Sustained localized presentation of RNA interfering molecules from in situ forming hydrogels to guide stem cell osteogenic differentiation

To date, RNA interfering molecules have been used to differentiate stem cells on two-dimensional (2D) substrates that do not mimic three-dimensional (3D) microenvironments in the body. Here, in situ forming poly(ethylene glycol) (PEG) hydrogels were engineered for controlled, localized and sustained delivery of RNA interfering molecules to differentiate stem cells encapsulated within the 3D polymer network. RNA interfering molecules were released from the hydrogels in a sustained and controlled manner over the course of 3–6 weeks, and exhibited high bioactivity. Importantly, it was demonstrated that the delivery of siRNA and/or miRNA from the hydrogel constructs enhanced the osteogenic differentiation of encapsulated stem cells. Prolonged delivery of siRNA and/or miRNA from this polymeric scaffold permitted extended regulation of cell behavior, unlike traditional siRNA experiments performed in vitro. This approach presents a powerful new methodology for controlling cell fate, and is promising for multiple applications in tissue engineering and regenerative medicine.     

Biodegradable,phosphate-containing,dual-gelling macromers for cellular delivery in bone tissue engineering

Injectable, biodegradable, dual-gelling macromer solutions were used to encapsulate mesenchymal stem cells (MSCs) within stable hydrogels when elevated to physiologic temperature. Pendant phosphate groups were incorporated in the N-isopropyl acrylamide-based macromers to improve biointegration and facilitate hydrogel degradation. The MSCs were shown to survive the encapsulation process, and live cells were detected within the hydrogels for up to 28 days in vitro. Cell-laden hydrogels were shown to undergo significant mineralization in osteogenic medium. Cell-laden and acellular hydrogels were implanted into a critical-size rat cranial defect for 4 and 12 weeks. Both cell-laden and acellular hydrogels were shown to degrade in vivo and help to facilitate bone growth into the defect. Improved bone bridging of the defect was seen with the incorporation of cells, as well as with higher phosphate content of the macromer. Furthermore, direct bone-to-hydrogel contact was observed in the majority of implants, which is not commonly seen in this model. The ability of these macromers to deliver stem cells while forming in situ and subsequently degrade while facilitating bone ingrowth into the defect makes this class of macromers a promising material for craniofacial bone tissue engineering.     

