Multiscale-Engineered Muscle Constructs: PEG Hydrogel Micro-Patterning on an Electrospun PCL Mat Functionalized with Gold Nanoparticles.

The development of new, viable, and functional engineered tissue is a complex and challenging task. Skeletal muscle constructs have specific requirements as cells are sensitive to the stiffness, geometry of the materials, and biological micro-environment. The aim of this study was thus to design and characterize a multi-scale scaffold and to evaluate it regarding the differentiation process of C2C12 skeletal myoblasts. The significance of the work lies in the microfabrication of lines of polyethylene glycol, on poly(ε-caprolactone) nanofiber sheets obtained using the electrospinning process, coated or not with gold nanoparticles to act as a potential substrate for electrical stimulation. The differentiation of C2C12 cells was studied over a period of seven days and quantified through both expression of specific genes, and analysis of the myotubes' alignment and length using confocal microscopy. We demonstrated that our multiscale bio-construct presented tunable mechanical properties and supported the different stages skeletal muscle, as well as improving the parallel orientation of the myotubes with a variation of less than 15°. These scaffolds showed the ability of sustained myogenic differentiation by enhancing the organization of reconstructed skeletal muscle. Moreover, they may be suitable for applications in mechanical and electrical stimulation to mimic the muscle's physiological functions.

Monitoring mechanical stimulation for optimal tendon tissue engineering: A mechanical and biological multiscale study.

To understand the effect of mechanical stimulation on cell response, bone marrow stromal cells were cultured on electrospun scaffolds under two distinct mechanical conditions (static and dynamic). Comparison between initial and final mechanical and biological properties of the cell-constructs were conducted over 14 days for both culturing conditions. As a result, mechanically stimulated constructs, in contrast to their static counterparts, showed evident mechanical-induced cell orientation, an effective aligned collagen and tenomodulin extracellular matrix. This orientation provides clues on the importance of mechanical stimulation to induce a tendon-like differentiation. In addition, cell and collagen orientation lead to enhanced storage modulus observed under dynamic stimulation. Altogether mechanical stimulation lead to (a) cell and matrix orientation through the sense of the stretch and (b) a dominant elastic response in the cell-constructs with a minor contribution of the viscosity in the global mechanical behavior. Such a correlation could help in further studies to better understand the effect of mechanical stimulation in tissue engineering.

Manufacturing of Human Tissues as off-the-Shelf Grafts Programmed to Induce Regeneration.

Design criteria for tissue-engineered materials in regenerative medicine include robust biological effectiveness, off-the-shelf availability, and scalable manufacturing under standardized conditions. For bone repair, existing strategies rely on primary autologous cells, associated with unpredictable performance, limited availability and complex logistic. Here, a conceptual shift based on the manufacturing of devitalized human hypertrophic cartilage (HyC), as cell-free material inducing bone formation by recapitulating the developmental process of endochondral ossification, is reported. The strategy relies on a customized human mesenchymal line expressing bone morphogenetic protein-2 (BMP-2), critically required for robust chondrogenesis and concomitant extracellular matrix (ECM) enrichment. Following apoptosis-driven devitalization, lyophilization, and storage, the resulting off-the-shelf cartilage tissue exhibits unprecedented osteoinductive properties, unmatched by synthetic delivery of BMP-2 or by living engineered grafts. Scalability and pre-clinical efficacy are demonstrated by bioreactor-based production and subsequent orthotopic assessment. The findings exemplify the broader paradigm of programming human cell lines as biological factory units to engineer customized ECMs, designed to activate specific regenerative processes.

Oleic acid synthesized in the periventricular zone promotes axonogenesis in the striatum during brain development.

Our previous works showed that oleic acid synthesized in vitro by astrocytes in response to albumin behaves as a neurotrophic factor in neurons, up-regulating several proteins, such as the axonal growth marker growth-associated protein 43(GAP-43). Although the molecular mechanism of this process is fairly known, there is no evidence pinpointing the region/s in which oleic acid is synthesized. In this study, we show that the rate-limiting enzyme in oleic acid synthesis, stearoyl-CoA desaturase (SCD-1), is located in the periventricular zone of the brain of newborn rats, simultaneously to an increase in the amount of free oleic acid in the forebrain. In addition, the spatio-temporal presence of albumin - the signal that promotes oleic acid synthesis - and that of GAP-43 are correlated with that of SCD-1. Using organotypic slice cultures, we found that albumin up-regulates SCD-1 and stimulates the growth of GAP-43-positive axons in the striatum. The effect of albumin on GAP-43 was reduced when SCD-1 was silenced by siRNA. In conclusion, our results suggest that albumin up-regulates axonogenesis in the striatum by increasing the amount of the neurotrophic factor oleic acid synthesized by SCD-1 in the periventricular zone of the newborn brain.

