The regenerative capability of peripheral nerves is very limited, and several strategies have been proposed to increase nerve regeneration. In the present work, we have analyzed the
usefulness of a ...novel nanostructured fibrin-agarose bio-artificial nerve substitute (Nano) used alone or in combination with NeuraGen
collagen type I conduits (Coll-Nano) in laboratory rats with a 10-mm sciatic nerve defect. Control animals were subjected to the gold-standard autograft technique (Auto). Results first demonstrated that the percentage of self-amputations was lower in Nano and Coll-Nano groups as compared to the Auto group. Neurotrophic ulcers were more abundant in the Auto group (60%, with 66.6% of them being >2-mm) than Nano and Coll-Nano groups (0%) at 4 weeks, although Nano showed more ulcers after 12 weeks. Foot length was significantly altered in Auto animals due to neurogenic retraction, but not in Nano and Coll-Nano groups after 12 weeks. At the functional level, all animals showed a partial sensory recovery as determined by the pinch test, especially in Nano and Auto groups, but did not reach the levels of native animals. Toe-spread test revealed a partial motor function recovery only in Nano animals at 4 weeks and Auto and Nano at 12 weeks. Electromyography showed clear denervation signs in all experimental groups, with few differences between Auto and Nano animals. After 12 weeks, an important denervation decrease and an increase of the reinnervation process was found in Auto and Nano groups, with no differences between these groups. Histological analyses demonstrated an active peripheral nerve regeneration process with newly formed peripheral nerve fascicles showing S-100, GAP-43 and myelin in all experimental groups. The peripheral nerve regeneration process was more abundant in Auto group, followed by Nano group, and both were better than Coll-Nano group. Muscle histology confirmed the electromyography results and showed some atrophy and fibrosis signs and an important weight and volume loss in all groups, especially in the Coll-Nano group (56.8% weight and 60.4% volume loss). All these results suggest that the novel Nano substitutes used in
were able to contribute to bridge a 10-mm peripheral nerve defect in rats.
Reconstruction of skin defects is often a challenging effort due to the currently limited reconstructive options. In this sense, tissue engineering has emerged as a possible alternative to replace or ...repair diseased or damaged tissues from the patient's own cells. A substantial number of tissue-engineered skin substitutes (TESSs) have been conceived and evaluated in vitro and in vivo showing promising results in the preclinical stage. However, only a few constructs have been used in the clinic. The lack of standardization in evaluation methods employed may in part be responsible for this discrepancy. This review covers the most well-known and up-to-date methods for evaluating the optimization of new TESSs and orientative guidelines for the evaluation of TESSs are proposed.
Development of an ideal biomaterial for clinical use is one of the main objectives of current research in tissue engineering. Marine-origin polysaccharides, in particular agaroses, have been widely ...explored as scaffolds for tissue engineering. We previously developed a biomaterial based on a combination of agarose with fibrin, that was successfully translated to clinical practice. However, in search of novel biomaterials with improved physical and biological properties, we have now generated new fibrin-agarose (FA) biomaterials using 5 different types of agaroses at 4 different concentrations. First, we evaluated the cytotoxic effects and the biomechanical properties of these biomaterials. Then, each bioartificial tissue was grafted in vivo and histological, histochemical and immunohistochemical analyses were performed after 30 days. Ex vivo evaluation showed high biocompatibility and differences in their biomechanical properties. In vivo, FA tissues were biocompatible at the systemic and local levels, and histological analyses showed that biointegration was associated to a pro-regenerative process with M2-type CD206-positive macrophages. These results confirm the biocompatibility of FA biomaterials and support their clinical use for the generation of human tissues by tissue engineering, with the possibility of selecting specific agarose types and concentrations for applications requiring precise biomechanical properties and in vivo reabsorption times.
The myelin sheath is a lipoprotein-rich, multilayered structure capable of increasing conduction velocity in central and peripheral myelinated nerve fibers. Due to the complex structure and ...composition of myelin, various histological techniques have been developed over the centuries to evaluate myelin under normal, pathological or experimental conditions. Today, methods to assess myelin integrity or content are key tools in both clinical diagnosis and neuroscience research. In this review, we provide an updated summary of the composition and structure of the myelin sheath and discuss some histological procedures, from tissue fixation and processing techniques to the most used and practical myelin histological staining methods. Considering the lipoprotein nature of myelin, the main features and technical details of the different available methods that can be used to evaluate the lipid or protein components of myelin are described, as well as the precise ultrastructural techniques.
Nervous system traumatic injuries are prevalent in our society, with a significant socioeconomic impact. Due to the highly complex structure of the neural tissue, the treatment of these injuries is ...still a challenge. Recently, 3D printing has emerged as a promising alternative for producing biomimetic scaffolds, which can lead to the restoration of neural tissue function. The objective of this work was to compare different biomaterials for generating 3D-printed scaffolds for use in neural tissue engineering. For this purpose, four thermoplastic biomaterials, ((polylactic acid) (PLA), polycaprolactone (PCL), Filaflex (FF) (assessed here for the first time for biomedical purposes), and Flexdym (FD)) and gelatin methacrylate (GelMA) hydrogel were subjected to printability and mechanical tests, in vitro cell-biomaterial interaction analyses, and in vivo biocompatibility assessment. The thermoplastics showed superior printing results in terms of resolution and shape fidelity, whereas FD and GelMA revealed great viscoelastic properties. GelMA demonstrated a greater cell viability index after 7 days of in vitro cell culture. Moreover, all groups displayed connective tissue encapsulation, with some inflammatory cells around the scaffolds after 10 days of in vivo implantation. Future studies will determine the usefulness and in vivo therapeutic efficacy of novel neural substitutes based on the use of these 3D-printed scaffolds.
