastructurally investigated, and its association with age, gender, biomicroscopic type of cataract, the coexistence of exfoliation syndrome (XFS), diabetes mellitus, and glaucoma was statistically correlated. Results We detected apoptotic cells in nine of the 21 patients. Morphological features indicative of apoptosis in the nuclei included degradation, nuclear membrane irregularity, reduction of nuclear volume, condensation, and margination of chromatin. The cytoplasm either appeared denser or contained vacuoles. Budding with membrane blebbing and pinopode-like projections were frequently observed. Apoptotic cells appeared smaller, exhibiting loose connections with neighboring cells and the basement membrane (BM). Interestingly, apoptotic bodies were also detected. Conclusions None of the examined risk factors showed a connection to apoptosis, whereas neighboring lens epithelial cells (LECs) phagocytose apoptotic bodies, seemingly assumed the role of macrophages. Comparing apoptosis rates between populations with different sun exposure levels could help reveal the relationship between ultraviolet B radiation exposure, apoptosis, and cataract formation.

Histological Alterations in Hashimoto's Disease: A Case-Series Ultrastructural Study.

BACKGROUND: Hashimoto's thyroiditis (HT) is an autoimmune disease exhibiting stromal fibrosis and follicular cell destruction due to lymphoplasmacytic infiltration. Besides deprecated analyses, histopathological approaches have not employed the use of electron microscopy adequately toward delineating subcellular-level interactions. METHODS: Biopsies for ultrastructural investigations were obtained from the thyroids of five patients with HT after a thyroidectomy. Transmission electron microscopy (TEM) was utilized to study representative tissue specimens. RESULTS: Examination indicated interstitial extravasated blood cells and a plethora of plasma cells, based on their subcellular identity landmarks. These antibody-secreting cells were profoundly spotted near follicular cells, fibroblasts, and cell debris entrenched in collagenous areas. Pathological changes persistently affected subcellular components of the thyrocytes, including the nucleus, endoplasmic reticulum (ER), Golgi apparatus, mitochondria, lysosomes, and other intracellular vesicles. Interestingly, significant endothelial destruction was observed, specifically in the larger blood vessels, while the smaller vessels appeared comparatively unaffected. CONCLUSIONS: Our TEM findings highlight the immune-related alterations occurring within the thyroid stroma. The impaired vasculature component and remodeling have not been described ultrastructurally before; thus, further exploration is needed with regards to angiogenesis in HT in order to achieve successful prognostic, diagnostic, and treatment-monitoring strategies.

CNS Border-Associated Macrophages: Ontogeny and Potential Implication in Disease.

Being immune privileged, the central nervous system (CNS) is constituted by unique parenchymal and non-parenchymal tissue-resident macrophages, namely, microglia and border-associated macrophages (BAMs), respectively. BAMs are found in the choroid plexus, meningeal and perivascular spaces, playing critical roles in maintaining CNS homeostasis while being phenotypically and functionally distinct from microglial cells. Although the ontogeny of microglia has been largely determined, BAMs need comparable scrutiny as they have been recently discovered and have not been thoroughly explored. Newly developed techniques have transformed our understanding of BAMs, revealing their cellular heterogeneity and diversity. Recent data showed that BAMs also originate from yolk sac progenitors instead of bone marrow-derived monocytes, highlighting the absolute need to further investigate their repopulation pattern in adult CNS. Shedding light on the molecular cues and drivers orchestrating BAM generation is essential for delineating their cellular identity. BAMs are receiving more attention since they are gradually incorporated into neurodegenerative and neuroinflammatory disease evaluations. The present review provides insights towards the current understanding regarding the ontogeny of BAMs and their involvement in CNS diseases, paving their way into targeted therapeutic strategies and precision medicine.

Effects of Whole-Body Vibration and Manually Assisted Locomotor Therapy on Neurotrophin-3 Expression and Microglia/Macrophage Mobilization Following Thoracic Spinal Cord Injury in Rats.

