Signalling strategies for osteogenic differentiation of human umbilical cord mesenchymal stromal cells for 3D bone tissue engineering

Advancing Regenerative Cellular Therapies in Non-Scarring Alopecia

Alopecia or baldness is a common diagnosis in clinical practice. Alopecia can be scarring or non-scarring, diffuse or patchy. The most prevalent type of alopecia is non-scarring alopecia, with the majority of cases being androgenetic alopecia (AGA) or alopecia areata (AA). AGA is traditionally treated with minoxidil and finasteride, while AA is treated with immune modulators; however, both treatments have significant downsides. These drawbacks compel us to explore regenerative therapies that are relatively devoid of adverse effects. A thorough literature review was conducted to explore the existing proven and experimental regenerative treatment modalities in non-scarring alopecia. Multiple treatment options compelled us to classify them into growth factor-rich and stem cell-rich. The growth factor-rich group included platelet-rich plasma, stem cell-conditioned medium, exosomes and placental extract whereas adult stem cells (adipose-derived stem cell-nano fat and stromal vascular fraction; bone marrow stem cell and hair follicle stem cells) and perinatal stem cells (umbilical cord blood-derived mesenchymal stem cells (hUCB-MSCs), Wharton jelly-derived MSCs (WJ-MSCs), amniotic fluid-derived MSCs (AF-MSCs), and placental MSCs) were grouped into the stem cell-rich group. Because of its regenerative and proliferative capabilities, MSC lies at the heart of regenerative cellular treatment for hair restoration. A literature review revealed that both adult and perinatal MSCs are successful as a mesotherapy for hair regrowth. However, there is a lack of standardization in terms of preparation, dose, and route of administration. To better understand the source and mode of action of regenerative cellular therapies in hair restoration, we have proposed the "À La Mode Classification". In addition, available evidence-based cellular treatments for hair regrowth have been thoroughly described.

An injectable and antibacterial calcium phosphate scaffold inhibiting Staphylococcus aureus and supporting stem cells for bone regeneration

Staphylococcus aureus (S. aureus) is the major pathogen for osteomyelitis, which can lead to bone necrosis and destruction. There has been no report on antibacterial calcium phosphate cement (CPC) against S. aureus. The aims of this study were to: (1) develop novel antibacterial CPC-chitosan-alginate microbead scaffold; (2) investigate mechanical and antibacterial properties of CPC-chitosan-penicillin-alginate scaffold; (3) evaluate the encapsulation and delivery of human umbilical cord mesenchymal stem cells (hUCMSCs). Flexural strength, elastic modulus and work-of-fracture of the CPC-chitosan-penicillin-alginate microbeads scaffold and CPC-chitosan scaffold were evaluated. Penicillin release profile and antibacterial effects on S. aureus were determined. The hUCMSC delivery and release from penicillin-alginate microbeads were investigated. Injectable CPC-chitosan-penicillin-alginate microbeads scaffold was developed for the first time. CPC-chitosan-penicillin-alginate microbeads scaffold had a flexural strength of 3.16 ± 0.55 MPa, matching that of cancellous bone. With sustained penicillin release, the new scaffold had strong antibacterial effects on S. aureus, with an inhibition zone diameter of 32.2 ± 2.5 mm, greater than that of penicillin disk control (15.1 ± 2.0 mm) (p < 0.05). Furthermore, this injectable and antibacterial scaffold had no toxic effects, yielding excellent hUCMSC viability, which was similar to that of CPC control without antibacterial activity (p > 0.05). CPC-chitosan-penicillin-microbeads scaffold had injectability, good strength, strong antibacterial effects, and good biocompatibility to support stem cell viability for osteogenesis. CPC-chitosan-penicillin-microbeads scaffold is promising for dental, craniofacial and orthopedic applications to combat infections and promote bone regeneration.

Evaluation of Proliferation and Osteogenic Differentiation of Human Umbilical Cord-Derived Mesenchymal Stem Cells in Porous Scaffolds

INTRODUCTION

Human umbilical cord-derived mesenchymal stem cells (UCMSCs) are multiple potential stem cells that can differentiate into various kinds of functional cells, including adipocytes, osteoblasts, and chondroblasts. Thus, UCMSCs have recently been used in both stem cell therapy and tissue engineering applications to produce various functional tissues. This study aimed to evaluate the proliferation and differentiation of UCMSCs on porous scaffolds.

METHODS

UCMSCs were established in a previous study and kept in liquid nitrogen. They were thawed and expanded in vitro to yield enough cells for further experiments. The cells were characterized as having MSC phenotype. They were seeded onto culture medium-treated porous scaffolds or on non-treated porous scaffolds at different densities of UCMSCs (10⁵, 2.1 × 10⁵, and 5 × 10⁵ cells/0.005 g scaffold). The existence of UCMSCs on the scaffold was evaluated by nucleic staining using Hoechst 33342 dye, while cell proliferation on the scaffold was determined by MTT assay. Osteogenic differentiation was evaluated by changes in cellular morphology, accumulation of extracellular calcium, and expression of osteoblast-specific genes (including runx2, osteopontin (OPN), and osteocalcin (OCN)).

RESULTS

The data showed that UCMSCs could attach, proliferate, and differentiate on both treated and non-treated scaffolds but were better on the treated scaffold. At a cell density of 10⁵ cells/0.005 g scaffold, the adherent and proliferative abilities of UCMSCs were higher than that of the other densities after 14 days of culture (p < 0.05). Adherent UCMSCs on the scaffold could be induced into osteoblasts in the osteogenic medium after 21 days of induction. These cells accumulated calcium in the extracellular matrix that was positive with Alizarin Red staining. They also expressed some genes related to osteoblasts, including runx2, OPN, and OCN.

CONCLUSION

UCMSCs could adhere, proliferate, and differentiate into osteoblasts on porous scaffolds. Therefore, porous scaffolds (such as Variotis) may be suitable scaffolds for producing bone tissue in combination with UCMSCs.

Osteogenic Potential of Human Umbilical Cord Mesenchymal Stem Cells on Coralline Hydroxyapatite/Calcium Carbonate Microparticles

Coralline hydroxyapatite/calcium carbonate (CHACC) is a biodegradable and osteoconductive bone graft material with promising clinical performance. CHACC has been shown to support proliferation and osteogenic differentiation of human bone marrow mesenchymal stem cells (MSCs) in vitro and demonstrated to work as a functional scaffold for bone formation in vivo. Umbilical cord matrix is a more accessible and abundant tissue source of MSCs, but its osteogenic capacity in comparison to human bone marrow when cultured on CHACC has not yet been demonstrated. In this study, we assessed the osteogenic differentiation capacity of human MSCs, isolated from bone marrow and umbilical cord matrix and characterised by flow cytometry, when cultured on 200–300 μm CHACC granules. The 3D cultures were characterised by brightfield and scanning electron microscopy (SEM). Osteogenic potential was assessed by immunocytochemistry and qPCR for key markers of bone differentiation (alkaline phosphatase, runx2, type I collagen, and osteocalcin). By day 1, the MSCs had enveloped the surface of the CHACC granules to form organoids, and by day 7, cells had proliferated to bridge nearby organoids. Extracellular matrix deposition and osteogenic differentiation were demonstrated by MSCs from both tissue sources at day 21. However, MSCs from bone marrow demonstrated superior osteogenic differentiation capability compared to those from umbilical cord matrix. In conclusion, it is possible to culture and induce osteogenic differentiation of umbilical cord matrix MSCs on CHACC. Further research is required to optimise the osteogenicity of umbilical cord matrix MSCs to release their full potential as a readily available, accessible, and abundant tissue source for bone tissue engineering.

