Post Doctoral Scientist Cedars-Sinai Board of Governors Regenerative Medicine Institute LOS ANGELES, California, United States
Abstract: Intervertebral disc (IVD) degeneration is a major cause of low back pain, with limited treatment success. Stem cell-based therapy offers a promising treatment option. Direct cell delivery faces challenges like cell leakage and low cell survival due to stressing microenvironment in the IVD. To address this challenge, we developed an injectable photo-cross-linkable methacrylated fibrinogen-based (FibMA) microgel system to encapsulate and precondition the cells, improving their stability. Human nucleus pulposus-derived progenitor cells were used as the target cells in this study. Cell-encapsulated microgels fabrication process was optimized for FibMA concentration, UV crosslinking intensity, and exposure duration. No DNA damage occurred in cells with this protocol. With an optimized process we have prepared and compared two different sizes of microgels. Microgels with 120µm and 450µm diameters after 7 days in culture exhibited cell viability of about 250% and about 100%, respectively and ECM gene expression after 5 weeks of culture. The larger microgels (450µm) facilitate greater cell cytoskeleton formation and spreading throughout the microgel compared to the smaller ones (120µm) and immunostaining confirms the secretion of COL2 and ACAN matrix proteins within the microgels. Furthermore, we assessed the safety and efficacy of the cell-loaded microgel using the rat lumbar disc needle puncture model. Disc regeneration analysis was done by CT imaging and histopathological analysis. Additionally, biobehavioral studies, including cold sensitivity and von Frey tests, were used to test if the treatment not only facilitates disc regeneration but also alleviates pain. To investigate the cell fate of the human encapsulated cells in the rat disc single cell RNA sequencing was used. This study demonstrates that the optimized FibMA microgel system supports high-quality cell encapsulation, and stability, and promotes tissue regeneration in vivo. The advanced injectable microgels and stem cell therapies offer promising prospects for clinical applications to treat discogenic low back pain.
Funding Source: This study was supported by NIH R34NS126032, CIRM DISC2-14049 and CIRM scholarship (to NM) EDUC4-12751
