Generating human skeletal myoblast spheroids for vascular myogenic tissue engineering

Engineered myogenic microtissues derived from human skeletal myoblasts offer unique opportunities for varying skeletal muscle tissue engineering applications, such asin vitrodrug-testing and disease modelling. However, more complex models require the incorporation of vascular structures, which remains to be challenging. In this study, myogenic spheroids were generated using a high-throughput, non-adhesive micropatterned surface. Since monoculture spheroids containing human skeletal myoblasts were unable to remain their integrity, co-culture spheroids combining human skeletal myoblasts and human adipose-derived stem cells were created. When using the optimal ratio, uniform and viable spheroids with enhanced myogenic properties were achieved. Applying a pre-vascularization strategy, through addition of endothelial cells, resulted in the formation of spheroids containing capillary-like networks, lumina and collagen in the extracellular matrix, whilst retaining myogenicity. Moreover, sprouting of endothelial cells from the spheroids when encapsulated in fibrin was allowed. The possibility of spheroids, from different maturation stages, to assemble into a more large construct was proven by doublet fusion experiments. The relevance of using three-dimensional microtissues with tissue-specific microarchitecture and increased complexity, together with the high-throughput generation approach, makes the generated spheroids a suitable tool forin vitrodrug-testing and human disease modeling.

Efficient co-isolation of microvascular endothelial cells and satellite cell-derived myoblasts from human skeletal muscle

Vascularization of tissue-engineered constructs remains a key challenge in the field of skeletal muscle tissue engineering. One strategy for vascularizing organoids is in vitro pre-vascularization, relying on de novo assembly of undifferentiated endothelial cells into capillaries, a process termed vasculogenesis. In most endothelial cell research to date, human umbilical vein endothelial cells have been used primarily because of their availability. Nevertheless, this endothelial cell type is naturally not occurring in skeletal muscle tissue. Since endothelial cells display a tissue-specific phenotype, it is of interest to use muscle-specific microvascular endothelial cells to study pre-vascularization in skeletal muscle tissue engineering research. Thus far, tissue biopsies had to be processed in two separate protocols to obtain cells from the myogenic and the endothelial compartment. Here, we describe a novel, detailed protocol for the co-isolation of human skeletal muscle microvascular endothelial cells and satellite cell-derived myoblasts. It incorporates an automated mechanical and enzymatic tissue dissociation followed by magnetically activated cell sorting based on a combination of endothelial and skeletal muscle cell markers. Qualitative, quantitative, and functional characterization of the obtained cells is described and demonstrated by representative results. The simultaneous isolation of both cell types from the same donor is advantageous in terms of time efficiency. In addition, it may be the only possible method to isolate both cell types as the amount of tissue biopsy is often limited. The isolation of the two cell types is crucial for further studies to elucidate cell crosstalk in health and disease. Furthermore, the use of muscle-specific microvascular endothelial cells allows a shift towards engineering more physiologically relevant functional tissue, with downstream applications including drug screening and regenerative medicine.

Visually controlled matching of pattern movement

Subjects were asked to match the speeds of two moving random-dot patterns seen through circular apertures. The speed of one pattern that moved horizontally toward the right of a computer screen changed continuously. The speed of this pattern represented the target. It was to be matched with the speed of the second pattern, which moved in the opposite direction. The subject controlled the speed of the second pattern by means of an isometric joystick. The distance between the apertures on the screen as well as the subject's distance from the screen served as experimental parameters. In this way, the effects of both spatial and temporal transients of pattern speed on human tracking performance were studied. To avoid anticipation by the subject, the amplitude and the frequency of the target pattern speed changed pseudorandomly. The accuracy with which the subject performed the matching task was influenced by the mean pattern speed and the parameters of the visual field. Within lower velocity ranges, the subject's sensitivity to the instantaneous speed differences varied according to Weber's law. The cross-correlation of the velocity time courses decreased when the mean speed of the target pattern was increased. Two stimulus parameters had a strong influence on the modulation of the correlation value: (1) the angular size of the stimulus on the retina and (2) the retinal eccentricity of the stimulus.

