Smooth muscle can be stimulated by pacesetter cells, by the autonomic nervous system, by hormones, spontaneously, or by stretching. The fibers in some smooth muscle have latch-bridges, cross-bridges that cycle slowly without the need for ATP; these muscles can maintain low-level contractions for long periods.
What are the specialized smooth muscle cells?
Myofibroblasts represent a special type of smooth muscle cell which additionally have qualities of fibrocytes. They produce connective tissue proteins such as collagen and elastin for which reason they are also referred to as fixed (or stationary) connective tissue cells.
What is smooth muscle cell migration?
Smooth muscle cell migration occurs during vascular development, in response to vascular injury, and during atherogenesis. Promigratory stimuli activate signal transduction cascades that trigger remodeling of the cytoskeleton, change the adhesiveness of the cell to the matrix, and activate motor proteins.
How are smooth muscle cells connected together?
Smooth muscle cells are connected to each other through regions called adherens junctions. These regions contain many fibrous proteins for strength when the cells pull against each other. The junctions also contain small gaps, which allow the cell membranes of two neighboring cells to join.
Where are smooth muscle cells located?
Smooth muscle fibers are located in walls of hollow visceral organs (such as the liver, pancreas, and intestines), except the heart, appear spindle-shaped, and are also under involuntary control. Skeletal muscle fibers occur in muscles which are attached to the skeleton.
Where are the unitary smooth muscles located?
Single-unit smooth muscle, or visceral smooth muscle is a type of smooth muscle found in the uterus, gastro-intestinal tract, and the bladder.
How does smooth muscle appear different at the cellular level?
At a cellular level, smooth muscle functions as an involuntary non-striated muscle. Smooth muscle contains thick and thin filaments that do not arrange into sarcomeres, resulting in a non-striated pattern. On microscopic examination, it appears homogenous.
How does actin help cell migration?
Cell migration is dependent on different actin filament structures. (A) In a cell, motility is initiated by an actin-dependent protrusion of the cell’s leading edge, which is composed of armlike structures called lamellipodia and filopodia. (D) Then, retraction fibers pull the rear of the cell forward.
How are smooth and actin myosin arranged?
In skeletal and cardiac muscle, the actin filaments are attached to Z plates, which hold many actin filaments and show up as dark bands under the microscope. In smooth muscle, the actin and myosin fibers are arranged an angles to each other as they run through the cell.
How do you design a muscle-specific promoter?
A straightforward way to design a muscle-specific promoter is to use the naturally occurring promoter of the gene with high expression levels in muscles. To reduce the size of the full-length natural promoter, only the core promoter and some proximal elements are left and supplemented with distal
Why design short regulatory sequences for therapeutic transgene expression?
There is an urgent need for the design of short, regulatory sequences that would drive a high and robust expression of a therapeutic transgene in skeletal muscles, the diaphragm, and the heart, while exhibiting limited activity in non-target tissues.
What is gene replacement therapy for muscular disorders?
Many genetic diseases that are responsible for muscular disorders have been described to date. Gene replacement therapy is a state-of-the-art strategy used to treat such diseases. In this approach, the functional copy of a gene is delivered to the affected tissues using viral vectors.