低聚乙二醇富马酸酯水凝胶中骨髓来源间充质干细胞的生物学行为

文章快速阅读：  文题释义：水凝胶：是以水为分散介质的凝胶,具有网状交联结构的水溶性高分子中引入一部分疏水基团和亲水残基,亲水残基与水分子结合,将水分子连接在网状内部,而疏水残基遇水膨胀的交联聚合物。是一种高分子网络体系,性质柔软,能保持一定的形状,能吸收大量的水。凡是水溶性或亲水性的高分子,通过一定的化学交联或物理交联,都可以形成水凝胶。这些高分子按其来源可分为天然和合成两大类。天然的亲水性高分子包括多糖类(淀粉、纤维素、海藻酸、透明质酸,壳聚糖等)和多肽类(胶原、聚L-赖氨酸、聚L-谷胺酸等)。合成的亲水高分子包括醇、 丙烯酸及其衍生物类(聚丙烯酸,聚甲基丙烯酸,聚丙烯酰胺,聚N-聚代丙烯酰胺等)。低聚乙二醇富马酸酯水凝胶：是由聚乙二醇和延胡索酸酯与聚乙二醇二丙烯酸酯化学交联而成,具有良好的组织相容性和生物可降解性。实验证明低聚乙二醇富马酸酯水凝胶随着相对分子质量的升高其溶胀度降增加,溶胀比增加引起水凝胶降解速度加快及力学强度减弱。故研制与筛选具有合适溶胀比的低聚乙二醇富马酸酯水凝胶材料是进行骨组织工程支架材料研究的前提。   背景：低聚乙二醇富马酸酯水凝胶是一种具有良好生物相容性及可注射性和可降解性的生物材料。不同相对分子质量水凝胶之间的特性有所差异,将骨髓间充质干细胞包裹其中并诱导细胞成骨分化,相对分子质量相当的水凝胶更有利于细胞增殖和分化,所以采用该材料为骨组织工程支架提供了新的选择。目的：探讨不同相对分子质量的低聚乙二醇富马酸酯水凝胶材料体外包裹大鼠骨髓间充质干细胞的增殖和分化的影响。方法：低聚乙二醇富马酸酯通过氧化还原基团引发系统产生交联,制备出相对分子质量为1000,3000,10000,35 000的低聚乙二醇富马酸酯水凝胶,对水凝胶的溶胀和降解性能进行检测。将骨髓间充质干细胞包裹到4种相对分子质量的水凝胶中,在成骨培养液中诱导1-3周,通过组织学染色(苏木精-伊红染色和茜素红染色)和免疫荧光染色检测水凝胶材料对骨髓间充质干细胞形态的影响以及成骨分化的效果。 结果与结论：①随着水凝胶相对分子质量的增加,成胶时间变短,凝胶的溶胀度明显增加,且随着时间的推移,水凝胶的降解速率与相对分子质量成正比;②细胞复合水凝胶支架材料的组织学与免疫荧光染色结果表明,细胞经过诱导后,在具有适当溶胀与降解特性的相对分子质量为3 000与10 000的水凝胶中所形成的矿化结节数量显著多于在其它两种相对分子质量中的,说明有利于细胞的增殖与分化;③结果表明,低聚乙二醇富马酸酯水凝胶具有良好的生物相容性,且相对分子质量为3 000与     10 000的水凝胶对间充质干细胞的成骨分化有一定的良性调节作用。 中国组织工程研究杂志出版内容重点：生物材料;骨生物材料; 口腔生物材料; 纳米材料; 缓释材料; 材料相容性;组织工程 ORCID:0000-0002-0616-3754(魏丽君)     

Postnatal epithelium and mesenchyme stem/progenitor cells in bioengineered amelogenesis and dentinogenesis

Rodent incisors provide a classic model for studying epithelial–mesenchymal interactions in development. However, postnatal stem/progenitor cells in rodent incisors have not been exploited for tooth regeneration. Here, we characterized postnatal rat incisor epithelium and mesenchyme stem/progenitor cells and found that they formed enamel- and dentin-like tissues in vivo. Epithelium and mesenchyme cells were harvested separately from the apical region of postnatal 4–5 day rat incisors. Epithelial and mesenchymal phenotypes were confirmed by immunocytochemistry, CFU assay and/or multi-lineage differentiation. CK14+, Sox2+ and Lgr5+ epithelium stem cells from the cervical loop enhanced amelogenin and ameloblastin expression upon BMP4 or FGF3 stimulation, signifying their differentiation towards ameloblast-like cells, whereas mesenchyme stem/progenitor cells upon BMP4, BMP7 and Wnt3a treatment robustly expressed Dspp, a hallmark of odontoblastic differentiation. We then control-released microencapsulated BMP4, BMP7 and Wnt3a in transplants of epithelium and mesenchyme stem/progenitor cells in the renal capsule of athymic mice in vivo. Enamel and dentin-like tissues were generated in two integrated layers with specific expression of amelogenin and ameloblastin in the newly formed, de novo enamel-like tissue, and DSP in dentin-like tissue. These findings suggest that postnatal epithelium and mesenchyme stem/progenitor cells can be primed towards bioengineered tooth regeneration.     