A hydrodynamic model of cerebrospinal fluid flow in man

A hydrodynamic bi-compartmental model for the cerebrospinal fluid (CSF) flow in humans is presented which combines anatomical and physiological conditions in the central nervous system with results of special radioisotope diagnostic techniques. Normal and disturbed conditions, the diagnostic methods and the results are explained. A differential equation for the time behaviour of regional radioisotope concentrations is derived by applying to the model mathematical procedures which are familiar from the description of radioactive decay series, or reaction kinetics of chemical or pharmaceutical processes. The solutions are analysed and discussed with respect to findings of isotope diagnostics, and parameters for the complete and quantitative evaluation of CSF flow systems are derived. A system factor is introduced for classification purposes and, in conjunction with basic principles of hydrodynamics, is used to postulate a similarity law of CSF flow systems. The diagnostical and therapeutical value of the model for analysis and simulation of CSF flow systems is discussed. Practical applications to other disciplines are proposed.

Mechanical loading of peripheral nerves during remobilisation of the affected member after end-to-end anastomosis

Our study involved simulating end-to-end neurorrhaphy of the sciatic nerve in a number of rabbits and analysing in vivo the mechanical loads acting on the nerve while the affected member was being remobilised. We found both the suture and mobilisation loads to be related to the size of the nerve defect. In each case, traction force, strain, and stress were proportional. The effect which these experimental findings may have on the future use of flexing neighbouring joints as a "manipulative" measure to achieve a tension-free nerve suture will be discussed.

New aspects of cerebrospinal fluid dynamics in humans investigated by sequential gamma camera cisternography, with data evaluation by the digital multichannel analyzer. Part 4: A unifying criterion of the development of hydrocephalic syndrome. Its dynamic basis

In the final part of this series we present all of the clinical material, and the patients are classified by different cisternographic syndromes on the dynamic basis offered for our method: dynamic disconnection between ventricular system and basal cisterns, brain atrophy, initial dynamic decompensation or prehydrocephalus, communicating hydrocephalus with and without epicortical fluid circulation. A nomogram method for clinical estimation of CSF production based on the mathematical properties of our analysis of the ventricular reflux is proposed. The different normal and pathological characteristics of fluid movements in the spinal canal are given, and their importance as signs of turbulence in the posterior fossa are emphasized. Different aspects of the dynamics of CSF production are shown and discussed, and an evolving conception of hydrocephalus development is presented.

New aspects of cerebrospinal fluid dynamics in humans investigated by sequential gammacamera cisternography, with data evaluation by the digital multichannel analyzer. Part 3: Physiopathology of the ventricular reflux

Although well described and intensively used for diagnostic purposes, the ventricular reflux as a gammacisternographic phenomen has not yet been satisfactorily explained, and its physiopathology is a subject of controversy. Based on our method of quantitative gammacisternography and gammaventriculography we study the evolution of the tracer concentrations in two main chambers:--the basal cisterns together with the upper cervical canal, considered as a functional unity (the distribution area) and--the ventricular system. We propose the mathematical analysis of a theoretical model which represents the normal and pathological situations of these two chambers, as a method for measuring ventricular volume and ventricular tracer clearance. From the correlation in results with patients and models, we suggest turbulence as the main factor in generating backmixing or total mixing, the appearance of which is called ventricular reflux. We deny the existence of a real inversion of CSF flow. The spinal canal velocity of isotope flow is proposed as additional evidence of turbulence. The normal general dynamics of CSF are delineated, and we propose the following factors that lead to ventricular reflux:--partial obstruction to epicortical CSF flow;--total obstruction to epicortical CSF flow. Their principal characteristics are given, and the importance of using their quantitative parameters in descriptions of patients is stressed. Different aspects in the evolution of hydrocephalus, transependymal resorption, and factors involved in hydrodynamic changes etc. are discussed.