Leptin secreted from testicular microenvironment modulates hedgehog signaling to augment the endogenous function of Leydig cells

Himanshu Arora,Madhumita Parmar,Ranjith Ramasamy,Joshua M Hare,Kajal Khodamoradi,Isabelle Catherine Issa,Dolores Lamb,Robert Sackstein,Deepa Seetharam,Derek J Van Booven,Rehana Qureshi

doi:10.1038/s41419-022-04658-3

Himanshu Arora, Madhumita Parmar + Show 9 more

Open Access

https://doi.org/10.1038/s41419-022-04658-3

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Abstract

Although testosterone deficiency (TD) may be present in one out of five men 40 years or older, the factors responsible for TD remain largely unknown. Leydig stem cells (LSCs) differentiate into adult Leydig cells (ALC) and produce testosterone in the testes under the pulsatile control of luteinizing hormone (LH) from the pituitary gland. However, recent studies have suggested that the testicular microenvironment (TME), which is comprised of Sertoli and peritubular myoid cells (PMC), plays an instrumental role in LSC differentiation and testosterone production under the regulation of the desert hedgehog signaling pathway (DHH). It was hypothesized that the TME releases paracrine factors to modulate LSC differentiation. For this purpose, cells (Sertoli, PMCs, LSCs, and ALCs) were extracted from men undergoing testis biopsies for sperm retrieval and were evaluated for the paracrine factors in the presence or absence of the TME (Sertoli and PMC). The results demonstrated that TME secretes leptin, which induces LSC differentiation and increases testosterone production. Leptin’s effects on LSC differentiation and testosterone production, however, are inversely concentration-dependent: positive at low doses and negative at higher doses. Mechanistically, leptin binds to the leptin receptor on LSCs and induces DHH signaling to modulate LSC differentiation. Leptin-DHH regulation functions unidirectionally insofar as DHH gain or loss of function has no effect on leptin levels. Taken together, these findings identify leptin as a key paracrine factor released by cells within the TME that modulates LSC differentiation and testosterone release from mature Leydig cells, a finding with important clinical implications for TD.

Highlights

Male hypogonadism is a symptomatic clinical syndrome caused by testosterone deficiency (TD) [1]
We defined the potential of subcutaneously autografting Leydig stem cells (LSCs) in combination with the testicular microenvironment (TME) (Sertoli and peritubular myoid cells (PMC)) to increase serum testosterone without affecting the HPG axis
Autograft survival and testosterone production are impaired in the absence of the TME (Sertoli and PMCs), suggesting the relevance of the TME on LSC function and the understudied role of paracrine factors released from the TME in the regulation of LSCs

Summary

INTRODUCTION

Male hypogonadism is a symptomatic clinical syndrome caused by testosterone deficiency (TD) [1]. The testis is comprised of Leydig cells, Sertoli cells, peritubular myoid cells, and germ cells Together these cell types perform two important functions—spermatogenesis and testosterone production [9–12]. We showed that in the absence of Sertoli and PMCs (which together constitute the testicular microenvironment (TME)), the function and rate of differentiation of Leydig stem cells (LSCs) is severely impaired [15]. This observation has been supported by independent studies [16], suggesting that cells within the TME release paracrine factors that are critical for stimulating the differentiation of LSCs [15, 16]. These outcomes led us to hypothesize that the TME releases paracrine factors that are important in modulating DHH signaling-induced LSC differentia-

RESULTS

Arora et al 3

DISCUSSION

Findings

METHODS