Matrix elasticity,replicative senescence and DNA methylation patterns of mesenchymal stem cells

Matrix elasticity guides differentiation of mesenchymal stem cells (MSCs) but it is unclear if these effects are only transient – while the cells reside on the substrate – or if they reflect persistent lineage commitment. In this study, MSCs were continuously culture-expanded in parallel either on tissue culture plastic (TCP) or on polydimethylsiloxane (PDMS) gels of different elasticity to compare impact on replicative senescence, in vitro differentiation, gene expression, and DNA methylation (DNAm) profiles. The maximal number of cumulative population doublings was not affected by matrix elasticity. Differentiation towards adipogenic and osteogenic lineage was increased on soft and rigid biomaterials, respectively – but this propensity was no more evident if cells were transferred to TCP. Global gene expression profiles and DNAm profiles revealed relatively few differences in MSCs cultured on soft or rigid matrices. Furthermore, only moderate DNAm changes were observed upon culture on very soft hydrogels of human platelet lysate. Our results support the notion that matrix elasticity influences cellular behavior while the cells reside on the substrate, but it does not have major impact on cell-intrinsic lineage determination, replicative senescence or DNAm patterns.     

The performance of human mesenchymal stem cells encapsulated in cell-degradable polymer-peptide hydrogels

Thiol-ene photopolymerization offers a unique platform for the formation of peptide-functionalized poly(ethylene glycol) hydrogels and the encapsulation, culture and differentiation of cells. Specifically, this photoinitiated polymerization scheme occurs at neutral pH and can be controlled both spatially and temporally. Here, we have encapsulated human mesenchymal stem cells (hMSCs) in matrix metalloproteinase (MMP) degradable and cell-adhesive hydrogels using thiol-ene photopolymerization. We find that hMSCs survive equally well in this system, regardless of MMP-degradability. When hMSCs are encapsulated in these cell-degradable hydrogels, they survive and are able to proliferate. In classic hMSC differentiation medias, hMSCs locally remodel their microenvironment and take on characteristic morphologies; hMSCs cultured in growth or osteogenic differentiation media are less round, as measured by elliptical form factor, and are smaller than hMSCs cultured in chondrogenic or adipogenic differentiation media. In addition, hMSCs encapsulated in completely cell-degradable hydrogels and cultured in osteogenic, chondrogenic, or adipogenic differentiation media generally express increased levels of specific differentiation markers as compared to cells in hydrogels that are not cell-degradable. These studies demonstrate the ability to culture and differentiate hMSCs in MMP-degradable hydrogels polymerized via a thiol-ene reaction scheme and that increased cell-mediated hydrogel degradability facilitates directed differentiation of hMSCs.     

Engineering cell matrix interactions in assembled polyelectrolyte fiber hydrogels for mesenchymal stem cell chondrogenesis

Cell–cell and cell–matrix interactions are important events in directing stem cell chondrogenesis, which can be promoted in matrix microenvironments presenting appropriate ligands. In this study, interfacial polyelectrolyte complexation (IPC) based hydrogels were employed, wherein the unique formation of submicron size fibers facilitated spatial orientation of ligands within such hydrogels. The influence of aligned, collagen type I (Col I) presentation in IPC hydrogel on chondrogenic differentiation of human mesenchymal stem cells (MSC) was investigated. Early morphological dynamics, onset of N-cadherin/β-catenin mediated chondrogenic induction and differentiation were compared between MSCs encapsulated in IPC-Col I and IPC-control (without Col I) hydrogels, and a conventional Col I hydrogel. MSCs in IPC-Col I hydrogel aligned and packed uniformly, resulting in enhanced cell–cell interactions and cellular condensation, facilitating superior chondrogenesis and the generation of mature hyaline neocartilage, with notable downregulation of fibrocartilaginous marker. Inhibition study using function blocking β1-integrin antibodies reversed the aforementioned outcomes, indicating the importance of coupling integrin mediated cell–matrix interactions and N-cadherin/β-catenin mediated downstream signaling events. This study demonstrated the significance of oriented ligand presentation for MSC chondrogenesis, and the importance of facilitating an orderly sequence of differentiation events, initiated by proximal interactions between MSCs and the extracellular matrix for robust neocartilage formation.     

