Application and limitations of chloromethyl-benzamidodialkylcarbocyanine for tracing cells used in bone Tissue engineering

Gingival-derived mesenchymal stem cell therapy regenerated the radiated salivary glands: functional and histological evidence in murine model

BACKGROUND

Radiotherapy in head and neck cancer management causes degeneration of the salivary glands (SG). This study was designed to determine the potential of gingival mesenchymal stem cells (GMSCs) as a cell-based therapy to regenerate irradiated parotid SG tissues and restore their function using a murine model.

METHODS

Cultured isolated cells from gingival tissues of 4 healthy guinea pigs at passage 3 were characterized as GMSCSs using flow cytometry for surface markers and multilineage differentiation capacity. Twenty-one Guinea pigs were equally divided into three groups: Group I/Test, received single local irradiation of 15 Gy to the head and neck field followed by intravenous injection of labeled GMSCs, Group II/Positive control, which received the same irradiation dose followed by injection of phosphate buffer solution (PBS), and Group III/Negative control, received (PBS) injection only. Body weight and salivary flow rate (SFR) were measured at baseline, 11 days, 8-, 13- and 16-weeks post-irradiation. At 16 weeks, parotid glands were harvested for assessment of gland weight and histological and immunohistochemical analysis.

RESULTS

The injected GMSCs homed to degenerated glands, with subsequent restoration of the normal gland histological acinar and tubular structure associated with a significant increase in cell proliferation and reduction in apoptotic activity. Subsequently, a significant increase in body weight and SFR, as well as an increase in gland weight at 16 weeks in comparison with the irradiated non-treated group were observed.

CONCLUSION

The study provided a new potential therapeutic strategy for the treatment of xerostomia by re-engineering radiated SG using GMSCs.

Refined high-content imaging-based phenotypic drug screening in zebrafish xenografts

Zebrafish xenotransplantation models are increasingly applied for phenotypic drug screening to identify small compounds for precision oncology. Larval zebrafish xenografts offer the opportunity to perform drug screens at high-throughput in a complex in vivo environment. However, the full potential of the larval zebrafish xenograft model has not yet been realized and several steps of the drug screening workflow still await automation to increase throughput. Here, we present a robust workflow for drug screening in zebrafish xenografts using high-content imaging. We established embedding methods for high-content imaging of xenografts in 96-well format over consecutive days. In addition, we provide strategies for automated imaging and analysis of zebrafish xenografts including automated tumor cell detection and tumor size analysis over time. We also compared commonly used injection sites and cell labeling dyes and show specific site requirements for tumor cells from different entities. We demonstrate that our setup allows us to investigate proliferation and response to small compounds in several zebrafish xenografts ranging from pediatric sarcomas and neuroblastoma to glioblastoma and leukemia. This fast and cost-efficient assay enables the quantification of anti-tumor efficacy of small compounds in large cohorts of a vertebrate model system in vivo. Our assay may aid in prioritizing compounds or compound combinations for further preclinical and clinical investigations.

Mesenchymal Stem Cells Combined with Tissue Fusion Technology Promoted Wound Healing in Porcine Bowel Anastomosis

Objective

To evaluate the possible biological effect of allogenic mesenchymal stem cells (MSCs) combined with tissue fusion technology on the anastomosis.

Methods

Sixteen pigs were divided into a 7 d group and 14 d group, each of which was further subdivided into an MSC-treated group and a control group. Five anastomoses per animal were established using LigaSure ForceTriad (Covidien, MA, USA), a tissue sealing system. Cell migration and tissue-specific differentiation potency, in addition to potential cytokine and genetic changes, were investigated.

Results

There were no significant between-group differences in postoperative complications and anastomosis burst pressure. The number of proliferating cell nuclear antigen- (PCNA-) positive cells was significantly higher in the MSC-treated group as compared with that in the control group (P = 0.021). Labeled MSCs were found in the mucosal layer, villus, and lamina propria, as well as in the lamina muscularis mucosae, where they exhibited characteristics of smooth muscle cells.

Conclusions

Grafted MSCs significantly promoted epithelial and connective cell proliferation and maintained their cell migration capacity and differentiation potential in the fused anastomotic tissues, without causing severe postoperative complications.

Angiogenic and osteogenic regeneration in rats via calcium phosphate scaffold and endothelial cell co-culture with human bone marrow mesenchymal stem cells (MSCs), human umbilical cord MSCs, human induced pluripotent stem cell-derived MSCs and human embryonic stem cell-derived MSCs

Angiogenesis is a limiting factor in regenerating large bone defects. The objective of this study was to investigate angiogenic and osteogenic effects of co-culture on calcium phosphate cement (CPC) scaffold using human umbilical vein endothelial cells (hUVECs) and mesenchymal stem cells (MSCs) from different origins for the first time. hUVECs were co-cultured with four types of cell: human umbilical cord MSCs (hUCMSCs), human bone marrow MSCs (hBMSCs) and MSCs from induced pluripotent stem cells (hiPSC-MSCs) and embryonic stem cells (hESC-MSCs). Constructs were implanted in 8 mm cranial defects of rats for 12 weeks. CPC without cells served as control 1. CPC with hBMSCs served as control 2. Microcapillary-like structures were successfully formed on CPC in vitro in all four co-cultured groups. Microcapillary lengths increased with time (p < 0.05). Osteogenic and angiogenic gene expressions were highly elevated and mineralization by co-cultured cells increased with time (p < 0.05). New bone amount and blood vessel density of co-cultured groups were much greater than controls (p < 0.05) in an animal study. hUVECs co-cultured with hUCMSCs, hiPSC-MSCs and hESC-MSCs achieved new bone and vessel density similar to hUVECs co-cultured with hBMSCs (p > 0.1). Therefore, hUCMSCs, hiPSC-MSCs and hESC-MSCs could serve as alternative cell sources to hBMSCs, which require an invasive procedure to harvest. In conclusion, this study showed for the first time that co-cultures of hUVECs with hUCMSCs, hiPSC-MSCs, hESC-MSCs and hBMSCs delivered via CPC scaffold achieved excellent osteogenic and angiogenic capabilities in vivo. The novel co-culture constructs are promising for bone reconstruction with improved angiogenesis for craniofacial/orthopaedic applications. Copyright © 2017 John Wiley & Sons, Ltd.

