Human umbilical cord mesenchymal stem cell-derived exosomes loaded into a composite conduit promote functional recovery after peripheral nerve injury in rats

Complete transverse injury of peripheral nerves is challenging to treat.Exosomes secreted by human umbilical cord mesenchymal stem cells are considered to play an important role in intercellular communication and regulate tissue regeneration.In previous studies,a collagen/hyaluronic acid sponge was shown to provide a suitable regeneration environment for Schwann cell proliferation and to promote axonal regeneration.This three-dimensional(3D)composite conduit contains a collagen/hyaluronic acid inner sponge enclosed in an electrospun hollow poly(lactic-co-glycolic acid)tube.However,whether there is a synergy between the 3D composite conduit and exosomes in the repair of peripheral nerve injury remains unknown.In this study,we tested a comprehensive strategy for repairing long-gap(10 mm)peripheral nerve injury that combined the 3D composite conduit with human umbilical cord mesenchymal stem cell-derived exosomes.Repair effectiveness was evaluated by sciatic functional index,sciatic nerve compound muscle action potential recording,recovery of muscle mass,measuring the cross-sectional area of the muscle fiber,Masson trichrome staining,and transmission electron microscopy of the regenerated nerve in rats.The results showed that transplantation of the 3D composite conduit loaded with human umbilical cord mesenchymal stem cell-derived exosomes promoted peripheral nerve regeneration and restoration of motor function,similar to autograft transplantation.More CD31-positive endothelial cells were observed in the regenerated nerve after transplantation of the loaded conduit than after transplantation of the conduit without exosomes,which may have contributed to the observed increase in axon regeneration and distal nerve reconnection.Therefore,the use of a 3D composite conduit loaded with human umbilical cord mesenchymal stem cell-derived exosomes represents a promising cell-free therapeutic option for the treatment of peripheral nerve injury.

Injectable collagen scaffold with human umbilical cordderived mesenchymal stem cells promotes functional recovery in patients with spontaneous intracerebral hemorrhage:phase Ⅰ clinical trial

Animal expe riments have shown that injectable collagen scaffold with human umbilical cord-derived mesenchymal stem cells can promote recovery from spinal cord injury.To investigate whether injectable collagen scaffold with human umbilical cord-derived mesenchymal stem cells can be used to treat spontaneous intracerebral hemorrhage,this non-randomized phase I clinical trial recruited patients who met the inclusion criteria and did not meet the exclusion crite ria of spontaneous intracerebral hemorrhage treated in the Characteristic Medical Center of Chinese People’s Armed Police Force from May 2016 to December 2020.Patients were divided into three groups according to the clinical situation and patient benefit:control(n=18),human umbilical cord-derived mesenchymal stem cells(n=4),and combination(n=8).The control group did not receive any transplantation.The human umbilical cord-derived mesenchymal stem cells group received human umbilical cord-derived mesenchymal stem cell transplantation.The combination group received injectable collagen scaffold with human umbilical cord-derived mesenchymal stem cells.Patients who received injectable collagen scaffold with human umbilical cord-derived mesenchymal stem cells had more remarkable improvements in activities of daily living and cognitive function and smaller foci of intra cerebral hemorrhage-related encephalomalacia.Severe adve rse events associated with cell transplantation were not observed.Injectable collagen scaffold with human umbilical cord-derived mesenchymal stem cells appears to have great potential treating spontaneous intracerebral hemorrhage.

Collagen-chitosan scaffold impregnated with bone marrow mesenchymal stem cells for treatment of traumatic brain injury