Efficient differentiation of stem cells encapsulated in a cytocompatible phospholipid polymer hydrogel with tunable physical properties

A large number of lineage-committed progenitor cells are required for advanced regenerative medicine based on cell engineering. Due to their ability to differentiate into multiple cells lines, multipotent stem cells have emerged as a vital source for generating transplantable cells for use in regenerative medicine. Increment in differentiation efficiency of the mesenchymal stem cell was obtained by using hydrogel to adjust the proliferation cycle of encapsulated cells to signal sensitive phase. Three dimensional (3-D) polymer networks composed of poly(2-methacyloyloxyethyl phosphorylcholine (MPC)-co-n-butyl methacrylate (BMA)-co-p-vinylphenylboronic acid (VPBA)) (PMBV) and poly(vinyl alcohol) (PVA) were prepared as a hydrogel. The proliferation of cells encapsulated in the PMBV/PVA hydrogel was highly sensitive to the storage modulus (G′) of the hydrogel. That is, when the G′ value of the hydrogel was higher than 1.0 kPa, the cell proliferation was ceased and the proliferation cycle of cells was converged to G1 phase, whereas when the G′ value was below 1.0 kPa, cell proliferation proceeded. By changing the G′ value of hydrogels under encapsulation the cells, proliferation cycle of encapsulated mesenchymal stem cells was regulated to G1 phase and thus signal sensitivity were increased. 3-D polymer networks as hydrogels with tunable physical properties can be effectively used to control proliferation and lineage-restricted differentiation of stem cells.     

Transfer stamping of human mesenchymal stem cell patches using thermally expandable hydrogels with tunable cell-adhesive properties

Development of stem cell delivery system with ability of control over mutilineage differentiation and improved engraft efficiency is imperative in regenerative medicine. We herein report transfer stamping of human mesenchymal stem cells (hMSCs) patches using thermally expandable hydrogels with tunable cell-adhesive properties. The hydrogels were prepared from functionalized four arm copolymer of Tetronic^®, and the cell adhesion on the hydrogel was modulated by incorporation of fibronectin (FN) or cell-adhesive peptide (RGD). The resulting hydrogels showed spontaneous expansion in size within 10 min in response to the temperature reduction from 37 to 4°C. The adhesion and proliferation of hMSCs on FN-hydrogels were positively tunable in proportion to the amount of FN within hydrogels with complete monolayer of hMSCs (hMSC patch) being successfully achieved. The hMSC patch on the hydrogel was faced to the target substrate, which was then easily detached and re-attached to the target when the temperature was reduced from 37°C up to 4°C. We found that the transfer stamping of cell patch was facilitated at lower temperature of 4°C relative to 25°C, with the use of thinner hydrogels (0.5 mm in thickness relatively to 1.0 or 1.5 mm) and longer transfer time (>15 min). Notably, the hMSC patch was simply transferred from the hydrogel to the subcutaneous mouse skin tissue within 15 min with cold saline solution being dropped to the hydrogel. The hMSC patch following osteogenic or adipogenic commitment was also achieved with long-term culture of hMSCs on the hydrogel, which was successfully detached to the target surface. These results suggest that the hydrogels with thermally expandable and tunable cell-adhesive properties may serve as a universal substrate to harvest hMSC patch in a reliable and effective manner, which could potentially be utilized in many cell-sheet based therapeutic applications.     

