Cell sourcing for bone tissue engineering: amniotic fluid stem cells have a delayed, robust differentiation compared to mesenchymal stem cells

Undifferentiated Human Amniotic Fluid Progenitor Cells Promote Bone Regeneration in Vivo

The treatment of large bone defects requires bone tissue substitutes. However, the lack of accessible autologous bone, especially in newborns with spina bifida or cleft palate conditions, severely limits therapeutic options involving bone grafts. Here, an engineering approach to reconstruct bone is presented by combining human amniocentesis-derived amniotic fluid progenitor cells (hAFCs) and a biomimetic, injectable, and fully synthetic poly(ethylene glycol) hydrogel that is crosslinked enzymatically by transglutaminase FXIII (TG-PEG). hAFCs are isolated by their colony-forming capacity, expanded in vitro, and undergo osteogenic, chondrogenic, or adipogenic differentiation under appropriate stimulation. When encapsulated in TG-PEG hydrogels, hAFCs rapidly deposit endogenous extracellular matrix (ECM) in vitro. hAFC-laden TG-PEG hydrogels containing low concentrations of bone morphogenetic protein (BMP-2) promote formation of ectopic bone organoids in vivo in a murine model without requiring prior in vitro differentiation. Strikingly, hAFC-induced constructs form as much bone in this model as adult bone marrow-derived stromal cells (hBMSCs), and significantly more than adipose-derived stromal cells (hASCs).  Utilization of autologous hAFCs embedded in TG-PEG hydrogels presents a promising therapeutic strategy for bone replacement, particularly in fetuses and newborns where limited stem cell availability can be overcome through minimally invasive harvest of amniotic fluid.

An In Vivo Assessment of Different Mesenchymal Stromal Cell Tissue Types and Their Differentiation State on a Shape Memory Polymer Scaffold for Bone Regeneration

A combined biomaterial and cell-based solution to heal critical size bone defects in the craniomaxillofacial area is a promising alternative therapeutic option to improve upon autografting, the current gold standard. A shape memory polymer (SMP) scaffold, composed of biodegradable poly(ε-caprolactone) and coated with bioactive polydopamine, was evaluated with mesenchymal stromal cells (MSCs) derived from adipose (ADSC), bone marrow (BMSC), or umbilical cord (UCSC) tissue in their undifferentiated state or pre-differentiated toward osteoblasts for bone healing in a rat calvarial defect model. Pre-differentiating ADSCs and UCSCs resulted in higher new bone volume fraction (15.69% ± 1.64%) compared to empty (i.e., untreated) defects and scaffold-only (i.e., unseeded) groups (4.41% ± 1.11%). Notably, only differentiated UCSCs exhibited a significant increase in new bone volume, surpassing both undifferentiated UCSCs and unseeded scaffolds. Further, differentiated ADSCs and UCSCs had significantly higher trabecular numbers than their undifferentiated counterparts, unseeded scaffolds, and untreated defects. Although the mineral density regenerated within the unseeded scaffold surpassed that achieved with cell seeding, the connectivity of this bone was diminished, as the regenerated tissue confined itself to the spherical morphology of the scaffold pores. The SMP scaffold alone, with undifferentiated BMSCs, with undifferentiated and differentiated ADSCs, and differentiated UCSCs (29.72 ± 1.49 N) demonstrated significant osseointegration compared to empty defects (14.34 ± 2.21 N) after 12 weeks of healing when assessed by mechanical push-out testing. Based on these results and tissue availability to obtain the cells, pre-differentiated ADSCs and UCSCs emerge as particularly promising candidates when paired with the SMP scaffold for repairing critical size bone defects in the craniofacial skeleton.

Biodegradable interbody cages for lumbar spine fusion: Current concepts and future directions