Combinations of biomaterials and cells can effectively target delivery of cells or other therapeutic factors to the brain to rebuild damaged nerve pathways after brain injury.Porous collagen-chitosan scaffolds were prepared by a freeze-drying method based on brain tissue engineering.The scaffolds were impregnated with rat bone marrow mesenchymal stem cells.A traumatic brain injury rat model was established using the 300 g weight free fall impact method.Bone marrow mesenchymal stem cells/collagen-chitosan scaffolds were implanted into the injured brain.Modified neurological severity scores were used to assess the recovery of neurological function.The Morris water maze was employed to determine spatial learning and memory abilities.Hematoxylin-eosin staining was performed to measure pathological changes in brain tissue.Immunohistochemistry was performed for vascular endothelial growth factor and for 5-bromo-2-deoxyuridine(BrdU)/neuron specific enolase and BrdU/glial fibrillary acidic protein.Our results demonstrated that the transplantation of bone marrow mesenchymal stem cells and collagen-chitosan scaffolds to traumatic brain injury rats remarkably reduced modified neurological severity scores,shortened the average latency of the Morris water maze,increased the number of platform crossings,diminished the degeneration of damaged brain tissue,and increased the positive reaction of vascular endothelial growth factor in the transplantation and surrounding areas.At 14 days after transplantation,increased BrdU/glial fibrillary acidic protein expression and decreased BrdU/neuron specific enolase expression were observed in bone marrow mesenchymal stem cells in the injured area.The therapeutic effect of bone marrow mesenchymal stem cells and collagen-chitosan scaffolds was superior to stereotactic injection of bone marrow mesenchymal stem cells alone.To test the biocompatibility and immunogenicity of bone marrow mesenchymal stem cells and collagen-chitosan scaffolds,immunosuppressive cyclosporine was intravenously injected 12 hours before transplantation and 1-5 days after transplantation.The above indicators were similar to those of rats treated with bone marrow mesenchymal stem cells and collagen-chitosan scaffolds only.These findings indicate that transplantation of bone marrow mesenchymal stem cells in a collagen-chitosan scaffold can promote the recovery of neuropathological injury in rats with traumatic brain injury.This approach has the potential to be developed as a treatment for traumatic brain injury in humans.All experimental procedures were approved by the Institutional Animal Investigation Committee of Capital Medical University,China(approval No.AEEI-2015-035)in December 2015.

Collagen scaffold combined with human umbilical cord-mesenchymal stem cells transplantation for acute complete spinal cord injury

Currently, there is no effective strategy to promote functional recovery after a spinal cord injury. Collagen scaffolds can not only provide support and guidance for axonal regeneration, but can also serve as a bridge for nerve regeneration at the injury site. They can additionally be used as carriers to retain mesenchymal stem cells at the injury site to enhance their effectiveness. Hence, we hypothesized that transplanting human umbilical cord-mesenchymal stem cells on collagen scaffolds would enhance healing following acute complete spinal cord injury. Here, we test this hypothesis through animal studies and a phase I clinical trial.(1) Animal experiments: Models of completely transected spinal cord injury were established in rats and canines by microsurgery. Mesenchymal stem cells derived from neonatal umbilical cord tissue were adsorbed onto collagen scaffolds and surgically implanted at the injury site in rats and canines;the animals were observed after 1 week–6 months. The transplantation resulted in increased motor scores, enhanced amplitude and shortened latency of the motor evoked potential, and reduced injury area as measured by magnetic resonance imaging.(2) Phase I clinical trial: Forty patients with acute complete cervical injuries were enrolled at the Characteristic Medical Center of Chinese People's Armed Police Force and divided into two groups. The treatment group(n = 20) received collagen scaffolds loaded with mesenchymal stem cells derived from neonatal umbilical cordtissues;the control group(n = 20) did not receive the stem-cell loaded collagen implant. All patients were followed for 12 months. In the treatment group, the American Spinal Injury Association scores and activities of daily life scores were increased, bowel and urinary functions were recovered, and residual urine volume was reduced compared with the pre-treatment baseline. Furthermore, magnetic resonance imaging showed that new nerve fiber connections were formed, and diffusion tensor imaging showed that electrophysiological activity was recovered after the treatment. No serious complication was observed during follow-up. In contrast, the neurological functions of the patients in the control group were not improved over the follow-up period. The above data preliminarily demonstrate that the transplantation of human umbilical cord-mesenchymal stem cells on a collagen scaffold can promote the recovery of neurological function after acute spinal cord injury. In the future, these results need to be confirmed in a multicenter, randomized controlled clinical trial with a larger sample size. The clinical trial was approved by the Ethics Committee of the Characteristic Medical Center of Chinese People's Armed Police Force on February 3, 2016(approval No. PJHEC-2016-A8). All animal experiments were approved by the Ethics Committee of the Characteristic Medical Center of Chinese People's Armed Police Force on May 20, 2015(approval No. PJHEC-2015-D5).

