Effects of Thyroid Hormone on Leydig Cell Regeneration in the Adult Rat Following Ethane Dimethane Sulphonate Treatment1

Abstract

We tested the effects of thyroid hormone on Leydig cell (LC) regeneration in the adult rat testis after ethane dimethyl sulphonate (EDS) treatment. Ninety-day-old, thyroid-intact (n = 96) and thyroidectomized (n = 5) male Sprague-Dawley rats were injected intraperitoneally (single injection) with EDS (75 mg/kg) to destroy LC. Thyroid-intact, EDS-treated rats were equally divided into three groups (n = 32 per group) and treated as follows: control (saline-injected), hypothyroid (provided 0.1% propyl thiouracil in drinking water), and hyperthyroid (received daily subcutaneous injections of tri-iodothyronine, 100 microg/kg). Testing was done at Days 2, 7, 14, and 21 for thyroid-intact rats and at Day 21 for thyroidectomized rats after the EDS treatment. Leydig cells were absent in control and hyperthyroid rats at Days 2, 7, and 14; in hypothyroid rats at all ages; and in thyroidectomized rats at Day 21. The LC number per testis in hyperthyroid rats was twice as those of controls at Day 21. 3beta-Hydroxysteroid dehydrogenase (LC marker) immunocytochemistry results agreed with these findings. Mesenchymal cell number per testis was similar in the three treatment groups of thyroid-intact rats on Days 2 and 7, but it was different on Days 14 and 21. The highest number was in the hypothyroid rats, and the lowest was in the hyperthyroid rats. Serum testosterone levels could be measured in control rats only on Day 21, were undetectable in hypothyroid rats at all stages, and were detected in hyperthyroid rats on Days 14 and 21. These levels in hyperthyroid rats were twofold greater than those of controls on Day 21. Serum androstenedione levels could be measured only in the hyperthyroid rats on Day 21. Testosterone and androstenedione levels in the incubation media showed similar patterns to those in serum, but with larger values. These findings indicate that hypothyroidism inhibits LC regeneration and hyperthyroidism results in accelerated differentiation of more mesenchymal cells into LC following the EDS treatment. The observations of the EDS-treated, thyroidectomized rats confirmed that the findings in hypothyroid rats were, indeed, due to the deficiency of thyroid hormone.

Leydig cell re-generation and expression of cell signaling molecules in the germ cell-free testis

“…Previous studies of adult Leydig cell differentiation, either during normal development or following EDS in the adult, have identified peritubular, spindleshaped/mesenchymal cells as the immediate precursor cells (Haider et al 1995, Russell et al 1995, Ariyaratne et al 2000a, 2000b. In addition, spindle-shaped peritubular cells have been described recently as Leydig cell stem cells (Ge et al 2006).…”

“…A number of studies have indicated that Leydig cell precursor cells are predominantly peritubular, based on morphological and immunohistochemical evidence (Haider et al 1995, Russell et al 1995, Haider & Sevros 1998, Ariyaratne et al 2000a, 2000b. A recent study, however, has reported that the progenitor cells are vascular smooth muscle cells and pericytes, based on the apparent neuronal and glial properties of these cells (Davidoff et al 2004).…”

Brief maternal exposure of rats to the xenobiotics dibutyl phthalate or diethylstilbestrol alters adult-type Leydig cell development in male offspring

“…Microscope images were captured on Spot analysis software (Diagnostic Instruments Inc., Sterling Heights, MI, USA) using a 3100 oil-free Figure 1 Diagram to illustrate the treatment and sampling regimen applied (small dots above the bar indicate approximate blood sampling times). The morphological changes during pubertal Leydig cell differentiation (after [16][17][18] ) are illustrated at their corresponding times in the upper section of the figure. GD, gestational day; PND, postnatal day; DBP, dibutyl phthalate; DES, diethylstilbestrol.…”

“…Leydig cells were recognized by their oval to spherical nucleus with a thin rim of heterochromatin and prominent nucleolus. [16][17][18] Finally, the entire testis cross-section was captured with 31.25 objective for determination of the surface area of each testis section. The total number of Leydig cells within the whole testis was estimated by the formula 19 : Nˆ5Q31/f 1 31/f 2 31/f 3 , where Nˆis the estimated total number, Q is the number of Leydig cells counted in the disector, f 1 is the fraction of tissue (i.e., number of randomly selected slices/number of total slices), f 2 is the fraction of sections (i.e., total number of randomly selected sections/number of total sections) and f 3 is the sampling fraction (i.e., S volume of dissectors/S volume of the entire testis section).…”

Effects of Ethane Dimethane Sulfonate on the Functional Structure of the Adult Rat Testis

“…This regenerative process of LC involves differentiation of mesenchymal cells into new LC [22,27] and mitotic divisions of newly formed LC [22,27] similar to LC differentiation in the prepubertal rat testis. Despite the considerable body of information available on cellular changes during prepubertal development [1,17], only a few investigations have attempted to study the changes in testicular interstitium quantitatively following EDS treatment [4,15,32]. None of these studies have analyzed the kinetic changes that occur in all interstitial cell types in the testis during this repopulation process and the changes in the testicular steroidogenic function after EDS administration.…”