Bioorthogonal DOPA-NGF activated tissue engineering microunits for recovery from traumatic brain injury by microenvironment regulation

Stem cell treatment is vital for recovery from traumatic brain injury (TBI). However, severe TBI usually leads to excessive inflammation and neuroinhibitory factors in the injured brain, resulting in poor neural cell survival and uncontrolled formation of glial scars. In this study, a bioorthogonal microenvironment was constructed on biodegradable poly(lactide-co-glycolide) (PLGA) microcarriers through immobilization of mussel-inspired bioorthogonal 3,4-dihydroxyphenylalanine-containing recombinant nerve growth factor (DOPA-NGF) and human umbilical cord mesenchymal stem cells (hUMSCs) for minimally invasive therapy of TBI. Cell culture and RNA-seq analysis revealed enhanced extracellular matrix (ECM) secretion and viability of hUMSCs on PLGA microcarriers compared to 2D culture. Immobilized DOPA-NGF further promoted adhesion, proliferation, and gene expression in RSC96 neurotrophic cells and hUMSCs. Specifically, the neurotrophin receptor of NT-3 (NTRK3) in hUMSCs was activated by DOPA-NGF, leading to MYC transcription and paracrine enhancement to build an adjustable biomimetic microenvironment. After transplantation of microunits in animal models, the motor and learning-memory ability of TBI mice were improved through rollbacks of overactivated inflammatory reaction regulation, neuronal death, and glial scar formation after injury. This was attributed to the paracrine enhancement of hUMSCs activated by the DOPA-NGF. Our study provides a neural regenerative microenvironment-based therapeutic strategy to advance the effects of transplanted hUMSCs in cell-based regenerative medicine for TBI therapy. Extensive studies have demonstrated the importance of the microenvironment for posttraumatic brain injury recovery. However, an efficient method that can mimic the neural regenerative microenvironment to strengthen stem cell therapy and brain injury recovery is still absent. In this study, the minimally invasive transplantation of DOPA-NGF immobilized biodegradable microcarriers with mesenchymal stem cells was found to be an effective method for regeneration of injured brain. Moreover, transcriptome analysis revealed that neurotrophin receptor of NT-3 (NTRK3) was activated by DOPA-NGF for MYC transcription and paracrine enhancement to build a kind of adjustable biomimetic microenvironment for brain injury therapy. This study provides a neural regenerative microenvironment-based therapeutic strategy to advance the transplanted hUMSCs in cell-based regenerative medicine for neural recovery.