Combination of mesenchymal stem cells and three-dimensional collagen scaffold preserves ventricular remodeling in rat myocardial infarction model

BACKGROUND Cardiovascular diseases are the major cause of mortality worldwide.Regeneration of the damaged myocardium remains a challenge due to mechanical constraints and limited healing ability of the adult heart tissue.Cardiac tissue engineering using biomaterial scaffolds combined with stem cells and bioactive molecules could be a highly promising approach for cardiac repair.Use of biomaterials can provide suitable microenvironment to the cells and can solve cell engraftment problems associated with cell transplantation alone.Mesenchymal stem cells(MSCs)are potential candidates in cardiac tissue engineering because of their multilineage differentiation potential and ease of isolation.Use of DNA methyl transferase inhibitor,such as zebularine,in combination with three-dimensional(3D)scaffold can promote efficient MSC differentiation into cardiac lineage,as epigenetic modifications play a fundamental role in determining cell fate and lineage specific gene expression.AIM To investigate the role of collagen scaffold and zebularine in the differentiation of rat bone marrow(BM)-MSCs and their subsequent in vivo effects.METHODS MSCs were isolated from rat BM and characterized morphologically,immunophenotypically and by multilineage differentiation potential.MSCs were seeded in collagen scaffold and treated with 3μmol/L zebularine in three different ways.Cytotoxicity analysis was done and cardiac differentiation was analyzed at the gene and protein levels.Treated and untreated MSC-seeded scaffolds were transplanted in the rat myocardial infarction(MI)model and cardiac function was assessed by echocardiography.Cell tracking was performed by DiI dye labeling,while regeneration and neovascularization were evaluated by histological and immunohistochemical analysis,respectively.RESULTS MSCs were successfully isolated and seeded in collagen scaffold.Cytotoxicity analysis revealed that zebularine was not cytotoxic in any of the treatment groups.Cardiac differentiation analysis showed more pronounced results in the type 3 treatment group which was subsequently chosen for the transplantation in the in vivo MI model.Significant improvement in cardiac function was observed in the zebularine treated MSC-seeded scaffold group as compared to the MI control.Histological analysis also showed reduction in fibrotic scar,improvement in left ventricular wall thickness and preservation of ventricular remodeling in the zebularine treated MSC-seeded scaffold group.Immunohistochemical analysis revealed significant expression of cardiac proteins in DiI labeled transplanted cells and a significant increase in the number of blood vessels in the zebularine treated MSC-seeded collagen scaffold transplanted group.CONCLUSION Combination of 3D collagen scaffold and zebularine treatment enhances cardiac differentiation potential of MSCs,improves cell engraftment at the infarcted region,reduces infarct size and improves cardiac function.

Repair of Rat Segmental Defects with Mineralized Collagen Grafts Combined with or without Mesenchymal Stem Cells and BMP-2

The aim of the present study was to investigate and compare the bone formation capacity with three different grafts. Four millimeter segmental defects were created in adult rat tibias and were either left empty （control defects） or implanted with （1） nano-hydroxyapatite/collagen/PIA （nHAC/PIA） composite, （2） nHAC/ PIA composite added with bone marrow mesenchymal tem cells （ BMSCs ）, （ 3 ） nHAC/ PIA composite added with bone morphogenetic protein 2 （ BMP- 2）. Radiographs of the defects were taken weekly post-surgery. After 1 or 2 months, the rats were eathaaized. Histologic analyses were performed on the harvested tissue. nHAC/ PIA composite could enhance the repair of rat tibia segmental defects. Addition of BMSCs or BMP- 2 to nHAC/ PIA led to an increase in osteogenesis, nHAC/ PIA composite could be an Meal alternative bone-grafi material and it could also be used as an Meal carrier of BMSCs or BMP- 2.

