12/03/2019
Reproductive Biotechnologies – Andrology I
The spermatogenesis
Prof. Alberto Contri
The spermatogenesis
Characteristics of the spermatozoon
1) Aploid cell with high condensed DNA
2) Forward motility - flagellum
3) Enzymes for the oocyte penetration - acrosome 12/03/2019
The spermatogenesis
Definition
Differentiative process that produce spermatozoa from spermatogonia
During this process the sperm modify largely the aspect and lost most of the intracytoplasmic structures - only essentials structures
The spermatogenesis
Anatomic place of the spermatogenesis
In the testis – seminiferous tubule
3 functional compartments
Interstitial
Basal
Adluminal 12/03/2019
The spermatogenesis
Main phases of the spermatogenesis
Differents phases for different cells involved
Spermatogonia
spermatocytogenesis
Spermatocytes
meiosis
Spermatids
Spermatozoa 12/03/2019
The spermatogenesis
Spermatocytogenesis
Characterized by mitotic divisions
Spermatogonia of different type
Spermatogonia from gonocytes (2 nd moNth of gestation)
Stem cell spermatogonia (Spermatogonia A)
Committed spermatogonia (Spermatogonia B)
Spermatogonia A1 The spermatogenesis - Flattened nucleus -
Spermatogonia A Spermatogonia A2 - Large nucleus with euchromatin -
Spermatogonia A3 - Larger nucleus with nucleolus/i) -
Spermatogonia B1 - Large nucleus with chromatin flakes - Spermatogonia B Spermatogonia B2 - Small nucleus with small ch. flakes - 12/03/2019
The spermatogenesis
Spermatocytogenesis
Two functions Initiate spermatogenesis (by committment of the spermatogonia)
maintain a stem cell population
Spermatogenesis is a continous process from the puberty to the dead or the disease
The spermatogenesis
Meiosis (only in gonads)
From spermatocytes to spermatids
1) Haploid
2) genetic material exchange between homologous chromosomes 12/03/2019
The spermatogenesis
Meiosis (only in gonads)
Mitosis of the B 2 spermatogonia to Primary spermatocytes in preleptotene phase
Start of the meiosis Primary spermatocytes in the adluminal compartment
The spermatogenesis
Meiosis (only in gonads)
Primary spermatocyte (DNA replication)
Secondary spermatocyte Secondary spermatocyte (Haploid with double chrom) (Haploid with double chrom)
Spermatid Spermatid Spermatid Spermatid (Haploid) (Haploid) (Haploid) (Haploid)
Cells maintained intercellular bridges - interconnection 12/03/2019
The spermatogenesis
Spermiogenesis
Morphological differentiation of spermatids
Sermatids Round small cells Round nucleus No DNA synthesis and repair
The spermatogenesis
Spermiogenesis
Four different phases
Related to the maturative changes in the spermatids
Golgi Cap ElongaTion Maturation 12/03/2019
Spermiogenesis
The spermatogenesis
Spermiogenesis Golgi phase
Predominant Golgi apparatus Formation of small vesicles Small vesicles fuse in a large
Migration of the centrioles near the nuclear envelope
Indentation of the nuclear envelope – articular fossa
Formation of an flagellar canal - tubular infolding of the PM 12/03/2019
The spermatogenesis
Spermiogenesis
Cap Phase
Acrosome vesicle flattens Surround a side of the nucleus - cap Spherical nucleus Golgi apparatus reduces Flagellar structure out of the shape of spermatid
The spermatogenesis
Spermiogenesis
ELONGATION PHASE
NUCLEUS MOVE ON THE OUTSKIRT OF THE CELL DEVELOPMENT OF THE MANCHETTE • transient microtubular structure • from the caudal region of the nucleus to the flagellum • elongation of the nucleus and the cytoplasma 12/03/2019
The spermatogenesis
Spermiogenesis
Maturation phase
Caudal migration of the manchette and lost with the residual body
Movement of the annulus in the final position
Mitochondria follow the annulus
Flagellation – synthesis of the proteins of the flagellum
The spermatogenesis
Spermiogenesis
Spermiation
Release of individual spermatozoa in the lumen Counterpart of the ovulation
Small amount of cytoplasma remained in the midpiece
Elimination of the residual body – phagocytized by Sertoli cells 12/03/2019
The spermatogenesis
Spermiogenesis
Spermiation
The spermatogenesis
Spermiogenesis
From each spermatogonium – hundreds/thousands of spermatozoa
Spermatids/spermatozoa with intercellular bridges until spermiation
Regular feature of the cell associations within the seminuferous tubule
Spermatogenic cycle 12/03/2019
The spermatogenesis
Spermatogenic cycle
Changes in a given section of the seminiferous tubule between two identical differentiation stages
Conventionally, spermiation is used as reference point
Spermatogenic cycle is the complex of the events between two consecutive spermiations
The spermatogenesis
Spermatogenic cycle
Cell association is repeated regularly along the seminiferous tubule - stage of the spermatogenic cycle –
Stage classified on presence of specific germ cells (B-spermatogonia, primary spermatocytes, secondary spermatocytes, spermatids) aspect of the spermatids (phase of the spermiogenesis)
Move by spermatogeneTic waves along the seminiferous tubule 12/03/2019
The spermatogenesis
Spermatogenic cycle
The spermatogenesis Spermatogenic cycle LengTH Time between two consecutive spermiation in near tractS of the seminiferous tubule Species-specific differences
swine 8.6 days hamster 8.7 d mouse 8.9 d ram 10.4 d horse/rabbit 12.2 d rat 12.9 d bull 13.5 d dog 13.6 d human 16 d 12/03/2019
The spermatogenesis
The spermatogenesis Length of the Spermatogenesis Related to the committment of the A-spermatogonium
4-5 generations of germ cells found in the seminiferous cycle
Conventionally spermatogenesis is 4.5 times the spermatogenic cycle lengTH
boar 39 days ram 47 days stallion 57 days rat 60 days bull and dog 61 days human 74 days 12/03/2019
Sperm excretion
After spermiation
Immotile spermatozoa Immature spermatozoa
Move in the excurrent ducts Diluted in the secretion of the Sertoli cells Move by peristaltic contration of smooth musculature
Epididymal transit and maturation
In summary
Concentrate (INCREASED OF 10 5-fold)
Maturate
Transport
Store
REQUIRE 7 DAYS (ESTIMATION) 12/03/2019
Epididymal transit and maturation
Action by modify the milieu
Presence of a blood-epididymis barrier
Metabolic modifications
Increase in intracellular AMP-c
Increase in disulfide bond of protamines
Acquiring sperm motility
Translocation and lost of the cytoplasmic droplet