Lumbar fusion often remains the last treatment option for various acute and chronic spinal conditions, including infectious and degenerative diseases. Placement of a cage in the intervertebral space has become a routine clinical treatment for spinal fusion surgery to provide sufficient biomechanical stability, which is required to achieve bony ingrowth of the implant. Routinely used cages for clinical application are made of titanium (Ti) or polyetheretherketone (PEEK). Ti has been used since the 1980s; however, its shortcomings, such as impaired radiographical opacity and higher elastic modulus compared to bone, have led to the development of PEEK cages, which are associated with reduced stress shielding as well as no radiographical artefacts. Since PEEK is bioinert, its osteointegration capacity is limited, which in turn enhances fibrotic tissue formation and peri-implant infections. To address shortcomings of both of these biomaterials, interdisciplinary teams have developed biodegradable cages. Rooted in promising preclinical large animal studies, a hollow cylindrical cage (Hydrosorb™) made of 70:30 poly-l-lactide-co-d, l-lactide acid (PLDLLA) was clinically studied. However, reduced bony integration and unfavourable long-term clinical outcomes prohibited its routine clinical application. More recently, scaffold-guided bone regeneration (SGBR) with application of highly porous biodegradable constructs is emerging. Advancements in additive manufacturing technology now allow the cage designs that match requirements, such as stiffness of surrounding tissues, while providing long-term biomechanical stability. A favourable clinical outcome has been observed in the treatment of various bone defects, particularly for 3D-printed composite scaffolds made of medical-grade polycaprolactone (mPCL) in combination with a ceramic filler material. Therefore, advanced cage design made of mPCL and ceramic may also carry initial high spinal forces up to the time of bony fusion and subsequently resorb without clinical side effects. Furthermore, surface modification of implants is an effective approach to simultaneously reduce microbial infection and improve tissue integration. We present a design concept for a scaffold surface which result in osteoconductive and antimicrobial properties that have the potential to achieve higher rates of fusion and less clinical complications. In this review, we explore the preclinical and clinical studies which used bioresorbable cages. Furthermore, we critically discuss the need for a cutting-edge research program that includes comprehensive preclinical in vitro and in vivo studies to enable successful translation from bench to bedside. We develop such a conceptual framework by examining the state-of-the-art literature and posing the questions that will guide this field in the coming years.

A comprehensive review on methods for promotion of mechanical features and biodegradation rate in amniotic membrane scaffolds

Amniotic membrane (AM) is a biological tissue that surrounds the fetus in the mother's womb. It has pluripotent cells, immune modulators, collagen, cytokines with anti-fibrotic and anti-inflammatory effect, matrix proteins, and growth factors. In spite of the biological characteristics, some results have been released in preventing the adhesion on traumatized surfaces. Application of the AM as a scaffold is limited due to its low biomechanical resistance and rapid biodegradation. Therefore, for using the AM during surgery, its modification by different methods such as cross-linking of the membrane collagen is necessary, because the cross-linking is an effective way to reduce the rate of biodegradation of the biological materials. In addition, their cross-linking is likely an efficient way to increase the tensile properties of the material, so that they can be easily handled or sutured. In this regard, various methods related to cross-linking of the AM subsuming the composite materials, physical cross-linking, and chemical cross-linking with the glutraldehyde, carbodiimide, genipin, aluminum sulfate, etc. are reviewed along with its advantages and disadvantages in the current work.

The effects of cryopreserved human amniotic membrane on fracture healing: Animal study

Objective

The aim of this study was to investigate the effects of human amniotic membrane (HAM) on fracture healing in an animal model.

Methods

Standard tibial diaphysial fractures were created in twenty-eight Wistar-Albino rats and treated with intramedullary Kirschner wire (K-wire) and HAM (HAM (+) group) or K-wire only (HAM (–) group). Fracture healing was evaluated by histological analysis, radiologic X-ray views and callus diameter measurements at 3rd and 6th weeks postoperatively.

Results

Fracture healing was histologically better in the HAM (+) group and the difference was statistically significant at both 3rd and 6th weeks postoperatively (p < 0.05). The highest histologic scores and entire woven bone formation (Huo Stage 8–9) were obtained at 6th weeks postoperatively in the HAM (+) group. Histological examination also revealed predominant fibrous tissue and partial cartilage formation (Huo Stage 2) at the postoperative 3rd week in the HAM (-) group. Equal amounts of woven bone and cartilage formation (Huo Stage 6–7) were observed at 3rd weeks postoperatively in the HAM (+) group and at 6th weeks postoperatively in the HAM (-) group. The callus diameters were greater in the HAM (+) group and the difference was statistically significant (p < 0.05) at 3rd and 6th weeks postoperatively. Although there was only a statistically significant difference (p < 0.05) at the postoperative 3rd week, radiological scores tended to be higher in the HAM (+) group at both the 3rd and 6th weeks postoperatively.

Conclusion

HAM is a cheap and easily accessible alternative biological material. HAM may be used to support surgical treatment of fractures, particularly where bone healing is expected to last longer.