Proliferation and tenogenic differentiation of bone marrow mesenchymal stem cells in a porous collagen sponge scaffold

BACKGROUND Collagen is one of the most commonly used natural biomaterials for tendon tissue engineering.One of the possible practical ways to further enhance tendon repair is to combine a porous collagen sponge scaffold with a suitable growth factor or cytokine that has an inherent ability to promote the recruitment,proliferation,and tenogenic differentiation of cells.However,there is an incomplete understanding of which growth factors are sufficient and optimal for the tenogenic differentiation of rat bone marrow mesenchymal stem cells(BMSCs)in a collagen sponge-based 3D culture system.AIM To identify one or more ideal growth factors that benefit the proliferation and tenogenic differentiation of rat BMSCs in a porous collagen sponge scaffold.METHODS We constructed a 3D culture system based on a type I collagen sponge scaffold.The surface topography of the collagen sponge scaffold was observed by scanning electron microscopy.Primary BMSCs were isolated from Sprague-Dawley rats.Cell survival on the surfaces of the scaffolds with different growth factors was assessed by live/dead assay and CCK-8 assay.The mRNA and protein expression levels were confirmed by quantitative real-time polymerase chain reaction and Western blot,respectively.The deposited collagen was assessed by Sirius Red staining.RESULTS Transforming growth factorβ1(TGF-β1)showed great promise in the tenogenic differentiation of BMSCs compared to growth differentiation factor 7(GDF-7)and insulin-like growth factor 1(IGF-1)in both the 2D and 3D cultures,and the 3D culture enhanced the differentiation of BMSCs into tenocytes well beyond the level of induction in the 2D culture after TGF-β1 treatment.In the 2D culture,the proliferation of the BMSCs showed no significant changes compared to the control group after TGF-β1,IGF-1,or GDF-7 treatment.However,TGF-β1 and GDF-7 could increase the cell proliferation in the 3D culture.Strangely,we also found more dead cells in the BMSC-collagen sponge constructs that were treated with TGF-β1.Moreover,TGF-β1 promoted more collagen deposition in both the 2D and 3D cultures.CONCLUSION Collagen sponge-based 3D culture with TGF-β1 enhances the responsiveness of the proliferation and tenogenic differentiation of rat BMSCs.

In vivo hepatic differentiation potential of human umbilical cord-derived mesenchymal stem cells: Therapeutic effect on liver fibrosis/cirrhosis

AIM To investigate the hepatic differentiation potential of human umbilical cord-derived mesenchymal stem cells(h UC-MSCs) and to evaluate their therapeutic effect on liver fibrosis/cirrhosis.METHODS A CCl4-induced liver fibrotic/cirrhotic rat model was used to assess the effect of h UC-MSCs. Histopathology was assessed by hematoxylin and eosin(H&E), Masson trichrome and Sirius red staining. The liver biochemical profile was measured using a Beckman Coulter analyzer. Expression analysis was performed using immunofluorescent staining, immunohistochemistry, Western blot, and real-time PCR.RESULTS We demonstrated that the infused h UC-MSCs could differentiate into hepatocytes in vivo. Functionally, the transplantation of h UC-MSCs to CCl4-treated rats improved liver transaminases and synthetic function, reduced liver histopathology and reversed hepatobiliary fibrosis. The reversal of hepatobiliary fibrosis was likely due to the reduced activation state of hepatic stellate cells, decreased collagen deposition, and enhanced extracellular matrix remodeling via the up-regulation of MMP-13 and down-regulation of TIMP-1. CONCLUSION Transplanted h UC-MSCs could differentiate into functional hepatocytes that improved both the biochemical and histopathologic changes in a CCl4-induced rat liver fibrosis model. h UC-MSCs may offer therapeutic opportunities for treating hepatobiliary diseases, including cirrhosis.

The effect of reduced glutathione on the chondrogenesis of human umbilical cord mesenchymal stem cells