In vivo human adipose-derived mesenchymal stem cell tracking after intra-articular delivery in a rat osteoarthritis model

Background

Human adipose-derived mesenchymal stem cells (haMSCs) have shown efficacy in treating osteoarthritis (OA) both preclinically and clinically via intra-articular (IA) injection. However, understanding the mode of action of the cell therapy has been limited by cell tracking capability and correlation between the pharmacokinetics of the injected cells and the intended pharmacodynamics effect. This study aims to explore methodology and to understand in vivo biodistribution of clinical-grade haMSCs labeled with fluorescent dye and injected into an immunocompetent OA rat model.

Methods

haMSCs labeled with fluorescent dye were investigated for their proliferation and differentiation capabilities. Labeled cells were used to establish detection threshold of a noninvasive biofluorescent imaging system before the cells (2.5 × 10⁶) were injected into a conventional rat OA model induced by medial meniscectomy for 8 weeks. We attempted to reveal the existence of labeled cells in vivo by imaging and a molecular biomarker approach, and to correlate with the in vivo efficacy and physical presence over a follow-up period up to 10 weeks.

Results

In vitro proliferation and differentiation of haMSCs were not affected by the labeling of DiD dye. Detection thresholds of the labeled cells in vitro and in vivo were determined to be 10⁴ and 10⁵ cells, respectively. When 2.5 × 10⁶ haMSCs were injected into the joints of a rat OA model, fluorescent signals (or >10⁵ cells) lasted for about 10 weeks in the surgical knee joint at the same time as efficacy was observed. Signals in nonsurgical rats only lasted for 4 weeks. The human MSCs were shown to engraft to the rat joint tissues and were proliferative. Human FOXP2 gene was only detected in the knee joint tissue, suggesting limited biodistribution locally to the joints.

Conclusions

The current study represents the first attempt to correlate cell therapy efficacy on OA with the physical presence of the injected haMSCs in the OA model, and demonstrates that human adipose-derived mesenchymal stem cells persisted for 10 weeks locally in the rat joint, coinciding with the efficacy observed. It is postulated that persistence and/or proliferation of the haMSCs in the joint is required in order to exert their functions on promoting joint regeneration and/or cartilage protection, further supporting the safety and feasibility of IA injection of MSCs for the treatment of OA patients.

The Dose of Intravenously Transplanted Bone Marrow Stromal Cells Determines the Therapeutic Effect on Vascular Remodeling in a Rat Model of Ischemic Stroke

The therapeutic benefits of bone marrow-derived mesenchymal stem cell (BM-MSC) transplantation for ischemic stroke have been extensively demonstrated. However, studies on the optimal cell dose for intravenous administration are still limited. This study aimed to determine an appropriate cell dose for BM-MSC intravenous transplantation and to investigate the effect of cell dose on vascular remodeling in a rat model of ischemic stroke. BM-MSCs at doses of 5104 (low-dose group), 5105 (medium-dose group), and 2106 (high-dose group) were intravenously injected into rats at 72 h after ischemia. The therapeutic efficacy of BM-MSCs was evaluated by measuring infarct volume, vascular diameters, capillary area in the peri-infarct zone, level of basic fibroblast growth factor (bFGF) in the peri-infarct zone, and serum vascular endothelial growth factor (VEGF) level at 7 days after ischemia. Compared with the low-dose and control groups, medium-dose and high-dose BM-MSC transplantation significantly reduced the volume of the infarct area, enlarged the diameters of pial vessels and the basilar artery, and increased the capillary area in the peri-infarct zone of the cerebral cortex. Furthermore, transplanted BM-MSCs elevated the expressions of bFGF in the peri-infarct zone and the serum VEGF level. Administration of 5105 BM-MSCs is an appropriate cell dose for ischemic stroke therapy in rats. These findings may be helpful for designing future clinical trials.

Long-Term Tracking of the Osteogenic Differentiation of Mouse BMSCs by Aggregation-Induced Emission Nanoparticles

Bone marrow-derived mesenchymal stem cells (BMSCs) have shown great potential for bone repair due to their strong proliferation ability and osteogenic capacity. To evaluate and improve the stem cell-based therapy, long-term tracking of stem cell differentiation into bone-forming osteoblasts is required. However, conventional fluorescent trackers such as fluorescent proteins, quantum dots, and fluorophores with aggregation-caused quenching (ACQ) characteristics have intrinsic limitations of possible interference with stem cell differentiation, heavy metal cytotoxicity, and self-quenching at a high labeling intensity. Herein, we developed aggregation-induced emission nanoparticles decorated with the Tat peptide (AIE-Tat NPs) for long-term tracking of the osteogenic differentiation of mouse BMSCs without interference of cell viability and differentiation ability. Compared with the ability of the commercial Qtracker 655 for tracking of only 6 passages of mouse BMSCs, AIE-Tat NPs have shown a much superior performance in long-term tracking for over 12 passages. Moreover, long-term tracking of the osteogenic differentiation process of mouse BMSCs was successfully conducted on the biocompatible hydroxyapatite scaffold, which is widely used in bone tissue engineering. Thus, AIE-Tat NPs have promising applications in tracking stem cell fate for bone repair.