Menaquinone-4 enhances osteogenic potential of human amniotic fluid mesenchymal stem cells cultured in 2D and 3D dynamic culture systems

Menaquinones, also known as Vitamin K2 family, regulate calcium homeostasis in a 'bone-vascular cross-talk' and recently received particular attention for their positive effect on bone formation. Given that the correlation between menaquinones and bone metabolism to date is still unclear, the objective of our study was to investigate the possible role of menaquinone-4 (MK-4), an isoform of the menaquinones family, in the modulation of osteogenesis. For this reason, we used a model of human amniotic fluid mesenchymal stem cells (hAFMSCs) cultured both in two-dimensional (2D) and three-dimensional (3D; RCCS™bioreactor) in vitro culture systems. Furthermore, to mimic the 'bone remodelling unit' in vitro, hAFMSCs were co-cultured in the 3D system with human monocyte cells (hMCs) as osteoclast precursors. The results showed that in a conventional 2D culture system, hAFMSCs were responsive to the MK-4, which significantly improved the osteogenic process through γ-glutamyl carboxylase-dependent pathway. The same results were obtained in the 3D dynamic system where MK-4 treatment supported the osteoblast-like formation promoting the extracellular bone matrix deposition and the expression of the osteogenic-related proteins (alkaline phosphatase, osteopontin, collagen type-1 and osteocalcin). Notably, when the hAFMSCs were co-cultured in a 3D dynamic system with the hMCs, the presence of MK-4 supported the cellular aggregate formation as well as the osteogenic function of hAFMSCs, but negatively affected the osteoclastogenic process. Taken together, our results demonstrate that MK-4 supported the aggregate formation of hAFMSCs and increased the osteogenic functions. Specifically, our data could help to optimize bone regenerative medicine combining cell-based approaches with MK-4 treatment.

Amniotic fluid-derived stem cells mixed with platelet rich plasma for restoration of rat alveolar bone defect

Stem cells isolated from the amniotic fluid have been shown as a promising candidate for cell therapy and tissue engineering. However, the experimental and preclinical applications of amniotic fluid-derived stem cells (AFSCs) in the very field of maxillofacial bone tissue engineering are still limited. In this study, rat AFSCs were successfully harvested and characterized in vitro. The rat AFSCs showed typical fibroblastoid morphology, stable proliferation activity and multi-differentiation potential. Flow-cytometry analysis demonstrated that these cells were positive for CD29, CD44, and CD90, while negative for hematopoietic markers such as CD34 and CD45. The regenerative performance of AFSCs-premixed with platelet rich plasma (PRP) gel in restoration of alveolar bone defect was further investigated using a modified rat maxillary alveolar defect model. Micro-computer tomography and histological examination showed a superior regenerative capacity of AFSCs-premixed with PRP gel at both 4 and 8 weeks after operation comparing with control groups. Moreover, the implanted AFSCs can survive in the defect site and directly participate in the bone tissue regeneration. Taken together, these results indicated the feasibility of an AFSCs-based alveolar bone tissue engineering strategy for alveolar defect restoration.

Comparative study on characterization and wound healing potential of goat (Capra hircus) mesenchymal stem cells derived from fetal origin amniotic fluid and adult bone marrow

Caprine amniotic fluid (cAF) and bone marrow cells (cBM) were isolated, expanded and phenotypically characterized by mesenchymal stem cells (MSCs) specific cell surface markers. Both cell types were compared for multilineage differentiation potential by flow cytometry using specific antibodies against lineage specific markers. Furthermore, in vitro expanded cAF-MSCs showed higher expression of trophic factors viz. VEGF and TGF-β1 as compared to cBM-MSCs. Full-skin thickness excisional wounds created on either side of the dorsal midline (thoracolumbar) of New Zealand White rabbits were randomly assigned to subcutaneous injection of either fetal origin cAF-MSCs (n=4) or adult cBM-MSCs (n=4) or sterile PBS (control, n=4). The rate of wound closure was found faster (p<0.05) in cAF-MSCs treated wounds as compared with cBM-MSCs and PBS treated wounds especially on 21st day post-skin excision. Histomorphological examination of the healing tissue showed that wound healing was improved (p<0.05) by greater epithelialization, neovascularization and collagen development in cAF-MSCs as compared to cBM-MSCs and PBS treated wounds.