Encapsulation of mesenchymal stem cells in chitosan/β-glycerophosphate hydrogel for seeding on a novel calcium phosphate cement scaffold

Due to its moldability, biocompatibility, osteoconductivity and resorbability, calcium phosphate cement (CPC) is a highly promising scaffold material for orthopedic applications. However, pH changes and ionic activity during the CPC setting reaction may adversely affect cells seeded directly on CPC. Moreover, a lack of macropores in CPC limits ingrowth of new bone. The objectives of this study were to prepare macroporous CPC scaffolds via porogen leaching, using mannitol crystals as the porogen and to evaluate the in vitro proliferation and osteogenic differentiation of mesenchymal stem cells (MSCs) encapsulated in chitosan/β-glycerophosphate (C/GP) hydrogel prior to exposure to the novel CPC scaffold. MSCs were found to be adhered to the surfaces of CPC macropores via scanning electron microscopy. The viability and osteogenic differentiation of MSCs in C/GP hydrogel with or without exposure to CPC constructs containing mannitol crystals indicated that coating with C/GP hydrogel protected the cells during cement mixing and setting. In conclusion, novel, macroporous CPC scaffolds were prepared, and our data indicate that a hydrogel encapsulation-based strategy can be used to protect cells during scaffold formation. Thus, the MSC-laden CPC scaffolds show promise for the delivery of stem cells to promote bone regeneration.

Functional organic cation transporters mediate osteogenic response to metformin in human umbilical cord mesenchymal stromal cells

BACKGROUND

Compelling evidence indicates that metformin, a low-cost and safe orally administered biguanide prescribed to millions of type 2 diabetics worldwide, induces the osteoblastic differentiation of mesenchymal stromal cells (MSCs) through the 5' adenosine monophosphate (AMP)-activated protein kinase (AMPK) pathway. As a highly hydrophilic cationic compound, metformin uptake is facilitated by cell membrane organic cation transporters (OCTs) of the solute carrier 22A gene family. We hypothesized that to effectively enhance osteogenic differentiation, and ultimately bone regeneration, metformin must gain access into functional OCT-expressing MSCs.

METHODS

Data was obtained through immunoblotting, cellular uptake, mineralization and gene expression assays.

RESULTS

We demonstrate for the first time that functional OCTs are expressed in human-derived MSCs from umbilical cord Wharton's jelly, an inexhaustible source of nonembryonic MSCs with proven osteogenic potential. A clinically relevant concentration of metformin led to AMPK activation, enhanced mineralized nodule formation and increased expression of the osteogenic transcription factor Runt-related transcription factor 2 (RUNX2). Indeed, targeting OCT function through pharmacological and genetic approaches markedly blunted these responses.

CONCLUSIONS

Our findings indicate that functional OCT expression in UC-MSCs is a biological prerequisite that facilitates the intracellular uptake of metformin to induce an osteogenic effect. Future pre-clinical studies are warranted to investigate whether the expression of functional OCTs may serve as a potential biomarker to predict osteogenic responses to metformin.

Human Umbilical Cord MSCs as New Cell Sources for Promoting Periodontal Regeneration in Inflammatory Periodontal Defect

Human periodontal ligament stem cells (hPDLSCs) transplantation represents a promising approach for periodontal regeneration; however, the cell source is limited due to the invasive procedure required for cell isolation. As human umbilical cord mesenchymal stem cells (hUCMSCs) can be harvested inexpensively and inexhaustibly, here we evaluated the regenerative potentials of hUCMSCs as compared with hPDLSCs to determine whether hUCMSCs could be used as new cell sources for periodontal regeneration.

Methods The characteristics of hUCMSCs, including multi-differentiation ability and anti-inflammatory capability, were determined by comparison with hPDLSCs. We constructed cell aggregates (CA) using hUCMSCs and hPDLSCs respectively. Then hPDLSCs-CA and hUCMSCs-CA were combined with β-tricalcium phosphate bioceramic (β-TCP) respectively and their regenerative potentials were determined in a rat inflammatory periodontal defect model.

Results hPDLSCs showed higher osteogenic differentiation potentials than hUCMSCs. Meanwhile, hUCMSCs showed higher extracellular matrix secretion and anti-inflammatory abilities than hPDLSCs. Similar to hPDLSCs, hUCMSCs were able to contribute to regeneration of both soft and hard periodontal tissues under inflammatory periodontitis condition. There were more newly formed bone and periodontal ligaments in hPDLSCs and hUCMSCs groups than in non-cell treated group. Moreover, no significant differences of regenerative promoting effects between hPDLSCs and hUCMSCs were found.

Conclusion: hUCMSCs generated similar promoting effects on periodontal regeneration compared with hPDLSCs, and can be used as new cell sources for periodontal regeneration.

Decellularized Wharton's Jelly from human umbilical cord as a novel 3D scaffolding material for tissue engineering applications

In tissue engineering, an ideal scaffold attracts and supports cells thus providing them with the necessary mechanical support and architecture as they reconstruct new tissue in vitro and in vivo. This manuscript details a novel matrix derived from decellularized Wharton’s jelly (WJ) obtained from human umbilical cord for use as a scaffold for tissue engineering application. This decellularized Wharton’s jelly matrix (DWJM) contained 0.66 ± 0.12 μg/mg sulfated glycosaminoglycans (GAGs), and was abundant in hyaluronic acid, and completely devoid of cells. Mass spectroscopy revealed the presence of collagen types II, VI and XII, fibronectin-I, and lumican I. When seeded onto DWJM, WJ mesenchymal stem cells (WJMSCs), successfully attached to, and penetrated the porous matrix resulting in a slower rate of cell proliferation. Gene expression analysis of WJ and bone marrow (BM) MSCs cultured on DWJM demonstrated decreased expression of proliferation genes with no clear pattern of differentiation. When this matrix was implanted into a murine calvarial defect model with, green fluorescent protein (GFP) labeled osteocytes, the osteocytes were observed to migrate into the matrix as early as 24 hours. They were also identified in the matrix up to 14 days after transplantation. Together with these findings, we conclude that DWJM can be used as a 3D porous, bioactive and biocompatible scaffold for tissue engineering and regenerative medicine applications.

Potential mechanisms underlying ectodermal differentiation of Wharton's jelly mesenchymal stem cells

Wharton's jelly mesenchymal stem cells (WJMSCs) are being increasingly recognized for their ectodermal differentiation potential. Previously, we demonstrated that when WJMSC were seeded onto an acellular matrix material derived from Wharton's jelly and cultured in osteogenic induction media, generated CK19 positive cells and hair-like structures indicative of ectodermal differentiation of WJMSCs. In this manuscript, we examine the underlying mechanism behind this observation using a variety of microscopy and molecular biology techniques such as western blotting and qPCR. We demonstrate that these hair-like structures are associated with live cells that are positive for epithelial and mesenchymal markers such as cytokeratin-19 and α-smooth muscle actin, respectively. We also show that up-regulation of β-catenin and noggin, along with the expression of TGF-β and SMAD and inhibition of BMP4 could be the mechanism behind this ectodermal differentiation and hair-like structure formation.

Current View on Osteogenic Differentiation Potential of Mesenchymal Stromal Cells Derived from Placental Tissues

Mesenchymal stromal cells (MSC) isolated from human term placental tissues possess unique characteristics, including their peculiar immunomodulatory properties and their multilineage differentiation potential. The osteogenic differentiation capacity of placental MSC has been widely disputed, and continues to be an issue of debate. This review will briefly discuss the different MSC populations which can be obtained from different regions of human term placenta, along with their unique properties, focusing specifically on their osteogenic differentiation potential. We will present the strategies used to enhance osteogenic differentiation potential in vitro, such as through the selection of subpopulations more prone to differentiate, the modification of the components of osteo-inductive medium, and even mechanical stimulation. Accordingly, the applications of three-dimensional environments in vitro and in vivo, such as non-synthetic, polymer-based, and ceramic scaffolds, will also be discussed, along with results obtained from pre-clinical studies of placental MSC for the regeneration of bone defects and treatment of bone-related diseases.

The effects of human Wharton's jelly cell transplantation on the intervertebral disc in a canine disc degeneration model

Introduction

Cell-based therapy was a promising treatment method for disc degenerative diseases. Wharton’s jelly cell (WJC) has been explored to cure various human diseases, while it still remains unknown about this MSC for disc repair. In our prior work, WJCs could differentiate into nucleus pulposus (NP)-like cells by co-culturing with NP cells in vitro. Thence, the aim of this study was further to investigate the survival and function of WJCs in vivo after transplantation into degenerated canine discs.

