159
10.2.3 Germ Cell Activity
Several decades ago, we have hypothesized that germ cell control Sertoli cell structure and function by three major mechanisms: i) morpho-regulatory mechanisms
and the involvement of plasma membrane molecules; ii) the transfer of material and
cell-shape changes; and iii) the production of germ cell soluble factors. Regarding
the latter pathway, it has been demonstrated that germ cells can regulate the activity
of Sertoli cell through the secretion of factors of proteinaceous nature (for a review
see [18]. Changes in the composition of the germ cell complement and in germ cell
size and shape, as well as germ cell divisions and migration, will profoundly affect
Sertoli cell morphology and function.
10.2.4 The Peritubular Cell-Seminiferous Epithelium
Communication System
The dialog between the myoid peritubular cells, which border the seminiferous epithelium and the Sertoli cells is very important during fetal and post-natal development of the testis The myoid cells contribute to the constitution of the BTB, insure
the structural cohesion and contraction of the tubules, and produce, in cooperation
with the Sertoli cells, the extracellular matrix, which separates Sertoli from myoid
cells. This matrix is required for the promotion and maintenance of Sertoli cell
polarity and migration, but also cord formation in the fetal testis.
10.2.5 The Sertoli Cell-Leydig Cell Communication System
Because the seminiferous tubules and the interstitium are anatomically distinct,
cells inside the tubules and Leydig cells can only communicate through soluble
signals. Indeed, this communication system is simpler than the intratubular communication network. The interdependence of Sertoli cells and Leydig cells, and the
crucial role played by testosterone on peritubular and Sertoli cells, and thus on
spermatogenesis are well established [19, 20], although, apart from testosterone, the
identity of signals these cells may exchange remains poorly known.
10.2.6 Regulation of Spermatogenesis
Spermatogenesis is a very complex process controlled by juxtacrine, paracrine and
endocrine factors and conditioned by the successive activation and/or repression of
thousands of genes and proteins [21]. In this regard, the local regulation of
10 An Overview of Male Reproductive Toxicants: Facts and Opinions
10.2.3 Germ Cell Activity
Several decades ago, we have hypothesized that germ cell control Sertoli cell structure and function by three major mechanisms: i) morpho-regulatory mechanisms
and the involvement of plasma membrane molecules; ii) the transfer of material and
cell-shape changes; and iii) the production of germ cell soluble factors. Regarding
the latter pathway, it has been demonstrated that germ cells can regulate the activity
of Sertoli cell through the secretion of factors of proteinaceous nature (for a review
see [18]. Changes in the composition of the germ cell complement and in germ cell
size and shape, as well as germ cell divisions and migration, will profoundly affect
Sertoli cell morphology and function.
10.2.4 The Peritubular Cell-Seminiferous Epithelium
Communication System
The dialog between the myoid peritubular cells, which border the seminiferous epithelium and the Sertoli cells is very important during fetal and post-natal development of the testis The myoid cells contribute to the constitution of the BTB, insure
the structural cohesion and contraction of the tubules, and produce, in cooperation
with the Sertoli cells, the extracellular matrix, which separates Sertoli from myoid
cells. This matrix is required for the promotion and maintenance of Sertoli cell
polarity and migration, but also cord formation in the fetal testis.
10.2.5 The Sertoli Cell-Leydig Cell Communication System
Because the seminiferous tubules and the interstitium are anatomically distinct,
cells inside the tubules and Leydig cells can only communicate through soluble
signals. Indeed, this communication system is simpler than the intratubular communication network. The interdependence of Sertoli cells and Leydig cells, and the
crucial role played by testosterone on peritubular and Sertoli cells, and thus on
spermatogenesis are well established [19, 20], although, apart from testosterone, the
identity of signals these cells may exchange remains poorly known.
10.2.6 Regulation of Spermatogenesis
Spermatogenesis is a very complex process controlled by juxtacrine, paracrine and
endocrine factors and conditioned by the successive activation and/or repression of
thousands of genes and proteins [21]. In this regard, the local regulation of
10 An Overview of Male Reproductive Toxicants: Facts and Opinions