Opening the "White Box" in Tissue Engineering: Visualization of Cell Aggregates in Optically Scattering Scaffolds

The noninvasive and longitudinal imaging of cells or cell aggregates in large optically scattering scaffolds is still a largely unresolved problem in tissue engineering. In this work, we investigated the potential of near-infrared (NIR) photoacoustic (PA) tomography imaging to address this issue. We used clinically relevant sizes of highly light scattering polyethersulfone multibore(®) hollow fiber scaffolds seeded with cells. Since cells have little optical absorption at NIR wavelengths, we studied labeling of cells with absorbers. Four NIR labels were examined for their suitability based on absorption characteristics, resistance to bleaching, and influence on cell viability. On the basis of these criteria, carbon nanoparticles proved most suitable in a variety of cells. For PA imaging, we used a research setup, based on computed tomography geometry. As proof of principle, using this imager we monitored the distribution and clustering of labeled rat insulinoma beta cell aggregates in the scaffolds. This was performed for the duration of 1 week in a nondestructive manner. The results were validated using fluorescence imaging, histology, and light microscopy imaging. Based on our findings, we conclude that PA tomography is a powerful tool for the nondestructive imaging of cells in optically scattering tissue-engineered scaffolds.

Combining mesenchymal stem cell sheets with platelet-rich plasma gel/calcium phosphate particles: a novel strategy to promote bone regeneration

Background

Promotion of bone regeneration is important for successful repair of bony defects. This study aimed to investigate whether combining bone marrow-derived mesenchymal stem cell (BMSC) sheets with platelet-rich plasma (PRP) gel/calcium phosphate particles could promote bone formation in the femoral bone defects of rats.

Methods

The proliferation and differentiation of BMSCs or BMSC sheets cultured with calcium phosphate particles and/or PRP were investigated in in vitro. In vivo, 36 2.5 × 5 mm bone defects were randomly divided into groups and treated with either BMSCs/PRP gel, calcium phosphate particles, PRP gel/calcium phosphate particles, a BMSC sheet/calcium phosphate particles, a BMSC sheet/PRP gel/calcium phosphate particles, or were left untreated (n = 6/group). A further 15 bone defects were treated with chloromethyl-benzamidodialkylcarbocyanine (CM-Dil)-labelled BMSC sheet/PRP gel/calcium phosphate particles and observed using a small animal in vivo fluorescence imaging system to trace the implanted BMSCs at 1 day, 3 days, 7 days, 2 weeks, and 4 weeks after surgery.

Results

The expression of collagen type I and osteocalcin genes of BMSCs or BMSC sheets treated with PRP and calcium phosphate particles was significantly higher than that of BMSCs or BMSC sheets treated with calcium phosphate particles or the controls (P <0.05). PRP can promote gene expression of collagen III and tenomodulin by BMSCs and in BMSC sheets. The VEGF, collagen I and osteocalcin gene expression levels were higher in the BMSC sheet than in cultured BMSCs (P <0.05). Moreover, alizarin red staining quantification, ALP quantification and calcein blue fluorescence showed the osteogenic potential of BMSCs treated with PRP and calcium phosphate particles The implanted BMSCs were detectable at 1 day, 3 days, 7 days, 2 weeks and 4 weeks after surgery by a small animal in vivo fluorescence imaging system and were visualized in the defect zones by confocal microscopy. At 4 weeks after implantation, the defects treated with the BMSC sheet/PRP gel/calcium phosphate particles showed significantly more bone formation than the other five groups.

Conclusions

Incorporation of an BMSC sheet into the PRP gel/calcium phosphate particles greatly promoted bone regeneration. These BMSC sheet and tissue engineering strategies offer therapeutic opportunities for promoting bone defect repair clinically.

Fibrin-mediated delivery of an ovarian follicle pool in a mouse model of infertility

The cryopreservation and autotransplantation of ovarian tissue is emerging as a powerful approach for preserving fertility. However, for cancer patients, it may not be possible to transplant ovarian tissue due to the risk of re-seeding disease. We investigated strategies for transplantation of individually isolated follicles to minimize the risk of re-introducing cancer cells present within the vasculature of ovarian stroma. Procedures for large-scale isolation of early-stage follicles and their encapsulation into fibrin hydrogels were developed. For in vivo validation studies, mice were ovariectomized and transplanted with encapsulated follicles into the ovarian bursa. A substantial increase in the number of secondary follicles was observed in the graft at 9 days after transplantation, and antral follicles by day 21, demonstrating primordial follicle recruitment into the growing pool. Initially, elevated follicle-stimulating hormone levels declined substantially by day 21, indicating feedback from the graft; presence of corpora lutea showed the graft's capability of restoring hormone cyclicity. Taken together, the transplanted follicles were able to engraft, mature, and restore ovarian function in an infertile mouse. This biomaterial may, thus, provide a platform for follicle transplantation with a low risk of cancer contamination and for developing strategies that preserve fertility for women facing a cancer diagnosis.