Modulus-dependent characteristics of Wharton’s jelly mesenchymal stem cells (WJMSC) encapsulated in hydrogel microspheres

Recent studies revealing stem cell behavior dependence on mechanical properties of a substrate has initiated the need to probe matrix mechanics and its influence on stem cell fate in a physiologically relevant three-dimensional (3D) microenvironment. We investigated the proliferative and osteogenic potentials of Wharton’s jelly mesenchymal stem cells (WJMSCs) immobilized in alginate microspheres with respect to the mechanical properties of alginate hydrogels (1, 1.5 and 2% (w/v)) post incubation in a simulated in vivo environment. Compressive moduli, degradation profile, and swelling kinetics of the hydrogels varied proportionally with alginate concentration and with exposure to simulated conditions. Degradation profile and morphological analysis showed that hydrogels exhibiting high modulus (2% w/v) remained the most intact at the end of day 21. High cell viability in all conditions was observed throughout the culture period. Low-modulus hydrogels (1% w/v) facilitated proliferation of WJMSCs whereas high-modulus hydrogels demonstrated better osteogenic differentiation inferred by an up regulation of osteo-specific genes, expressions of osteocalcin, and quantification of calcium deposition. These findings present a step forward in the development of application-specific hydrogel matrices for stem cell-based tissue engineering.     

Silk ionomers for encapsulation and differentiation of human MSCs

The response of human bone marrow derived human mesenchymal stem cells (hMSCs) encapsulated in silk ionomer hydrogels was studied. Silk aqueous solutions with silk-poly-l-lysine or silk-poly-l-glutamate were formed into hydrogels via ultrasonication in situ with different net charges. hMSCs were encapsulated within the hydrogels and the impact of matrix charge was assessed over weeks in osteogenic, adipogenic and maintenance growth media. These modified silk charged polymers supported cell viability and proliferative potential, and the hMSCs were able to differentiate toward osteogenic or adipogenic lineages in the corresponding differentiation media. The silk/silk-poly-l-lysine hydrogels exhibited a positive effect on selective osteogenesis of hMSCs, inducing differentiation toward an osteogenic lineage even in the absence of osteogenic supplements, while also inhibiting adipogenesis. In contrast, silk/silk fibroin-poly-l-glutamate hydrogels supported both osteogenic and adipogenic differentiation of hMSCs when cultured under induction conditions. The results demonstrate the potential utility of silk-based ionomers in gel formats for hMSCs encapsulation and for directing hMSCs long term functional differentiation toward specific lineages.     

A comparison of bone regeneration with human mesenchymal stem cells and muscle-derived stem cells and the critical role of BMP

Adult multipotent stem cells have been isolated from a variety of human tissues including human skeletal muscle, which represent an easily accessible source of stem cells. It has been shown that human skeletal muscle-derived stem cells (hMDSCs) are muscle-derived mesenchymal stem cells capable of multipotent differentiation. Although hMDSCs can undergo osteogenic differentiation and form bone when genetically modified to express BMP2; it is still unclear whether hMDSCs are as efficient as human bone marrow mesenchymal stem cells (hBMMSCs) for bone regeneration. The current study aimed to address this question by performing a parallel comparison between hMDSCs and hBMMSCs to evaluate their osteogenic and bone regeneration capacities. Our results demonstrated that hMDSCs and hBMMSCs had similar osteogenic-related gene expression profiles and had similar osteogenic differentiation capacities in vitro when transduced to express BMP2. Both the untransduced hMDSCs and hBMMSCs formed very negligible amounts of bone in the critical sized bone defect model when using a fibrin sealant scaffold; however, when genetically modified with lenti-BMP2, both populations successfully regenerated bone in the defect area. No significant differences were found in the newly formed bone volumes and bone defect coverage between the hMDSC and hBMMSC groups. Although both cell types formed mature bone tissue by 6 weeks post-implantation, the newly formed bone in the hMDSCs group underwent quicker remodelling than the hBMMSCs group. In conclusion, our results demonstrated that hMDSCs are as efficient as hBMMSCs in terms of their bone regeneration capacity; however, both cell types required genetic modification with BMP in order to regenerate bone in vivo.     

