C. elegans touch receptor neurons direct mechanosensory complex organization via repurposing conserved basal lamina proteins.

The sense of touch is conferred by the conjoint function of somatosensory neurons and skin cells. These cells meet across a gap filled by a basal lamina, an ancient structure found in metazoans. Using Caenorhabditis elegans, we investigate the composition and ultrastructure of the extracellular matrix at the epidermis and touch receptor neuron (TRN) interface. We show that membrane-matrix complexes containing laminin, nidogen, and the MEC-4 mechano-electrical transduction channel reside at this interface and are central to proper touch sensation. Interestingly, the dimensions and spacing of these complexes correspond with the discontinuous beam-like extracellular matrix structures observed in serial-section transmission electron micrographs. These complexes fail to coalesce in touch-insensitive extracellular matrix mutants and in dissociated neurons. Loss of nidogen reduces the density of mechanoreceptor complexes and the amplitude of the touch-evoked currents they carry. Thus, neuron-epithelium cell interfaces are instrumental in mechanosensory complex assembly and function. Unlike the basal lamina ensheathing the pharynx and body wall muscle, nidogen recruitment to the puncta along TRNs is not dependent upon laminin binding. MEC-4, but not laminin or nidogen, is destabilized by point mutations in the C-terminal Kunitz domain of the extracellular matrix component, MEC-1. These findings imply that somatosensory neurons secrete proteins that actively repurpose the basal lamina to generate special-purpose mechanosensory complexes responsible for vibrotactile sensing.

Cutaneous Superficial Basal Cell Carcinoma is a Basal Cell Carcinoma In Situ: Electron Microscopy of a Case Series of Basal Cell Carcinomas.

Basal cell carcinoma (BCC) is the most common skin cancer. Skin cancers may present either as a non-invasive tumor or an invasive malignancy. The terminology of carcinoma in situ is used when the tumor is either just limited to epidermis or not present as single cells or nests in the dermis. However, currently the terminology superficial BCC is inappropriately used instead of BCC in situ when the skin cancer is limited to epidermis. In this study we compare the pathologic changes of superficial, nodular, and infiltrative BCCs using electron microscopy to identify the ultrastructural characteristics and validate the previously proposed terminology. Three cases of BCC (superficial BCC, nodular BCC, and infiltrative BCC) diagnosed by dermatopathologists at our institute were selected for review. Paraffin block tissues from these cases were sent for electron microscopy studies which demonstrated disruption of basal lamina in both nodular and infiltrative type of BCC, while it remains intact in BCC superficial type after extensive examination. Therefore, similar to other in situ skin cancers, there is no invasion of the neoplasm in superficial BCC into the dermis. Hence, the older term superficial BCC should be appropriately replaced with the newer terminology BCC in situ.

Electron-translucency and partial defects of synaptic basal lamina in the electrocyte synapse of an electric ray (Narke japonica) in 3D embedment-free section electron microscopy.

The synaptic basal lamina of the electrocytes was disclosed to be electron-translucent to some extent when viewed in an en-face direction in embedment-free section transmission electron microscopy (EFS-TEM), and synaptic vesicles located close to the presynaptic membrane were seen through the synaptic basal lamina together with the presynaptic and postsynaptic membranes. This feature of translucency has the potential to analyze possible spatial interrelations in situ between bioactive molecules in the synaptic basal lamina and the synaptic vesicles in further studies. The synaptic basal lamina, appearing as an electron-dense line sandwiched by two parallel lines representing the presynaptic and postsynaptic membranes in ultrathin sections cut right to the synaptic junctional plane in conventional TEM, was not fully continuous but randomly intermittent along its trajectory. Compatible with the intermittent line appearance, the en-face 3D view in embedment-free section TEM revealed for the first time partial irregular defects of the synaptic basal lamina. Considering the known functional significance of several molecules contained in the synaptic basal lamina in the maintenance and exertion of the synapse, its partial defects may not represent its rigid structural features, but its immature structure under remodeling or its dynamic changes in consistency such as the sol/gel transition, whose validity needs further examination. RESEARCH HIGHLIGHTS: In embedment-free section TEM, a 3D en-face view of synaptic basal lamina in situ is reliably possible. The basal lamina en-face is electron-translucent, which makes it possible to analyze spatial interrelation between pre- and post-synaptic components. Partial irregular defects in the basal lamina are revealed in Torpedo electrocytes, suggesting its remodeling or dynamic changes in consistency.

