Enhancing hMSC Attachment to Fibrin Microthreads

Purpose: A limiting factor to the success of cellular therapies for cardiac regeneration is the lack of an efficient and targeted delivery system. Our lab has developed a fibrin suture based approach that has a delivery efficiency of over 60%. However, the method used to seed cells onto the fibrin sutures remains inefficient; this study seeks to improve cell-loading efficiency. Methods: 2cm long fibrin sutures, comprised of 24 microthreads twisted together around the eye of a needle to form a suture, were seeded with 100ul of a 2.5x10⁵, 5.0x10⁵, and 1x10⁶ human mesenchymal stem cells/1ml suspension for 6, 12, and 24 hours.  Cell attachment on the suture was visualized through phalloidin (F-actin) and Hoechst staining. Cell quantity, obtained through a Cyquant assay, and seeding efficiency were calculated. Results: No statistical significance was found in cell attachment or seeding efficiency between the different incubation times, indicating that cells seed equally well at all time points. There were no significant differences in cell attachment for the 5.0x10⁵ and 1x10⁶ groups; the 2.5x10⁵  group was significantly different than the previous groups . However, there was a significant difference in percent efficiency between the 5.0x10⁵ and 1x10⁶ groups, indicating that seeding fewer cells yields a more efficient cell attachment.  Conclusions: These data indicate that incubating fibrin sutures with fewer cells compared to previously reported studies yield higher loading efficiency and shorter loading times. This improved cell loading efficiency results, together with improved delivery efficiency, reduces the number of cells that need to be grown for implantation in the heart.