Method

WJCs were isolated from human umbilical cords and labeled with EGFP. The degeneration of L4-5, L5-6, and L6-7 discs of beagles was induced by aspirating the NP tissues. Four weeks after the operation, the injured discs were left to be no treatment at L4-5 (DS group), injected with 0.9 % saline at L5-6 (FS group), and transplanted with EGFP-labeled WJCs at L6-7 (TS group). In all animals, the intact disc L3-4 served as a control (CS group). The animals were followed up for 24 weeks after initial operation. Spine imaging was evaluated at 4, 8, 12, and 24 weeks, respectively. Histologic, biomechanics and gene expression analyses were performed at 24 weeks. Immunohistochemistry for aggrecan, types II collagen, SOX-9 was employed to investigate the matrix formation in the NP.

Results

The TS group showed a significantly smaller reduction in the disc height and T2-weighted signal intensity, and a better spinal segmental stability than DS and FS groups. Histologic assay demonstrated that WJCs were specifically detected in TS group at 24 weeks and the discs of TS group maintained a relatively well preserved structure as compared to the discs of DS and FS groups. Furthermore, real-time PCR and immunohistochemistry demonstrated that expressions of disc matrix genes, aggrecan, type II collagen, and SOX-9, were up-regulated in TS group compared to DS and FS groups.

Conclusion

WJCs could not only survive in the degenerate IVDs, but also promote the disc matrix formation of aggrecan and type II collagen in the degenerate IVDs. It may have value in cell-based therapy for degenerative disc disease.

Mesenchymal stem cells from the human umbilical cord ameliorate fulminant hepatic failure and increase survival in mice

BACKGROUND

Cell therapy has been promising for various diseases. We investigated whether transplantation of human umbilical cord mesenchymal stem cells (hUCMSCs) has any therapeutic effects on D-galactosamine/lipopolysaccharide (GalN/LPS)-induced fulminant hepatic failure in mice.

METHODS

hUCMSCs isolated from human umbilical cord were cultured and transplanted via the tail vein into severe combined immune deficiency mice with GalN/LPS-induced fulminant hepatic failure. After transplantation, the localization and differentiation of hUCMSCs in the injured livers were investigated by immunohistochemical and genetic analyses. The recovery of the injured livers was evaluated histologically. The survival rate of experimental animals was analyzed by the Kaplan-Meier method and log-rank test.

RESULTS

hUCMSCs expressed high levels of CD29, CD73, CD13, CD105 and CD90, but did not express CD31, CD79b, CD133, CD34, and CD45. Cultured hUCMSCs displayed adipogenic and osteogenic differentiation potential. Hematoxylin and eosin staining revealed that transplantation of hUCMSCs reduced hepatic necrosis and promoted liver regeneration. Transplantation of hUCMSCs prolonged the survival rate of mice with fulminant hepatic failure. Polymerase chain reaction for human alu sequences showed the presence of human cells in mouse livers. Positive staining for human albumin, human alpha-fetoprotein and human cytokeratin 18 suggested the formation of hUCMSCs-derived hepatocyte-like cells in vivo.

CONCLUSIONS

hUCMSC was a potential candidate for stem cell based therapies. After transplantation, hUCMSCs partially repaired hepatic damage induced by GalN/LPS in mice. hUCMSCs engrafted into the injured liver and differentiated into hepatocyte-like cells.

The effects of secretion factors from umbilical cord derived mesenchymal stem cells on osteogenic differentiation of mesenchymal stem cells

Factors synthesized by mesenchymal stem cells (MSCs) contain various growth factors, cytokines, exosomes and microRNAs, which may affect the differentiation abilities of MSCs. In the present study, we investigated the effects of secretion factors of human umbilical cord derived mesenchymal stem cells (hUCMSCs) on osteogenesis of human bone marrow derived MSCs (hBMSCs). The results showed that 20 μg/ml hUCMSCs secretion factors could initiate osteogenic differentiation of hBMSCs without osteogenic induction medium (OIM), and the amount of calcium deposit (stained by Alizarin Red) was significantly increased after the hUCMSCs secretion factors treatment. Real time quantitative reverse transcription-polymerase chain reaction (real time qRT-PCR) demonstrated that the expression of osteogenesis-related genes including ALP, BMP2, OCN, Osterix, Col1α and Runx2 were significantly up-regulated following hUCMSCs secretion factors treatment. In addition, we found that 10 μg hUCMSCs secretion factors together with 2×10(5) hBMSCs in the HA/TCP scaffolds promoted ectopic bone formation in nude mice. Local application of 10 μg hUCMSCs secretion factors with 50 μl 2% hyaluronic acid hydrogel and 1×10(5) rat bone marrow derived MSCs (rBMSCs) also significantly enhanced the bone repair of rat calvarial bone critical defect model at both 4 weeks and 8 weeks. Moreover, the group that received the hUCMSCs secretion factors treatment had more cartilage and bone regeneration in the defect areas than those in the control group. Taken together, these findings suggested that hUCMSCs secretion factors can initiate osteogenesis of bone marrow MSCs and promote bone repair. Our study indicates that hUCMSCs secretion factors may be potential sources for promoting bone regeneration.

Human umbilical mesenchymal stem cells-seeded bladder acellular matrix grafts for reconstruction of bladder defects in a canine model

Background

The goal of this study was to explore the feasibility of utilizing human umbilical mesenchymal stem cells (HUMSCs)-seeded Bladder acellular matrix graft (BAMG) for bladder reconstruction in a canine model.

Methodology/Principal Findings

HUMSCs were isolated from newborn umbilical cords and identified by flow cytometry. Partial cystectomy was performed in the experimental and control group. Bladder defects were repaired with HUMSCs-BAMG in the experimental group and repaired with unseeded-BAMG in control group. The implanted grafts were harvested after surgery. H&E and immunohistochemistry staining were performed to evaluate the regeneration of the bladder defect. Primary cultured HUMSCs displayed typical fibroblast morphology with spindle-shaped. Flow cytometry indicated that these cells were positive for CD105 (97.3%) and CD44 (99%), but negative for CD34 (2.8%), CD31 (2.1%), and CD45 (1.7%). Immunohistochemistry staining showed that a multilayered urothelium and well-developed smooth muscle were observed at 12 weeks in experiment group. In contrast, multilayered urothelial tissues were also observed at 12 weeks in group B, but well-developed smooth muscle bundles were observed.

Conclusions/Significance

Our preliminary results demonstrate that UMSC-seeded BAMGs are superior to unseeded BAMGs to promote the regeneration of bladder defects. Our findings indicated that HUMSCs may be a potential cell source for bladder tissue engineering.

Human umbilical cord mesenchymal stromal cells exhibit immature nucleus pulposus cell phenotype in a laminin-rich pseudo-three-dimensional culture system

Introduction

Cell supplementation to the herniated or degenerated intervertebral disc (IVD) is a potential strategy to promote tissue regeneration and slow disc pathology. Human umbilical cord mesenchymal stromal cells (HUCMSCs) – originating from the Wharton’s jelly – remain an attractive candidate for such endeavors with their ability to differentiate into multiple lineages. Previously, mesenchymal stem cells (MSCs) have been studied as a potential source for disc tissue regeneration. However, no studies have demonstrated that MSCs can regenerate matrix with unique characteristics matching that of immature nucleus pulposus (NP) tissues of the IVD. In our prior work, immature NP cells were found to express specific laminin isoforms and laminin-binding receptors that may serve as phenotypic markers for evaluating MSC differentiation to NP-like cells. The goal of this study is to evaluate these markers and matrix synthesis for HUCMSCs cultured in a laminin-rich pseudo-three-dimensional culture system.

Methods

HUCMSCs were seeded on top of Transwell inserts pre-coated with Matrigel™, which contained mainly laminin-111. Cells were cultured under hypoxia environment with three differentiation conditions: NP differentiation media (containing 2.5% Matrigel™ solution to provide for a pseudo-three-dimensional laminin culture system) with no serum, or the same media supplemented with either insulin-like growth factor-1 (IGF-1) or transforming growth factor-β1 (TGF-β1). Cell clustering behavior, matrix production and the expression of NP-specific laminin and laminin-receptors were evaluated at days 1, 7, 13 and 21 of culture.

