Aligned Collagen Scaffold Combined With Human Stem Cells For Complete-Transection Spinal Cord Injury Repair

Spinal cord injury(SCI)is a severe traumatic injury that conveys a considerable emotional,physical and financial burden on patients and their families worldwide.The damaged spinal cord is generally difficult to be repaired and reconstructed,and the main reasons may be as follows: current therapies cannot well simulate the microenvironment required for the growth of spinal cord tissue in adult mammals and lack of neurotrophic factors that promote neural regeneration after injury;the depositon of glial scars and neural regeneration inhibitory molecules formed in the lesion microenvironment,which inhibit the signal transmission between neurons;the lack of biomaterial scaffolds which promote cell adhesion and neuron growth.Stem cell combined with biomaterial scaffold transplantation is considered to be an effective therapeutic method for SCI repair.The application of biomaterial scaffold is expected to bridge the lesion sites and provide a supporting platform to retain grafted cells in the injuried area.Furthermore,compared with random scaffolds,aligned-structure biomaterials performed better capabilities to encourage cell migration and direct axially axonal regeneration.Collagen,a main component of the extracellular matrix and widely distributed in human body,has been shown to be the most suitable natural material for functional recovery because of its low immunogenicity,excellent biocompatibility,and biodegradability.Besides,single collagen molecule has a super-helical rope-like structure that is conducive to cell adhesion and growth.Stem cell-based therapy is expected to replenish lost cells by transplanting into the lesion cavity and create a favorable condition for neural regeneration.Among these stem cell types,MSCs are widely applied in SCI studies mainly because of their simple culture method,rapid proliferation ability,anti-inflammatory ability,autocrine and paracrine effects efficiently facilitate neurons and vascular regeneration in the SCI area,and reduction of cell apoptosis.Among various types of MSCs,human umbilical cord-derived mesenchymal stem cells(human MSCs,hMSCs)have the advantages of sufficient sources,lower infection risk and immunogenicity,and free from ethical and moral constraints.Additionally,NSPC implantation has also been shown to be an effective treatment method for SCI.Grafted NSPCs can differentiate into functional mature neurons,oligodendrocytes and astrocytes at the implantation site,improve the SCI microenvironment by decreasing neuroinflammation and glial scar formation.Numerous studies have used human brain-derived NSPCs(hbNSPCs)and human spinal cord-derived NSPCs(hscNSPCs)in SCI studies.This paper mainly consists of two parts:1.Comparison of effects of transplanting three-dimensional longitudinal scaffold loaded-hMSCs and hNSCs on Spinal Cord Completely Transected RatsRecently,both hMSCs and hNSCs have been applied in clinical trials for complete/partial SCI repair by multiple counties.There're 41 registered clinal programs of stem cell transplantation,and among them,32 using MSC(4 using hMSCs)and 4 using hNSC(Information from https://clinicaltrials.gov/).However,either hMSCs or hNSCs are better for cell-based SCI therapy is not well studied.In this study,we seeded hMSCs or hNSCs on longitudinal collagen scaffolds,respectively,and then implanted the cell-scaffold constructs into completely transected SCI rats.In vitro,collagen biomaterial scaffolds with porous ordered structure were prepared and characterized;Subsequently,we detected the adhesion and growth of these 3D culture cells.In vivo,we compared the effects of cell survival and neuronal differentiation,inflammatory response and the formation of glial scars,as well as the motor function recovery of rats under the treatment of two kinds of stem cells.The results showed that both hMSCs and hNSCs had equivalent effects on reducing glial scar formation around the lesion gap.More neuronal class III ?-tubulin-positive neurons and neurofilament-positive nerve fibers were found in the lesion cavity after hNSCs implantation.In addition,hNSCs had better capabilities to improve motor function and decrease the quantity of CD68-positive immune cells than hMSCs.2.Aligned collagen scaffolds implants,seeded with hscNSPCs,improve SCI repair by promoting neuronal differentiation and attenuating inflammationAccording to the research,both hbNSPCs and hscNSPCs displayed positive effects on SCI repair.However,either hMSCs or hNSPCs,especially for the hbNSPCs and hscNSPCs,are better for cell-based SCI therapy is not well studied;Whether the combined transplantation of hNSPCs and collagen scaffold would have a better repair effect.Thus,we further investigated the regenerative effects of transplanting aligned collagen sponge scaffold(ACSS)loaded-hbNSPCs and hscNSPCs on spinal cord completely transected rats.In this study,we focused on the differentiation and maturation of neurons and glial cells in the lesion area,the inflammatory response and the distribution of glial scars by immunofluorescence staining.Finally,we evaluated the improvement of motor function of rats by electrophysiological examination,the Basso,Beattie and Bresnahan(BBB)locomotor rating scale and the inclined plane assay.We found that the hscNSPCs+ACSS effectively promoted long-term cell survival and neuronal differentiation,improved the SCI microenvironment by reducing inflammation and glial scar formation compared with the hbNSPCs+ACSS.Furthermore,the transplanted hscNSPC-ACSS resulted in improved recovery of locomotor function.Although both hMSCs and hNSPCs had equivalent effects on reducing glial scar formation,hNSPCs,especially for hscNSPCs,exhibited a better performance on long-term cell survival,neuronal differentiation,the reduction of inflammation.Therefore,hscNSPCs may be a better choice for SCI therapy,with greater potential clinical application,than hbNSPCs.These encouraging results provide a clinical basis for future stem cell-based SCI therapies.