Umbilical cord-derived mesenchymal stem cells regulate thymic epithelial cell development and function in Foxn1(-/-) mice

Thymic microenvironments are essential for the maturation of thymocytes, which can be anatomically compartmentalized into cortical and medullar regions. The absence of the gene encoding the transcription factor forkhead box n1 (Foxn1) causes epithelial differentiation to stall in the precursor stage, resulting in the formation of an abnormal thymus. In this study, we used human umbilical cord-derived mesenchymal stem cells (UC-MSCs) to treat Foxn1(-/-) mice, and then analyzed the maturation and distribution of thymic epithelial cells in the Foxn1(-/-) thymic rudiment and the thymopoiesis of this newly developed rudiment. Our data showed a well-organized cortex-medulla architecture and an obvious improvement in the maturation of thymic epithelial cells along with the appearance of UEA-1(+)MHCII(hi) thymic epithelial cells in the rudiment. We further demonstrated improved thymopoiesis and the enhanced export of mature T cells with increased numbers of regulatory T cells into the peripheral blood. Furthermore, we observed that MSCs can engraft into thymic tissue and express many cytokines or proteins, particularly keratinocyte growth factor (KGF) and CD248, which are essential for thymic development. Collectively, our data identified a new mechanism for MSCs, which may provide a proper microenvironment for the reconstitution and functional maturation of the thymus in Foxn1(-/-) mice. Additionally, we elicited additional insights into the therapeutic efficacy of MSCs in several autoimmune diseases.

Improved Method of Producing Human Neural Progenitor Cells of High Purity and in Large Quantities from Pluripotent Stem Cells for Transplantation Studies

Transplantation of human neural progenitor cells (hNPCs) is a promising therapeutic approach for various diseases of the central nervous system (CNS). Reliable testing of hNPC transplantation in animal models of neurological diseases requires that these cells can be produced in sufficient amounts, show consistent homogeneity as a neural cell population, and be reliably labeled for in vivo tracking. In addition, the cells should be characterized as being at the optimal state of differentiation favoring successful engraftment. Here, we show that high numbers of purified hNPCs can be produced from human embryonic stem cells (hESCs) by manually selecting specifically sized and shaped spheres followed by fluorescence-activated cell sorting based on the relative cell size. In addition, we report that labeling of hNPCs with ultra-small superparamagnetic iron oxide (USPIO) particles does not affect the cellular morphology or growth. More importantly, we show that the transduction with lentiviral vector encoding green fluorescent protein (GFP) decreases the neurality of the cell population. We conclude that our cost-effective protocol of generating hNPCs is widely applicable for preclinical studies on CNS disorders. This improved method of producing large quantities of high-purity hNPCs maybe useful also when generating hNPCs from human induced pluripotent stem (hiPS) cell lines. However, caution should be used when lenti-GFP transduction is applied for hNPC labeling.

Repair of bone defect by using vascular bundle implantation combined with Runx II gene-transfected adipose-derived stem cells and a biodegradable matrix

A large hurdle in orthopedics today is the difficulty of dealing with the non-union of fractured bones. We therefore evaluated the effects of runt-related transcription factor II (Runx II), a factor used to create gene-modified tissue-engineered bone, combined with vascular bundle implantation for repairing segmental bone defects. Adenovirus Runx II gene (Ad-Runx II)-modified rabbit adipose-derived stem cells (ADSCs) were seeded onto polylactic acid/polycaprolacton (PLA/PCL) scaffolds to construct gene-modified tissue-engineered bone. The following four methods were used for repair in rabbit radial-defect (1.5 cm long) models: gene-modified tissue-engineered bone with vascular bundle (Group A), gene-modified tissue-engineered bone (Group B), non-gene-modified tissue-engineered bone with vascular bundle (Group C), and PLA/PCL scaffolds only (Group D). X-ray, histological examination, biomechanics analysis, and micro-angiography were conducted 4, 8, and 12 weeks later to determine angiogenesis and osteogenesis. The volume and speed of production of newly formed bones in Group A were significantly superior to those in other groups, and de-novo vascular network circulation from the vessel bundle through newly formed bone tissue was observed, with the defect being completely repaired. Group B showed a slightly better effect in terms of speed and quality of bone formation than Group C, whereas the bone defect in Group D was replaced by fibrous tissue. The maximal anti-bending strength in Group A was significantly higher than that in the other groups. Runx II gene therapy combined with vascular bundle implantation thus displays excellent abilities for osteoinduction and vascularization and is a promising method for the treatment of bone non-union and defect.

Commonly used mesenchymal stem cell markers and tracking labels: Limitations and challenges

