Assessment of potential genetic markers for diabetic foot ulcer among Moscow residents.

PURPOSE: Diabetic foot ulcer (DFU) is one of the most severe complications of type 2 diabetes, which is manifested in chronic skin ulcers of lower extremities. DFU treatment remains complex and expensive despite the availability of well-established protocols. Early prediction of potential DFU development at the onset of type 2 diabetes can greatly improve the aftermath of this complication. METHODS: To assess potential genetic markers for DFU, a group of diabetic patients from Moscow region with and without DFU was genotyped for a number of SNPs previously reported to be associated with the DFU. RESULTS: Obtained results did not confirm previously claimed association of rs1024611, rs3918242, rs2073618, rs1800629, rs4986790, rs179998, rs1963645 and rs11549465 (respectively, in MCP1, MMP9, TNFRSF11B, TNFα, TLR4, eNOS, NOS1AP and HIF1α genes) with the DFU. Surprisingly, the t allele of rs7903146 in the TCF7l2 gene known as one of the most prominent risk factors for type 2 diabetes has shown a protective effect on DFU with OR(95%) = 0.68(0.48-0.96). CONCLUSION: Non-replication of previously published SNP associations with DFU suggests that the role of genetic factors in the DFU onset is either highly variable in different populations or is not as significant as the role of non-genetic factors.

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.

Effect of collagen denaturation degree on mechanical properties and biological activity of nanofibrous scaffolds.

Further progress in regenerative medicine and bioengineering highly depends on the development of 3D polymeric scaffolds with active biological properties. The most attention is paid to natural extracellular matrix components, primarily collagen. Herein, nonwoven nanofiber materials with various degrees of collagen denaturation and fiber diameters 250-500 nm were produced by electrospinning, stabilized by genipin, and characterized in detail. Collagen denaturation has been confirmed using DSC and FTIR analysis. The comparative study of collagen and gelatin nonwoven materials (NWM) revealed only minor differences in their biocompatibility with skin fibroblasts and keratinocytes in vitro. In long-term subcutaneous implantation study, the inflammation was less evident on collagen than on gelatin NWM. Remarkably, the pronounced calcification was revealed in the collagen NWM only. The results obtained can be useful in terms of improving the electrospinning technology of collagen from aqueous solutions, as well as emphasize the importance of long-term study to ensure proper implementation of the material, taking into account the ability of collagen to provoke calcification.

Nonwoven spidroin materials as scaffolds for ex vivo cultivation of aortic fragments and dorsal root ganglia.

Recombinant spidroins (RS; the analogues of silk proteins of spider's web) have multiple properties beneficial for bioengineering, including their suitability for electrospinning and thus, for production of materials with oriented fibers. This makes RS-based matrices potentially effective in stimulating regeneration of peripheral nerves. The restoration of injured nerves also depends on prompt regrowth of blood vessels. Therefore, prospective scaffold materials for neuro-regenerative therapy should positively affect both the nerves and the blood vessels. Currently, the experimental models suitable for culturing and quantitative assessment of the vascular and neuronal cells on the same material are lacking. Here, we assessed the suitability of electrospun RS-based matrices for cultivation of the mouse aorta and dorsal root ganglia (DRG) explants. We also quantified the effects of matrix topography upon both types of tissues. The RS-based materials have effectively supported aortic explants survival and sprouting. The cumulative length of endothelial sprouts on rS1/9-coated inserts was significantly higher as compared to type I collagen coatings, suggesting stimulatory effects on angiogenesis in vitro. In contrast to matrices with random fibers, on matrices with parallel fibers the migration of both smooth muscle and endothelial cells was highly oriented. Furthermore, alignment of RS fibers effectively directs the growth of axons and the migration of Schwann cells from DRGs. Thus, the electrospun RS matrices are highly suitable to culture both, the DRGs and aortic explants and to study the effects of matrix topography on cell migration. This model has a high potential for further endeavor into interactions of nerve and vascular cells and tissues.

