(092) Leptin Increases T-cells in Testis to Modulate Leydig Stem Cell Function
Authors: Arora H , Deepa S , Firdaus F , Ledisma B 
Published: May 2023

Abstract

Introduction
Testis microenvironment which is comprised of cells like Sertoli and peritubular cells releases paracrine factors which could potentially modulate testicular functions. In our previous studies, we identified Leptin as a key paracrine factor in the testicular microenvironment, released by Sertoli and peritubular cells and goes to bind its receptor in Leydig cells. Once this association happens it further induces the expression of the desert hedgehog signaling pathway, which is known to play an important role in the Leydig Stem cell’s differentiation to Adult Lydig Cells, which are capable of producing testosterone. However, one of the limitations in our study was that the model we used were from human cells that were extracted from testes’ biopsies which lacked an intact immune microenvironment. In the present study we explored the influence of Leptin on an intact testicular immune microenvironment.

Objective
To explore the influence of Leptin on an intact testicular immune microenvironment.

Methods
We used 6-weeks old C57BL6 mice which were exposed to two different concentrations of Leptin, 10 and 100 mg/ml for seven days. After seven days of treatment, these animals were humanly sacrificed and we collected their blood and testes. Blood was subjected to the CBC differential profile performed using EDTA anti-coagulated blood samples with a Hemavet Mascot Multispecies Hematology System Counter 1500R (CDC Technologies, Inc., Oxford, CT). Samples were counted no longer than five minutes after blood was drawn. In addition to that, the testes were used and subjected to comprehensive immunophenotyping that allowed us to evaluate in detail the impact of Leptin treatment at different doses on different immune cell types which are found within the testes.

Results
Results showed that Leptin at low dose (10mg/ml) showed increased levels of serum Testosterone (13.20 + 0.37 ng/dl) but were not significant, LH and FSH (LH 0.016 + 0.02 ng/ml, FSH in 51.71 + 12.93 ng/ml) showed significant (p&lt;0.05) increase. On the contrary, animals which received Leptin at 100mg/ml showed no significant changes in hormone levels. CBC profiling suggested that amongst all the factors that were compared, Lymphocytes and Platelets were significantly influenced specifically upon low doses of Leptin. Interestingly, comprehensive immunophenotyping highlighted that the animals that received Leptin at low doses had a significant increase in the total number of CD4+ (helper T cells) and CD8+ (Cytotoxic T lymphocytes) cells. This pattern was not observed in animals which received high doses of Leptin.

Conclusions
The observation made in this study highlights unexplored aspects of influence of paracrine factors released by Sertoli and peritubular myoid cells on modulating immune microenvironment within the testis to potentially influence testosterone production. In future studies we will be exploring how the changes in the different immune cell types are correlated directly with the increase in T cells and how this correlation can influence the Leydig Stem Cell differentiation into Leydig Adult Cells.

Disclosure
No