Early observations that cultured mesenchymal stem cells (MSCs) could be induced to exhibit certain characteristics of osteocytes and chondrocytes led to the proposal that they could be transplanted for tissue repair through cellular differentiation. Therefore, many subsequent preclinical studies with transplanted MSCs have strived to demonstrate that cellular differentiation was the underlying mechanism for the therapeutic effect. These studies generally followed the minimal criteria set by The International Society for Cellular Therapy in assuring MSC identity by using CD70, CD90, and CD105 as positive markers and CD34 as a negative marker. However, the three positive markers are co-expressed in a wide variety of cells, and therefore, even when used in combination, they are certainly incapable of identifying MSCs in vivo. Another frequently used MSC marker, Stro-1, has been shown to be an endothelial antigen and whether it can identify MSCs in vivo remains unknown. On the other hand, the proposed negative marker CD34 has increasingly been shown to be expressed in native MSCs, such as in the adipose tissue. It has also helped establish that MSCs are likely vascular stem cells (VSCs) that reside in the capillaries and in the adventitia of larger blood vessels. These cells do not express CD31, CD104b, or α-SMA, and therefore are designated as CD34+CD31-CD140b-SMA-. Many preclinical MSC transplantation studies have also attempted to demonstrate cellular differentiation by using labeled MSCs. However, all commonly used labels have shortcomings that often complicate data interpretation. The β-gal (LacZ) gene as a label is problematic because many mammalian tissues have endogenous β-gal activities. The GFP gene is similarly problematic because many mammalian tissues are endogenously fluorescent. The cell membrane label DiI can be adsorbed by host cells, and nuclear stains Hoechst dyes and DAPI can be transferred to host cells. Thymidine analog BrdU is associated with loss of cellular protein antigenicity due to harsh histological conditions. Newer thymidine analog EdU is easier to detect by chemical reaction to azide-conjugated Alexa fluors, but certain bone marrow cells are reactive to these fluors in the absence of EdU. These caveats need to be taken into consideration when designing or interpreting MSC transplantation experiments.

Intra-articular delivery of purified mesenchymal stem cells from C57BL/6 or MRL/MpJ superhealer mice prevents posttraumatic arthritis

Joint injury dramatically enhances the onset of osteoarthritis (OA) and is responsible for an estimated 12% of OA. Posttraumatic arthritis (PTA) is especially common after intra-articular fracture, and no disease-modifying therapies are currently available. We hypothesized that the delivery of mesenchymal stem cells (MSCs) would prevent PTA by altering the balance of inflammation and regeneration after fracture of the mouse knee. Additionally, we examined the hypothesis that MSCs from the MRL/MpJ (MRL) "superhealer" mouse strain would show increased multilineage and therapeutic potentials as compared to those from C57BL/6 (B6) mice, as MRL mice have shown exceptional in vivo regenerative abilities. A highly purified population of MSCs was prospectively isolated from bone marrow using cell surface markers (CD45-/TER119-/PDGFRα+/Sca-1+). B6 MSCs expanded greater than 100,000-fold in 3 weeks when cultured at 2% oxygen and displayed greater adipogenic, osteogenic, and chondrogenic differentiation as compared to MRL MSCs. Mice receiving only a control saline injection after fracture demonstrated PTA after 8 weeks, but the delivery of 10,000 B6 or MRL MSCs to the joint prevented the development of PTA. Cytokine levels in serum and synovial fluid were affected by treatment with stem cells, including elevated systemic interleukin-10 at several time points. The delivery of MSCs did not reduce the degree of synovial inflammation but did show increased bone volume during repair. This study provides evidence that intra-articular stem cell therapy can prevent the development of PTA after fracture and has implications for possible clinical interventions after joint injury before evidence of significant OA.

Angioneural crosstalk in scaffolds with oriented microchannels for regenerative spinal cord injury repair

The aim of our work is to utilize the crosstalk between the vascular and the neuronal system to enhance directed neuritogenesis in uniaxial guidance scaffolds for the repair of spinal cord injury. In this study, we describe a method for angioneural regenerative engineering, i.e., for generating biodegradable scaffolds, produced by a combination of controlled freezing (freeze-casting) and lyophilization, which contain longitudinally oriented channels, and provide uniaxial directionality to support and guide neuritogenesis from neuronal cells in the presence of endothelial cells. The optimized scaffolds, composed of 2.5 % gelatin and 1 % genipin crosslinked, were characterized by an elastic modulus of ~51 kPa and longitudinal channels of ~50 μm diameter. The scaffolds support the growth of endothelial cells, undifferentiated or NGF-differentiated PC12 cells, and primary cultures of fetal chick forebrain neurons. The angioneural crosstalk, as generated by first forming endothelial cell monolayers in the scaffolds followed by injection of neuronal cells, leads to the outgrowth of long aligned neurites in the PC12/endothelial cell co-cultures also in the absence of exogenously added nerve growth factor. Neuritogenesis was not observed in the scaffolds in the absence of the endothelial cells. This methodology is a promising approach for neural tissue engineering and may be applicable for regenerative spinal cord injury repair.

Stem cell therapy for erectile dysfunction: a critical review

Erectile dysfunction (ED) is a prevailing health problem that seriously impacts quality of life. Current treatment options are less effective for patients having cavernous nerve (CN) injury or diabetes mellitus-related ED. These 2 types of ED are thus the main focus of past and current stem cell (SC) therapy studies. In a total of 16 studies so far, rats were exclusively used as disease models and SCs were mostly derived from bone marrow, adipose tissue, or skeletal muscle. For tracking, SCs were labeled with LacZ, green fluorescent protein, 4',6-diamidino-2-phenylindole, DiI, bromodeoxyuridine, or 5-ethynyl-2-deoxyuridine, some of which might have led to data misinterpretation. SC transplantation was done exclusively by intracavernous (IC) injection, which has been recently shown to have systemic effects. Functional assessment was done exclusively by measuring increases of IC pressure during electrostimulation of CN. Histological assessment usually focused on endothelial, smooth muscle, and CN contents in the penis. In general, favorable outcomes have been obtained in all trials so far, although whether SCs had differentiated into specific cell lineages remains controversial. Recent studies have shown that intracavernously injected SCs rapidly escaped the penis and homed into bone marrow. This could perhaps explain why intracavernously injected SCs had systemic antidiabetic effects and prolonged anti-ED effects. These hypotheses and the differentiation-versus-paracrine debate require further investigation.