Dual nature of mouse periderm structure, function and fate.

The periderm is the outer layer of embryonic skin, which is essential for the development of the epidermis and the establishment of its barrier function. In humans, the periderm is a monolayer and is shed prenatally. The structure and fate of the mouse periderm remain puzzling. Using electron microscopy of mouse skin between the embryonic day 14.5 and the postnatal Day 2, we have assessed the periderm structure and its shedding patterns. In contrast to human periderm, the mouse periderm appears to be bilayered, comprising a presumably absorptive outer periderm with numerous microvilli and an inner periderm packed with specific (glycogen-containing?) granules. The desmosomes between the inner periderm and the underlying epidermis are scarce, and they are totally absent between the inner and the outer periderm. The inner and outer periderms in mice are shed at different stages of development: the outer periderm is shed in utero in conjunction with barrier acquisition (E16-18), while the inner periderm is retained postnatally. We assume that the bilayered structure of the mouse periderm and the postnatal retention of its inner layer represent the evolutionary adaptations in ancestral rodents which helps altricial newborns of their extant descendants to cope with acute dehydration right after birth and/or provides a substrate for proper bacterial colonization of newborn skin.

Mechanisms driving the initiation and direction of endothelial sprouting in organotypic co-culture of aorta and spinal cord tissues.

The resumption of blood supply in spinal cord (SC) after injury is a prerequisite of its recovery. To expose the mechanisms of damaged SC revascularization we have used an organotypic SC/aortic fragments (AF) co-culture where, as we showed previously, damaged SC tissue induces AF cell sprouting but repels them away. Supplementation of culture medium with exogenous VEGF-A165 redirects the migrating aortic endothelial cells towards SC tissue. This effect and the pattern of sFlt1 expression (a soluble form of VEGFR1) suggest that the low level of SC-secreted VEGF and the presence of sFlt1 in SC slices together prevent the migration of aortic CD31+ cells to the SC in the absence of exogenous VEGF. VEGF-A165 supplementation sequesters this inhibitory activity of sFlt1 by direct binding thus allowing CD31+ cell migration in to SC tissue. Proteome analysis has shown that migration/proliferation of CD31+ and αSMA+ aortic cells in neuronal culture medium used in our SC/AF model (which obstruct sprouting by itself) was resumed by combined action of several pro- (aFGF, bFGF, Osteopontin, TF, IGFBP2, SDF1) and anti-angiogenic (Endostatin/Collagen18) factors. The mutual influence of AF and SC tissues is a key factor balancing these factors and thus driving endothelial sprouting in SC injury zone.

Sodium alginate-based composites as a collagen substitute for skin bioengineering.

The skin is a combination of two different types of tissue-epithelial and connective (mesenchymal). The outer protective layer of the skin, the epidermis, consists of multiple layers of keratinocytes residing on the basement membrane that separates them from the underlying dermis, which consists of a well-vascularized fibrous extracellular matrix seeded mainly by fibroblasts and mesenchymal stromal cells. These skin features suggest that the development of a fibroblast-friendly porous scaffold covered with a flat dense sheath mimicking the basement membrane, and sufficient to support keratinocyte attachment, would be a reasonable approach in the generation of clinically-relevant skin substitutes useful for reconstructive dermatology and burn treatment. Therefore, we developed a procedure to obtain biocompatible composite bilayer scaffolds comprising a spongy dermis-like body (supporting vascularization and appropriate fibroblast and multipotent stromal cell activity) fused with a film-like cover (supporting keratinocyte attachment, growth and differentiation). The sodium alginate (SA), an algae-derived biopolymer, has been used as a base component for these scaffolds while collagen (CL) and fibrinogen (FG) were used as minor additives in variable concentrations. The slow rates of composite SA-based scaffold biodegradation were achieved by using Ba2+ as cross-linking cations. By manipulating the SA/CL/FG ratio we managed to obtain sponge scaffolds with highly interconnected porous structures, with an average pore size ranging from 60 to 300 µm, and sufficient tensile strength (3.12-5.26 MPa). The scaffolds biocompatibility with the major human skin cell types was confirmed by seeding the scaffold sponge compartment with primary skin fibroblasts and subcutaneous adipose-derived stromal cells while the film side biocompatibility was tested using primary human keratinocytes. The obtained results have shown that bilayer alginate-based scaffolds have biological and mechanical properties comparable with CL scaffolds but surpass them in cost efficiency and vascularization ability in the subcutaneous implantation model in laboratory mice.