Fibroblasts and polymer composition are essential for bioengineering of airway epithelium on nonwoven scaffolds.

To make tissue engineering a truly effective tool, it is necessary to understand how the patterns of specific tissue development are modulated by and depend on the artificial environment. Even the most advanced approaches still do not fully meet the requirements of practical engineering of tracheobronchial epithelium. This study aimed to test the ability of the synthetic and natural nonwoven scaffolds to support the formation of morphological sound airway epithelium including the basement membrane (BM). We also sought to identify the potential role of fibroblasts in this process. Our results showed that nonwoven scaffolds are generally suitable for producing well-differentiated tracheobronchial epithelium (with cilia and goblet cells), while the structure and functionality of the equivalents appeared to be highly dependent on the composition of the scaffolds. Unlike natural scaffolds, synthetic ones supported the formation of the epithelium only when epithelial cells were cocultured with fibroblasts. Fibroblasts also appeared to be obligatory for basal lamina formation, regardless of the type of the nonwoven material used. However, even in the presence of fibroblasts, the synthetic scaffolds were unable to support the formation of the epithelium and of the BM (in particular, basal lamina) as effectively as the natural scaffolds did.

Basal lamina: A novel pH regulator at the neuromuscular junction.

Proton concentration can change within the cleft during synaptic activity due to vesicular release and Ca2+ extrusion from cellular compartments. These changes within the synaptic cleft can impact neural activity by proton-dependent modulation of ion channel function. The pH transient differs in magnitude and direction between synapses, requiring different synapse types to be measured to generate a complete understanding of this mechanism and its impacts on physiology. With a focus on the mouse neuromuscular junction (NMJ), the recently published "Postsynaptic Calcium Extrusion at the Mouse Neuromuscular Junction Alkalinizes the Synaptic Cleft" measured synaptic cleft pH at a cholinergic synapse and found a biphasic pH transient. The study demonstrated that the changes in proton concentration found were due to postsynaptic signaling when measuring pH at the muscle membrane, despite the expectation of a presynaptic contribution. This result suggests a diffusional barrier within the NMJ isolates pH transients to presynaptic versus postsynaptic compartments. Generating a Donnan equilibrium that impacts protons, evidence suggests the basal lamina may be a key regulator of pH at the NMJ. Exploring synaptic pH, proton regulating factors, and downstream pH transient effects at presynaptic versus postsynaptic membranes may lead to new insight for a variety of diseases.

Peroxidasin is required for full viability in development and for maintenance of tissue mechanics in adults.

Basement membranes are thin strong sheets of extracellular matrix. They provide mechanical and biochemical support to epithelia, muscles, nerves, and blood vessels, among other tissues. The mechanical properties of basement membranes are conferred in part by Collagen IV (Col4), an abundant protein of basement membranes that forms an extensive two-dimensional network through head-to-head and tail-to-tail interactions. After the Col4 network is assembled into a basement membrane, it is crosslinked by the matrix-resident enzyme Peroxidasin to form a large covalent polymer. Peroxidasin and Col4 crosslinking are highly conserved throughout the animal kingdom, indicating they are important, but homozygous mutant mice have mild phenotypes. To explore the role of Peroxidasin, we analyzed mutants in Drosophila, including a new CRISPR-generated catalytic null, and found that homozygotes were mostly lethal with 13 % viable escapers. Mouse mutants also show semi-lethality, with Mendelian analysis demonstrating ∼50 % lethality and ∼50 % escapers. Despite the strong mutations, the homozygous fly and mouse escapers had low but detectable levels of Col4 crosslinking, indicating the existence of inefficient alternative crosslinking mechanisms, probably responsible for the viable escapers. Fly mutant phenotypes are consistent with decreased basement membrane stiffness. Interestingly, we found that even after basement membranes are assembled and crosslinked in wild-type animals, continuing Peroxidasin activity is required in adults to maintain tissue stiffness over time. These results suggest that Peroxidasin crosslinking may be more important than previously appreciated.