E13.5 retinal progenitors induce mouse bone marrow mesenchymal stromal cells to differentiate into retinal progenitor-like cells

BACKGROUND AIMS

Retinal progenitor cells (RPC) are an excellent resource for retinal replacement therapy but usually unavailable. We attempted to induce bone marrow mesenchymal stromal cells (BMSC) into RPC.

METHODS

BMSC and embryonic day 13.5 (E13.5) RPC derived from wild-type or enhanced green fluorescence protein (EGFP) transgenic (Egfp(+/+)) mice were co-cultured in a transwell or re-aggregation system. Gene and protein expressions were investigated by reverse transcription-polymerase chain reaction (PCR) and immunofluorescence, respectively. Spontaneous cell fusion was evaluated by Chloromethylbenzamido derivative of 1,1'- dioctadecyl-3,3,3',3' - tetramethylindocarbocyanine perchlorate (CM-DiI) labeling together with EGFP tracing.

RESULTS

BMSC from both wild-type and Egfp(+/+) mice displayed similar spindle shapes. The undifferentiated BMSC already expressed immature neural markers but did not express Nfl, Gfap or the retina-related genes Pax6, Math5 and Brn3b. When co-cultured with E13.5 RPC in the transwell system, BMSC displayed transient expression of early retinal development genes, including Pax6, Math5 and Brn3b at 3 days, as well as long-term expression of Nfl (up to 21 days). No expression of the late photoreceptor gene rhodopsin could be detected at any time. In re-aggregation co-culture, E13.5 RPC induced EGFP-positive BMSC to express not only the early retinal development genes but also the late gene rhodopsin. Furthermore, a small fraction of BMSC could be induced to express the synaptophysin protein. Re-aggregation co-culture of CM-DiI-labeled BMSC and EGFP-positive E13.5 RPC displayed minimal co-localization of the two fluorescence signals.

CONCLUSIONS

E13.5 RPC are capable of inducing BMSC towards an RPC fate. The differentiation is independent of cell fusion. Cytokines and cell-cell interactions exert this induction effect, but they have different functions.

The restoration of full-thickness cartilage defects with BMSCs and TGF-beta 1 loaded PLGA/fibrin gel constructs

Poly(lactide-co-glycolide) (PLGA) sponge was filled with fibrin gel, bone marrow mesenchymal stem cells (BMSCs) and transforming growth factor-β1 (TGF-β1) to obtain a construct for cartilage restoration in vivo. The PLGA sponge lost its weight steadily in vitro, but degraded much faster in the construct of PLGA/fibrin gel/BMSCs implanted in the full-thickness cartilage defects. The in vivo degradation of the fibrin gel inside the construct was prolonged to 12 wk too. The CM-DiI labeled allogenic BMSCs were detectable after transplantation (implantation) into the defects for 12 wk by small animal in vivo fluorescence imaging and confocal laser scanning microscopy. In vivo repair experiments were firstly performed by implantation of the PLGA/fibrin gel/BMSCs and PLGA/BMSCs constructs into full-thickness cartilage defects (3 mm in diameter and 4 mm in depth) of New Zealand white rabbits for 12 wk. The defects implanted with the PLGA/fibrin gel/BMSCs constructs were filled with cartilage-like tissue containing collagen type II and glycosaminoglycans (GAGs), while those by the PLGA/BMSCs constructs were filled with fibrous-like tissues. To repair the defects of larger size (4 mm in diameter), addition of growth factors was mandatory as exemplified here by further loading of TGF-β1. Implantation of the PLGA/fibrin gel/BMSCs/TGF-β1 constructs into the full-thickness cartilage defects for 12 wk resulted in full restoration of the osteochondral tissue. The neo-cartilage integrated well with its surrounding cartilage and subchondral bone. Immunohistochemical and GAGs staining confirmed the similar distribution of collagen type II and GAGs in the regenerated cartilage as that of hyaline cartilage. The quantitative reverse transcription-polymerase chain reaction (qRT-PCR) revealed that the cartilage special genes were significantly up-regulated compared with those of the TGF-β1 absent constructs.

Survival, differentiation, and reversal of heroin neurobehavioral teratogenicity in mice by transplanted neural stem cells derived from embryonic stem cells

Cell therapies in animal models of neurobehavioral defects are normally derived from neural stem cells (NSC) of the developing cortex. However, the clinical feasibility of NSC therapies would be greatly improved by deriving transplanted cells and from a tissue culture source that is self-renewing, containing cells that potentially differentiate into the desired neuronal phenotypes. These cultures can be engineered to contain the appropriate factors to support their therapeutic action and likely evoke lesser immune reactions. In the current study, we employed our model of mice neurobehaviorally impaired via prenatal exposure to heroin, to test the therapeutic efficacy of NSC derived from murine embryonic stem cells culture (ESC). The culture contained elongated bipolar cells, 90% of which are positive for nestin, the intermediate filament protein found in neural precursors. After removal of growth factors, the NSC differentiated into neurons (34.0% +/- 3.8% NF-160 positive), including cholinergic cells (ChAT positive), oligodendrocytes (29.9% +/- 4.2% O(4)), and astrocytes (36.1% +/- 4.7% GFAP positive). Reverse transcriptase polymerase chain reaction (RT-PCR) analysis confirmed the immunocytochemical findings. Mice made deficient in Morris maze behavior by prenatal heroin exposure (10 mg/kg heroin s.c. on gestational days 9-18) were transplanted into the hippocampus region on postnatal day 35 with the ES culture-derived NSC (ES-NSC) labeled with dialkylcarbocyanine (Dil) cell tracker. Dil+ and NF160+ cells were detected in the hippocampal region (50% +/- 8% survival). The transplantation completely restored maze performance to normal; e.g., on day 3, transplantation improved the behavior from the deficient level of 11.9-sec latency to the control of 5.6-sec latency (44.5% improvement).