Non-woven bilayered biodegradable chitosan-gelatin-polylactide scaffold for bioengineering of tracheal epithelium.

OBJECTIVES: The conversion of tissue engineering into a routine clinical tool cannot be achieved without a deep understanding of the interaction between cells and scaffolds during the process of tissue formation in an artificial environment. Here, we have investigated the cultivation conditions and structural features of the biodegradable non-woven material in order to obtain a well-differentiated human airway epithelium. MATERIALS AND METHODS: The bilayered scaffold was fabricated by electrospinning technology. The efficiency of the scaffold has been evaluated using MTT cell proliferation assay, histology, immunofluorescence and electron microscopy. RESULTS: With the use of a copolymer of chitosan-gelatin-poly-l-lactide, a bilayered non-woven scaffold was generated and characterized. The optimal structural parameters of both layers for cell proliferation and differentiation were determined. The basal airway epithelial cells differentiated into ciliary and goblet cells and formed pseudostratified epithelial layer on the surface of the scaffold. In addition, keratinocytes formed a skin equivalent when seeded on the same scaffold. A comparative analysis of growth and differentiation for both types of epithelium was performed. CONCLUSIONS: The structural parameters of nanofibres should be selected experimentally depending on polymer composition. The major challenges on the way to obtain the well-differentiated equivalent of respiratory epithelium on non-woven scaffold include the following: the balance between scaffold permeability and thickness, proper combination of synthetic and natural components, and culture conditions sufficient for co-culturing of airway epithelial cells and fibroblasts. For generation of skin equivalent, the lack of diffusion is not so critical as for pseudostratified airway epithelium.

Spinal cord tissue affects sprouting from aortic fragments in ex vivo co-culture.

It is a well-known fact, that there is a close interconnection between vascular and neural structures in both embryonic development and postnatal life. Different models have been employed to dissect the mechanisms of these interactions, ranging from in vitro systems (e.g., co-culture of neural and endothelial cells) to in vivo imaging of central neural system recovery in laboratory animals after artificially induced trauma. Nevertheless, most of these models have serious limitations. Here, we describe an ex vivo model, representing an organotypic co-culture of aortic fragments (AF) with longitudinal slices of mouse neonatal spinal cord (SC) or dorsal root ganglia (DRG). The samples were co-cultured in a medium adapted for SC tissue and lacking any pro-angiogenic or neurotrophic growth factors. It was found, that cultivation of AFs in the SC injury zone (transversal dissection of a SC slice) resulted in the initiation of active aortic sprouting. Remarkably, the endothelial cells exiting the AFs never invaded the SC tissue, concentrating in a nearby area (negative taxis). In contrast, the DRGs, while also promoting the sprouting, were a target of active endothelial CD31+ cell invasion (positive taxis). Thus, the tissues of both central and peripheral nervous systems have a prominent positive effect on aortic sprouting, while the vector of endothelial cell expansion is strictly nervous-tissue-type dependent. The ex vivo AF co-culture with SC or DRG appeared to be a useful and promising model for a further endeavor into the mechanisms driving the complex interactions between neural and endothelial tissues.

Primary culture of mouse embryonic spinal cord neurons: cell composition and suitability for axonal regeneration studies.