High-Resolution Imaging Mass Spectrometry of Human Donor Eye: Photoreceptors Cells and Basal Laminar Deposit of Age-Related Macular Degeneration.

Pathologies of the retina are clinically visualized in vivo with OCT and ex vivo with immunohistochemistry. Although both techniques provide valuable information on prognosis and disease state, a comprehensive method for fully elucidating molecular constituents present in locations of interest is desirable. The purpose of this work was to use multimodal imaging technologies to localize the vast number of molecular species observed with matrix-assisted laser desorption ionization imaging mass spectrometry (MALDI IMS) in aged and diseased retinal tissues. Herein, MALDI IMS was utilized to observe molecular species that reside in photoreceptor cells and also a basal laminar deposit from two human donor eyes. The molecular species observed to accumulate in these discrete regions can be further identified and studied to attempt to gain a greater understanding of biological processes occurring in debilitating eye diseases such as age-related macular degeneration (AMD).

Astrocytoma and glioblastoma IDH1-wildtype cells colonize tumor vessels and deploy vascular mimicry.

Gliomas are the most prevalent type of malignant brain tumors with a very dismal prognosis. Angiogenesis in glioma has recently gotten more attention and its molecular aspects have been published; however, these were not complemented with ultrastructural evidence. Our ultrastructural examination of glioma vessels reveals several unique and critical features related to their mechanisms of progression and metastasis strategy. The detailed ultrastructural survey of 18 isocitrate dehydrogenase-wildtype (IDH1-wt) glioblastomas and 12 isocitrate dehydrogenase-mutant (IDH1-mt) High-grade gliomas indicated that tumor vessels of both types had undergone deformities such as the thickening of the vessel wall (VW) and proliferation of the basement membrane, contour distortions, abnormal and discontinuous basal lamina, tumor cells' invasion and colonization of VW, disappearance of endothelial cells (ECs), pericytes, and smooth muscle cells, as well as the formation of a continuous ring of tumor cells attached to the luminal side of VW in numerous cases. The latter feature is a clear sign of vascular mimicry (VM) that was previously suggested in gliomas but never shown by TEM. Additionally, the vascular invasion was carried out by a large number of tumor cells and was accompanied by the accumulation of tumor lipids in the vessels' lumina and VWs; these two features are distinct for gliomas and may alter the course of the clinical presentation and overall prognosis. This raises the issue of how to specifically target tumor cells involved in vascular invasion in order to optimize prognosis and overcome these mechanisms employed by the tumor cells.

Expression of Basement Membrane Molecules by Wharton Jelly Stem Cells (WJSC) in Full-Term Human Umbilical Cords, Cell Cultures and Microtissues.

Wharton's jelly stem cells (WJSC) from the human umbilical cord (UC) are one of the most promising mesenchymal stem cells (MSC) in tissue engineering (TE) and advanced therapies. The cell niche is a key element for both, MSC and fully differentiated tissues, to preserve their unique features. The basement membrane (BM) is an essential structure during embryonic development and in adult tissues. Epithelial BMs are well-known, but similar structures are present in other histological structures, such as in peripheral nerve fibers, myocytes or chondrocytes. Previous studies suggest the expression of some BM molecules within the Wharton's Jelly (WJ) of UC, but the distribution pattern and full expression profile of these molecules have not been yet elucidated. In this sense, the aim of this histological study was to evaluate the expression of main BM molecules within the WJ, cultured WJSC and during WJSC microtissue (WJSC-MT) formation process. Results confirmed the presence of a pericellular matrix composed by the main BM molecules-collagens (IV, VII), HSPG2, agrin, laminin and nidogen-around the WJSC within UC. Additionally, ex vivo studies demonstrated the synthesis of these BM molecules, except agrin, especially during WJSC-MT formation process. The WJSC capability to synthesize main BM molecules could offer new alternatives for the generation of biomimetic-engineered substitutes where these molecules are particularly needed.

