Effects of GDNF and LIF on mouse spermatogonial stem cells proliferation in vitro

Spermatogonial stem cells (SSCs) are the only type of cells that transmit genes to the subsequent generations. The proliferation, cultivation and identification of SSCs in vitro are critical to understanding of male infertility, genetic resources and conservation of endangered species. To investigate the effects of glial cell-derived neurotrophic factor (GDNF) and leukemia inhibitory factor (LIF) on the proliferation of mouse SSCs in vitro, supplement of GDNF and/or LIF were designed to culture SSCs. The testes of 6–8 d mouse were harvested and digested by two-step enzyme digestion method. The SSCs and Sertoli cells were separated by differential plating. Then the SSCs were identified by alkaline phosphatase staining, RT-PCR and indirect immunofluorescence cell analysis. The cellular proliferation capacity was measured by methyl thiazolyl tetrazolium assay. The results showed that addition of 20 and 40 ng/ml of GDNF could strongly promote growth of mouse SSCs (p < 0.05). There was no significant difference between LIF treatment groups and the control group in promoting proliferation of the mouse SSCs (p > 0.05). However, the combination of 20 ng/ml GDNF and 1,000 U/ml LIF could significantly enhance the invitro proliferation of mouse SSCs (p < 0.05), and the OD₄₉₀ value was 0.696 at day 5 of culture when the density of SSCs was 5–10 × 10⁴ cells/ml.     

Bone regeneration via skeletal cell lineage plasticity: All hands mobilized for emergencies

An emerging concept is that quiescent mature skeletal cells provide an important cellular source for bone regeneration. It has long been considered that a small number of resident skeletal stem cells are solely responsible for the remarkable regenerative capacity of adult bones. However, recent in vivo lineage‐tracing studies suggest that all stages of skeletal lineage cells, including dormant pre‐adipocyte‐like stromal cells in the marrow, osteoblast precursor cells on the bone surface and other stem and progenitor cells, are concomitantly recruited to the injury site and collectively participate in regeneration of the damaged skeletal structure. Lineage plasticity appears to play an important role in this process, by which mature skeletal cells can transform their identities into skeletal stem cell‐like cells in response to injury. These highly malleable, long‐living mature skeletal cells, readily available throughout postnatal life, might represent an ideal cellular resource that can be exploited for regenerative medicine.