Osteogenic Potential of Multipotent Adult Progenitor Cells for Calvaria Bone Regeneration

Osteogenic cells derived from rat multipotent adult progenitor cells (rMAPCs) were investigated for their potential use in bone regeneration. rMAPCs are adult stem cells derived from bone marrow that have a high proliferation capacity and the differentiation potential to multiple lineages. They may also offer immunomodulatory properties favorable for applications for regenerative medicine. rMAPCs were cultivated as single cells or as 3D aggregates in osteogenic media for up to 38 days, and their differentiation to bone lineage was then assessed by immunostaining of osteocalcin and collagen type I and by mineralization assays. The capability of rMAPCs in facilitating bone regeneration was evaluated in vivo by the direct implantation of multipotent adult progenitor cell (MAPC) aggregates in rat calvarial defects. Bone regeneration was examined radiographically, histologically, and histomorphometrically. Results showed that rMAPCs successfully differentiated into osteogenic lineage by demonstrating mineralized extracellular matrix formation in vitro and induced new bone formation by the effect of rMAPC aggregates in vivo. These outcomes confirm that rMAPCs have a good osteogenic potential and provide insights into rMAPCs as a novel adult stem cell source for bone regeneration.

A Mini Overview of Isolation, Characterization and Application of Amniotic Fluid Stem Cells

Amniotic fluid represents rich sources of stem cells that can be used in treatments for a wide range of diseases. Amniotic fluid- stem cells have properties intermediate between embryonic and adult mesenchymal stem cells which make them particularly attractive for cellular regeneration and tissue engineering. Furthermore, scientists are interested in these cells because they come from the amniotic fluid that is routinely discarded after birth. In this review we give a brief introduction of amniotic fluid followed by a description of the cells present within this fluid and aim to summarize the all existing isolation methods, culturing, characterization and application of these cells. Finally, we elaborate on the differentiation and potential for these cells to promote regeneration of various tissue defects, including fetal tissue, the nervous system, heart, lungs, kidneys, bones, and cartilage in the form of table.

Comparative investigation of human amniotic epithelial cells and mesenchymal stem cells for application in bone tissue engineering

Emerging evidence suggests amniotic epithelial cells (AECs) as a promising source of progenitor cells in regenerative medicine and bone tissue engineering. However, investigations comparing the regenerative properties of AECs with other sources of stem cells are particularly needed before the feasibility of AECs in bone tissue engineering can be determined. This study aimed to compare human amniotic epithelial cells (hAECs), human bone marrow mesenchymal stem cells (hBMSCs), and human amniotic fluid derived mesenchymal stem cells (hAFMSCs) in terms of their morphology, proliferation, immunophenotype profile, and osteogenic capacity in vitro and in vivo. Not only greatly distinguished by cell morphology and proliferation, hAECs, hAFMSCs, and hBMSCs exhibited remarkably different signature regarding immunophenotypical profile. Microarray analysis revealed a different expression profile of genes involved in ossification along the three cell sources, highlighting the impact of different anatomical origin and molecular response to osteogenic induction on the final tissue-forming potential. Furthermore, our data indicated a potential role of FOXC2 in early osteogenic commitment.

Perinatal stem cells: A promising cell resource for tissue engineering of craniofacial bone

In facing the mounting clinical challenge and suboptimal techniques of craniofacial bone defects resulting from various conditions, such as congenital malformations, osteomyelitis, trauma and tumor resection, the ongoing research of regenerative medicine using stem cells and concurrent advancement in biotechnology have shifted the focus from surgical reconstruction to a novel stem cell-based tissue engineering strategy for customized and functional craniofacial bone regeneration. Given the unique ontogenetical and cell biological properties of perinatal stem cells, emerging evidence has suggested these extraembryonic tissue-derived stem cells to be a promising cell source for extensive use in regenerative medicine and tissue engineering. In this review, we summarize the current achievements and obstacles in stem cell-based craniofacial bone regeneration and subsequently we address the characteristics of various types of perinatal stem cells and their novel application in tissue engineering of craniofacial bone. We propose the promising feasibility and scope of perinatal stem cell-based craniofacial bone tissue engineering for future clinical application.