Results

Data show that a pseudo-three-dimensional culture condition (laminin-1 rich) promoted HUCMSC differentiation under no serum conditions. Starting at day 1, HUCMSCs demonstrated a cell clustering morphology similar to that of immature NP cells in situ and that observed for primary immature NP cells within the similar laminin-rich culture system (prior study). Differentiated HUCMSCs under all conditions were found to contain glycosaminoglycan, expressed extracellular matrix proteins of collagen II and laminin α5, and laminin receptors (integrin α3 and β4 subunits). However, neither growth factor treatment generated distinct differences in NP-like phenotype for HUCMSC as compared with no-serum conditions.

Conclusions

HUCMSCs have the potential to differentiate into cells sharing features with immature NP cells in a laminin-rich culture environment and may be useful for IVD cellular therapy.

Comparison of uncultured marrow mononuclear cells and culture-expanded mesenchymal stem cells in 3D collagen-chitosan microbeads for orthopedic tissue engineering

Stem cell-based therapies have shown promise in enhancing repair of bone and cartilage. Marrow-derived mesenchymal stem cells (MSC) are typically expanded in vitro to increase cell number, but this process is lengthy, costly, and there is a risk of contamination and altered cellular properties. Potential advantages of using fresh uncultured bone marrow mononuclear cells (BMMC) include heterotypic cell and paracrine interactions between MSC and other marrow-derived cells including hematopoietic, endothelial, and other progenitor cells. In the present study, we compared the osteogenic and chondrogenic potential of freshly isolated BMMC to that of cultured-expanded MSC, when encapsulated in three-dimensional (3D) collagen-chitosan microbeads. The effect of low and high oxygen tension on cell function and differentiation into orthopedic lineages was also examined. Freshly isolated rat BMMC (25 × 10(6) cells/mL, containing an estimated 5 × 10(4) MSC/mL) or purified and culture-expanded rat bone marrow-derived MSC (2 × 10(5) cells/mL) were added to a 65-35 wt% collagen-chitosan hydrogel mixture and fabricated into 3D microbeads by emulsification and thermal gelation. Microbeads were cultured in control MSC growth media in either 20% O2 (normoxia) or 5% O2 (hypoxia) for an initial 3 days, and then in control, osteogenic, or chondrogenic media for an additional 21 days. Microbead preparations were evaluated for viability, total DNA content, calcium deposition, and osteocalcin and sulfated glycosaminoglycan expression, and they were examined histologically. Hypoxia enhanced initial progenitor cell survival in fresh BMMC-microbeads, but it did not enhance osteogenic potential. Fresh uncultured BMMC-microbeads showed a similar degree of osteogenesis as culture-expanded MSC-microbeads, even though they initially contained only 1/10th the number of MSC. Chondrogenic differentiation was not strongly supported in any of the microbead formulations. This study demonstrates the microbead-based approach to culturing and delivering cells for tissue regeneration, and suggests that fresh BMMC may be an alternative to using culture-expanded MSC for bone tissue engineering.

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.

Recent Patents Pertaining to Immune Modulation and Musculoskeletal Regeneration with Wharton's Jelly Cells

Umbilical cord mesenchymal stromal cells (UCMSCs) are isolated from Wharton's jelly in the umbilical cord at birth, and offer advantages over adult mesenchymal stromal cells (MSCs) such as highly efficient isolation, faster proliferation in vitro, a broader differentiation potential, and non-invasive harvesting procedure. Their expansion and differentiation potential renders them a promising cell source for tissue engineering and clinical applications. This review discusses recent updates on the differentiation strategies for musculoskeletal tissue engineering including cartilage, bone, and muscle. In addition to tissue engineering applications, UCMSCs can be utilized to support hematopoiesis and modulate immune response. We review the patents relevant to the application of MSCs including UCMSCs in hematopoiesis and immune modulation. Finally, the current hurdles in the clinical translation of UCMSCs are discussed. During clinical translation, it is critical to develop large-scale manufacturing of UCMSCs as well as the composition of expansion and differentiation media. Four clinical trials to date have examined the safety and efficacy of UCMSCs. Once public banking of UCMSCs is available to supply matched allogeneic units and once UCMSC manufacturing is standardized, we anticipate that UCMSCs will be more widely used in clinical trials.

Hybrid hydroxyapatite nanoparticle colloidal gels are injectable fillers for bone tissue engineering

Injectable bone fillers have emerged as an alternative to the invasive surgery often required to treat bone defects. Current bone fillers may benefit from improvements in dynamic properties such as shear thinning during injection and recovery of material stiffness after placement. Negatively charged inorganic hydroxyapatite (HAp) nanoparticles (NPs) were assembled with positively charged organic poly(d,l-lactic-co-glycolic acid) (PLGA) NPs to create a cohesive colloidal gel. This material is held together by electrostatic forces that may be disrupted by shear to facilitate extrusion, molding, or injection. Scanning electron micrographs of the dried colloidal gels showed a well-organized, three-dimensional porous structure. Rheology tests revealed that certain colloidal gels could recover after being sheared. Human umbilical cord mesenchymal stem cells were also highly viable when seeded on the colloidal gels. HAp/PLGA NP colloidal gels offer an attractive scheme for injectable filling and regeneration of bone tissue.

Human mesenchymal stem cells: a bank perspective on the isolation, characterization and potential of alternative sources for the regeneration of musculoskeletal tissues

The continuous discovery of human mesenchymal stem cells (hMSCs) in different tissues is stirring up a tremendous interest as a cell source for regenerative medicine therapies. Historically, hMSCs have been always considered a sub-population of mononuclear cells present in the bone marrow (BM). Although BM-hMSCs are still nowadays considered as the most promising mesenchymal stem cell population to reach the clinics due to their capacity to differentiate into multiple tissues, hMSCs derived from other adult and fetal tissues have also demonstrated to possess similar differentiation capacities. Furthermore, different reports have highlighted a higher recurrence of hMSCs in some of these tissues as compared to BM. This offer a fascinating panorama for cell banking, since the creation of a stem cell factory could be envisioned where hMSCs are stocked and used for ad hoc clinical applications. In this review, we summarize the main findings and state of the art in hMSCs isolation, characterization, and differentiation from alternative tissue sources and we attempt to compare their potency for musculoskeletal regeneration.

Generating CK19-positive cells with hair-like structures from Wharton's jelly mesenchymal stromal cells

Wharton's jelly mesenchymal stromal cells (WJMSCs) are considered mesenchymal, multipotent, and capable of differentiating into cells of mesodermal origin. Ectodermal differentiation from mesenchymal cells has been recently reported. Herein, we show for the first time that we can generate cytokeratin 19-positive cells and hair-like structures from WJMSCs in vitro using 2 separate methodologies that utilize osteogenic media to induce WJMSCs to undergo osteogenic differentiation. In one method, WJMSCs were seeded on a matrix isolated from Wharton's jelly following decellularization. In the other method, WJMSCs were cultured to form spheroids. Our findings demonstrate that WJMSCs may have the capacity for ectodermal differentiation.

Strategies for controlled delivery of growth factors and cells for bone regeneration

The controlled delivery of growth factors and cells within biomaterial carriers can enhance and accelerate functional bone formation. The carrier system can be designed with pre-programmed release kinetics to deliver bioactive molecules in a localized, spatiotemporal manner most similar to the natural wound healing process. The carrier can also act as an extracellular matrix-mimicking substrate for promoting osteoprogenitor cellular infiltration and proliferation for integrative tissue repair. This review discusses the role of various regenerative factors involved in bone healing and their appropriate combinations with different delivery systems for augmenting bone regeneration. The general requirements of protein, cell and gene therapy are described, with elaboration on how the selection of materials, configurations and processing affects growth factor and cell delivery and regenerative efficacy in both in vitro and in vivo applications for bone tissue engineering.