Adult Stem Cell Driven Genesis of Human-Shaped Articular Condyle

Uniform design of synovial articulations across mammalian species is challenged by their common susceptibility to joint degeneration. The present study was designed to investigate the possibility of creating human-shaped articular condyles by rat bone marrow-derived mesenchymal stem cells (MSCs) encapsulated in a biocompatible poly(ethylene glycol)-based hydrogel. Rat MSCs were harvested, expanded in culture, and treated with either chondrogenic or osteogenic supplements. Rat MSC-derived chondrogenic and osteogenic cells were loaded in hydrogel suspensions in two stratified and yet integrated hydrogel layers that were sequentially photopolymerized in a human condylar mold. Harvested articular condyles from 4-week in vivo implantation demonstrated stratified layers of chondrogenesis and osteogenesis. Parallel in vitro experiments using goat and rat MSCs corroborated in vivo data by demonstrating the expression of chondrogenic and osteogenic markers by biochemical and mRNA analyses. Ex vivo incubated goat MSC-derived chondral constructs contained cartilage-related glycosaminoglycans and collagen. By contrast, goat MSC-derived osteogenic constructs expressed alkaline phosphatase and osteonectin genes, and showed escalating calcium content over time. Rat MSC-derived osteogenic constructs were stiffer than rat MSC-derived chondrogenic constructs upon nanoindentation with atomic force microscopy. These findings may serve as a primitive proof of concept for ultimate tissue-engineered replacement of degenerated articular condyles via a single population of adult mesenchymal stem cells.     

Enhanced chondrogenesis of mesenchymal stem cells in collagen mimetic peptide-mediated microenvironment

A new type of synthetic hydrogel scaffold that mimics certain aspects of structure and function of natural extracellular matrix (ECM) has been developed. We previously reported the conjugation of collagen mimetic peptide (CMP) to poly(ethylene oxide) diacrylate (PEODA) to create a polymer-peptide hybrid scaffold for a suitable cell microenvironment. In this study, we showed that the CMP-mediated microenvironment enhances the chondrogenic differentiation of mesenchymal stem cells (MSCs). MSCs were harvested and photo-encapsulated in CMP-conjugated PEODA (CMP/PEODA). After 3 weeks, the histological and biochemical analysis of the CMP/PEODA gel revealed twice as much glycosaminoglycan and collagen contents as in control PEODA hydrogels. Moreover, MSCs cultured in CMP/PEODA hydrogel exhibited a lower level of hypertrophic markers, core binding factor alpha 1, and type X collagen than MSCs in PEODA hydrogel as revealed by gene expression and immunohistochemisty. These results indicate that CMP/PEODA hydrogel provides a favorable microenvironment for encapsulated MSCs and regulates their downstream chondrogenic differentiation.     

Recapitulation of in vivo-like paracrine signals of human mesenchymal stem cells for functional neuronal differentiation of human neural stem cells in a 3D microfluidic system

Paracrine signals produced from stem cells influence tissue regeneration by inducing the differentiation of endogenous stem or progenitor cells. However, many recent studies that have investigated paracrine signaling of stem cells have relied on either two-dimensional transwell systems or conditioned medium culture, neither of which provide optimal culture microenvironments for elucidating the effects of paracrine signals in vivo. In this study, we recapitulated in vivo-like paracrine signaling of human mesenchymal stem cells (hMSCs) to enhance functional neuronal differentiation of human neural stem cells (hNSCs) in three-dimensional (3D) extracellular matrices (ECMs) within a microfluidic array platform. In order to amplify paracrine signaling, hMSCs were genetically engineered using cationic polymer nanoparticles to overexpress glial cell-derived neurotrophic factor (GDNF). hNSCs were cultured in 3D ECM hydrogel used to fill central channels of the microfluidic device, while GDNF-overexpressing hMSCs (GDNF-hMSCs) were cultured in channels located on both sides of the central channel. This setup allowed for mimicking of paracrine signaling between genetically engineered hMSCs and endogenous hNSCs in the brain. Co-culture of hNSCs with GDNF-hMSCs in the 3D microfluidic system yielded reduced glial differentiation of hNSCs while significantly enhancing differentiation into neuronal cells including dopaminergic neurons. Neuronal cells produced from hNSCs differentiating in the presence of GDNF-hMSCs exhibited functional neuron-like electrophysiological features. The enhanced paracrine ability of GDNF-hMSCs was finally confirmed using an animal model of hypoxic-ischemic brain injury. This study demonstrates the presented 3D microfluidic array device can provide an efficient co-culture platform and provide an environment for paracrine signals from transplanted stem cells to control endogenous neuronal behaviors in vivo.     