On the one hand, M. Mata et al. published the article entitled “In Vivo Articular Cartilage Regeneration Using Human Dental Pulp Stem Cells Cultured in an Alginate Scaffold: A Preliminary Study” in ...which they demonstrated, through different histological approaches, that human dental pulp stem cells have a positive impact on the regeneration of articular cartilage in rabbits. ...in these nine articles, authors rigorously discussed and demonstrated the high versatility of different kinds of stem cells to differentiate, promote tissue healing, modulate host immune response, and serve as feeder platform for the ex vivo expansion of differentiated cells. ...the articles published in this special issue provide new tissue engineered-based strategies and scientific evidence that support the potential clinical usefulness of stem cells in regenerative medicine.
Lipids are a heterogeneous group of substances characterized by their solubility in organic solvents and insolubility in water. Lipids can be found as normal components of different tissues and ...organs, and they can be affected by several pathological conditions. The histochemical identification of lipids plays an important role in histopathological diagnosis and research, but successful staining depends on adequate fixation and processing of the tissue. Here we describe methods to fix and process tissue samples for the histochemical identification of lipids in frozen or paraffin-embedded tissues.
(1) Background: Frontal fibrosing alopecia (FFA) is a scarring alopecia that predominantly affects postmenopausal women; (2) Methods: A retrospective, observational, single-center study was conducted ...in the Hospital General Universitario in Ciudad Real, Spain, including all patients diagnosed with FFA between 2010 and 2021; (3) Results: A total of 306 patients (296 women and 10 men) were included in our study. The mean age of onset was 59.5 years. The severity of this disease was evenly distributed between mild (147 patients) and severe (149 patients) forms. There was a positive, statistically significant, medium correlation between the severity of the disease and its time of progression. Moreover, hypothyroidism was present in 70 patients (22.9%) and classic signs of concomitant lichen planopilaris were observed in just 30 patients (9.8%), while other forms of lichen planus were uncommon. The estimated prevalence in our population is 0.15% and the incidence is 15.47 new cases per 100,000 inhabitants; (4) Conclusions: The time of progression was positively correlated with the severity of FFA. However, the presence of clinical signs, such as inflammatory trichoscopic signs, was not associated with the progression of this condition.
For the histopathologic diagnosis of melanocytic lesions, it could be necessary to identify the melanin pigment because its visualization is unspecific with hematoxylin-eosin (HE). The Fontana-Masson ...(FM) technique is used in histopathology in this type of lesion, which allows the identification of the pigment, but it loses all the morphologic parameters. The authors describe a modification to the FM method, for the evaluation of the morphology, the argentaffin reaction of the melanin, and collagens fibers of the extracellular matrix simultaneously, for which they have developed the Fontana-Masson picrosirius (FMPS) method. Biopsies of different melanocytic lesions were used for the performance of the HE, FM, and FMPS methods. The pixel intensity of the reaction for melanin, collagen, and epithelium was determined with ImageJ software. The FMPS method allows the evaluation of morphological characteristics, identifying the melanin pigment and collagen fibers with high intensity simultaneously. This method does not differ significantly from FM in the identification of melanin, maintaining its sensitivity and specificity. In addition, it does not differ in the demonstration of the morphology with HE. However, FMPS is significantly superior in the identification of collagen fibers. The FMPS method combines morphological and histochemical parameters that could be useful in the study of pigmented lesions of melanocytic origin.
Generation of biocompatible and biomimetic tissue-like biomaterials is crucial to ensure the success of engineered substitutes in tissue repair. Natural biomaterials able to mimic the structure and ...composition of native extracellular matrices typically show better results than synthetic biomaterials. The aim of this study was to perform an
in vivo
time-course biocompatibility analysis of fibrin-agarose tissue-like hydrogels at the histological, imagenological, hematological, and biochemical levels. Tissue-like hydrogels were produced by a controlled biofabrication process allowing the generation of biomechanically and structurally stable hydrogels. The hydrogels were implanted subcutaneously in 25 male Wistar rats and evaluated after 1, 5, 9, and 12 weeks of
in vivo
follow-up. At each period of time, animals were analyzed using magnetic resonance imaging (MRI), hematological analyses, and histology of the local area in which the biomaterials were implanted, along with major vital organs (liver, kidney, spleen, and regional lymph nodes). MRI results showed no local or distal alterations during the whole study period. Hematology and biochemistry showed some fluctuation in blood cells values and in some biochemical markers over the time. However, these parameters were progressively normalized in the framework of the homeostasis process. Histological, histochemical, and ultrastructural analyses showed that implantation of fibrin-agarose scaffolds was followed by a progressive process of cell invasion, synthesis of components of the extracellular matrix (mainly, collagen) and neovascularization. Implanted biomaterials were successfully biodegraded and biointegrated at 12 weeks without any associated histopathological alteration in the implanted zone or distal vital organs. In summary, our
in vivo
study suggests that fibrin-agarose tissue-like hydrogels could have potential clinical usefulness in engineering applications in terms of biosafety and biocompatibility.
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