Calcium phosphate cement with biofunctional agents and stem cell seeding for dental and craniofacial bone repair

OBJECTIVE

Calcium phosphate cement (CPC) can be injected to harden in situ and is promising for dental and craniofacial applications. However, human stem cell attachment to CPC is relatively poor. The objectives of this study were to incorporate biofunctional agents into CPC, and to investigate human umbilical cord mesenchymal stem cell (hUCMSC) seeding on biofunctionalized CPC for osteogenic differentiation for the first time.

METHODS

Five types of biofunctional agents were used: RGD (Arg-Gly-Asp) peptides, human fibronectin (Fn), fibronectin-like engineered polymer protein (FEPP), extracellular matrix Geltrex, and human platelet concentrate. Five biofunctionalized CPC scaffolds were fabricated: CPC-RGD, CPC-Fn, CPC-FEPP, CPC-Geltrex, and CPC-Platelets. The hUCMSC attachment, proliferation, osteogenic differentiation and mineral synthesis were measured.

RESULTS

The hUCMSCs on biofunctionalized CPCs had much better cell attachment, proliferation, actin fiber expression, osteogenic differentiation and mineral synthesis, compared to the traditional CPC control. Cell proliferation was increased by an order of magnitude via incorporation of biofunctional agents in CPC (p<0.05). Mineral synthesis on biofunctionalized CPCs was 3-5 folds of those of control (p<0.05). hUCMSCs differentiated with high alkaline phosphatase, Runx2, osteocalcin, and collagen I gene expressions. Mechanical properties of biofunctionalized CPC matched the reported strength and elastic modulus of cancellous bone.

SIGNIFICANCE

A new class of biofunctionalized CPCs was developed, including CPC-RGD, CPC-Fn, CPC-FEPP, CPC-Geltrex, and CPC-Platelets. hUCMSCs on biofunctionalized CPCs had cell density, cell proliferation, actin fiber density, and bone mineralization that were dramatically better than those on traditional CPC. Novel biofunctionalized CPC scaffolds with greatly enhanced human stem cell proliferation and differentiation are promising to facilitate bone regeneration in a wide range of dental, craniofacial and orthopedic applications.

Umbilical cord stem cells released from alginate-fibrin microbeads inside macroporous and biofunctionalized calcium phosphate cement for bone regeneration

The need for bone repair has increased as the population ages. The objectives of this study were to (1) develop a novel biofunctionalized and macroporous calcium phosphate cement (CPC) containing alginate-fibrin microbeads encapsulating human umbilical cord mesenchymal stem cells (hUCMSC) and, for the first time, (2) investigate hUCMSC proliferation and osteogenic differentiation inside the CPC. A macroporous CPC was developed using calcium phosphate powder, chitosan, and a gas-foaming porogen. Five types of CPC were fabricated: a CPC control, CPC+0.05% fibronectin (Fn), CPC+0.1% Fn, CPC+0.1% arginine-glycine-aspartate (RGD), and CPC+0.1% Fn+0.1% RGD. Alginate-fibrin microbeads containing 10(6) hUCMSC per ml were encapsulated in the CPC paste. After the CPC had set, the degradable microbeads released hUCMSC within it. The hUCMSC proliferated inside the CPC, with the cell density after 21 days being 4-fold that on day1. CPC+0.1% RGD had the highest cell density, which was 4-fold that of the CPC control. The released cells differentiated along the osteogenic lineage and synthesized bone mineral. The hUCMSC inside the CPC+0.1% RGD construct expressed the genes alkaline phosphatase, osteocalcin and collagen I, at twice the level of the CPC control. Mineral synthesis by hUCMSC inside the CPC+0.1% RGD construct was 2-fold that in the CPC control. RGD and Fn incorporation in the CPC did not compromise its strength, which matched the reported strength of cancellous bone. In conclusion, degradable microbeads released hUCMSC which proliferated, differentiated and synthesized minerals inside the macroporous CPC. The CPC with RGD greatly enhanced cell function. The novel biofunctionalized and macroporous CPC-microbead-hUCMSC construct is promising for bone tissue engineering applications.

Exogenous mineralization of cell-seeded and unseeded collagen-chitosan hydrogels using modified culture medium

Induced biomineralization of materials has been employed as a strategy to increase integration with host tissue, and more recently as a method to control cell function in tissue engineering. However, mineralization is typically performed in the absence of cells, since hypertonic solutions that lack the nutrients and culture components required for the maintenance of cell viability are often used. In the present study, we exposed fibroblast-seeded three-dimensional collagen-chitosan hydrogels to a defined culture medium modified to have specific concentrations of ions involved in biomineralization. The modified medium caused a significant increase in calcium deposition in collagen-chitosan gels, relative to constructs incubated in a standard medium, though serum supplementation attenuated mineral deposition. Collagen-chitosan constructs became opaque over 3 days of mineralization in modified Dulbecco's modified Eagle medium (DMEM), in contrast to translucent control gels incubated in standard DMEM. Histological staining confirmed increased levels of mineral in the treated constructs. Rheological characterization showed that both the storage and loss moduli increased significantly in mineralized materials. Mineralization of fibroblast-seeded constructs resulted in decreased cell viability and proliferation rate over 3 days of incubation in modified medium, but the cell population remained over 75% viable and regained its proliferative potential after rescue in standard culture medium. The ability to mineralize protein matrices in the presence of cells could be useful in creating mechanically stable tissue constructs, as well as to study the effects of the tissue microenvironment on cell function.

Non-rigid calcium phosphate cement containing hydrogel microbeads and absorbable fibres seeded with umbilical cord stem cells for bone engineering

The need for bone repair has increased as the population ages. Non-rigid calcium phosphate scaffolds could provide compliance for micro-motions within the tissues and yet have load-supporting strength. The objectives of this study were to: (a) develop a non-rigid calcium phosphate cement (CPC) with microbeads and fibre reinforcement; and (b) investigate human umbilical cord mesenchymal stem cell (hUCMSC) proliferation, osteodifferentiation and mineralization on non-rigid CPC for the first time. Non-rigid CPC was fabricated by adding extra tetracalcium phosphate in the traditional CPC and by incorporating chitosan, absorbable fibres and hydrogel microbeads. The non-rigid CPC-microbead scaffold possessed a strain-at-failure of 10.7%, much higher than the traditional CPC's strain of 0.05% which is typical for brittle bioceramics. Flexural strength of non-rigid CPC-microbead was 4-fold that of rigid CPC-microbead scaffold, while work-of-fracture (toughness) was increased by 20-fold. The strength of non-rigid CPC-microbead-fibre scaffold matched that of cancellous bone. hUCMSCs on non-rigid CPC proliferated from 100 cells/mm(2) at 1 day to 600 cells/mm(2) at 8 days. Alkaline phosphatase, osteocalcin and collagen gene expressions of hUCMSCs were greatly increased, and the cells synthesized bone minerals. hUCMSCs on non-rigid CPC-microbead-fibre constructs had higher bone markers and more mineralization than those on rigid CPC controls. In conclusion, this study developed the first non-rigid, in situ-setting calcium phosphate-microbead-fibre scaffold with a strain-at-failure exceeding 10%. hUCMSCs showed excellent proliferation, osteodifferentiation and mineralization on non-rigid CPC scaffold. The novel non-rigid CPC-hUCMSC construct with good strength, high strain-at-failure and toughness, as well as superior stem cell proliferation, osteodifferentiation and mineralization, is promising for load-bearing bone regeneration applications.

