In situ control of mesenchymal stem cell behavior using programmable biomaterials
Final Report Abstract
Our understanding of "In situ control of mesenchymal stem cell behavior using programmable biomaterials" has advanced considerably through the project. Project Obiective: This project tested the hypothesis that programmable biomaterials can be used in situ to specifically recruit expand and differentiate host bone marrow stromal mesenchymal stem cells (BMSCs) in a critical size bone defect and promote functional restoration of the tissue. Adult bone marrow derived mesenchymal stem cells (BMSC) represent an important source of cells for tissue regeneration, and biomaterials that bypass the need for ex vivo BMSC manipulation and transplantation by instead recruiting native BMSCs to aid in regeneration are very promising. The specific aims of this study were to (i) identify a chemokine to recruit BMSCs, and (ii) design a biomaterial system to deliver this chemokine in a bone defect in order to recruit BMSCs and provide recruited cells an environment to proliferate and differentiate. Identification of a chemokine to recruit BMSCs: Using a transwell assay to screen a number of candidate chemokines, it was observed that primary BMSCs showed best migratory response to Thymus Chemokine 1 (TCK 1) (upto 2.5 fold increase, p<0.05). BMSCs were also shown to respond in a dosage dependent manner when exposed to TCK 1 (10^-11,-10,-9,-8,-7 M; p<0.05). Furthermore, in a 3D migration assay using a micro-fabrication setup, BMSCs were shown to migrate to a TCK 1 gradient in a directional manner (Chemotaxis, p<0.05). Further, no inhibitory effects of TCK 1 were observed on MSC proliferation and differentiation in vitro. Design of a biomaterial svstem to deliver TCK 1: Two compartment, macroporous scaffolds were fabricated from alginate to allow for TCK 1 delivery and cell recruitment. One compartment was comprised of a slowly degrading alginate "bulk" polymer, and was intended for sustained slow release of TCK 1. The second compartment was fabricated from a rapidly degrading oxidized alginate "porogen"s in order to release TCK 1 rapidly. TCK 1 was encapsulated in each of the two compartments, and its subsequent release quantified. Encapsulation of TCK 1 in the nanoporous (control), bulk, and porogen phase's resulted in different release profiles; nanoprorous with burst release (30-35ng/day), bulk (15-20ng/day), porogen (10-15ng/day). Using the two component system it was possible to tune the release rate of TCK 1 at 15-20 ng/ day as desired for our application. The bulk alginate in the two component system was RGD modified such that when the rapidly degrading porogens result in voids, the recruited BMSCs would infiltrate the bulk gels, attach, and proliferate. Five in vivo groups were used to test our hypothesis in a rat femur defect model: (i) control-empty defect, (ii) chemokine (TCK 1) encapsulated in nanoporous, (iii) empty nanoporous gels, (iv) chemokine encapsulated in macroporous gels, and (v) empty macroporous gels. 1.2 mm defects were made in rat femurs and the gels were placed in the defects and monitored postoperatively at 3 and 10 Days. Qualitative immunehistology for MSC mariners, and microCT results indicate gels with chemokine to perform best in MSC recruitment and bone formation. The results from this study demonstrate the use of biomaterial based delivery of a chemokine (TCK-1) to recruit bone man-ow mesenchymal stem cells and its behavior.
Publications
- Biomaterial delivery of morphogens to mimic the natural heating cascade in bone. Adv Drug Detiv Rev. 2012 Sep;64(12):1257-76
Mehta M, Schmidt-Bleek K, Duda GN, Mooney DJ
(See online at https://doi.org/10.1016/j.addr.2012.05.006) - In vivo tracking of segmental bone defect healing reveals callus patterning is related to eariy mechanical stimuli. Eur Cell Mater. 2012 Nov 2;24:358-71; discussion 371
Mehta M, Checa S, Lineau J, Hutmacher DW, Duda GN
(See online at https://doi.org/10.22203/eCM.v024a26)