The combination of a poly-caprolactone/nano-hydroxyapatite honeycomb scaffold and mesenchymal stem cells promotes bone regeneration in rat calvarial defects.

Bone tissue engineering goes beyond the limitations of conventional methods of treating bone loss, such as autograft-induced morbidity and a lack of integration for large grafts. Novel biomimicry approaches (using three-dimensional [3D] electrospinning and printing techniques) have been designed to offer the most appropriate environment for cells and thus promote bone regeneration. In the present study, we assessed the bone regeneration properties of a composite 3D honeycomb structure from the electrostatic template-assisted deposition process by an alternate deposition of electrospun polycaprolactone (PCL) nanofibers and electrosprayed hydroxyapatite nanoparticles (nHA) on a honeycomb micropatterned substrate. We first confirmed the cytocompatibility of this honeycomb PCL-nHA scaffold in culture with bone marrow-derived mesenchymal stem cells (BM-MSCs). The scaffold was then implanted (alone or with seeded MSCs) for 2 months in a rat critical-sized calvarial defect model. The observation of new bone synthesis in situ (monitored using microcomputed tomography every 2 weeks and a histological assessment upon extraction) demonstrated that the honeycomb PCL-nHA scaffold was osteoconductive. Moreover, the combination of the scaffold with BM-MSCs was associated with significantly greater bone volume and mineralized regeneration during the 2-month experiment. The combination of the biomimetic honeycomb PCL-nHA scaffold with patient mesenchymal stem cells might therefore have great potential for clinical applications and specifically in maxillofacial surgery.

Biomaterials in Tendon and Skeletal Muscle Tissue Engineering: Current Trends and Challenges.

Tissue engineering is a promising approach to repair tendon and muscle when natural healing fails. Biohybrid constructs obtained after cells’ seeding and culture in dedicated scaffolds have indeed been considered as relevant tools for mimicking native tissue, leading to a better integration in vivo. They can also be employed to perform advanced in vitro studies to model the cell differentiation or regeneration processes. In this review, we report and analyze the different solutions proposed in literature, for the reconstruction of tendon, muscle, and the myotendinous junction. They classically rely on the three pillars of tissue engineering, i.e., cells, biomaterials and environment (both chemical and physical stimuli). We have chosen to present biomimetic or bioinspired strategies based on understanding of the native tissue structure/functions/properties of the tissue of interest. For each tissue, we sorted the relevant publications according to an increasing degree of complexity in the materials’ shape or manufacture. We present their biological and mechanical performances, observed in vitro and in vivo when available. Although there is no consensus for a gold standard technique to reconstruct these musculo-skeletal tissues, the reader can find different ways to progress in the field and to understand the recent history in the choice of materials, from collagen to polymer-based matrices.

Poly(ε-caprolactone)/Hydroxyapatite 3D Honeycomb Scaffolds for a Cellular Microenvironment Adapted to Maxillofacial Bone Reconstruction.

The elaboration of biomimetic materials inspired from the specific structure of native bone is one the main goal of tissue engineering approaches. To offer the most appropriate environment for bone reconstruction, we combined electrospinning and electrospraying to elaborate an innovative scaffold composed of alternating layers of polycaprolactone (PCL) and hydroxyapatite (HA). In our approach, the electrospun PCL was shaped into a honeycomb-like structure with an inner diameter of 160 µm, capable of providing bone cells with a 3D environment while ensuring the material biomechanical strength. After 5 days of culture without any differentiation factor, the murine embryonic cell line demonstrated excellent cell viability on contact with the PCL-HA structures as well as active colonization of the scaffold. The cell differentiation, as tested by RT-qPCR, revealed a 6-fold increase in the expression of the RNA of the Bglap involved in bone mineralization as compared to a classical 2D culture. This differentiation of the cells into osteoblasts was confirmed by alkaline phosphatase staining of the scaffold cultivated with the cell lineage. Later on, organotypic cultures of embryonic bone tissues showed the high capacity of the PCL-HA honeycomb structure to guide the migration of differentiated bone cells throughout the cavities and the ridge of the biomaterial, with a colonization surface twice as big as that of the control. Taken together, our results indicate that PCL-HA honeycomb structures are biomimetic supports that promotes in vitro osteocompatibility, osteoconduction, and osteoinduction and could be suitable for being used for bone reconstruction in complex situations such as the repair of maxillofacial defects.