Gas-foaming calcium phosphate cement scaffold encapsulating human umbilical cord stem cells

Tissue engineering approaches are promising to meet the increasing need for bone regeneration. Calcium phosphate cement (CPC) can be injected and self-set to form a scaffold with excellent osteoconductivity. The objectives of this study were to develop a macroporous CPC-chitosan-fiber construct containing alginate-fibrin microbeads encapsulating human umbilical cord mesenchymal stem cells (hUCMSCs) and to investigate hUCMSC release from the degrading microbeads and proliferation inside the porous CPC construct. The hUCMSC-encapsulated microbeads were completely wrapped inside the CPC paste, with the gas-foaming porogen creating macropores in CPC to provide for access to culture media. Increasing the porogen content in CPC significantly increased the cell viability, from 49% of live cells in CPC with 0% porogen to 86% of live cells in CPC with 15% porogen. The alginate-fibrin microbeads started to degrade and release the cells inside CPC at 7 days. The released cells started to proliferate inside the macroporous CPC construct. The live cell number inside CPC increased from 270 cells/mm(2) at 1 day to 350 cells/mm(2) at 21 days. The pore volume fraction of CPC increased from 46.8% to 78.4% using the gas-foaming method, with macropore sizes of approximately 100 to 400 μm. The strength of the CPC-chitosan-fiber scaffold at 15% porogen was 3.8 MPa, which approximated the reported 3.5 MPa for cancellous bone. In conclusion, a novel gas-foaming macroporous CPC construct containing degradable alginate-fibrin microbeads was developed that encapsulated hUCMSCs. The cells had good viability while wrapped inside the porous CPC construct. The degradable microbeads in CPC quickly released the cells, which proliferated over time inside the porous CPC. Self-setting, strong CPC with alginate-fibrin microbeads for stem cell delivery is promising for bone tissue engineering applications.

Effects of electrospun submicron fibers in calcium phosphate cement scaffold on mechanical properties and osteogenic differentiation of umbilical cord stem cells

Fibrous scaffolds are promising for tissue engineering because of the high surface area and fibrous features mimicking the extracellular matrix in vivo. Calcium phosphate cements (CPCs) can be injected and self-set in the bone defect. A literature search revealed that there have been no reports on stem cell seeding on CPC containing electrospun submicron fibers. The objective of this study was to investigate for the first time the effects of electrospun fibers in CPC on mechanical properties and human umbilical cord mesenchymal stem cell (hUCMSC) proliferation, osteogenic differentiation and mineralization. Poly(D,L-lactide-co-glycolide) fibers were made via an electrospinning technique to yield an average fiber diameter of 650 nm. The fibers were incorporated into CPC consisting of tetracalcium phosphate, dicalcium phosphate anhydrous and chitosan lactate. Fiber volume fractions were 0%, 2.5%, 5% and 10%. CPC with 10% fibers had a flexural strength that was twice that of CPC without fibers, and a work-of-fracture (toughness) that was an order of magnitude larger than that of CPC without fibers. hUCMSCs proliferated rapidly and synthesized bone minerals when attached to the electrospun fiber-CPC scaffolds. Alkaline phosphatase, osteocalcin and collagen I expressions of hUCMSCs were doubled, while mineralization was increased by 40%, when fiber volume fraction in CPC was increased from 0% to 10%. The enhanced cell function was attributed to the high surface area and biomimetic features of the fiber-CPC scaffold. In conclusion, incorporating submicron fibers into CPC greatly improved the strength and toughness of the CPC. Creating submicron fibrous features in CPC was a useful method for enhancing the osteogenic differentiation and mineralization of stem cells. The novel electrospun fiber-CPC-hUCMSC construct is promising for stem cell delivery and bone tissue engineering.

Collagen-calcium phosphate cement scaffolds seeded with umbilical cord stem cells for bone tissue engineering

Human umbilical cord mesenchymal stem cells (hUCMSCs) avoid the invasive procedure required to harvest bone marrow MSCs. The addition of collagen fibers into self-setting calcium phosphate cement (CPC) may increase the scaffold strength, and enhance cell attachment and differentiation. The objectives of this study were to develop a novel class of collagen-CPC composite scaffolds, and to investigate hUCMSC attachment, proliferation, and osteogenic differentiation on collagen-CPC scaffolds for the first time. Collagen fibers in CPC improved the load-bearing capability. Flow cytometry showed that the hUCMSCs expressed cell surface markers characteristic of MSCs, and were negative for hematopoietic and endothelial cell markers. hUCMSCs proliferated rapidly in all CPC composite scaffolds, with cell number increasing by sevenfold in 8 days. Cellular function was enhanced with collagen fibers in CPC scaffolds. Cell density increased from (645±60) cells/mm(2) on CPC with 0% collagen, to (1056±65) cells/mm(2) on CPC with 8% collagen (p<0.05). The actin stress fibers inside the hUCMSCs were stained, and the fluorescence intensity was doubled when the collagen in CPC was increased by 0% to 8%. RT-PCR showed that hUCMSCs on CPC with collagen had higher osteogenic expression than those on CPC without collagen. Alizarin Red S staining revealed a great increase in mineralization by hUCMSCs on CPC with collagen than that without collagen. In conclusion, hUCMSCs showed excellent proliferation, differentiation, and synthesis of bone minerals in collagen-CPC composite scaffolds for the first time. The novel hUCMSC-seeded collagen-CPC construct with superior cell function and load-bearing capability is promising to enhance bone regeneration in a wide range of orthopedic and craniofacial applications.

The fast release of stem cells from alginate-fibrin microbeads in injectable scaffolds for bone tissue engineering

Stem cell-encapsulating hydrogel microbeads of several hundred microns in size suitable for injection, that could quickly degrade to release the cells, are currently unavailable. The objectives of this study were to: (1) develop oxidized alginate-fibrin microbeads encapsulating human umbilical cord mesenchymal stem cells (hUCMSCs); (2) investigate microbead degradation, cell release, and osteogenic differentiation of the released cells for the first time. Three types of microbeads were fabricated to encapsulate hUCMSCs: (1) Alginate microbeads; (2) oxidized alginate microbeads; (3) oxidized alginate-fibrin microbeads. Microbeads with sizes of about 100-500 μm were fabricated with 1 × 10(6) hUCMSCs/mL of alginate. For the alginate group, there was little microbead degradation, with very few cells released at 21 d. For oxidized alginate, the microbeads started to slightly degrade at 14 d. In contrast, the oxidized alginate-fibrin microbeads started to degrade at 4 d and released the cells. At 7 d, the number of released cells greatly increased and showed a healthy polygonal morphology. At 21 d, the oxidized alginate-fibrin group had a live cell density that was 4-fold that of the oxidized alginate group, and 15-fold that of the alginate group. The released cells had osteodifferentiation, exhibiting highly elevated bone marker gene expressions of ALP, OC, collagen I, and Runx2. Alizarin staining confirmed the synthesis of bone minerals by hUCMSCs, with the mineral concentration at 21 d being 10-fold that at 7 d. In conclusion, fast-degradable alginate-fibrin microbeads with hUCMSC encapsulation were developed that could start to degrade and release the cells at 4 d. The released hUCMSCs had excellent proliferation, osteodifferentiation, and bone mineral synthesis. The alginate-fibrin microbeads are promising to deliver stem cells inside injectable scaffolds to promote tissue regeneration.

Effect of cell seeding density on proliferation and osteodifferentiation of umbilical cord stem cells on calcium phosphate cement-fiber scaffold

Calcium phosphate cement (CPC) can fill complex-shaped bone defects and set in situ to form a scaffold with intimate adaptation to neighboring bone. The objectives of this study were to determine (1) the effects of fiber length and alginate microbead volume fraction on CPC mechanical properties, and (2) the effect of cell seeding density of human umbilical cord mesenchymal stem cells (hUCMSCs) on their proliferation and osteodifferentiation on CPC. Adding microbeads to CPC degraded the strength. However, increasing the fiber length improved the mechanical properties. Strength and elastic modulus of CPC-microbead-fiber scaffold matched those reported for cancellous bone. When the cell seeding density was increased from 50k to 300k, the cell viability, osteodifferentiation, and bone mineral synthesis also increased. When the seeding density was further increased to 500k, the osteodifferentiation and mineralization decreased. Hence, the 300k seeding density was optimal for CPC-microbead-fiber under the specified conditions. At day 8, alkaline phosphatase (ALP) gene expression of hUCMSCs with seeding density of 300k was threefold the ALP at 150k, and 200-fold the ALP at 50k. At day 14, osteocalcin and runt-related transcription factor 2 with cell seeding density of 300k was fourfold those at 50k. At day 14, mineralization by hUCMSCs at seeding density of 300k was 5-fold the mineralization at 150k, and 25-fold that at 50k. In conclusion, the effect of stem cell seeding density on CPC was determined for the first time. At low cell densities, cell viability and mineralization increased with seeding density. However, a higher seeding density was not necessarily better, and an optimal seeding density on CPC resulted in the best osteodifferentiation and mineralization. The stem cell-seeded CPC-fiber scaffold with excellent osteodifferentiation and mineralization is promising for orthopedic and craniofacial applications.