Microcomputed tomography: approaches and applications in bioengineering

Microcomputed tomography (microCT) has become a standard and essential tool for quantifying structure-function relationships, disease progression, and regeneration in preclinical models and has facilitated numerous scientific and bioengineering advancements over the past 30 years. In this article, we recount the early events that led to the initial development of microCT and review microCT approaches for quantitative evaluation of bone, cartilage, and cardiovascular structures, with applications in fundamental structure-function analysis, disease, tissue engineering, and numerical modeling. Finally, we address several next-generation approaches under active investigation to improve spatial resolution, acquisition time, tissue contrast, radiation dose, and functional and molecular information.

A novel method for differentiation of human mesenchymal stem cells into smooth muscle-like cells on clinically deliverable thermally induced phase separation microspheres

Muscle degeneration is a prevalent disease, particularly in aging societies where it has a huge impact on quality of life and incurs colossal health costs. Suitable donor sources of smooth muscle cells are limited and minimally invasive therapeutic approaches are sought that will augment muscle volume by delivering cells to damaged or degenerated areas of muscle. For the first time, we report the use of highly porous microcarriers produced using thermally induced phase separation (TIPS) to expand and differentiate adipose-derived mesenchymal stem cells (AdMSCs) into smooth muscle-like cells in a format that requires minimal manipulation before clinical delivery. AdMSCs readily attached to the surface of TIPS microcarriers and proliferated while maintained in suspension culture for 12 days. Switching the incubation medium to a differentiation medium containing 2 ng/mL transforming growth factor beta-1 resulted in a significant increase in both the mRNA and protein expression of cell contractile apparatus components caldesmon, calponin, and myosin heavy chains, indicative of a smooth muscle cell-like phenotype. Growth of smooth muscle cells on the surface of the microcarriers caused no change to the integrity of the polymer microspheres making them suitable for a cell-delivery vehicle. Our results indicate that TIPS microspheres provide an ideal substrate for the expansion and differentiation of AdMSCs into smooth muscle-like cells as well as a microcarrier delivery vehicle for the attached cells ready for therapeutic applications.

HB-EGF augments the ability of mesenchymal stem cells to attenuate intestinal injury

BACKGROUND

We have previously demonstrated that heparin-binding EGF-like growth factor (HB-EGF) and mesenchymal stem cell (MSC) administration protect the intestines from ischemia/reperfusion (I/R) injury in vivo, with amniotic fluid-derived MSC (AF-MSC) being more efficacious than bone marrow-derived MSC (BM-MSC). The goal of the current study was to determine whether the protective effects of HB-EGF were from direct effects on MSC or via alternative mechanisms.

METHODS

Murine MSC were transfected with an HB-EGF plasmid or control plasmid by electroporation. Mice were subjected to segmental intestinal I/R injury and received either BM-MSC or AF-MSC either with or without exogenous HB-EGF, or BM-MSC or AF-MSC that endogenously over-expressed HB-EGF. MSC engraftment, intestinal histologic injury, and intestinal permeability were quantified.

RESULTS

There was increased MSC engraftment into injured compared to uninjured intestine. HB-EGF increased AF-MSC engraftment into injured intestine. Administration of HB-EGF and MSC improved intestinal histology and intestinal permeability after I/R injury, with AF-MSC being most efficacious. The effect of HB-EGF on MSC was similar when the growth factor was administered exogenously, or when it was overexpressed endogenously.

CONCLUSIONS

The effect of HB-EGF on AF-MSC was similar with both exogenous administration and endogenous overexpression of the growth factor, implying that HB-EGF has a direct effect on AF-MSC. This information may assist in guiding potential future AF-MSC-based therapies for patients at risk of intestinal ischemic injuries.

Stem cells from fetal membranes and amniotic fluid: markers for cell isolation and therapy

Stem cell therapy is in constant need of new cell sources to conceive regenerative medicine approaches for diseases that are still without therapy. Scientists drew the attention toward amniotic membrane and amniotic fluid stem cells, since these sources possess many advantages: first of all as cells can be extracted from discarded foetal material it is inexpensive, secondly abundant stem cells can be obtained and finally, these stem cell sources are free from ethical considerations. Many studies have demonstrated the differentiation potential in vitro and in vivo toward mesenchymal and non-mesenchymal cell types; in addition the immune-modulatory properties make these cells a good candidate for allo- and xenotransplantation. This review offers an overview on markers characterisation and on the latest findings in pre-clinical or clinical setting of the stem cell populations isolated from these sources.

