Both Juxtacrine and Paracrine Signaling Indispensable in Spermatogonial Stem Cell Cultures

Objective To prove that juxtacrine and paracrine signaling are essential in the culture of spermatogonial stem cells (SSCs) with Sertoli cell feeder layer in vitro. Methods Mice aged 7 d were chosen to harvest testes. A two-step enzyme digestion method was applied in testis suspension. The SSCs and Sertoli cells were separated by adherence distinguishing methods and biologically identified by immunofluorescence and Oil Red O staining methods. Flow cytometry was used to analyze purity of SSCs. Three groups were constructed according to different culture conditions: SSC and Sertoli cell co-culture group, SSC conditional culture group and SSC routine culture group. The conditional medium was collected from supernate of culture Sertoli cell in vitro and double-concentrated with DMEM/F12 and fetal bovine serum in a proportion of 4.5 : 4.5 : 1. The routine medium was DMEM/F12 containing 10% fetal bovine serum. Adherence rates were measured by Trypan blue staining. Absorbance of SSCs of each group was measured by MTT assay and proliferation curves shown to demonstrate proliferative features of SSCs. Proliferative features and colony formation were observed by inverted microscope. With 24 h difference in adherence rates, proliferations were compared and analyzed. Results The adherence rate of co-culture group was greater than that in the others (P 0.05). SSCs of co-culture group showed stable proliferation immediately following inoculation. A stable colony formed within 7–10 d and maintained for 30 d. SSCs in conditional culture group and routine group decreased rapidly following transient proliferation. Conclusion The actions of SSCs in Sertoli cell cultures in vitro depended on both juxtacrine and paracrine signaling, Sertoli cell paracrine signaling was unable to promote SSC adherence and proliferation alone.