System, method and apparatus for carrying out isometric exercises for therapeutic purposes. More specifically, this semi-permeable microcapsule has a bead enclosing a material such as living cells, covalently linked to a semi-permeable layer, made of a polycation cross-linking derivative, covering the bead. It can be usefully used in treating neurodegerative diseases such as aging, cancer, diabetes, ischemic stroke, Parkin’s disease, dementia and Huntinton’s disease.