Synergistic effects of HB-EGF and mesenchymal stem cells in a murine model of intestinal ischemia/reperfusion injury

BACKGROUND

We have previously demonstrated that heparin-binding EGF-like growth factor (HB-EGF) administration protects the intestines from ischemia/reperfusion (I/R) injury in vivo. We have also shown that HB-EGF promotes mesenchymal stem cell (MSC) proliferation and migration in vitro. The goals of the current study were to examine the effects of HB-EGF and both bone marrow (BM)- and amniotic fluid (AF)-derived MSC on intestinal I/R injury in vivo.

MATERIALS AND METHODS

MSC were isolated from pan-EGFP mice, expanded, and purified. Pluripotency was confirmed by induced differentiation. Mice were subjected to terminal ileum I/R and received either: (1) no therapy; (2) HB-EGF; (3) BM-MSC; (4) HB-EGF+BM-MSC; (5) AF-MSC; or (6) HB-EGF+AF-MSC. MSC engraftment, histologic injury, and intestinal permeability were quantified.

RESULTS

There was increased MSC engraftment into injured compared to uninjured intestine for all experimental groups, with significantly increased engraftment for AF-MSC+HB-EGF compared to AF-MSC alone. Administration of HB-EGF and MSC improved intestinal histology and intestinal permeability after I/R injury. The greatest improvement was with combined administration of HB-EGF+AF-MSC.

CONCLUSIONS

Both HB-EGF alone and MSC alone can protect the intestines from I/R injury, with synergistic efficacy occurring when HB-EGF and AF-MSC are administered together.

Differentiation patterns of embryonic stem cells in two- versus three-dimensional culture

Pluripotent stem cells are attractive candidates as a cell source for regenerative medicine and tissue engineering therapies. Current methods of differentiation result in low yields and impure populations of target phenotypes, with attempts for improved efficiency often comparing protocols that vary multiple parameters. This basic science study focused on a single variable to understand the effects of two-dimensional (2D) versus three-dimensional (3D) culture on directed differentiation. We compared mouse embryonic stem cells (ESCs) differentiated on collagen type I-coated surfaces (SLIDEs), embedded in collagen type I gels (GELs), and in suspension as embryoid bodies (EBs). For a systematic analysis in these studies, key parameters were kept identical to allow for direct comparison across culture configurations. We determined that all three configurations supported differentiation of ESCs and that the kinetics of differentiation differed greatly for cells cultured in 2D versus 3D. SLIDE cultures induced overall differentiation more quickly than 3D configurations, with earlier expression of cytoskeletal and extracellular matrix proteins. For 3D culture as GELs or EBs, cells clustered similarly, formed complex structures and promoted differentiation towards cardiovascular phenotypes. GEL culture, however, also allowed for contraction of the collagen matrix. For differentiation towards fibroblasts and smooth muscle cells which actively remodel their environment, GEL culture may be particularly beneficial. Overall, this study determined the effects of dimensionality on differentiation and helps in the rational design of protocols to generate phenotypes needed for tissue engineering and regenerative medicine.

In vitro osteogenic differentiation of human amniotic fluid-derived stem cells on a poly(lactide-co-glycolide) (PLGA)-bladder submucosa matrix (BSM) composite scaffold for bone tissue engineering

Stem cells have become an important component of tissue regeneration, as they are able to differentiate into various cell types if guided appropriately. It is well known that cellular differentiation is greatly influenced by the surrounding microenvironment. We have developed a composite scaffold system using a collagen matrix derived from porcine bladder submucosa matrix (BSM) and poly(lactide-co-glycolide) (PLGA). In this study, we investigated whether a composite scaffold composed of naturally derived matrix combined with synthetic polymers would provide a microenvironment to facilitate the induction of osteogenic differentiation. We first showed that human amniotic fluid-derived stem cells (hAFSCs) adhered to the composite scaffolds and proliferated over time. We also showed that the composite scaffolds facilitated the differentiation of hAFSCs into an osteogenic lineage. The expression of osteogenic genes, including RUNX2, osteopontin (OPN) and osteocalcin (OCN) was upregulated in cells cultured on the composite scaffolds incubated in the osteogenic medium compared with ones without. Increased alkaline phosphatase (ALP) activity and calcium content indicates that hAFSCs seeded on 3D porous BSM-PLGA composite scaffolds resulted in higher mineralization rates as the duration of induction increased. This was also evidenced by the mineralized matrix within the scaffolds. The composite scaffold system provides a proper microenvironment that can facilitate osteogenic differentiation of AFSCs. This scaffold system may be a good candidate material for bone tissue engineering.