It has been discussed whether reduced glutathione (GSH) could promote the chondrogenic differentiation ability of human umbilical cord mesenchymal stem cells (hUC-MSCs). hUC-MSCs were isolated from human umbilical cord and their specificity was identified, then induced into cartilage-like cells in chondrogenic induction medium with transforming growth factor beta 1 (TGF-β1), especially with GSH. The morphological change before and after induction was observed through inverted phase contrast microscope, Type II collagen (COL2-A1) and glycosaminoglycan (GAG) were analyzed qualitatively by Toluidine blue and immunofluorescence technique, respectively, the contents of COL2-A1 and GAG were estimated from the determination of hydroxyproline content and Alcian Blue method separately. The mRNA expressions of GAG and COL2-A1 were assayed by real-time fluorescence quantitative PCR. After continuously cultured for 21 days with GSH, Toluidine blue staining and immunofluorescence reaction were all positive in basic induction medium group (group B), basic induction medium +0.5% dimethylsulfoxide (DMSO) group (group BD) and basic induction medium +0.5% DMSO +500 μM GSH group (group BDG). Moreover, compared with group B and group BD, the contents of COL2-A1 and GAG in group BDG relatively increased and the mRNA expression level of COL2-A1 and GAG also comparatively increased (P < 0.05) and both had a significant statistical significance (P < 0.05). So GSH might promote the induction of hUC-MSCs to differentiate into cartilage-like cells.

A construct of adipose-derived mesenchymal stem cells—laden collagen scaffold for fertility restoration by inhibiting fibrosis in a rat model of endometrial injury

Severe endometrium damage causes pathological conditions such as thin endometrium and intrauterine adhesion,resulting in uterine factor infertility.Mesenchymal stem cell(MSC)therapy is a promising strategy in endometrial repair;yet,exogenous MSCs still raise concerns for safety and ethical issues.Human adipose-derived mesenchymal stem cells(ADMSCs)residing in adipose tissue have high translational potentials due to their autologous origin.To harness the high translation potentials of ADMSC in clinical endometrium regeneration,here we constructed an ADMSCs composited porous scaffold(CS/ADMSC)and evaluated its effectiveness on endometrial regeneration in a rat endometrium-injury model.We found that CS/ADMSC intrauterine implantation(i)promoted endometrial thickness and gland number,(ii)enhanced tissue angiogenesis,(iii)reduced fibrosis and(iv)restored fertility.We ascertained the pro-proliferation,pro-angiogenesis,immunomodulating and anti-fibrotic effects of CS/ADMSC in vitro and revealed that the CS/ADMSC influenced extracellular matrix composition and organization by a transcriptomic analysis.Our results demonstrated the effectiveness of CS/ADMSC for endometrial regeneration and provided solid proof for our future clinical study.

Layer-by-layer assembly of procyanidin and collagen promotes mesenchymal stem cell proliferation and osteogenic differentiation in vitro and in vivo

Collagen,commonly used in tissue engineering,is widespread in various tissues.During bone tissue regeneration,collagen can stimulate the cellular response and determine the fate of cells.In this work,we integrated collagen type II with procyanidin(PC)onto an implant coating by applying a layer-by-layer technique to demonstrate that collagen and PC can participate in the construction of new biomaterials and serve as multifunctional components.The effects of PC/collagen multilayers on the viability of cocultured bone marrow mesenchymal stem cells(BMSCs)were analyzed by cell counting kit-8 analysis and phalloidin staining.The reactive oxygen species level of BMSCs was revealed through immunofluorescent staining and flow cytometry.Osteogenesis-related genes were detected,and in vivo experiment was performed to reveal the effect of newly designed material on the osteogenic differentiation of BMSCs.Our data demonstrated that in BMSCs PC/collagen multilayers accelerated the proliferation and osteogenic differentiation through Wnt/β-catenin signaling pathway and enhanced bone generation around the implant in the bone defect model of rabbit femurs.In summary,combination of collagen and PC provided a new sight for the research and development of implant materials or coatings in the future.

Human hair follicle-derived mesenchymal stem cells promote tendon repair in a rabbit Achilles tendinopathy model

