Cell Biology
C.S. Sureka, C. Armpilia in Radiation Biology for Medical Physicists, 2017
In plants and animals, there are two major types of cells: germ cells and somatic cells. Germ cells are involved in reproduction, for example, egg cells in female and sperm cells in male. All other cells in the body are somatic cells. Each human somatic cell contains two complete sets of chromosomes (one from each parent). This number is known as the diploid (2n) number. For example, in humans, somatic cells contain 46 chromosomes organized into 23 pairs. But germ cells have unpaired chromosomes and are known as the haploid (n) number. In humans, this number is 23 unpaired chromosomes. Out of 23 pairs of chromosomes in human cells, there are two types: 22 pairs are autosomes and 1 pair is allosome (sex chromosome). Sex chromosomes in females are homozygous (XX) and in males are heterozygous (XY).
Gametogenesis
Frank J. Dye in Human Life Before Birth, 2019
The cells of the body may be classified into two categories: somatic cells and germ cells. Somatic cells are not directly involved in reproduction, and include muscle cells, skin cells, and bone cells. By contrast, germ cells are directly involved in reproduction. The subset of germ cells directly involved in fertilization are called gametes or sex cells and include spermatozoa and ova (or sperm and eggs). The formation of gametes is gametogenesis and comes in two varieties: spermatogenesis in men and oogenesis in women. Gametogenesis is the only process in the body involving meiosis (all other cell divisions are mitotic) and is confined to the gonads. However, during development, the germ cells arise outside the embryonic body and subsequently migrate into the developing gonads.
Genetics and exercise: an introduction
Adam P. Sharples, James P. Morton, Henning Wackerhage in Molecular Exercise Physiology, 2022
It is important to understand the distinction between germ cells and somatic cells. Male and female germ cells, sperm and oocyte, respectively, are termed gametes. A mature germ cell has only 22 autosomes plus one sex chromosome (i.e. 23 chromosomes in total) in its nucleus instead of the full complement of 46 chromosomes seen in somatic cells (i.e. body cells or non-germ cells). A germ cell containing 23 chromosomes is said to be “haploid”, whereas normal somatic cells contain a “diploid” set of chromosomes. When a haploid sperm and a haploid oocyte fuse, they form a diploid, fertilized oocyte, termed zygote, which is the first cell of the new organism. It has 2 × 22 autosomes plus either two X chromosomes (XX, a female) or an X and a Y (XY, a male) chromosome.
Three-dimensional bioprinting of artificial ovaries by an extrusion-based method using gelatin-methacryloyl bioink
Published in Climacteric, 2022
T. Wu, Y. Y. Gao, J. Su, X. N. Tang, Q. Chen, L. W. Ma, J. J. Zhang, J. M. Wu, S. X. Wang
Much work needs be done to confirm the efficacy of 3D bioprinting in the reproductive medicine field, such as further animal experiments, more complex printed architecture and comparison with conventional in vitro follicle culturing. The 3D printing system is sophisticated and requires expensive equipment, which limits its clinical application. An artificial ovary should enable both restoration of fertility and resumption of endocrine function. In terms of seeding cells, most studies used adult somatic cells. Cell-based hormone replacement constructs, containing GCs and theca cells, could function for as long as 90 days [9]. Adding mesenchymal stem cells or progenitor cells of GCs or TICs to the artificial ovary construction may further prolong function. Stem cells might be advantageous for ovarian bioengineering since they support GCs and steroid secretion and have follicle-rejuvenating effects when transplanted into the ovary [51–53].
The existence and potential of germline stem cells in the adult mammalian ovary
Published in Climacteric, 2019
Complete oogenesis has been achieved in vitro starting from induced pluripotent stem cells derived from mice31–34. These studies clearly demonstrate the crucial role of somatic cells in supporting germ cell development from these earliest stages. Recapitulating this process in vitro using human-derived induced pluripotent stem cells has been much more problematic and so far can only reach the stage of oogonia (Science paper Saitou group).32 In contrast, isolated human putative OSCs form oocyte/follicle structures in vitro and after transplantation in vivo7,15. The ability to obtain formation of follicles/oocytes from these cells enables characterization studies to be carried out. Expression patterns of factors required for early oocyte development as well as factors associated with entry into meiosis need to be determined, as well as detailed sequencing of populations of cells isolated from the adult ovary. Alongside characterization studies, the challenge will be to determine whether functional oocytes can be obtained from putative OSCs and this will require the development of defined culture systems. Systems that support the growth and development of immature human oocytes in vitro have been developed35,36 and will be invaluable for this work, although requiring optimization.
3D bioprinting for organ and organoid models and disease modeling
Published in Expert Opinion on Drug Discovery, 2023
Amanda C. Juraski, Sonali Sharma, Sydney Sparanese, Victor A. da Silva, Julie Wong, Zachary Laksman, Ryan Flannigan, Leili Rohani, Stephanie M. Willerth
There exists a need for an in vitro biomimetic testicular model to evaluate human testicular function, and to perform medication, drug and toxicology screens. The spermatogenic niche consists of somatic cells and supports spermatogenesis and testosterone production. These somatic cells consist of Sertoli cells, myoid cells, Leydig cells, endothelial cells, and macrophages. These cells help coordinate a complex, highly regulated sequence of processes to support the differentiation of spermatogonial stem cells (SSC) to haploid spermatids, referred to as spermatogenesis; as well as the morphologic maturation of round spermatids to elongated spermatozoa, termed spermiogenesis. The somatic cells of the testicular microenvironment govern the temporal and spatial regulation of these events through direct contact, juxtracrine and paracrine signaling.
Related Knowledge Centers
- Cell Biology
- Multicellular Organism
- Sexual Reproduction
- Cellular Differentiation
- Gamete
- Stem Cell
- Germ Cell
- Mitosis
- Cell
- Gametocyte