Deficiency of CDKN1A or both CDKN1A and CDKN1B affects the pubertal development of mouse Leydig cells

Area of Science:

• Reproductive biology
• Molecular endocrinology
• Cell cycle regulation

Background:

• Cyclin-dependent kinase inhibitors p21 (CDKN1A) and p27 (CDKN1B) are expressed in Leydig cells.
• Previous studies showed Cdkn1b knockout increased Leydig cell proliferation but reduced steroidogenesis.
• The distinct roles of CDKN1A and CDKN1B in Leydig cell regulation were not fully understood.

Purpose of the Study:

• To investigate the relative importance of CDKN1A and CDKN1B in regulating Leydig cell proliferation and steroidogenesis.
• To compare Leydig cell characteristics in wild-type, Cdkn1a knockout, and double knockout mice.

Main Methods:

• Whole-body knockout of CDKN1A (Cdkn1a(-/-)) and combined CDKN1A/CDKN1B (DBKO) in mice.
• Analysis of Leydig cell number, proliferation (5-bromo-2-deoxyuridine incorporation), and steroidogenesis.
• Quantification of steroidogenic enzyme mRNA and protein levels, including LHCGR, STAR, CYP11A1, CYP17A1, and HSD17B3.

Main Results:

• DBKO mice exhibited a doubled Leydig cell number per testis compared to wild-type.
• Cdkn1a(-/-) mice showed no change in Leydig cell number but had lower LHCGR mRNA levels.
• DBKO mice displayed significantly reduced testicular testosterone levels and expression of key steroidogenic enzymes.
• Steroidogenesis was significantly decreased in DBKO mice, despite increased Leydig cell numbers.

Conclusions:

• Cdkn1a knockout alone did not increase Leydig cell numbers but impaired Leydig cell function.
• Combined knockout of Cdkn1a and Cdkn1b (DBKO) significantly increased Leydig cell proliferation.
• DBKO resulted in a marked decrease in steroidogenesis, indicating a critical role for both inhibitors in maintaining Leydig cell function and steroid production.