Factors Affecting Arbovirus Midgut Escape in Mosquitoes.

Arboviral diseases spread by mosquitoes cause significant morbidity and mortality throughout much of the world. The treatment and prevention of these diseases through medication and vaccination is often limited, which makes controlling arboviruses at the level of the vector ideal. One way to prevent the spread of an arbovirus would be to stop its vector from developing a disseminated infection, which is required for the virus to make its way to the saliva of the mosquito to be potentially transmitted to a new host. The midgut of the mosquito provides one such opportunity to stop an arbovirus in its tracks. It has been known for many years that in certain arbovirus-vector combinations, or under certain circumstances, an arbovirus can infect and replicate in the midgut but is unable to escape from the tissue to cause disseminated infection. This situation is known as a midgut escape barrier. If we better understand why this barrier occurs, it might aid in the development of more informed control strategies. In this review, we discuss how the midgut escape barrier contributes to virus-vector specificity and possible mechanisms that may allow this barrier to be overcome in successful virus-vector combinations. We also discuss several of the known factors that either increase or decrease the likelihood of midgut escape.

Melatonin signalling in Schwann cells during neuroregeneration.

It has widely been thought that in the process of nerve regeneration Schwann cells populate the injury site with myelinating, non-myelinating, phagocytic, repair, and mesenchyme-like phenotypes. It is now clear that the Schwann cells modify their shape and basal lamina as to accommodate re-growing axons, at the same time clear myelin debris generated upon injury, and regulate expression of extracellular matrix proteins at and around the lesion site. Such a remarkable plasticity may follow an intrinsic functional rhythm or a systemic circadian clock matching the demands of accurate timing and precision of signalling cascades in the regenerating nervous system. Schwann cells react to changes in the external circadian clock clues and to the Zeitgeber hormone melatonin by altering their plasticity. This raises the question of whether melatonin regulates Schwann cell activity during neurorepair and if circadian control and rhythmicity of Schwann cell functions are vital aspects of neuroregeneration. Here, we have focused on different schools of thought and emerging concepts of melatonin-mediated signalling in Schwann cells underlying peripheral nerve regeneration and discuss circadian rhythmicity as a possible component of neurorepair.

Diagnostic and prognostic role of protein and ultrastructural alterations at cell-extracellular matrix junctions in neoplastic progression of human oral malignancy.

Despite advancements in technology and increase in favorable outcomes associated with oral cancer, early detection remains the most significant factor in limiting mortality. The current study aimed to develop early diagnostic and prognostic markers for oral tumorigenesis. Protein and ultrastructural alterations at cell-extracellular matrix (ECM) adhesion junctions were examined concurrently using immunohistochemistry (IHC) and transmission electron microscopy (TEM) on progressive grade of oral carcinomas (n = 285). The expression of hemidesmosome (HD) proteins-integrin ß4, BP180, and laminin-5 increased in hyperplasia as compared to normal, and significantly increased further, as the disease progressed. TEM analysis in parallel tissues revealed a significant decrease in HD number and increase in the length of basal lamina (BL) in hyperplasia. With cancer progression, the severity of ultrastructural alterations increased gradually and significantly. Overexpression of HD proteins, decrease in HD number and increase in BL length significantly correlated with nodal metastasis, local recurrence, and recurrence-free survival of patients. Concurrent use of IHC and TEM can add value to early recognition of neoplastic changes in primary carcinomas of oral cavity. In this regard, altered expression of integrin ß4 and laminin-5, loss of HDs, and increased BL length could offer criteria for early diagnosis and prognosis of oral malignancy.