Human serum is a suitable supplement for the osteogenic differentiation of human adipose-derived stem cells seeded on poly-3-hydroxibutyrate-co-3-hydroxyvalerate scaffolds

Human adipose-derived stem cells (hASCs) are currently a point of focus for bone tissue engineering applications. However, the ex vivo expansion of stem cells before clinical application remains a challenge. Fetal bovine serum (FBS) is largely used as a medium supplement and exposes the recipient to infections and immunological reactions. In this study, we evaluated the osteogenic differentiation process of hASCs in poly-3-hydroxybutyrate-co-3-hydroxyvalerate (PHB-HV) scaffolds with the osteogenic medium supplemented with pooled allogeneic human serum (aHS). The hASCs grown in the presence of FBS or aHS did not show remarkable differences in morphology or immunophenotype. The PHB-HV scaffolds, which were developed by the freeze-drying technique, showed an adequate porous structure and mechanical performance as observed by micro-computed tomography, scanning electron microscopy (SEM), and compression test. The three-dimensional structure was suitable for allowing cell colonization, which was revealed by SEM micrographs. Moreover, these scaffolds were not toxic to cells as shown by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. The differentiation capacity of hASCs seeded on scaffolds was confirmed by the reduction of the proliferation, the alkaline phosphatase (AP) activity, expression of osteogenic gene markers (AP, collagen type I, Runx2, and osteocalcin), and the expression of bone markers, such as osteopontin, osteocalcin, and collagen type I. The osteogenic capacity of hASCs seeded on PHB-HV scaffolds indicates that this scaffold is adequate for cell growth and differentiation and that aHS is a promising supplement for the in vitro expansion of hASCs. In conclusion, this strategy seems to be useful and safe for application in bone tissue engineering.

Role of amniotic fluid mesenchymal cells engineered on MgHA/collagen-based scaffold allotransplanted on an experimental animal study of sinus augmentation

OBJECTIVES

The present research has been performed to evaluate whether a commercial magnesium-enriched hydroxyapatite (MgHA)/collagen-based scaffold engineered with ovine amniotic fluid mesenchymal cells (oAFMC) could improve bone regeneration process in vivo.

MATERIALS AND METHODS

Bilateral sinus augmentation was performed on eight adult sheep in order to compare the tissue regeneration process at 45 and 90 days after implantation of the oAFMC-engineered scaffold (Test Group) or of the scaffold alone (Ctr Group). The process of tissue remodeling was analyzed through histological, immunohistochemical, and morphometric analyses by calculating the proliferation index (PI) of oAFMC loaded on the scaffold, the total vascular area (VA), and vascular endothelial growth factor (VEGF) expression levels within the grafted area.

RESULTS

MgHA/collagen-based scaffold showed high biocompatibility preserving the survival of oAFMC for 90 days in grafted sinuses. The use of oAFMC increased bone deposition and stimulated a more rapid angiogenic reaction, thus probably supporting the higher cell PI recorded in cell-treated sinuses. A significantly higher VEGF expression (Test vs. Ctr Group; p = 0.0004) and a larger total VA (p = 0.0006) were detected in the Test Group at 45 days after surgery. The PI was significantly higher (p = 0.027) at 45 days and became significantly lower at 90 days (p = 0.0007) in the Test Group sinuses, while the PI recorded in the Ctr Group continued to increase resulting to a significantly higher PI at day 90 (CTR day 45 vs. CTR day 90; p = 0.022).

CONCLUSIONS

The osteoinductive effect of a biomimetic commercial scaffold may be significantly improved by the presence of oAFMC.

CLINICAL RELEVANCE

The amniotic fluid mesenchymal cell (AFMC) may represent a novel, largely and easily accessible source of mesenchymal stem cells to develop cell-based therapy for maxillofacial surgery.