Microglial cells play an important role in neuroinflammation and secondary damages after spinal cord injury (SCI). Progressive microglia/macrophage inflammation along the entire spinal axis follows SCI, and various factors may determine the microglial activation profile. Neurotrophin-3 (NT-3) is known to control the survival of neurons, the function of synapses, and the release of neurotransmitters, while also stimulating axon plasticity and growth. We examined the effects of whole-body vibration (WBV) and forms of assisted locomotor therapy, such as passive flexion-extension (PFE) therapy, at the neuronal level after SCI, with a focus on changes in NT-3 expression and on microglia/macrophage reaction, as they play a major role in the reconstitution of CNS integrity after injury and they may critically account for the observed structural and functional benefits of physical therapy. More specifically, the WBV therapy resulted in the best overall functional recovery when initiated at day 14, while inducing a decrease in Iba1 and the highest increase in NT-3. Therefore, the WBV therapy at the 14th day appeared to be superior to the PFE therapy in terms of recovery. Functional deficits and subsequent rehabilitation depend heavily upon the inflammatory processes occurring caudally to the injury site; thus, we propose that increased expression of NT-3, especially in the dorsal horn, could potentially be the mediator of this favorable outcome.

Hypoxia Promotes Cartilage Regeneration in Cell-Seeded 3D-Printed Bioscaffolds Cultured with a Bespoke 3D Culture Device.

In this study, we investigated the effect of oxygen tension on the expansion of ADMSCs and on their differentiation toward their chondrocytic phenotype, regenerating a lab-based cartilaginous tissue with superior characteristics. Controversial results with reference to MSCs that were cultured under different hypoxic levels, mainly in 2D culturing settings combined with or without other biochemical stimulus factors, prompted our team to study the role of hypoxia on MSCs chondrogenic differentiation within an absolute 3D environment. Specifically, we used 3D-printed honeycomb-like PCL matrices seeded with ADMSCs in the presence or absence of TGF and cultured with a prototype 3D cell culture device, which was previously shown to favor nutrient/oxygen supply, cell adhesion, and infiltration within scaffolds. These conditions resulted in high-quality hyaline cartilage that was distributed uniformly within scaffolds. The presence of the TGF medium was necessary to successfully produce cartilaginous tissues with superior molecular and increased biomechanical properties. Despite hypoxia's beneficial effect, it was overall not enough to fully differentiate ADMSCs or even promote cell expansion within 3D scaffolds alone.

Origin and Emergence of Microglia in the CNS-An Interesting (Hi)story of an Eccentric Cell.

Microglia belong to tissue-resident macrophages of the central nervous system (CNS), representing the primary innate immune cells. This cell type constitutes ~7% of non-neuronal cells in the mammalian brain and has a variety of biological roles integral to homeostasis and pathophysiology from the late embryonic to adult brain. Its unique identity that distinguishes its "glial" features from tissue-resident macrophages resides in the fact that once entering the CNS, it is perennially exposed to a unique environment following the formation of the blood-brain barrier. Additionally, tissue-resident macrophage progenies derive from various peripheral sites that exhibit hematopoietic potential, and this has resulted in interpretation issues surrounding their origin. Intensive research endeavors have intended to track microglial progenitors during development and disease. The current review provides a corpus of recent evidence in an attempt to disentangle the birthplace of microglia from the progenitor state and underlies the molecular elements that drive microgliogenesis. Furthermore, it caters towards tracking the lineage spatiotemporally during embryonic development and outlining microglial repopulation in the mature CNS. This collection of data can potentially shed light on the therapeutic potential of microglia for CNS perturbations across various levels of severity.

Addressing Spaceflight Biology through the Lens of a Histologist-Embryologist.

Embryogenesis and fetal development are highly delicate and error-prone processes in their core physiology, let alone if stress-associated factors and conditions are involved. Space radiation and altered gravity are factors that could radically affect fertility and pregnancy and compromise a physiological organogenesis. Unfortunately, there is a dearth of information examining the effects of cosmic exposures on reproductive and proliferating outcomes with regard to mammalian embryonic development. However, explicit attention has been given to investigations exploring discrete structures and neural networks such as the vestibular system, an entity that is viewed as the sixth sense and organically controls gravity beginning with the prenatal period. The role of the gut microbiome, a newly acknowledged field of research in the space community, is also being challenged to be added in forthcoming experimental protocols. This review discusses the data that have surfaced from simulations or actual space expeditions and addresses developmental adaptations at the histological level induced by an extraterrestrial milieu.