An avian model for the reversal of neurobehavioral teratogenicity with neural stem cells

A fast and simple model which uses lower animals on the evolutionary scale is beneficial for developing procedures for the reversal of neurobehavioral teratogenicity with neural stem cells. Here, we established a procedure for the derivation of chick neural stem cells, establishing embryonic day (E) 10 as optimal for progression to neuronal phenotypes. Cells were obtained from the embryonic cerebral hemispheres and incubated for 5-7 days in enriched medium containing epidermal growth factor (EGF) and basic fibroblast growth factor (FGF2) according to a procedure originally developed for mice. A small percentage of the cells survived, proliferated and formed nestin-positive neurospheres. After removal of the growth factors to allow differentiation (5 days), 74% of the cells differentiated into all major lineages of the nervous system, including neurons (Beta III tubulin-positive, 54% of the total number of differentiated cells), astrocytes (GFAP-positive, 26%), and oligodendrocytes (O4-positive, 20%). These findings demonstrate that the cells were indeed neural stem cells. Next, the cells were transplanted in two allograft chick models; (1) direct cerebral transplantation to 24-h-old chicks, followed by post-transplantation cell tracking at 24 h, 6 days and 14 days, and (2) intravenous transplantation to chick embryos on E13, followed by cell tracking on E19. With both methods, transplanted cells were found in the brain. The chick embryo provides a convenient, precisely-timed and unlimited supply of neural progenitors for therapy by transplantation, as well as constituting a fast and simple model in which to evaluate the ability of neural stem cell transplantation to repair neural damage, steps that are critical for progress toward therapeutic applications.

Reversal of chlorpyrifos neurobehavioral teratogenicity in mice by nicotine administration and neural stem cell transplantation

Identifying the mechanisms underlying the adverse effects of developmental neurotoxicants enables the design of therapies that can potentially reverse neurobehavioral deficits in adulthood. We administered chlorpyrifos (CPF), a model organophosphate pesticide to pregnant mice and identified visuospatial deficits in adult offspring using performance in the Morris maze. We then evaluated two strategies to reverse the effects, nicotine administration and transplantation of neural stem cells. Daily administration of nicotine prior to behavioral testing did not alter maze performance by itself, but completely reversed the deficits evoked by prenatal CPF exposure. Similarly, control animals grafted with neural stem cells in adolescence did not show any alterations in behavioral performance as adults, but the grafts completely reversed the effects of prenatal CPF treatment. This study thus provides a model for the development and application of both pharmacologic and cell-based therapies to offset the effects of neurobehavioral teratogens.

Differential cell viability of chondrocytes and progenitor cells in tissue-engineered constructs following implantation into osteochondral defects

Animal studies in cartilage tissue engineering usually include the transfer of cultured cells into chondral or osteochondral defects. Immediately at implantation, the cells are exposed to a dramatically changed environment. The aim of this study was to determine the viability of two cell types currently considered for cellular therapies of cartilage defects-chondrocytes and progenitor cells-shortly after exposure to an osteochondral defect in rabbit knees. To that end, autogenic chondrocytes and periosteal cells were labeled with CM-DiI fluorochrome, seeded or cultured in PEGT/PBT scaffolds for periods up to 2 weeks, transferred into osteochondral defects, harvested 5 days postimplantation, and analyzed for cell viability. In order to further elucidate factors effecting cell viability within our model system, we investigated the effect of serum, 2) extracellular matrix surrounding implanted cells, 3) scaffold interconnectivity, and 4) hyaluronan, as a known cell protectant. Controls included scaffolds with devitalized cells and scaffolds analyzed at implantation. We found that the viability of periosteum cells (14%), but not of chondrocytes (65-95%), was significantly decreased after implantation. The addition of hyaluronan increased periostium cell viability to 44% (p < 0.05). Surprisingly, cell viability in less interconnected compression-molded scaffolds was higher compared to that of fully interconnected scaffolds produced by rapid prototyping. All other factors tested did not affect viability significantly. Our data suggest chondrocytes as a suitable cell source for cartilage repair in line with clinical data on several chondrocyte-based therapies. Although we did not test progenitor cells other the periosteum cells, tissue-engineering approaches using such cell types should take cell viability aspects into consideration.

Transplantation of corneas reconstructed with cultured adult human corneal endothelial cells in nude rats

PURPOSE

The feasibility of corneal reconstruction with cultured adult human corneal endothelial cells (HCEC) was examined in a nude rat model.

METHODS

Endothelial cells were removed from the corneas of Lewis rats using a sterile cotton swab. Cultured adult HCEC labelled with a fluorescent marker chloromethyl-benzamidodialkylcarbocyanine (CM-Dil) were seeded onto the denuded Descemet's membrane. Then the corneas were centrifuged, incubated for 2 days, and transplanted into the eyes of nude rats using the penetrating keratoplasty technique (HCEC group). Control nude received corneas denuded of endothelium and without HCEC. The operated eyes were observed for 28 days after transplantation, and then were subjected to histological and fluorescein microscopic examination.

