Angiogenesis and vascular network of teratocarcinoma from embryonic stem cell transplant into seminiferous tubules

Abstract

BACKGROUND: Carcinoma in situ (CIS) of the testis is considered to be a precancerous germinal cell lesion, but the precise cellular and molecular mechanisms underlying transformation of CIS into invasive pluripotent cancer cells remain to be elucidated. Moreover, a satisfactory animal model for the experimental study of germinal tumours has not been developed to date. METHODS: We have developed a tumour model that involves the microinjection of green fluorescent protein-labelled embryonic stem (ES) cells (which are functionally equivalent to CIS cells) into syngenic mouse seminiferous tubules, a unique cell microenvironment in which germinal cells mature and CIS arise. To characterise the vascularisation of teratocarcinomas, which arise after cell transplant, we used immunohistochemistry, together with a qualitative and quantitative analysis of scanning electron microscopy images of corrosion casting samples. RESULTS: Embryonic stem cells transplanted into seminiferous tubules did not differentiate into germinal cells, but rather they behaved as invasive embryonal carcinoma (EC) stem cells. The vascular pattern of the experimental teratocarcinomas showed a highly disorganised architecture, and some of the neoplastic capillaries were derived, at least in part, from the original transplanted ES cells. CONCLUSION: The transplantation of pluripotent ES cells into seminiferous tubules efficiently recapitulates the early stages of development of teratocarcinomas. Consequently, this method constitutes a novel in vivo model to study the mechanisms of invasion and progression of experimental germinal tumours.

Anatomical basis for cell transplantation into mouse seminiferous tubules

“…The injection of self-polymerizing resins into hollow spaces of organs and tumors is a broadly used technique, especially in the study of blood and lymphatic capillaries (Ohtani & Ohtani 2008, Silván et al 2009. When employed in the study of testis anatomy, this approach resulted in replicas of the testicular luminal spaces that could be visualized under the scanning electron microscope.…”

“…Although cell transplantation into the mouse seminiferous tubules is a widely used technique for the study of germ cell differentiation and germinal cancer invasion processes (Parreira et al 1998, Li et al 2008, 2010, Silván et al 2009, 2010, 2011, the high-resolution anatomy of the seminiferous tubule network and its connections has never been precisely described. This knowledge would facilitate the transplantation technique and more in-depth analysis of the obtained results.…”

“…Until now, several different cell types have been used in transplantation experiments including adult spermatogonia (Brinster & Avarbock 1994, Avarbock et al 1996, Clouthier et al 1996, Ogawa et al 1999, 2000, Li et al 2010, primitive germinal cells and gonocytes (Jiang & Short 1998), embryonic stem cells (Silván et al 2009(Silván et al , 2010(Silván et al , 2011, bone marrow stem cells (Lue et al 2007), Sertoli cells (Shinohara et al 2003), and seminoma and embryonal carcinoma cell lines (Li et al 2008).…”

The role of microenvironment in testicular germ cell tumors

“…9 Taking advantage of the comparability between ES and EC cells, a similar model of ES-derived tumors based on the transplantation of ES cells into the seminiferous tubuli has been successfully used in the study of teratocarcinoma neovascularization and could be a useful tool for the analysis of the germ cell tumor microenvironment in vivo. 13,14 It is currently accepted that carcinoma in situ (CIS) or intratubular germ cell neoplasia, is the common precursor of both seminomas and non-seminomas (Fig. 1).…”

The spermatogonial stem cell niche in testicular germ cell tumors

“…Thus, it is possible that the undifferentiated cell population present in TGCTs takes advantage of the impaired blood supply and proliferates faster, originating, depending on the presence of additional growth factors, endothelial cells. In fact, transplantation of ES cells into the seminiferous tubules revealed their differentiation into endothelial cells that form part of the neoplastic vascular system (Silván et al, 2009a). Since the undifferentiated cell population of TGCTs has a differentiation potential comparable to that of ES cells (Aréchaga, 1993), it is likely that part of the vessels in spontaneous TGCTs as well arise from neoplastic cells.…”