Background:Hair follicles are easily accessible and contain stem cells with different developmental origins,including mesenchymal stem cells(MSCs),that consequently reveal the potential of human hair follicle(hHF)-derived MSCs in repair and regeneration.However,the role of hHF-MSCs in Achilles tendinopathy(AT)remains unclear.The present study investigated the effects of hHF-MSCs on Achilles tendon repair in rabbits.Methods:First,we extracted and characterized hHF-MSCs.Then,a rabbit tendinopathy model was constructed to analyze the ability of hHF-MSCs to promote repair in vivo.Anatomical observation and pathological and biomechanical analyses were performed to determine the effect of hHF-MSCs on AT,and quantitative real-time polymerase chain reaction,enzyme-linked immunosorbent assay,and immunohistochemical staining were performed to explore the molecular mechanisms through which hHF-MSCs affects AT.Furthermore,statistical analyses were performed using independent sample t test,one-way analysis of variance(ANOVA),and one-way repeated measures multivariate ANOVA as appropriate.Results:Flow cytometry,a trilineage-induced differentiation test,confirmed that hHF-derived stem cells were derived from MSCs.The effect of hHF-MSCs on AT revealed that the Achilles tendon was anatomically healthy,as well as the maximum load carried by the Achilles tendon and hydroxyproline proteomic levels were increased.Moreover,collagen I and III were upregulated in rabbit AT treated with hHF-MSCs(compared with AT group;P<0.05).Analysis of the molecular mechanisms revealed that hHF-MSCs promoted collagen fiber regeneration,possibly through Tenascin-C(TNC)upregulation and matrix metalloproteinase(MMP)-9 downregulation.Conclusions:hHF-MSCs can be a treatment modality to promote AT repair in rabbits by upregulating collagen I and III.Further analysis revealed that treatment of AT using hHF-MSCs promoted the regeneration of collagen fiber,possibly because of upregulation of TNC and downregulation of MMP-9,thus suggesting that hHF-MSCs are more promising for AT.

3D printed collagen/silk fibroin scaffolds carrying the secretome of human umbilical mesenchymal stemcells ameliorated neurological dysfunction after spinal cord injury in rats

Although implantation of biomaterials carrying mesenchymal stem cells(MSCs)is considered as a promising strategy for ameliorating neural function after spinal cord injury(SCI),there are still some challenges including poor cell survival rate,tumorigenicity and ethics concerns.The performance of the secretome derived from MSCs was more stable,and its clinical transformation was more operable.Cytokine antibody array demonstrated that the secretome of MSCs contained 79 proteins among the 174 proteins analyzed.Three-dimensional(3D)printed collagen/silk fibroin scaffolds carrying MSCs secretome improved hindlimb locomotor function according to the Basso–Beattie–Bresnahan scores,the inclined-grid climbing test and electrophysiological analysis.Parallel with locomotor function recovery,3D printed collagen/silk fibroin scaffolds carrying MSCs secretome could further facilitate nerve fiber regeneration,enhance remyelination and accelerate the establishment of synaptic connections at the injury site compared to 3D printed collagen/silk fibroin scaffolds alone group according to magnetic resonance imaging,diffusion tensor imaging,hematoxylin and eosin staining,Bielschowsky’s silver staining,immunofluorescence staining and transmission electron microscopy.These results indicated the implantation of 3D printed collagen/silk fibroin scaffolds carrying MSCs secretome might be a potential treatment for SCI.

Injectable collagen scaffold promotes swine myocardial infarction recovery by long-term local retention of transplanted human umbilical cord mesenchymal stem cells

Stem cell therapy is an attractive approach for recovery from myocardial infarction(MI)but faces the challenges of rapid diffusion and poor survival after transplantation.Here we developed an injectable collagen scaffold to promote the long-term retention of transplanted cells in chronic MI.Forty-five minipigs underwent left anterior descending artery(LAD)ligation and were equally divided into three groups 2 months later(collagen scaffold loading with human umbilical mesenchymal stem cell(hUMSC)group,hUMSC group,and placebo group(only phosphate-buffered saline(PBS)injection)).Immunofluorescence staining indicated that the retention of transplanted cells was promoted by the collagen scaffold.Echocardiography and cardiac magnetic resonance imaging(CMR)showed much higher left ventricular ejection fraction(LVEF)and lower infarct size percentage in the collagen/hUMSC group than in the hUMSC and placebo groups at 12 months after treatment.There were also higher densities of vWf-,α-sma-,and cTnT-positive cells in the infarct border zone in the collagen/cell group,as revealed by immunohistochemical analysis,suggesting better angiogenesis and more cardiomyocyte survival after MI.Thus,the injectable collagen scaffold was safe and effective on a large animal myocardial model,which is beneficial for constructing a favorable microenvironment for applying stem cells in clinical MI.