Myotendinous Junction: Exercise Protocols Can Positively Influence Their Development in Rats.

The myotendinous junction (MTJ) is an interface that different stimuli alter their morphology. One of the main stimuli to promote alterations in the MTJ morphology is physical exercise. The present study aimed to investigate the morphology and molecular MTJ adaptations of biceps brachii muscle in adult Wistar rats submitted to different ladder-based protocols. Forty Wistar rats (90 days old) were divided into four groups: Sedentary (S), Climbing (C), Overload Climbing (OC), Climbing, and Overload Climbing (COC). The results of light microscopy demonstrated the cell and collagen tissue reorganization in the experimental groups. The sarcomeres lengths of different regions showed a particular development according to the specific protocols. The sarcoplasmic invaginations and evaginations demonstrated positive increases that promoted the myotendinous interface development. In the extracellular matrix, the structures presented an increase principally in the COC group. Finally, the immunofluorescence analysis showed the telocytes disposition adjacent to the MTJ region in all experimental groups, revealing their network organization. Thus, we concluded that the different protocols contributed to the morphological adaptations with beneficial effects in distinct ways of tissue and cellular development and can be used as a model for MTJ remodeling to future proteomic and genetic analysis.

TNF-α regulates the composition of the basal lamina and cell-matrix adhesions in gingival epithelial cells.

Laminin 5, type 4 collagen, and α6ß4 integrin contribute to the formation of hemidesmosomes in the epithelia of periodontal tissues, which is critical for the development and maintenance of the dentogingival junction. As it is not known whether TNF-α alters the composition of the epithelial pericellular matrix, human gingival epithelial cells were cultured in the presence or absence of TNF-α. Treatment with TNF-α accelerated epithelial cell migration and closure of in vitro wounds. These data indicate unexpectedly, that TNF-α promotes the formation of the pericellular matrix around epithelial cells and enhances adhesion of epithelial cells to the underlying matrix, properties which are important for cell migration and the integrity of the dentogingival junction.

Folding of the syncytiotrophoblast basal plasma membrane increases the surface area available for exchange in human placenta.

INTRODUCTION: The placental syncytiotrophoblast is the primary barrier between the mother and the fetus. To cross the placenta, nutrients and wastes must be transported across the apical microvillous and basal plasma membranes. While the syncytiotrophoblast basal plasma membrane is typically represented as relatively smooth, it has been shown to have invaginations that may increase its surface area. This study aimed to quantify how folding of the syncytiotrophoblast basal membrane contributes to its surface area and to visualise three-dimensional structures of the basal membrane and cytotrophoblast cell structures. METHODS: Transmission electron microscope images of human term placenta were analysed using stereological approaches to quantify how folding of the syncytiotrophoblast basal plasma membrane affected surface area. Serial block-face scanning electron microscopy was used to visualise the three-dimensional structure of the syncytiotrophoblast basal membrane and cytotrophoblast cells. RESULTS: Syncytiotrophoblast basal membrane covered 69.1% of the basal lamina, with cytotrophoblast cells covering the remaining 30.9%. In basal lamina adjacent to syncytiotrophoblast, 34% was adjacent to smooth basal membrane and 66% to folded basal membrane. Syncytiotrophoblast basal membrane folds increased the surface area adjacent to basal lamina by 305%. Including regions overlying the cytotrophoblast cells, basal membrane folds increased syncytiotrophoblast basal membrane surface area by 4.4-fold relative to the basal lamina in terminal villi. Terminal and intermediate villi were similar in terms of trophoblast coverage of the basal lamina and basal membrane folding. The three-dimensional structures of the syncytiotrophoblast basal plasma membrane and cytotrophoblast cells were generated from serial block-face scanning electron microscopy image stacks. DISCUSSION: These findings indicate that the surface area of the syncytiotrophoblast basal plasma membrane is far larger than had been appreciated. We suggest that these folds increase the surface area available for transport to and from the fetus. Changes in the extent of basal membrane folding could affect nutrient transfer capacity and underlie pathological fetal growth, including fetal growth restriction and macrosomia.