Musculoskeletal tissue engineering with human umbilical cord mesenchymal stromal cells

Multipotent mesenchymal stromal cells (MSCs) hold tremendous promise for tissue engineering and regenerative medicine, yet with so many sources of MSCs, what are the primary criteria for selecting leading candidates? Ideally, the cells will be multipotent, inexpensive, lack donor site morbidity, donor materials should be readily available in large numbers, immunocompatible, politically benign and expandable in vitro for several passages. Bone marrow MSCs do not meet all of these criteria and neither do embryonic stem cells. However, a promising new cell source is emerging in tissue engineering that appears to meet these criteria: MSCs derived from Wharton's jelly of umbilical cord MSCs. Exposed to appropriate conditions, umbilical cord MSCs can differentiate in vitro along several cell lineages such as the chondrocyte, osteoblast, adipocyte, myocyte, neuronal, pancreatic or hepatocyte lineages. In animal models, umbilical cord MSCs have demonstrated in vivo differentiation ability and promising immunocompatibility with host organs/tissues, even in xenotransplantation. In this article, we address their cellular characteristics, multipotent differentiation ability and potential for tissue engineering with an emphasis on musculoskeletal tissue engineering.

Glyoxal crosslinking of cell-seeded chitosan/collagen hydrogels for bone regeneration

Chitosan and collagen are natural biomaterials that have been used extensively in tissue engineering, both separately and as composite materials. Most methods to fabricate chitosan/collagen composites use freeze drying and chemical crosslinking to create stable porous scaffolds, which subsequently can be seeded with cells. In this study, we directly embedded human bone marrow stem cells (hBMSC) in chitosan/collagen materials by initiating gelation using β-glycerophosphate at physiological temperature and pH. We further examined the use of glyoxal, a dialdehyde with relatively low toxicity, to crosslink these materials and characterized the resulting changes in matrix and cell properties. The cytocompatibility of glyoxal and the crosslinked gels were investigated in terms of hBMSC metabolic activity, viability, proliferation and osteogenic differentiation. These studies revealed that glyoxal was cytocompatible at concentrations below about 1mM for periods of exposure up to 15 h, though the degree of cell spreading and proliferation were dependent on matrix composition. Glyoxal-crosslinked matrices were stiffer and compacted less than uncrosslinked controls. It was further demonstrated that hBMSC can attach and proliferate in three-dimensional matrices composed of 50/50 chitosan/collagen, and that these materials supported osteogenic differentiation in response to stimulation. Such glyoxal-crosslinked chitosan/collagen composite materials may find utility as cell delivery vehicles for enhancing the repair of bone defects.

Mannitol-containing macroporous calcium phosphate cement encapsulating human umbilical cord stem cells

Stem cell-based tissue engineering offers immense promise for bone regeneration. The objective of this study was to develop a self-setting, mannitol-containing calcium phosphate cement (CPC) encapsulating human umbilical cord mesenchymal stem cells (hUCMSCs) for bone tissue engineering. hUCMSCs could be an inexhaustible and low-cost alternative to the gold-standard bone marrow MSCs, which require an invasive procedure to harvest. hUCMSCs were encapsulated in alginate beads and mixed into the CPC paste. Water-soluble mannitol porogen was incorporated into CPC to create macropores. The porosity was increased from 49% for the hUCMSC-encapsulating CPC to 64% after adding mannitol and absorbable-fibres (p < 0.05). Flexural strength of the construct was increased from 0.3 MPa to 2.0 MPa via fibres. Live cell percentage was > 80% for all constructs. The ALP and OC gene expressions were low at 1 day and greatly increased at 14 days. The constructs that contained mannitol had significantly higher ALP and OC expressions than that without mannitol. ALP activity of hUCMSCs inside CPC with mannitol and fibre was significantly higher than that without mannitol. At 14 days, mineralization by the encapsulated hUCMSCs was eight-fold higher than that at 1 day. In conclusion, a novel mannitol-containing porous CPC-hUCMSC construct was developed for bone tissue engineering. Its advantages include cell delivery inside a load-bearing CPC that has injectable and in situ setting capabilities. hUCMSCs inside CPC had good viability and successfully osteodifferentiated. The self-setting and strong hUCMSC-encapsulating CPC scaffold is promising for bone tissue engineering in a wide range of orthopaedic and craniofacial applications.

Osteogenic media and rhBMP-2-induced differentiation of umbilical cord mesenchymal stem cells encapsulated in alginate microbeads and integrated in an injectable calcium phosphate-chitosan fibrous scaffold

The need for bone tissue engineering has increased as the world population ages. The objectives of this study were to (1) develop a novel human umbilical cord mesenchymal stem cell (hUCMSC)-encapsulating, fiber-reinforced injectable calcium phosphate cement (CPCF) scaffold, and (2) investigate the effects of osteogenic media delivery, preosteodifferentiation, and bone morphogenetic protein-2 (BMP-2) delivery on hUCMSC osteodifferentiation inside CPCF for the first time. CPCF was developed using calcium phosphate powders, chitosan, and absorbable fibers. Four types of hUCMSC-encapsulating constructs were fabricated: control media in alginate hydrogel microbeads in CPCF; osteogenic media in microbeads; preosteodifferentiation; and recombinant human BMP-2 (rhBMP-2) in microbeads. The hUCMSCs inside CPCF maintained good viability, successfully differentiated into the osteogenic lineage, and synthesized bone minerals. The preosteodifferentiation method yielded high gene expressions of alkaline phosphatase, osteocalcin, collagen, and osterix, as well as alkaline phosphatase protein synthesis. The mineralization for the preosteodifferentiation constructs exceeded those of the rhBMP-2 group at 1-7 days, and was slightly lower than the rhBMP-2 group at 21 days. Mineralization of the rhBMP-2 group was 12-fold that of the control constructs at 21 days. In conclusion, although the BMP-2 delivery promoted osteodifferentiation, the preosteodifferentiation method and the ostegenic media method with hUCMSCs in CPCF were also promising for bone regeneration. hUCMSCs may be an effective alternative to the gold-standard bone marrow MSCs, which require an invasive procedure to harvest. The novel injectable stem cell-CPCF construct may be useful in minimally invasive and other orthopedic surgeries.

Human umbilical cord mesenchymal stromal cells in a sandwich approach for osteochondral tissue engineering

Cell sources and tissue integration between cartilage and bone regions are critical to successful osteochondral regeneration. In this study, human umbilical cord mesenchymal stromal cells (hUCMSCs), derived from Wharton's jelly, were introduced to the field of osteochondral tissue engineering and a new strategy for osteochondral integration was developed by sandwiching a layer of cells between chondrogenic and osteogenic constructs before suturing them together. Specifically, hUCMSCs were cultured in biodegradable poly-L-lactic acid scaffolds for 3 weeks in either chondrogenic or osteogenic medium to differentiate cells toward cartilage or bone lineages, respectively. A highly concentrated cell solution containing undifferentiated hUCMSCs was pasted onto the surface of the bone layer at week 3 and the two layers were then sutured together to form an osteochondral composite for another 3 week culture period. Chondrogenic and osteogenic differentiation was initiated during the first 3 weeks, as evidenced by the expression of type II collagen and runt-related transcription factor 2 genes, respectively, and continued with the increase of extracellular matrix during the last 3 weeks. Histological and immunohistochemical staining, such as for glycosaminoglycans, type I collagen and calcium, revealed better integration and transition of these matrices between two layers in the composite group containing sandwiched cells compared to other control composites. These results suggest that hUCMSCs may be a suitable cell source for osteochondral regeneration, and the strategy of sandwiching cells between two layers may facilitate scaffold and tissue integration.