CD117(+) amniotic fluid stem cells: state of the art and future perspectives

Broadly multipotent stem cells can be isolated from amniotic fluid by selection for the expression of the membrane stem cell factor receptor c-Kit, a common marker for multipotential stem cells. They have clonogenic capability and can be directed into a wide range of cell types representing the three primary embryonic lineages. Amniotic fluid stem cells maintained for over 250 population doublings retained long telomeres and a normal karyotype. Clonal human lines verified by retroviral marking were induced to differentiate into cell types representing each embryonic germ layer, including cells of adipogenic, osteogenic, myogenic, endothelial, neuronal and hepatic lineages. AFS cells could be differentiate toward cardiomyogenic lineages, when co-cultured with neonatal cardiomyocytes, and have the potential to generate myogenic and hematopoietic lineages both in vitro and in vivo. Very recently first trimester AFS cells could be reprogrammed without any genetic manipulation opening new possibilities in the field of fetal/neonatal therapy and disease modeling. In this review we are aiming to summarize the knowledge on amniotic fluid stem cells and highlight the most promising results.

Heparin-binding epidermal growth factor-like growth factor protects mesenchymal stem cells

BACKGROUND

We have previously demonstrated that mesenchymal stem cell (MSC) administration protects the intestines from injury in a mouse model of intestinal ischemia/reperfusion injury. We have also shown that heparin-binding epidermal growth factor-like growth factor (HB-EGF) is a potent intestinal cytoprotective agent in vivo that can protect the intestines by way of its effects on stem cells. The goal of the present study was to examine the effects of HB-EGF on both amniotic fluid (AF)- and bone marrow (BM)-derived MSCs in vitro.

METHODS

MSCs were isolated from the AF and BM of pan-EGFP mice, grown in MSC-specific culture medium, and purified by sequential passages according to their adherence properties. Pluripotency was confirmed by induced differentiation. After incubation of MSCs with HB-EGF, proliferation was quantified using the CyQuant cell proliferation assay kit under normoxic and anoxic conditions. Chemotaxis was quantified using the CHEMICON QCM cell migration kit, and apoptosis was determined using caspase-3 immunohistochemistry after exposure of the MSCs to anoxic stress.

RESULTS

AF-MSCs and BM-MSCs showed significantly increased proliferation and migration in response to HB-EGF. HB-EGF significantly protected AF-MSCs and BM-MSCs from anoxia-induced apoptosis. The proliferative and anti-apoptotic effects of HB-EGF were even more pronounced in AF-MSCs than in BM-MSCs.

CONCLUSIONS

These results have demonstrated that HB-EGF acts as a mitogenic and chemotactic agent for MSCs that protects MSCs from injury. These findings could have important implications for future experiments designed to use MSCs to protect the intestines from injury.

Amniotic fluid stem cells and their application in cell-based tissue regeneration

Advances in stem cell biotechnology hold great promise in the field of tissue engineering and regenerative medicine. Of interest are marrow mesenchymal stem cells (MSCs), embryonic stem cells (ESCs), and induced pluripotent stem cells (iPSCs). In addition, amniotic fluid stem cells (AFSCs) have attracted attention as a viable choice following the search for an alternative stem cell source. Investigators are interested in these cells because they come from the amniotic fluid that is routinely discarded after birth. There have been multiple investigations conducted worldwide in an attempt to better understand AF-SCs in terms of their potential use in regenerative medicine. In this review we give a brief introduction of amniotic fluid followed by a description of the cells present within this fluid. Their history related to stem cell discovery in the amniotic fluid as well as the main characteristics of AF-SCs are discussed. Finally, we elaborate on the potential for these cells to promote regeneration of various tissue defects, including fetal tissue, the nervous system, heart, lungs, kidneys, bones, and cartilage.

Chondrogenic potential of stem cells derived from amniotic fluid, adipose tissue, or bone marrow encapsulated in fibrin gels containing TGF-β3

In this study, several types of hMSCs, derived from bone marrow, adipose tissue, or amniotic fluid, were encapsulated in a fibrin hydrogel mixed with TGF-β3 and then evaluated for their capacity for differentiation in vitro and in vivo. For determination of stem cell differentiation, RT-PCR, real time quantitative PCR (qPCR), histology, and immunohistochemical assays were used for analysis of chondrogenesis. Using these analysis methods, several of the cultured hMSCS were found to highly express genes and proteins specific to cartilage forming tissues. Additionally, similar trends in expression were found in tissue recovered from nude mice transplanted with several types of hMSCs encapsulated in a fibrin hydrogel containing TGF-β3. The results of both in vitro and in vivo analyses showed that cultured or transplanted hMSCs mixed with TGF-β3 in a fibrin hydrogel differentiated into chondrocytes, suggesting that these cells would be suitable for reconstruction of hyaline articular cartilage.