Changes in the Concentration and Size of Testicular Macrophages during Development

Abstract

Structural and functional interactions exist between Leydig cells and testicular macrophages of adult rats. Since the function of Leydig cells changes during critical periods of development and postnatal maturation, it is possible that macrophages are in part involved in regulating this process. As a first step towards gaining an understanding of the development of this paracrine phenomenon, I have undertaken a series of studies designed to determine when macrophages first become identifiable in the fetal tests and to determine whether the concentration or size of macrophages changes during important stages of testicular maturation. Macrophages were identified immunohistochemically in frozen sections of testis from rats at various prenatal and postnatal ages using commercially available monoclonal antibodies to proteins specific to rat macrophages. It was found that macrophages positive for these antigens were found only within the interstitial compartment and were commonly associated with clusters of presumptive Leydig cells that were negative for these antigens. Macrophages were first identifiable in the testis at Day 19 of fetal development. The number of macrophages/unit area of interstitium increased 15-fold between Day 20 of gestation and Day 47 postpartum. The cross-sectional area of the macrophages increased 1.7-fold between Days 13 and 47 postpartum. These results demonstrate that the number and size of testicular macrophages changes with age, suggesting a role for these cells during important times of testicular development and maturation.

Yolk-sac–derived macrophages regulate fetal testis vascularization and morphogenesis

“…Although macrophages are known to populate the interstitium of the postnatal and adult rat testis (20,47), little is known about their fetal origins. Although some reports have documented the presence of macrophages in the fetal rat testis as early as E16.5-E19 (47,48), there has been no investigation of the role of macrophages during the initial steps of fetal testis organogenesis. Here we demonstrated that differentiated macrophages expressing wellcharacterized markers such as F4/80 and IBA1 are detectable in the UGR at the initial stages of gonad specification (E10.5).…”

Bismuth Uptake in Rat Testicular Macrophages: A Follow-up Observation Suggesting that Bismuth Alters Interactions Between Testicular Macrophages and Leydig Cells

“…Control procedures concerning the specificity of bismuth staining were applied as recommended and the procedures for ED-2 IHC were as described by Hutson (1990). All sections were counterstained with toluidine blue.…”

“…It was therefore suggested that bismuth had accumulated in rat Leydig cells, exhibiting a direct toxic effect on these cells. Because macrophages are found in the testis at a relatively high concentration (Miller et al 1983;Hutson 1990) and have been shown to phagocytose a variety of foreign substances (Wei et al 1988), we were interested in determining if these cells also accumulate bismuth. Because testicular macrophages exert local influences on Leydig cells, accumulation of bismuth in these cells could have functional significance (Hutson 1994(Hutson ,1998.…”

Building the mammalian testis: origins, differentiation, and assembly of the component cell populations

“…They are known to play important protective and functional roles during reproductive life (Hutson 2006;Pé rez et al 2013). When they first populate the testis is not clear: In rats, testicular macrophages were first reported to arise just before 19 dpc (Hutson 1990), but a subsequent study reported their presence ;3 d earlier (Livera et al 2006). It is commonly assumed that they arise from circulating blood monocytes (Hutson 2006).…”

“…Testicular macrophages have a distinctive phenotype, associating with Leydig cells to form junctional complexes (Christensen and Gillim 1969;Miller et al 1983;Hutson 1990). In the mature testis, macrophages influence steroidogenesis in Leydig cells, secreting 25-hydroxycholesterol, which is acquired by ALCs and used in testosterone synthesis (Lukyanenko et al , 2001Nes et al 2000).…”