Project 4: Delivery of microRNA 365 for Growth Plate Cartilage Repair

Principal Investigator: Yupeng Chen, PhD

Abstract

Injury to the growth plate in children represents a significant problem for a developing long bone. The overall goal of this project is to study the cartilage regeneration potential of delivery bioactive nucleic acids or proteins (such as microRNA 365 (miR-365)) into growth plate cartilage injuries in vivo. Recently, our laboratory has developed a biomimetic delivery system for improving cartilage regeneration and defect repair. Such delivery system is based on rosette nanotubes (RNTs), a family of biomimetic self-assembled delivery devices.

Under physiological conditions, RNT building blocks (generated from DNA base pairs) undergo a self-assembly process to form nanotubes. We have found that RNTs and delivery cargos (for instance, small RNAs) can self-assemble into non-covalent yet stable nanostructures, which we termed Nanopieces. Nanopieces presenting tiny, nano-rod morphology can effectively infiltrate cartilage matrix and release delivery cargos once they are internalized by cells. We have shown that Nanopieces can functionally deliver small RNAs into chondrocytes in vitro and cartilage in vivo.

Our published studies have also shown that RNTs have excellent biocompatibility for bone and cartilage cells, making them feasible and suitable delivery vehicles for cartilage. Especially, we have shown that microRNA 365 (miR-365), activated by mechanical loading of chondrocytes, stimulates chondrocyte proliferation and differentiation through inhibiting histone deacetylase 4 in the growth plate.

Therefore, we hypothesize delivery of miR-365 into the injury site of the growth plate will improve healing of the growth plate by stimulating chondrocyte growth and differentiation. Using an established grill-hole growth plate model to create growth plate injuries on rat proximal tibia, we will injection of Nanopiece delivered miR-365 into growth plate injury sites and then determine the extent of cartilage healing via faxitron X-ray, micro-CT and quantitative histology analysis. Moreover, we will study the underlying mechanism for growth plate cartilage regeneration at molecular and cellular levels.

Relevance

Injury to the growth plate in children represents a significant problem for a developing long bone. Approximately 1.4-percent of growth plate or physeal injuries result in some type of growth arrest. Currently no therapeutic approach is available in clinics. The proposed project is aiming to develop a novel therapeutic delivery strategy for growth plate cartilage repair, which can be injected shortly after injury occurs.