Umbilical cord and bone marrow mesenchymal stem cell seeding on macroporous calcium phosphate for bone regeneration in rat cranial defects

Human umbilical cord mesenchymal stem cells (hUCMSCs) are inexhaustible and can be harvested at a low cost without an invasive procedure. However, there has been no report on comparing hUCMSCs with human bone marrow MSCs (hBMSCs) for bone regeneration in vivo. The aim of this study was to investigate hUCMSC and hBMSC seeding on macroporous calcium phosphate cement (CPC), and to compare their bone regeneration in critical-sized cranial defects in rats. Cell attachment, osteogenic differentiation and mineral synthesis on RGD-modified macroporous CPC were investigated in vitro. Scaffolds with cells were implanted in 8-mm defects of athymic rats. Bone regeneration was investigated via micro-CT and histological analysis at 4, 12, and 24 weeks. Three groups were tested: CPC with hUCMSCs, CPC with hBMSCs, and CPC control without cells. Percentage of live cells and cell density on CPC in vitro were similarly good for hUCMSCs and hBMSCs. Both cells had high osteogenic expressions of alkaline phosphatase, osteocalcin, collagen I, and Runx2. Bone mineral density and trabecular thickness in hUCMSC and hBMSC groups in vivo were greater than those of CPC control group. New bone amount for hUCMSC-CPC and hBMSC-CPC constructs was increased by 57% and 88%, respectively, while blood vessel density was increased by 15% and 20%, than CPC control group at 24 weeks. hUCMSC-CPC and hBMSC-CPC groups generally had statistically similar bone mineral density, new bone amount and vessel density. In conclusion, hUCMSCs seeded on CPC were shown to match the bone regeneration efficacy of hBMSCs in vivo for the first time. Both hUCMSC-CPC and hBMSC-CPC constructs generated much more new bone and blood vessels than CPC without cells. Macroporous RGD-grafted CPC with stem cell seeding is promising for craniofacial and orthopedic repairs.     

The modulation of cardiac progenitor cell function by hydrogel-dependent Notch1 activation

Myocardial infarction is the leading cause of death worldwide and phase I clinical trials utilizing cardiac progenitor cells (CPCs) have shown promising outcomes. Notch1 signaling plays a critical role in cardiac development and in the survival, cardiogenic lineage commitment, and differentiation of cardiac stem/progenitor cells. In this study, we functionalized self-assembling peptide (SAP) hydrogels with a peptide mimic of the Notch1 ligand Jagged1 (RJ) to evaluate the therapeutic benefit of CPC delivery in the hydrogels in a rat model of myocardial infarction. The behavior of CPCs cultured in the 3D hydrogels in vitro including gene expression, proliferation, and growth factor production was evaluated. Interestingly, we observed Notch1 activation to be dependent on hydrogel polymer density/stiffness with synergistic increase in presence of RJ. Our results show that RJ mediated Notch1 activation depending on hydrogel concentration differentially regulated cardiogenic gene expression, proliferation, and growth factor production in CPCs in vitro. In rats subjected to experimental myocardial infarction, improvement in acute retention and cardiac function was observed following cell therapy in RJ hydrogels compared to unmodified or scrambled peptide containing hydrogels. This study demonstrates the potential therapeutic benefit of functionalizing SAP hydrogels with RJ for CPC based cardiac repair.