b2815 Tissue Engineering and Nanotheranostics “9.61x6.69”82 Tissue Engineering and Nanotheranosticsimplementation of stem cells or stem cell derived cell types. Successful
implantation of these cells could help replace damaged or failing tissues.
Other potential applications include treating diabetes, preventing heart
disease, and creating antitumor drugs. The development of in vitro dif-
ferentiation strategies that mimic in vivo events is crucial for the crea-
tion of stem cell derived cell therapies. The following sections provide
a description of each germ layer and summarize directed differentiation
methods for cell types derived from endoderm and mesoderm.
3.1. Ectoderm
The ectoderm is the outermost layer of cells developed during gastrula-
tion. Specified ectodermal cells sit in the upper hemisphere, or animal
pole, of the blastula in a region called the animal cap. As the embryo
proceeds to develop, the ectoderm tissue will further specify into three
more subsets: the external ectoderm, the neural crest, and neural tube.
From these subsets, the ectoderm is integrated into a wide variety of
organs and systems. Ectodermal products are listed in Table 1 with the
subpopulation of ectodermal tissue from which they derive.
3.2. Endoderm
While the ectoderm forms from the outermost layer of the invaginat-
ing blastula, the tissue forming the innermost germ layer develops
into the endoderm. Endoderm gives rise to cells making up the gas-
trointestinal and respiratory tracts, endocrine glands, and the urinary
Table 1. Specialized cells derived from the ectoderm.Subpopulation
of ectoderm Products
Surface ectoderm Epidermis, hair, nails, lens of the eye, sebaceous glands, cornea,
tooth enamel, the epithelium of the mouth and nose
Neural crest Peripheral nervous system, adrenal medulla, melanocytes,
facial cartilage, dentin of teeth
Neural tube Brain, spinal cord, posterior pituitary, motor neurons, retina