Objective: Primary culture is an effective experimental model to study molecular mechanisms that drive axonal regeneration after central nervous system injury. However, the culture of spinal cord (SC) cells remains poorly characterized. Here, we have analyzed the cell composition of a primary SC culture during its maturation. Methods: Primary cell culture was prepared from mouse embryo spinal cords. After 2, 7, and 14 days of cultivation, the cells were fixed and stained with antibodies against ß3-tubulin, nestin, crmp1, SMI-32, DCC or GFAP. We counted percentage of cells positive for the mentioned markers and measured the length of cell processes. Results: We found that ß3-tubulin and nestin were both expressed at day 2 of culture in vitro. Surprisingly (given the use of differentiation-supporting culture medium), the number of nestin+ cells has significantly increased during the first week of cultivation. The GFAP+ cells appeared only at the seventh day in vitro, and their fraction increased during the following cultivation. At 14 day in vitro, SC culture contained cells that expressed the markers typical of commissural and motor neurons. At this age, the neurons had the ability to repair injured neurites after mechanical damage. Conclusion: Primary culture of SC cells is a dynamically developing cell population that contains all main types of SC cells and is capable of self-repair. Therefore, the culture of mouse embryonic SC cells represents an adequate experimental model for studying cellular and molecular processes taking place in SC neurons after axonal damage in the absence of external inhibitors.

Endoscopic Endonasal Transclival Approach to Tumors of the Clivus and Anterior Region of the Posterior Cranial Fossa (Results of Surgical Treatment of 136 Patients).

INTRODUCTION: With the introduction into the neurosurgical practice of minimally invasive methods using endoscopic techniques, it became possible to effectively remove hard-to-reach tumors, including central tumors of the anterior region of the posterior cranial fossa. OBJECTIVE: To analyze the results of surgical treatment of patients with various centrally located tumors of the base of the skull that extend into the anterior region of the posterior cranial fossa using the endoscopic endonasal transclival approach. METHODS: The personal surgical experience of the first author is 136 patients with various tumors (e.g., chordomas, meningiomas, pituitary adenomas, and fibrous dysplasia). RESULTS: Radicality of tumor removal was total 61.03%; subtotal 25%; partial 13.23%; and insufficient removal 0.74%. Postoperative cerebrospinal fluid leaks occurred in 9 cases (6.62%) and meningitis in 13 cases (9.56%). In 2 cases, surgical treatment had a lethal outcome (1.47%). CONCLUSIONS: The endoscopic endonasal transclival approach can be used to obtain access to centrally located skull base tumors. This approach allows for a radical and low-risk removal of various skull base tumors of central localization that, until recently, were considered to be almost inoperable.

Experimental animal model for assessment of tracheal epithelium regeneration.

OBJECTIVES/HYPOTHESIS: To develop an experimental model in rabbits for assessment of tracheal epithelium regeneration through application of either natural or artificial polymer scaffolds. STUDY DESIGN: First, we identified the size of full-thickness mucosal defect, which does not allow self-healing (a "critical defect"), thus representing an adequate experimental model for regenerative therapy of tracheal epithelium damage. Then, two methods of polymer scaffold fixation at the site of the epithelium defect were compared: suturing and fixation with a stent. This was done through: 1) formation of a full-thickness anterolateral mucosal defect by tracheal mucosa excision; and 2) fixation of the scaffold at the site of the tracheal epithelium defect using sutures (through a tracheal wall "window") or a vascular stent (through a small tracheal incision). RESULTS: The dimension of a critical anterolateral mucosal defect of the trachea for rabbits was found to be 1.5 cm in length and more than 50% of the tracheal circumference. Fixation of the scaffold with a stent proved to be more efficient due to a uniform distribution of the pressure over the entire surface of the scaffold, whereas the suturing of the scaffold provided unsatisfactory results. In addition, fixation of the scaffold by suturing required formation of a large "window" in the tracheal wall. Thus, using the stent appeared to be technically less complicated and much less traumatic as compared to suturing. CONCLUSION: We present an experimental in vivo animal model of tracheal epithelium injury and recovery. It can be effectively used with certain further modifications as a basis for routine testing of bioengineered constructs. LEVEL OF EVIDENCE: NA Laryngoscope, 129:E213-E219, 2019.