Dynamic culture of a thermosensitive collagen hydrogel as an extracellular matrix improves the construction of tissue-engineered peripheral nerve

Tissue engineering technologies offer new treatment strategies for the repair of peripheral nerve injury, hut cell loss between seeding and adhesion to the scaffold remains inevitable. A thermosensitive collagen hydrogel was used as an extracellular matrix in this study and combined with bone marrow mesenchymal stem cells to construct tissue-engineered peripheral nerve composites in vitro. Dynamic culture was performed at an oscillating frequency of 0.5 Hz and 35° swing angle above and below the horizontal plane. The results demonstrated that bone marrow mesenchymal stem cells formed membrane-like structures around the poly-L-lactic acid scaffolds and exhibited regular alignment on the composite surface. Collagen was used to fill in the pores, and seeded cells adhered onto the poly-L-lactic acid fibers. The DNA content of the bone marrow mesenchymal stem cells was higher in the composites constructed with a thermosensitive collagen hydrogel compared with that in collagen I scaffold controls. The cellular DNA content was also higher in the thermosensitive collagen hydrogel composites constructed with the thermosensitive collagen hydrogel in dynamic culture than that in static culture. These results indicate that tissue-engineered composites formed with thermosensitive collagen hydrogel in dynamic culture can maintain larger numbers of seeded cells by avoiding cell loss during the initial adhe-sion stage. Moreover, seeded cells were distributed throughout the material.

Effect of type I collagen on the adhesion, proliferation, and osteoblastic gene expression of bone marrow-derived mesenchymal stem cells

Objective: To investigate the effects of porous poly lactide-co-glycolide (PLGA) modified by type I collagen on the adhesion, proliferation, and differentiation of rabbit marrow-derived mesenchymal stem cells (MSCs). Methods: The third generation MSCs isolated from mature rabbits by density gradient centrifugation were cultured at different initial concentrations on 0.3 cm×1.2 cm×2.0 cm 3-D porous PLGA coated by type I collagen in RPMI 1640 containing 10% fetal calf serum, while cultured on PLGA without type I collagen as control. The cells adhesive and proliferative behavior at 7, 14, and 21 days after inoculation was assessed by determining the incorporation rate of [3H]-TdR. In order to examine MSCs differentiation, the expression of osteoblasts marker genes, osteocalcin (OCN), alkaline phosphatase (ALP), osteopontin (OPN) mRNA, were evaluated by reverse transcription-polymerase chain reaction (RT-PCR), and further more, the cell morphology at 21 days was also observed by scanning electron microscope (SEM). Results: Type I collagen promoted cell adhesion on PLGA. The valve was significantly higher than controls (6 h, 2144 cpm±141cpm vs. 1797 cpm±118 cpm, P=0.017; 8 h, 2311 cpm±113 cpm vs. 1891 cpm±103 cpm, P=0.01). The cells which cultured on PLGA coated with type I collagen showed significantly higher cell proliferation than controls on the 7th day (1021 cpm±159 cpm vs. 451 cpm±67 cpm, P=0.002), the 14th day (1472 cpm±82 cpm vs. 583 cpm±67 cpm, P<0.001) and 21th day (1728 cpm±78 cpm vs. 632 cpm±55 cpm, P<0.001). Osteoblasts markers, OCN, ALP, OPN mRNA, were all detected on PLGA coated by type I collagen on the 21th day, but OCN, OPN mRNA could not be found in controls. Spindle and polygonal cells well distributed on the polymer coated by type I collagen while cylindric or round cells in controls. Conclusions: Type I collagen is effective in promoting the adhesion, proliferation and differentiation of MSCs on PLGA.

In vivo bone regeneration with injectable chitosan/hydroxyapatite/collagen composites and mesenchymal stem cells

For reconstruction of irregular bone defects, injectable biomaterials are more appropriate than the preformed biomaterials. We herein develop a biomimetic in situ-forming composite consisting of chitosan （CS） and mineralized collagen fibrils （nHAC）, which has a complex hierarchical structure similar to natural bone. The CSInHAC composites with or without mesenchymal stem cells （MSCs） are injected into cancellous bone defects at the distal end of rabbit femurs. Defects are assessed by radiographic, histological diagnosis and Raman microscopy until 12 weeks. The results show that MSCs improve the biocompatibility of CS/nHAC composites and enhance new bone formation in vivo at 12 weeks. It can be concluded that the injectable CSInHAC composites combined with MSCs may be a novel method for reconstruction of irregular bone defects.

