Microfluidic production of stem-cell microcapsules for spinal cord injury repair

Abstract

Stem cell therapy demonstrates much promise for the replacement of damaged tissue in several diseases, including spinal cord injury. However, challenges around the control of stem cell fate in situ still hinders effective recovery of the normal tissue function. Stem cell encapsulation permits their immobilization within biocompatible scaffolds, allowing for a better control of parameters such as proliferation, integration, migration and differentiation within the host tissue. A customized microfluidic device was developed for the production of alginate microcapsules. The diameter of such microcapsules could be easily controlled by the modification of the fluids flow rates, allowing for the reproducible production of highly monodisperse microcapsules. This microfluidic method was then successfully applied for the encapsulation of two different types of stem cells: (i) Neural Stem Cells and (ii) Dental Pulp Stem Cells. Both cell types demonstrated survival within the alginate microcapsules for up to three weeks in culture. However, an early egress of cells from inside to outside of the microcapsules was observed 3 days post-encapsulation. In order to delay such cell escape, alginate microcapsules were modified through the addition of type I collagen. The alginate-collagen microcapsules permitted similar rates of cell survival and permitted the delay of cell egress until 10 days after encapsulation. Stem cells demonstrated a retention of their stem cell and neuronal differentiation properties upon selective release from alginate-collagen microcapsules, as demonstrated by high proliferation rates and the production of stem cell and neuronal markers. When cell-laden microcapsules were transplanted into an ex vivo SCI model the microcapsules were able to effectively retain the transplanted stem cells at the site of implantation. Transplanted cells survived up to 10 days in culture after transplantation and demonstrated the production of neuronal markers within the cord cultures. The results presented in this thesis demonstrate the ability of stem cells to retain their viability and neuronal differentiation capacity within alginate-collagen microcapsules, thereby providing a promising future therapy for the treatment of spinal cord injury