Retinoic acid co-treatment aggravates severity of dioxin-induced skin lesions in hairless mice via induction of inflammatory response.

Exposure to toxic halogenated polyaromatic hydrocarbons, of which 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) is the most potent, induces diverse skin pathologies in humans, including chloracne, hyperkeratosis, hamartomas, etc. While the toxic effects of TCDD have been extensively studied, effective approaches to their treatment are still lacking. Retinoids are commonly used in therapy of acneiform skin diseases. In vitro, retinoids elicit antagonistic effects on keratinocyte differentiation and proliferation, as compared to TCDD, suggesting their potential in treatment of TCDD-induced skin lesions. Nevertheless, the modulation of TCDD activity in skin by retinoids in vivo was never reported. We have used N-TERT keratinocyte cell line and hairless (hr) mice to determine if retinoic acid (RA) can lessen or reverse TCDD-induced effects in vitro and in vivo. RA co-treatment suppressed TCDD-induced changes in the expression of differentiation-associated genes and N-TERT keratinocyte viability in vitro. However, in hairless mice (in vivo), RA/TCDD co-treatment produced more severe effects, than treatment with either of the two compounds individually. RA/TCDD co-application to mouse skin strongly stimulated keratinocyte proliferation, resulting in dramatic epidermal hyperplasia. It has also led to massive immune cell infiltration into the dermis, and increased mRNA expression of inflammation markers, including IL1ß, IL6 and S100A7. Thus, retinoids not only appeared ineffective in treatment of TCDD-induced skin lesions in hairless mice, but also resulted in their exaggeration. These in vivo results question previous cell culture-based claims that RA may reduce TCDD-induced skin effects and caution against the reliance on in vitro data in TCDD toxicology research.

Endoscopic Endonasal Transclival Approach to Tumors of the Clivus and Anterior Region of the Posterior Cranial Fossa: An Anatomic Study.

OBJECTIVE: To present the basic topographic and anatomic features of the clivus and adjacent structures with an objective of possible improvements and optimization of the extended endoscopic endonasal posterior (transclival) approach when removing tumors of the clivus and anterior regions of the posterior cranial fossa. MATERIALS AND METHODS: A craniometric study was conducted on 125 human skulls. A topographic anatomic study was conducted on 25 cadaver head specimens with arterial and venous beds stained with colored silicone, according to the method developed by us, to visualize its features and individual variability. RESULTS: The most important anatomic features of the external and internal regions of the clivus and the adjacent neural and vascular structures were analyzed. An accessible zone for the most effective transclival approach to the posterior cranial fossa is also specified. CONCLUSION: The endoscopic endonasal transclival approach can be used to obtain access to centrally located tumors of the posterior cranial fossa. It is an alternative to transcranial approaches in the surgical treatment of tumors of the clivus.

Functional anatomy of the hair follicle: The Secondary Hair Germ.

The secondary hair germ (SHG)-a transitory structure in the lower portion of the mouse telogen hair follicle (HF)-is directly involved in anagen induction and eventual HF regrowth. Some crucial aspects of SHG functioning and ontogenetic relations with other HF parts, however, remain undefined. According to recent evidence (in contrast to previous bulge-centric views), the SHG is the primary target of anagen-inducing signalling and a source of both the outer root sheath (ORS) and ascending HF layers during the initial (morphogenetic) anagen subphase. The SHG is comprised of two functionally distinct cell populations. Its lower portion (originating from lower HF cells that survived catagen) forms all ascending HF layers, while the upper SHG (formed by bulge-derived cells) builds up the ORS. The predetermination of SHG cells to a specific morphogenetic fate contradicts their attribution to the "stem cell" category and supports SHG designation as a "germinative" or a "founder" cell population. The mechanisms of this predetermination driving transition of the SHG from "refractory" to the "competent" state during the telogen remain unknown. Functionally, the SHG serves as a barrier, protecting the quiescent bulge stem cell niche from the extensive follicular papilla/SHG signalling milieu. The formation of the SHG is a prerequisite for efficient "precommitment" of these cells and provides for easier sensing and a faster response to anagen-inducing signals. In general, the formation of the SHG is an evolutionary adaptation, which allowed the ancestors of modern Muridae to acquire a specific, highly synchronized pattern of hair cycling.

