Contrast agents for photoacoustic imaging: a review of stem cell tracking.

With the advent of stem cell therapy for spinal cord injuries, stroke, burns, macular degeneration, heart diseases, diabetes, rheumatoid arthritis and osteoarthritis; the need to track the survival, migration pathways, spatial destination and differentiation of transplanted stem cells in a clinical setting has gained increased relevance. Indeed, getting regulatory approval to use these therapies in the clinic depends on biodistribution studies. Although optoacoustic imaging (OAI) or photoacoustic imaging can detect functional information of cell activities in real-time, the selection and application of suitable contrast agents is essential to achieve optimal sensitivity and contrast for sensing at clinically relevant depths and can even provide information about molecular activity. This review explores OAI methodologies in conjunction with the specific application of exogenous contrast agents in comparison to other imaging modalities and describes the properties of exogenous contrast agents for quantitative and qualitative monitoring of stem cells. Specific characteristics such as biocompatibility, the absorption coefficient, and surface functionalization are compared and how the labelling efficiency translates to both short and long-term visualization of mesenchymal stem cells is explored. An overview of novel properties of recently developed optoacoustic contrast agents and their capability to detect disease and recovery progression in clinical settings is provided which includes newly developed exogenous contrast agents to monitor stem cells in real-time for multimodal sensing.

The effect of infrasound on the growth of bone marrow mescenchymal stem cells / 中华物理医学与康复杂志

Objective To investigate the effect of infrasound on the growth of bone marrow mescenchymal stem cells (BMSCs) and seek the most reasonable duration for using infrasound. Methods The primary BMSCs were obtained from Sprague-Dawley rats through whole bone marrow adherent cultivation.The cells of passage 3 were divided into trial groups treated with infrasound for 10 min,30 min or 60 min,and control groups which were not treated with infrasound but exposed to air for the same durations.The vitality of cell proliferation was measured using the CCK8 method.Apoptosis and the cell cycle were analysed with flow cytometry (FACS). Results After cultivation for 72 h,the optical density (OD) values for BMSCs treated with infrasound for 10 min,30 min and 60 min were 1.480 ± 0.030,1.348 ± 0.030,1.493 ± 0.030 respectively and after 96 h they were 1.774 ± 0.030,1.731 ± 0.030 and 1.833 ± 0.030.All of which were significantly greater than in the control groups ( 1.479 ± 0.030,1.267 ±0.030 and 1.227 ± 0.030 after 72 h and 1.567 ± 0.030,1.563 ± 0.030 and 1.632 ± 0.030 after 96 h).With the extension of the treatment duration,the OD values of the BMSCs increased or increased after decreasing,and the OD value for BMSCs treated with infrasound for 60 min was the highest.The FACS results indicated no effect of infrasound on apoptosis of BMSCs when the treatment duration was 30 min,but that cell apoptosis could be inhibited when the treatment duration was 10 min or 60 min.The early phase apoptosis rates were 1.07％ ± 0.12％ and 0.97％ ±0.21％ in the trial groups treated for 10 min and 60 min respectively,and 1.43％ ± 0.06％ and 3.33％ ± 0.15％ in the respective control groups,a highly significant difference.The results of cell cycle analysis showed infrasound could disturb the cell division of BMSCs significantly when the treatment duration was less than 30 min,but there was no significant effect when the treatment duration was 60 min. Conclusions Infrasound can promote cell proliferation and disturb cell division,but it did not cause apoptosis of BMSCs.When the treatment duration was 60 min,cell proliferation improved steadily,the apoptosis rate decreased,and the cell cycle did not change.So 60 min is the most reasonable treatment duration for infrasound.