Immunosuppressants Affect Human Neural Stem Cells In Vitro but Not in an In Vivo Model of Spinal Cord Injury

Abstract

Clinical immunosuppression protocols use calcineurin inhibitors, such as cyclosporine A (CsA) or tacrolimus (FK506), or mammalian target of rapamycin (mTOR) inhibitors, such as sirolimus (rapamycin). These compounds alter immunophilin ligand signaling pathways, which are known to interact downstream with mediators for human neural stem cell (hNSC) differentiation and proliferation, suggesting that immunosuppressants may directly alter hNSC properties. We investigated whether immunosuppressants can exert direct effects on the differentiation, proliferation, survival, and migration of human central nervous system-derived stem cells propagated as neurospheres (hCNSSCns) in vitro and in an in vivo model of spinal cord injury. We identified unique, immunosuppressant-dependent effects on hCNS-SCns differentiation and proliferation in vitro. All immunosuppressants tested increased neuronal differentiation, and CsA and rapamycin inhibited proliferation in vitro. No immunosuppressant-mediated effects on hCNS-SCns survival or migration in vitro were detected. These data suggested that immunosuppressant administration could alter hCNS-SCns properties in vivo. We tested this hypothesis by administering immunosuppressants to constitutively immunodeficient spinal cord injured mice and assessed survival, proliferation, differentiation, and migration of hCNS-SCns after 14 weeks. In parallel, we administered immunosuppressants to immunocompetent spinal cord injury (SCI) mice and also evaluated hCNS-SCns engraftment and fate. We identified no effect of immunosuppressants on the overall hCNS-SCns fate profile in either xenotransplantation model. Despite a lower level of human cell engraftment in immunocompetent SCI mice, functional locomotor recovery was observed in animals receiving hCNS-SCns transplantation with no evidence of allodynia. These data suggest that local cues in the microenvironment could exert a stronger influence on hCNS-SCns than circulating levels of immunosuppressants; however, differences between human and rodent metabolism/pharmokinetics and xenograft versus allograft paradigms could be determining factors. STEM CELLS TRANSLATIONAL MEDICINE 2013;2: 731-744

Transplantation dose alters the dynamics of human neural stem cell engraftment, proliferation and migration after spinal cord injury

“…In our previous studies, hCNS-SCns transplanted at a dose of 75,000 cells exhibited an average of 250% expansion over the initial transplantation dose in this immunodeficient mouse SCI model by 12–16 WPT (Cummings et al 2005; Hooshmand et al 2009; Salazar et al 2010; Sontag et al 2013; Sontag et al 2014). To test the effect of dose on donor cell survival/expansion, we normalized the stereologically quantified number of human cells present to the initial transplantation dose to obtain the proportion of surviving cells at 2 and 16 WPT.…”

Cyclooxygenase-2 or Tumor Necrosis Factor-α Inhibitors Attenuate the Mechanotransductive Effects of Pulsed Focused Ultrasound to Suppress Mesenchymal Stromal Cell Homing to Healthy and Dystrophic Muscle

“…Using pFUS in combination with MSC infusion and drugs can provide insight into possible microenvironmental changes that would augment stem cell homing as part of regenerative medicine strategies . Evaluating the effects of various agents on stem cell homing is usually performed in controlled model systems where drugs or factors that interfere with stem cell migration in vitro may have no effect in vivo . For example, when MSC were exposed to either ibuprofen or etanercept were evaluated ex vivo (i.e., Boyden chamber), no differences in migration toward SDF‐1α in vitro were detected.…”

Safety of Human Neural Stem Cell Transplantation in Chronic Spinal Cord Injury

“…We have previously reported functional recovery following early chronic (30 DPI) [6] and subacute (9 DPI) hCNS‐SCns transplantation in immunodeficient NOD‐scid mice [4, 5], as well as in chronic (60 DPI) transplantation immunosuppressed C57BL/6 mice [92]. This study focused on evaluation of allodynia and hyperalgesia in an SCI model that exhibits cavitation.…”