Fibrinogen-modified sodium alginate as a scaffold material for skin tissue engineering.

In search for a new pro-angiogenic scaffold material suitable for skin bioengineering and grafting therapy, we have fabricated a number of composite sodium alginate (AG)-fibrinogen (FG) sponge scaffolds using the freeze-drying approach. Thrombin was added to drive FG/fibrin conversion, while ε-aminocapronic acid (εAc) was used as antifibrinolytic component. The slow rates of scaffold biodegradation were achieved by using Ca2+ and Mg2+ cations as cross-linking agents. The novel thrombin-modified AG-FG scaffolds with highly interconnected porous structure were evaluated using scanning electron microscopy, tensile testing and pycnometric analysis. The scaffolds were characterized by high porosity and tensile strength, possessing average pore size from about 60 to 300 µm depending on AG/FG ratio and fibrin stabilization. The biocompatibility of thrombin-modified scaffolds with a different AG/FG ratio was tested on human cells with potential applicability to skin tissue engineering: immortalized epidermal keratinocytes (N-TERT), primary skin fibroblasts, endothelial cells (HUVEC) and subcutaneous adipose-derived stromal cells. The scaffolds with low (15%) FG content have shown the highest adhesiveness and survival rates for all types of cells, as compared to the scaffolds with higher FG content. In unstabilized scaffolds, the addition of FG did not stimulate the aortic ring sprouting. At the same time, fibrin stabilization by εAc resulted in significant increase of aortic ring sprouting and more efficient formation of microvascular network. Altogether, obtained results suggest that thrombin-modified alginate sponges can be successfully used as a grafting material by itself to promote skin healing and regeneration and also as a scaffold for three-dimensional bioequivalent construction.

Endoscopic endonasal transclival removal of tumors of the clivus and anterior region of the posterior cranial fossa (results of surgical treatment of 140 patients).

BACKGROUND: Until recently, tumors of the clivus and the anterior region of the posterior cranial fossa were considered extremely difficult to access and often inoperable using standard transcranial approaches. With the introduction into the neurosurgical practice of minimally invasive methods utilizing endoscopic techniques, it became possible to effectively remove hard-to-reach tumors, including central tumors of the anterior region of the posterior cranial fossa. METHODS: From 2008 to the present time, the inpatient institution has operated on 140 patients with various tumors of the base of the skull, localized to the clivus and anterior region of the posterior cranial fossa (65 men and 75 women). The age of patients ranged from 3 to 74 years. Tumor distribution according to the histopathological features was as follows: chordomas, 103 (73.57%); meningiomas, 12 (8.57%); pituitary adenomas, 9 (6.43%); fibrous dysplasia, 4 (2.86%); cholesteatoma, 3 (2.14%); craniopharyngiomas, 2 (1.43%); plasmacytomas, 2 (1.43%); and other tumors (giant cell tumor, neurohypophyseal glioma, osteoma, carcinoid, chondroma), 5 (3.57%). The tumors had the following size distribution: giant (more than 60 mm), 35 (25%); large (35-59 mm), 83 (59.3%); medium (21-35 mm), 21 (15%); and small (less than 20 mm), 1 (0.7%). In 11 cases, intraoperative monitoring of the cranial nerves was performed (21 cranial nerves were identified). RESULTS: Upper, middle, and lower transclival approaches provide access to the anterior surface of the upper, middle, and lower neurovascular complexes of the posterior cranial fossa. The chordoma cases were distributed as follows according to extent of removal: total removal, 68 (66.02%); subtotal removal, 25 (24.27%); and partial removal, 10 (9.71%). The adenomas of the pituitary gland were removed totally in 6 cases, subtotally in 1 case and partially in 2 cases. The meningiomas were removed totally in 1 case, subtotally in 5 cases, and partially in 5 cases, with less than 50% of the tumor removed in 1 case. Other tumors (cholesteatoma, craniopharyngioma, fibrous dysplasia, giant cell tumor, glioma of the neurohypophysis, osteoma, plasmacytoma, carcinoid, and chondroma) were removed totally in 9 cases and subtotally in 7 cases. Postoperative CSF leaks occurred in 9 cases (6.43%) and meningitis in 13 cases (9.29%). Oculomotor disorders developed in 19 patients (13.57%), 12 of which regressed during the period from 4 to 38 days after surgery, and 7 of which were permanent. In 2 cases, surgical treatment had a lethal outcome (1.43%). CONCLUSION: The endoscopic endonasal transclival approach can be used to obtain access to the centrally located tumors of the posterior cranial fossa. It is an alternative to transcranial approaches in the surgical treatment of tumors of the clivus. The results of using this approach are comparable with the results of transcranial and transfacial approaches and, in some cases, surpass them in effectiveness. The extended endoscopic endonasal posterior (transclival) approach, considering its minimally invasive nature, allows fora radical and low-risk (in terms of postoperative complications and lethality) removal of various skull base tumors of central localization with the involvement and without the involvement of the clivus, which, until recently, were considered to be almost inoperable.

