D Motlagh | PubMed Health

PubMed2000

Fabrication of microtextured membranes for cardiac myocyte attachment and orientation.

To understand the role of tissue adaptation to altered physiological states, a more physiologically and dimensionally relevant in vitro model of cardiac myocyte organization has been developed. A microtextured polymeric membrane with micron range dimensions promotes myocyte adhesion through substrate/cell interlocking and, thus, provides a more suitable stretchable matrix for studying overlying cell populations. These microtextured membranes are created using photolithography and microfabrication techniques. Biologically, mechanically, and optically compatible interfaces with specified microarchitecture and surface chemistry have been designed, microfabricated, and characterized for this purpose. Cardiac myocytes plated on these membranes display greater attachment and cell height compared to conventional culture substrates. Advantages of the microtextured membranes include the high degree of reproducibility and the ability to create features on the micron and submicron size scale. Because of the flexibility of substrate material and the ease of creating micron size structures, this technique can be applied to many other physiological and biological systems.

Animals↗

PubMed2000

Form follows function: how muscle shape is regulated by work.

What determines the shape, size, and force output of cardiac and skeletal muscle? Chicago architect Louis Sullivan (1856-1924), father of the skyscraper, observed that "form follows function." This is as true for the structural elements of a striated muscle cell as it is for the architectural features of a building. Function is a critical evolutionary determinant, not form. To survive, the animal has evolved muscles with the capacity for dynamic responses to altered functional demand. For example, work against an increased load leads to increased mass and cross-sectional area (hypertrophy), which is directly proportional to an increased potential for force production. Thus a cell has the capacity to alter its shape as well as its volume in response to a need for altered force production. Muscle function relies primarily on an organized assembly of contractile and other sarcomeric proteins. From analysis of homogenized cells and molecular and biochemical assays, we have learned about transcription, translation, and posttranslational processes that underlie protein synthesis but still have done little in addressing the important questions of shape or regional cell growth. Skeletal muscles only grow in length as the bones grow; therefore, most studies of adult hypertrophy really only involve increased cross-sectional area. The heart chamber, however, can extend in both longitudinal and transverse directions, and cardiac cells can grow in length and width. We know little about the regulation of these directional processes that appear as a cell gets larger with hypertrophy or smaller with atrophy. This review gives a brief overview of the regulation of cell shape and the composition and aggregation of contractile proteins into filaments, the sarcomere, and myofibrils. We examine how mechanical activity regulates the turnover and exchange of contraction proteins. Finally, we suggest what kinds of experiments are needed to answer these fundamental questions about the regulation of muscle cell shape.

Adult↗