Valproic acid induced selective apoptosis of ocular fibrous tunic in mice fetuses.

BACKGROUND: Valproic acid (VPA), a prescribed drug commonly used for various neurological perturbations, has been implicated in teratogenic inflictions on developing fetuses during pregnancy. The purpose of this research was to delineate the gross morphological and histological effects of VPA in the developing eye tunics and lens. METHODS: A time-dependent administration of 500 mg/kg VPA to BALB/c groups of female mice was coordinated during organogenesis (gestational days 7, 8, and 9) and compared to controls that received normal saline. Seized fetuses were checked for macroscopic eye anomalies, histological malformations with Azan trichrome staining, and levels of apoptotic activity with the terminal deoxynucleotidyl transferase-mediated nick end labeling (TUNEL) assay. RESULTS: Histochemical analysis showed that VPA-treated groups exhibited collagen deficiency (2.5-50% decrease in aniline blue intensity) and a marked increase in TUNEL-positive cells (p < .05) in corneal stroma and sclera/choroid layers while less was detected in retina and lens, when compared to controls. CONCLUSIONS: Since the evaluation of the inner structures did not manifest major differences, we conclude that VPA teratogenic influence display eclectic toxicity, as seen by increased apoptosis to eye layers with high degree fibrous context, particularly the outer tunics.

Congenital Herpes Simplex Virus: A Histopathological View of the Placenta.

Congenital Herpes simplex virus (HSV) infection is considered a common pregnancy pathology that is not always easy to diagnose. This study aimed to present the spectrum of placental histopathological lesions in pregnancies complicated by HSV infection. MEDLINE and Google Scholar databases were searched using the keywords "HSV" and "placental histopathology" up to June 20, 2022. Study inclusion required presenting placental histopathological anomalies in pregnant women diagnosed with HSV infection antenatally, during labor, or postnatally. Herein, we briefly present placental pathogenesis conditions, which have been correlated with congenital HSV infection, providing clinicians with a short review describing herpetic placental pathology.

Developmental Cues and Molecular Drivers in Myelinogenesis: Revisiting Early Life to Re-Evaluate the Integrity of CNS Myelin.

The mammalian central nervous system (CNS) coordinates its communication through saltatory conduction, facilitated by myelin-forming oligodendrocytes (OLs). Despite the fact that neurogenesis from stem cell niches has caught the majority of attention in recent years, oligodendrogenesis and, more specifically, the molecular underpinnings behind OL-dependent myelinogenesis, remain largely unknown. In this comprehensive review, we determine the developmental cues and molecular drivers which regulate normal myelination both at the prenatal and postnatal periods. We have indexed the individual stages of myelinogenesis sequentially; from the initiation of oligodendrocyte precursor cells, including migration and proliferation, to first contact with the axon that enlists positive and negative regulators for myelination, until the ultimate maintenance of the axon ensheathment and myelin growth. Here, we highlight multiple developmental pathways that are key to successful myelin formation and define the molecular pathways that can potentially be targets for pharmacological interventions in a variety of neurological disorders that exhibit demyelination.

The inhibitory effect of tocilizumab on systemic bone loss and tendon inflammation in a juvenile Collagen-Induced arthritis rat model.

PURPOSE OF THE STUDY: Reduced Bone Mineral Density (BMD) is a prevalent comorbidity in Juvenile Idiopathic Arthritis (JIA). Enthesitis and other tendon abnormalities, such as tenosynovitis, tendinitis and tendon ruptures are, also, common extra-articular manifestations of the disease. The aim of the present study was to investigate the effect of tocilizumab, an antibody that binds the Interleukin-6 (IL-6) Receptor, on inflammation-related bone loss and tendon inflammation in an animal model of JIA. MATERIALS AND METHODS: The Collagen-Induced Arthritis (CIA) model was induced in male rats followed by intraperitoneal administration of tocilizumab for 8 weeks. Methotrexate, the most widely used Disease-Modifying Antirheumatic Drug in the management of JIA, was, also, administered, either as a monotherapy or as an add-on therapy to tocilizumab. BMD was evaluated with Micro-Computed Tomography (Micro-CT) and histopathological examination. Tendon damage was, also, assessed histologically. Finally, two pro-inflammatory cytokines, Tumor Necrosis Factor-alpha (TNF-a) and Interleukin-23 (IL-23) were quantified in tendon tissues by ELISA analysis. RESULTS: Tocilizumab-treated animals exhibited a significantly improved trabecular microarchitecture on micro-CT analysis and histological examination. Tendon morphology was also improved. Anti-IL-6 treatment led to a significant decrease in TNF-a and IL-23 expression in tendon tissue. CONCLUSIONS: The results of the present study provide evidence that tocilizumab reduces inflammation-related bone loss and suppresses tendon inflammation in a juvenile CIA rat model. These findings offer perspectives for the management of osteoporosis and enthesitis in JIA.

