Bone marrow mesenchymal stem cells stimulated with low‐intensity pulsed ultrasound: Better choice of transplantation treatment for spinal cord injury

Abstract

Summary Stem cell transplantation, especially treatment with bone marrow mesenchymal stem cells (BMSCs), has been considered a promising therapy for the locomotor and neurological recovery of spinal cord injury (SCI) patients. However, the clinical benefits of BMSCs transplantation remain limited because of the considerably low viability and inhibitory microenvironment. In our research, low‐intensity pulsed ultrasound (LIPUS), which has been widely applied to clinical applications and fundamental research, was employed to improve the properties of BMSCs. The most suitable intensity of LIPUS stimulation was determined. Furthermore, the optimized BMSCs were transplanted into the epicenter of injured spinal cord in rats, which were randomized into four groups: (a) Sham group (n = 10), rats received laminectomy only and the spinal cord remained intact. (b) Injury group (n = 10), rats with contused spinal cord subjected to the microinjection of PBS solution. (c) BMSCs transplantation group (n = 10), rats with contused spinal cord were injected with BMSCs without any priming. (d) LIPUS‐BMSCs transplantation group (n = 10), BMSCs stimulated with LIPUS were injected at the injured epicenter after contusion. Rats were then subjected to behavioral tests, immunohistochemistry, and histological observation. It was found that BMSCs stimulated with LIPUS obtained higher cell viability, migration, and neurotrophic factors expression in vitro. The rate of apoptosis remained constant. After transplantation of BMSCs and LIPUS‐BMSCs postinjury, locomotor function was significantly improved in LIPUS‐BMSCs transplantation group with higher level of brain‐derived neurotrophic factor (BDNF) and nerve growth factor (NGF) in the epicenter, and the expression of neurotrophic receptor was also enhanced. Histological observation demonstrated reduced cavity formation in LIPUS‐BMSCs transplantation group when comparing with other groups. The results suggested LIPUS can improve BMSCs viability and neurotrophic factors expression in vitro, and transplantation of LIPUS‐BMSCs could promote better functional recovery, indicating possible clinical application for the treatment of SCI.

Ultrasound Therapy: Experiences and Perspectives for Regenerative Medicine

“…Several studies have reported that LIPUS stimulates cell proliferation without impacting on cell viability [ 27 , 28 ] or apoptosis [ 36 ], establishing it as a safe tool to improve the properties of stem cells. Indeed, some studies have reported that ultrasound also enhances cell viability, as shown for human alveolar bone-derived MSC [ 37 ] and iPSC–NCSC [ 33 ].…”

“…However, with respect to potential clinical applications, the majority of differentiation studies with LIUS have been performed with MSC or their derivatives under specific conditions of differentiation. For MSC cultured in the specific induction medium, LIPUS enhances the expression of osteogenic [ 31 , 37 , 45 , 59 , 61 , 62 , 63 , 64 ], chondrogenic [ 64 , 65 , 66 , 67 , 68 , 69 , 70 ] and adipogenic [ 59 , 71 ] markers, and also hepatic [ 72 ] and neural [ 36 ] lineages and astrocytes [ 73 ].…”

“…Besides, differentiation of MSC to the neuronal lineage is also enhanced by LIPUS through the induction of neural markers and neurotrophic factors [ 36 , 79 ]. With regards to pluripotent stem cells, LIPUS induces neural differentiation in vitro in iPSC-NCSC [ 33 , 80 ], which has the potential for the regeneration of injured nerves.…”

“…Tissue engineering encounters many challenges, especially with regards to restoring adequate mechanical strength, which is correlated with matrix production by the engineered tissues. In a recent study using a rabbit spinal cord injury model, LIPUS was found to enhance cell expansion, differentiation, and matrix production by different cells [ 36 ]. Likewise, LIPUS stimulation led to better structural formation in the context of new osteogenic and chondrogenic tissue formation, and integration of the newly formed tissues and original bone [ 36 ].…”

SDF-1/CXCR4 Axis-mediated Migration of Systematically Transplanted Bone Marrow Mesenchymal Stem Cells Towards the Injured Spinal Cord in a Rat Model

“…Recent studies con rm the potential therapeutic application of bone marrow-derived MSCs in animal models of neurological disease, including SCI, stroke, and sclerosis [38][39][40]. The rat is the animal most frequently used in models of SCI, because of low cost, size, and accessibility.…”