Umbilical cord stem cell seeding on fast-resorbable calcium phosphate bone cement

Tissue engineering offers immense promise for bone regeneration. Human umbilical cord mesenchymal stem cells (hUCMSCs) can be collected without invasive procedures required for bone marrow MSCs. The objective of this study was to investigate the physical properties and the differentiation capacity of hUCMSCs on calcium phosphate cement (CPC) scaffolds with improved dissolution/resorption rates. CPC consisted of tetracalcium phosphate and dicalcium phosphate anhydrous, with various tetracalcium phosphate/dicalcium phosphate anhydrous ratios. At 1/3 ratio, CPC had a dissolution rate 40% faster than CPC control at 1/1. The faster-resorbable CPC had strength and modulus similar to CPC control. Their strength and modulus exceeded the reported values for cancellous bone, and were much higher than those of hydrogels and injectable polymers for cell delivery. hUCMSCs attached to the nano-apatitic CPC and proliferated rapidly. hUCMSCs differentiated into the osteogenic lineage, with significant increases in alkaline phosphatase activity, osteocalcin, collagen I, and osterix gene expression. In conclusion, in this study we reported that hUCMSCs attaching to CPC with high dissolution/resorption rate showed excellent proliferation and osteogenic differentiation. hUCMSCs delivered via high-strength CPC have the potential to be an inexhaustible and low-cost alternative to the gold-standard human bone marrow mesenchymal stem cells. These results may broadly impact stem-cell-based tissue engineering.

Three-dimensional macroscopic scaffolds with a gradient in stiffness for functional regeneration of interfacial tissues

A novel approach has been demonstrated to construct biocompatible, macroporous 3-D tissue engineering scaffolds containing a continuous macroscopic gradient in composition that yields a stiffness gradient along the axis of the scaffold. Polymeric microspheres, made of poly(D,L-lactic-co-glycolic acid) (PLGA), and composite microspheres encapsulating a higher stiffness nano-phase material (PLGA encapsulating CaCO(3) or TiO(2) nanoparticles) were used for the construction of microsphere-based scaffolds. Using controlled infusion of polymeric and composite microspheres, gradient scaffolds displaying an anisotropic macroscopic distribution of CaCO(3)/TiO(2) were fabricated via an ethanol sintering technique. The controllable mechanical characteristics and biocompatible nature of these scaffolds warrants further investigation for interfacial tissue engineering applications.

TRPC expression in mesenchymal stem cells

Transient receptor potential canonical (TRPC) channels are key players in calcium homeostasis and various regulatory processes in cell biology. Little is currently known about the TRPC subfamily members in mesenchymal stem cells (MSC), where they could play a role in cell proliferation. We report on the presence of TRPC1, 2, 4 and 6 mRNAs in MSC. Western blot and immunofluorescence staining indicate a membrane and intracellular distribution of TRPC1. Furthermore, the decrease in the level of TRPC1 protein caused by RNA interference is accompanied by the downregulation of cell proliferation. These results indicate that MSC express TRPC1, 2, 4 and 6 mRNA and that TRPC1 may play a role in stem cell proliferation.

Stem cell-calcium phosphate constructs for bone engineering

While human bone-marrow-derived mesenchymal stem cells (hBMSCs) have been investigated, human umbilical cord mesenchymal stem cells (hUCMSCs) are a relatively new cell source. Little has been reported on hUCMSC encapsulation in scaffolds for bone tissue engineering. The objective of this study was to encapsulate hBMSCs and hUCMSCs in calcium phosphate cement (CPC) scaffolds for dental, craniofacial, and orthopedic applications. Stem-cell-encapsulating CPC construct with chitosan and fiber reinforcement reached the strength of cancellous bone, which was much stronger than previous injectable carriers for cell delivery. hUCMSCs and hBMSCs inside the constructs showed excellent viability and osteo-differentiation. The encapsulated hUCMSCs synthesized nearly three-fold more bone minerals than the hBMSCs in vitro. Hence, stem-cell-encapsulating CPC-chitosan-fiber construct may be promising for dental and orthopedic applications. This study indicated that the hUCMSCs were a potent alternative to the gold-standard hBMSCs, which may have a broad impact on regenerative medicine and dental tissue engineering.

Osteogenic differentiation of human umbilical cord mesenchymal stromal cells in polyglycolic acid scaffolds

Although human umbilical cord mesenchymal stromal cells (hUCMSCs) have been shown to differentiate along an osteogenic lineage in monolayer culture, the potential of these cells has seldom before been investigated in three-dimensional scaffolds for bone tissue engineering applications. In this 6-week study, we observed osteogenic differentiation of hUCMSCs on polyglycolic acid (PGA) nonwoven mesh scaffolds, and compared seeding densities for potential use in bone tissue engineering. Cells were seeded into PGA meshes with densities of 5, 25, or 50 x 10(6) cells/mL scaffold and then cultured in osteogenic medium. Cell proliferation, osteogenic differentiation, and matrix formation were evaluated at weeks 0, 3, and 6. Osteogenic differentiation was observed based on positive alkaline phosphatase activity and an increase of collagen production and calcium incorporation into the extracellular matrix, which increased with higher cell density. During differentiation, runt-related transcription factor (RUNX2), type I collagen (CI), and osteocalcin (OCN) gene expression levels were also increased. In conclusion, exposed to osteogenic signals, hUCMSCs differentiated along an osteogenic lineage as determined by expression of osteogenic markers and matrix formation, and increasing the density of hUCMSCs seeded onto three-dimensional PGA scaffolds led to better osteogenic differentiation.

An injectable calcium phosphate-alginate hydrogel-umbilical cord mesenchymal stem cell paste for bone tissue engineering

The need for bone repair has increased as the population ages. Stem cell-scaffold approaches hold immense promise for bone tissue engineering. However, currently, preformed scaffolds for cell delivery have drawbacks including the difficulty to seed cells deep into the scaffold, and inability for injection in minimally-invasive surgeries. Current injectable polymeric carriers and hydrogels are too weak for load-bearing orthopedic applications. The objective of this study was to develop an injectable and mechanically-strong stem cell construct for bone tissue engineering. Calcium phosphate cement (CPC) paste was combined with hydrogel microbeads encapsulating human umbilical cord mesenchymal stem cells (hUCMSCs). The hUCMSC-encapsulating composite paste was fully injectable under small injection forces. Cell viability after injection matched that in hydrogel without CPC and without injection. Mechanical properties of the construct matched the reported values of cancellous bone, and were much higher than previous injectable polymeric and hydrogel carriers. hUCMSCs in the injectable constructs osteodifferentiated, yielding high alkaline phosphatase, osteocalcin, collagen type I, and osterix gene expressions at 7 d, which were 50-70 fold higher than those at 1 d. Mineralization by the hUCMSCs at 14 d was 100-fold that at 1 d. In conclusion, a fully injectable, mechanically-strong, stem cell-CPC scaffold construct was developed. The encapsulated hUCMSCs remained viable, osteodifferentiated, and synthesized bone minerals. The new injectable stem cell construct with load-bearing capability may enhance bone regeneration in minimally-invasive and other orthopedic surgeries.

Osteochondral interface tissue engineering using macroscopic gradients of bioactive signals

Continuous gradients exist at osteochondral interfaces, which may be engineered by applying spatially patterned gradients of biological cues. In the present study, a protein-loaded microsphere-based scaffold fabrication strategy was applied to achieve spatially and temporally controlled delivery of bioactive signals in three-dimensional (3D) tissue engineering scaffolds. Bone morphogenetic protein-2 and transforming growth factor-beta(1)-loaded poly(D,L-lactic-co-glycolic acid) microspheres were utilized with a gradient scaffold fabrication technology to produce microsphere-based scaffolds containing opposing gradients of these signals. Constructs were then seeded with human bone marrow stromal cells (hBMSCs) or human umbilical cord mesenchymal stromal cells (hUCMSCs), and osteochondral tissue regeneration was assessed in gradient scaffolds and compared to multiple control groups. Following a 6-week cell culture, the gradient scaffolds produced regionalized extracellular matrix, and outperformed the blank control scaffolds in cell number, glycosaminoglycan production, collagen content, alkaline phosphatase activity, and in some instances, gene expression of major osteogenic and chondrogenic markers. These results suggest that engineered signal gradients may be beneficial for osteochondral tissue engineering.