Alpha-fetoprotein (AFP) modulates the effect of serum albumin on brain development by restraining the neurotrophic effect of oleic acid.

We have previously shown that serum albumin controls perinatal rat brain development through the regulation of oleic acid synthesis by astrocytes. In fact, oleic acid synthesized and released by astrocytes promoted neurite growth, neuron migration and the arrangement of prospective synapses. In this work we show that alpha-fetoprotein (AFP) is also present in the brain during embryonic development, its concentrations peaking at E15.5 and at E19.5. However, after E19.5 AFP concentrations plummeted concurrently with a sharp increase in serum albumin concentrations. At E15.5, AFP is present in caudal regions of the brain, particularly in brain areas undergoing differentiation during this period, such as the thalamic reticular nucleus of the thalamus, the hypothalamus, the amygdala and the hippocampus. Albumin was not detected in the brain at E15.5 but stained brain cells substantially on day E19.5, showing a very similar distribution to that of AFP under the same circumstances. The concentrations of free oleic acid in the brain were inversely correlated with those of AFP, suggesting that the signals elicited by AFP and oleic acid can be inversely associated. GAP-43, a marker of axonal growth that is highly expressed by the presence of oleic acid, was not co-localized with AFP except in the marginal zone and areas delimiting the subplate. AFP prevented the increase in GAP-43 expression caused by the presence of oleic acid in neurons in primary culture in vitro and in organotypic cultures of embryonic rat brain ex vivo, suggesting that AFP may modulate the effect of serum albumin on brain development.

Las trayectorias del padecimiento: hombres adultos amputados y no amputados a causa de la diabetes mellitus / Suffering trajectories: amputed and non-amputed adult men because of diabetes mellitus

Se presenta a continuación un reporte de investigación que recupera los resultados de un trabajo de indagación de corte cualitativo cuyo objetivo era reconocer las diferencias en las trayectorias del padecimiento entre dos grupos de personas diabéticas con las mismas características en términos de edad, ocupación y nivel socioeconónico en general. En uno de los grupos las complicaciones diabéticas los llevaron a ser amputados de una o de ambas extremidades inferiores y en el otro estas complicaciones no se presentaron. La investigación se realizó básicamente con pacientes de una clínica universitaria ubicada en una colonia de nivel medio bajo en el municipio de Guadalupe, Nuevo León, México durante los años 2000 y 2001. La información se obtuvo con base en entrevistas con un guión semiestructurado de preguntas y la observación en grupos de autoayuda y en las casas de los pacientes. Los resultados principales se concentran en diferencias en el manejo de la dieta, el apoyo de la estructura familiar, las prácticas de autocuidado y atención médica. También es evidente el diferente manejo del estrés y en el consumo de bebidas alcohólicas.

Cálculo del poder del lente intraocular; ultrasonido vs. otros métodos / Lens intraocular calculation pawer, ultrasouds vs. other methods

En este estudio comparamos el cálculo del poder del lente intraocular por dos métodos: uno sin ecografía tomando una constante de 20D para el cristalino y la refracción del mismo ojo o en ocasiones del contralateral, y el otro con ecografía y la fórmula SRK. Fueron 22 ojos en total a los que se les realizó EECC más lente intraocular de cámara posterior. Tuvieron un seguimiento postoperatorio de 3 meses en promedio, obteniéndose los siguientes resultados: En el grupo sin ecografía se obtuvo una refracción final de + 1.00 a - ¿.75 y en el método con ecografía de + 1.50 a - 0.50. Nuestras conclusiones fueron: que el cálculo del poder de lente intraocular sin ecografía es posible en pacientes con ametropías menores de 2.50 D y en ametroías altas, anisometropías o duda en el antecedente refractivo ocular del paciente es necesaria la ecografía