Targeting of Stem Cell Niches Using Unconventional Genetic Tools.

Maintenance of hair follicle (HF) stem cell quiescence and self-renewal are key functions of a specific cellular niche represented by the HF bulge and adjacent cell populations. The unique context of this niche is crucial for normal HF functioning, but mechanisms implicated in its maintenance are still not quite clear. The Letter to the Editor by Sada et al. introduces a novel Slc1a3-CreER genetic mouse model which, in contrast to previously reported marking tools, selectively and highly efficiently demarcates the telogen bulge inner layer, one of the critical structural components of the bulge stem cell niche. The successful use of this tool identified the inner root sheath as a cellular source of telogen bulge inner layer and suggested its potential for further endeavors into fundamental and applied aspects of HF stem cell biology and club hair formation.

Putting the Human Hair Follicle Cycle on the Map.

A detailed characterization of the normal (in situ) human hair follicle cycle, supplemented with expressional data on specific hair follicle markers, has been awaited by basic hair researchers and dermatologists. Combining this hair cycle guide, together with a thorough analysis of the human-on-mouse hair xenograft model, provides solid ground for examining human hair cycle biology and pathology and for hair cycle-related pharmacological testing.

PDK1 regulation of mTOR and hypoxia-inducible factor 1 integrate metabolism and migration of CD8+ T cells.

mTORC1 (mammalian target of rapamycin complex 1) controls transcriptional programs that determine CD8+ cytolytic T cell (CTL) fate. In some cell systems, mTORC1 couples phosphatidylinositol-3 kinase (PI3K) and Akt to the control of glucose uptake and glycolysis. However, PI3K-Akt-independent mechanisms control glucose metabolism in CD8+ T cells, and the role of mTORC1 has not been explored. The present study now demonstrates that mTORC1 activity in CD8+ T cells is not dependent on PI3K or Akt but is critical to sustain glucose uptake and glycolysis in CD8+ T cells. We also show that PI3K- and Akt-independent pathways mediated by mTORC1 regulate the expression of HIF1 (hypoxia-inducible factor 1) transcription factor complex. This mTORC1-HIF1 pathway is required to sustain glucose metabolism and glycolysis in effector CTLs and strikingly functions to couple mTORC1 to a diverse transcriptional program that controls expression of glucose transporters, multiple rate-limiting glycolytic enzymes, cytolytic effector molecules, and essential chemokine and adhesion receptors that regulate T cell trafficking. These data reveal a fundamental mechanism linking nutrient and oxygen sensing to transcriptional control of CD8+ T cell differentiation.