Expression and localization of amelotin, laminin γ2 and odontogenesis-associated phosphoprotein (ODAPH) on the basal lamina and junctional epithelium.

At maturation stage of enamel development, a specialized basal lamina (sBL) was built between ameloblasts and enamel. After the teeth eruption, the ameloblasts transform into the inner cell layer of junctional epithelium. The inner cell layer forms the internal basal lamina of junctional epithelium. However, the composition of the sBL and internal basal lamina was not clarified. The objective of our study was to make a description of the localization of amelotin (AMTN), laminin γ2 (LAMC2) and Odontogenesis-associated phosphoprotein (ODAPH) on the sBL and internal basal lamina. In immunohistochemical study, AMTN, LAMC2 and ODAPH were detected on the sBL at maturation stage. AMTN was also detected in ameloblasts at maturation stage. The expression of AMTN decreased from early-to-late maturation stage. In contrast, the expression of LAMC2 and ODAPH was stable. Immunofluorescence double-staining showed the localization of AMTN was close to enamel surface. However, the localization of ODAPH was close to ameloblasts. LAMC2 and ODAPH were observed on internal basal lamina of junctional epithelium. In contrast, no expression of AMTN was detected on internal basal lamina of junctional epithelium. Our results suggested that ODAPH might participate in enamel maturation and periodontal health, which might provide a better understanding of enamel defects and periodontal disease in clinic.

Impact of metabolic disorders on the structural, functional, and immunological integrity of the blood-brain barrier: Therapeutic avenues.

Mounting evidence has linked the metabolic disease to neurovascular disorders and cognitive decline. Using a murine model of a high-fat high-sugar diet mimicking obesity-induced type 2 diabetes mellitus (T2DM) in humans, we show that pro-inflammatory mediators and altered immune responses damage the blood-brain barrier (BBB) structure, triggering a proinflammatory metabolic phenotype. We find that disruption to tight junctions and basal lamina due to loss of control in the production of matrix metalloproteinases (MMPs) and their inhibitors (TIMPs) causes BBB impairment. Together the disruption to the structural and functional integrity of the BBB results in enhanced transmigration of leukocytes across the BBB that could contribute to an initiation of a neuroinflammatory response through activation of microglia. Using a humanized in vitro model of the BBB and T2DM patient post-mortem brains, we show the translatable applicability of our results. We find a leaky BBB phenotype in T2DM patients can be attributed to a loss of junctional proteins through changes in inflammatory mediators and MMP/TIMP levels, resulting in increased leukocyte extravasation into the brain parenchyma. We further investigated therapeutic avenues to reduce and restore the BBB damage caused by HFHS-feeding. Pharmacological treatment with recombinant annexin A1 (hrANXA1) or reversion from a high-fat high-sugar diet to a control chow diet (dietary intervention), attenuated T2DM development, reduced inflammation, and restored BBB integrity in the animals. Given the rising incidence of diabetes worldwide, understanding metabolic-disease-associated brain microvessel damage is vital and the proposed therapeutic avenues could help alleviate the burden of these diseases.

Basal lamina changes in neurodegenerative disorders.