Infliximab and Tocilizumab Reduce Anxiety-Like Behaviour and Improve Cognitive Performance in a Juvenile Collagen-Induced Arthritis Rat Model.

Anxiety disorders and cognitive decline are highly prevalent in rheumatic diseases, including Juvenile Idiopathic Arthritis (JIA). In this study, we investigated the effect of long-term treatment with infliximab and tocilizumab on anxiety-like behaviour and cognitive performance in a juvenile collagen-induced arthritis (CIA) rat model. Forty-nine rats with established moderate arthritis were randomly allocated into 7 equal groups: negative control, vehicle, methotrexate, infliximab, tocilizumab, methotrexate + infliximab and methotrexate + tocilizumab groups. Behavioural tests were performed to evaluate anxiety-like behaviour and cognitive function. Neuropathological changes were investigated by histological examination at the level of the hippocampus, the amygdala and the prefrontal cortex. Also, the expression of Brain-Derived Neurotrophic Factor (BDNF), a biomarker associated with neuronal survival and plasticity, was determined in the hippocampus and the amygdala by RT-qPCR. We found that both infliximab and tocilizumab reduced anxiety-like behaviour in the elevated-plus and elevated-zero maze tests. Tocilizumab, also, improved cognitive function in the olfactory social memory and passive avoidance tests. Anti-cytokine treatment reversed the histopathological changes in the brain induced by CIA. BDNF expression was higher in all treatment groups and especially those receiving monoclonal antibodies combined with methotrexate. Our data provide evidence that chronic infliximab and tocilizumab treatment reduces anxiety-like behaviour, improves cognitive function, reverses neuropathological changes and increases central BDNF expression in a juvenile arthritis rat model. These findings may be translated to humans to address behavioural comorbidities associated with JIA.

Effects of long-term infliximab and tocilizumab treatment on anxiety-like behavior and cognitive function in naive rats.

BACKGROUND: Circulating cytokines have been proposed to be implicated in the development of mood disorders and cognitive impairment. This study aims to examine the effect of chronic treatment with infliximab, a tumor necrosis factor-alpha (TNF-alpha) inhibitor, and tocilizumab, an antibody against interleukin-6 (IL-6) receptor on anxiety-like behavior and cognitive function. METHODS: Twenty-eight male, Wistar rats were randomly allocated into negative control, vehicle, infliximab and tocilizumab groups. After 8 weeks of intraperitoneal drug administration, rats performed the elevated-plus maze, the elevated-zero maze, the olfactory social memory and the passive avoidance tests. Brain sections at the level of the hippocampus, the amygdala and the prefrontal cortex were histologically examined. Finally, hippocampal and amygdaloid brain-derived neurotrophic factor (BDNF) expression was determined by reverse transcription-quantitative polymerase chain reaction (RT-qPCR). RESULTS: Infliximab group exhibited a significantly higher number of entries and time spent into the open arms of the mazes, showing a lower level of anxiety. In the olfactory social memory test, tocilizumab significantly increased the ratio of interaction. Both infliximab- and tocilizumab-treated animals had a significantly lower latency time in the passive avoidance test that suggests an improved memory. Histological examination revealed similar morphology and neuronal density between groups. BDNF expression levels were significantly increased in the groups receiving anti-cytokine treatment. CONCLUSIONS: Our findings suggest that long-term peripheral TNF-alpha and IL-6 inhibition improves anxiety and cognitive function in rats and leads to an increased BDNF expression in the brain.