Conduction Properties in Peripheral Nerve Fibers Regenerated by Biodegradable Polymer Matrix

alpha-smooth muscle actin and contractile behavior of bovine meniscus cells seeded in type I and type II collagen-GAG matrices

Many types of injuries to the meniscus of the knee joint result in defects that do not heal, leading to pain and dysfunction. Several ongoing investigations are developing porous absorbable matrices to be used alone or seeded with cultured cells to facilitate regeneration of this tissue. The objective of this study was to evaluate in vitro the contractile behavior of meniscal cells seeded in type I and type II collagen matrices. In many connective tissues, fibroblasts that have assumed a contractile phenotype (myofibroblasts) have been found to play an important role in healing and in pathological conditions. This phenotype, if expressed by meniscal cells, could affect their behavior in cell-seeded matrices developed for tissue engineering. In this study, the presence of a contractile actin isoform, alpha-smooth muscle (alpha-SM) actin, was assessed by immunohistochemistry in normal calf meniscal tissue and in meniscal cells in 2- and 3-dimensional culture. Calf meniscus cells were seeded in type I and type II collagen-glycosaminoglycan (GAG) matrices. The diameter of the matrices was measured every 2-3 days. Immunohistochemical staining of the 2-dimensional cultures for alpha-SM actin was performed after 1, 3, and 7 days and the staining of the seeded matrices was at 1, 7, 14, and 21 days. Transmission electron microscopy (TEM) was performed on selected samples. After 3 weeks the seeded type I matrices displayed a significant shrinkage of almost 50% whereas the type II matrix and both types of unseeded controls showed almost no contraction over the same time period. Positive staining for the alpha-SM actin phenotype was seen in 10% of the cells of the normal tissue but was present in all cells seeded in monolayer and in both types of matrices. TEM of representative cell-seeded matrices showed microfilaments approximately 7 nm thick, consistent with the myofibroblast phenotype. This is the first report of alpha-SM actin containing cells in the knee meniscus. The finding that, under certain conditions, meniscal cells can express the myofibroblast phenotype warrants study of their role in meniscal healing and the tissue response to implants to facilitate tissue regeneration.

Implantable bioelectric interfaces for lost nerve functions

Neuronal cells are unique within the organism. In addition to forming long-distance connections with other nerve cells and non-neuronal targets, they lose the ability to regenerate their neurites and to divide during maturation. Consequently, external violations like trauma or disease frequently lead to their disappearance and replacement by non-neuronal, and thus not properly functioning cells. The advent of microtechnology and construction of artificial implants prompted to create particular devices for specialised regions of the nervous system, in order to compensate for the loss of function. The scope of the present work is to review the current devices in connection with their applicability and functional perspectives. (1) Successful implants like the cochlea implant and peripherally implantable stimulators are discussed. (2) Less developed and not yet applicable devices like retinal or cortical implants are introduced, with particular emphasis given to the reasons for their failure to replace very complex functions like vision. (3) Material research is presented both from the technological aspect and from their biocompatibility as prerequisite of any implantation. (4) Finally, basic studies are presented, which deal with methods of shaping the implants, procedures of testing biocompatibility and modification of improving the interfaces between a technical device and the biological environment. The review ends by pointing to future perspectives in neuroimplantation and restoration of interrupted neuronal pathways.