BACKGROUND: Neurodegenerative disorders are a group of age-associated diseases characterized by progressive degeneration of the structure and function of the CNS. Two key pathological features of these disorders are blood-brain barrier (BBB) breakdown and protein aggregation. MAIN BODY: The BBB is composed of various cell types and a non-cellular component---the basal lamina (BL). Although how different cells affect the BBB is well studied, the roles of the BL in BBB maintenance and function remain largely unknown. In addition, located in the perivascular space, the BL is also speculated to regulate protein clearance via the meningeal lymphatic/glymphatic system. Recent studies from our laboratory and others have shown that the BL actively regulates BBB integrity and meningeal lymphatic/glymphatic function in both physiological and pathological conditions, suggesting that it may play an important role in the pathogenesis and/or progression of neurodegenerative disorders. In this review, we focus on changes of the BL and its major components during aging and in neurodegenerative disorders, including Alzheimer's disease (AD), Parkinson's disease (PD), and amyotrophic lateral sclerosis (ALS). First, we introduce the vascular and lymphatic systems in the CNS. Next, we discuss the BL and its major components under homeostatic conditions, and summarize their changes during aging and in AD, PD, and ALS in both rodents and humans. The functional significance of these alterations and potential therapeutic targets are also reviewed. Finally, key challenges in the field and future directions are discussed. CONCLUSIONS: Understanding BL changes and the functional significance of these changes in neurodegenerative disorders will fill the gap of knowledge in the field. Our goal is to provide a clear and concise review of the complex relationship between the BL and neurodegenerative disorders to stimulate new hypotheses and further research in this field.

Contribution of Extracellular Matrix Component Landscapes in the Adult Subventricular Zone to the Positioning of Neural Stem/Progenitor Cells.

Neurogenesis persists in restricted regions of the adult brain, including the subventricular zone (SVZ). Adult neural stem cells (NSCs) in the SVZ proliferate and give rise to new neurons and glial cells depending on intrinsic and environmental cues. Among the multiple factors that contribute to the chemical, physical, and mechanical components of the neurogenic niche, we focused on the composition of the extracellular matrix (ECM) of vasculature and fractones in the SVZ. The SVZ consists of ECM-rich blood vessels and fractones during development and adulthood, and adult neural stem/progenitor cells (NS/PCs) preferentially attach to the laminin-rich basal lamina. To examine the ECM preference of adult NS/PCs, we designed a competition assay using cell micropatterning. Although both laminin and collagen type IV, which are the main components of basal lamina, act as physical scaffolds, adult NS/PCs preferred to adhere to laminin over collagen type IV. Interestingly, the ECM preference of adult NS/PCs could be manipulated by chemokines such as stromal-derived factor 1 (SDF1) and α6 integrin. As SDF1 re-routes NSCs and their progenitors toward the injury site after brain damage, these results suggest that the alteration in ECM preferences may provide a molecular basis for contextdependent NS/PC positioning.

Basal lamina characterization in frozen-thawed and long-term grafted human prepubertal ovarian tissue.

RESEARCH QUESTION: Are there differences in the composition and structure of the basal lamina surrounding follicles in prepubertal versus adult human ovarian tissue? DESIGN: Frozen-thawed human ovarian tissue from six prepubertal and seven adult patients was divided into three fragments in each case: two for non-grafted tissue evaluation and one for long-term xenografting to mice. Collagen IV and laminin expression were investigated by immunohistochemistry before and after grafting. The basal lamina was analysed by transmission electron microscopy on frozen-thawed tissue. RESULTS: In frozen-thawed tissue, collagen IV was significantly less expressed around prepubertal follicles than around adult follicles (primordial, P = 0.02; intermediate/growing follicles, P = 0.03), while laminin was significantly more expressed (primordial, P = 0.03; intermediate, P = 0.01). Collagen IV expression was significantly higher around prepubertal primordial follicles in grafted tissue than in non-grafted tissue, reaching similar levels to those in adult tissue. Ultrastructure analysis showed the basal lamina around follicles in prepubertal frozen-thawed tissue to be rather patchy and thinner than around adult follicles (primordial/intermediate, P = 0.001; primary, P = 0.02). CONCLUSIONS: In frozen-thawed tissue, the basal lamina around prepubertal follicles is less mature than around adult follicles, but it becomes similar in both prepubertal and adult subjects after grafting. Grafting could therefore induce maturation of the basal lamina around prepubertal follicles.