Polydopamine and collagen coated micro-grated polydimethylsiloxane for human mesenchymal stem cell culture

Natural tissues contain highly organized cellular architecture.One of the major challenges in tissue engineering is to develop engineered tissue constructs that promote cellular growth in physiological directionality.To address this issue,micro-patterned polydimethylsiloxane(PDMS)substrates have been widely used in cell sheet engineering due to their low microfabrication cost,higher stability,excellent biocompatibility,and most importantly,ability to guide cellular growth and patterning.However,the current methods for PDMS surface modification either require a complicated procedure or generate a non-uniform surface coating,leading to the production of poor-quality cell layers.A simple and efficient surface coating method is critically needed to improve the uniformity and quality of the generated cell layers.Herein,a fast,simple and inexpensive surface coating method was analyzed for its ability to uniformly coat polydopamine(PD)with or without collagen on micro-grated PDMS substrates without altering essential surface topographical features.Topographical feature,stiffness and cytotoxicity of these PD and/or collagen based surface coatings were further analyzed.Results showed that the PD-based coating method facilitated aligned and uniform cell growth,therefore holds great promise for cell sheet engineering as well as completely biological tissue biomanufacturing.

载骨髓间充质干细胞的高孔聚己内酯-胶原纳米纤维膜修复大鼠长期鼓膜穿孔

背景:近年来出现许多新颖的鼓膜修补材料,包括贴片、3D打印支架等,然而经过这些材料修补后的鼓膜在厚度和内部结构上不同于天然鼓膜。目的:探究载骨髓间充质干细胞的高孔聚己内酯-胶原纳米纤维膜修补大鼠长期鼓膜穿孔的效果。方法:利用静电纺丝技术分别制备聚己内酯、聚己内酯-胶原与高孔聚己内酯-胶原纳米纤维膜,表征支架的表面形态、孔隙率及细胞相容性。取50只雄性SD大鼠,使用无菌23号针头刺破双耳鼓膜后下部联合丝裂霉素C、氢化可的松用药法建立鼓膜穿孔模型;造模12周后,采用随机数字表法将大鼠分为5组:空白对照组不进行任何治疗,其他4组鼓膜穿孔处分别植入聚己内酯纳米纤维膜(聚己内酯组)、聚己内酯-胶原纳米纤维膜(聚己内酯-胶原组)、高孔聚己内酯-胶原纳米纤维膜(高孔聚己内酯-胶原组)与载骨髓间充质干细胞的高孔聚己内酯-胶原纳米纤维膜(载细胞高孔聚己内酯-胶原组),每组10只,支架植入1,2,3,4周利用耳内镜检查鼓膜愈合情况,植入4周后进行鼓膜组织苏木精-伊红、Masson染色与Ki-67免疫组化染色观察。结果与结论:①支架表征:扫描电镜显示相较于其他纳米纤维膜,高孔聚己内酯-胶原纳米纤维膜具有排列更加整齐的纳米纤维结构与更大的表面孔径,并且孔隙率更高(P<0.001);细胞活死染色显示,骨髓间充质干细胞在3种支架上附着良好,其中高孔聚己内酯-胶原纳米纤维膜上的活细胞数量多于其他两种支架;阿尔马兰染色显示,高孔聚己内酯-胶原纳米纤维膜上的骨髓间充质干细胞增殖率高于其他两种纤维膜;②动物实验:除空白对照组外,随着纤维膜植入时间的延长,其他4组大鼠鼓膜逐渐愈合,其中载细胞高孔聚己内酯-胶原组愈合速度最快;苏木精-伊红、Masson与Ki-67免疫组化染色显示,载细胞高孔聚己内酯-胶原组大鼠鼓膜厚度适中且具有3层结构,其中胶原纤维层均匀一致,与正常鼓膜相似,鼓膜修复质量好于其他纤维膜组;③结果表明:载骨髓间充质干细胞的高孔聚己内酯-胶原纳米纤维膜不仅能够快速修补鼓膜穿孔,而且新愈合鼓膜在组织结构和厚度上类似于正常鼓膜。