RESULTS

The mean corneal thickness was significantly smaller in the HCEC group than in the control group throughout the observation period. The corneal endothelial cell density of the grafts at 28 days postoperatively ranged from 2425 to 3250 cells mm(-2) (mean+/-sd, 2744+/-337 cells mm(-2)). Fluorescein microscopy at 28 days after surgery showed numerous DiI-labelled cells on the posterior corneal surface in the HCEC group. Frozen sections showed a monolayer of DiI-labelled cells on Descemet's membrane.

CONCLUSIONS

Cultured adult HCEC function well and maintain corneal transparency for 1 month after transplantation in nude rats.

Genetic marking with the DeltaLNGFR-gene for tracing goat cells in bone tissue engineering

The use of bone marrow derived stromal cells (BMSC's) for bone tissue engineering has gained much attention as an alternative for autologous bone grafting. Little is known however, about the survival and differentiation of the cells, especially in the clinical application. The aim of this study was to develop a method to trace goat BMSC's in vivo. We investigated retroviral genetic marking, which allows stable expression of the label with cell division. Goat BMSC's were subjected to an amphotropic envelope containing a MoMuLV-based vector expressing the human low affinity nerve growth factor receptor (DeltaLNGFR). Labeling efficiency and effect on the cells were analyzed. Furthermore, transduced cells were seeded onto porous ceramic scaffolds, implanted subcutaneously in nude mice and examined after successive implantation periods. Flow cytometry indicated a transduction efficiency of 40-60%. Immunohistochemistry showed survival and subsequent bone formation of the gene-marked cells in vivo. Besides, marked cells were also found in cartilage and fibrous tissue. These findings indicate the maintenance of the precursor phenotype following gene transfer as well as the ability of the gene to be expressed following differentiation. We conclude that retroviral gene marking with DeltaLNGFR is applicable to trace goat BMSC's in bone tissue engineering research.

Osteogenicity of autologous bone transplants in the goat

BACKGROUND

Little is known about the specific mechanisms that make autologous graft bone (AG) superior to the current alternatives. A potential mechanism is the active bone formation by the osteoprogenitor cells within the AG. However, whether these cells survive the transplantation is questionable, especially in nonvascularized, clinically sized grafts. In the present study, we investigated the role of viability in AG implanted ectopically and orthotopically in the goat.

METHODS

Eight goats were operated on twice. At the first operation, pieces of vital or devitalized autologous cortical bone were implanted in the paraspinal muscles. Eight weeks later, corticocancellous plugs were taken from the femoral condyles, morselized, and reimplanted as either vital or devitalized orthotopic grafts. The goats received fluorochrome labels at 5, 7, and 9 weeks after the first operation. At 12 weeks, the goats were killed, and the samples were examined histologically.

RESULTS

Ectopically, new bone had formed in both the vital and devitalized grafts. In the vital grafts, all three fluorochrome labels were present, indicating an early osteogenic mechanism. Within the devitalized grafts, only the 9-week label was observed. Histomorphometry indicated significantly more new bone in the vital grafts (10.3% vs. 1.7% in the devitalized grafts, P <0.01). Orthotopically, both vital and devitalized grafts showed new bone. Again, graft viability was advantageous in terms of new bone formation (14.5% vs. 9.3%, P <0.02).

CONCLUSION

The cells inside the autologous bone transplants most likely survived transplantation and were capable of initiating and sustaining new bone formation.

Optimization of bone tissue engineering in goats: a peroperative seeding method using cryopreserved cells and localized bone formation in calcium phosphate scaffolds1

BACKGROUND

Bone tissue engineering by combining cultured bone marrow stromal cells with a porous scaffold is a promising alternative for the autologous bone graft. Drawbacks of the technique include the delay necessary for cell culture and the complicated logistics. We investigated methods to bypass these drawbacks. Furthermore, we investigated the localization of bone formation inside the scaffold.

METHODS

Bone marrow stromal cells from seven goats were culture expanded and cryopreserved. One week before surgery, some of the cells were thawed, cultured, and seeded on porous calcium phosphate scaffolds. The constructs were cultured for another week until implantation. The remaining cryopreserved cells were thawed just before implantation and peroperatively resuspended in plasma before combining with the scaffold. Scaffolds impregnated with fresh bone marrow, devitalized cultured constructs, and empty scaffolds served as controls. All samples were implanted in the back muscles of the goats for 9 weeks.

RESULTS

Histologic examination showed minimal (<1%) bone in the empty and devitalized scaffolds, 4.2 +/- 5.1 bone area percent in the bone marrow samples, and significantly more bone in both the cultured and peroperatively seeded constructs (11.7 +/- 2.5 and 14.0 +/- 2.0%). The peripheral 350 microm of the implants contained significantly less bone.

CONCLUSION

Peroperative preparation of osteogenic constructs with cryopreserved cells is feasible. These constructs yield substantially more bone than the scaffolds alone or scaffolds impregnated with fresh bone marrow. Bone deposition is much less on the scaffold periphery.

Optimization of bone-tissue engineering in goats

Successful bone-tissue engineering (TE) has been reported for various strategies to combine cells with a porous scaffold. In particular, the period after seeding until implantation of the constructs may vary between hours and several weeks. Differences between these strategies can be reduced to (a) the presence of extracellular matrix, (b) the differentiation status of the cells, and (c) the presence of residual potentially immunogenic serum proteins. These parameters are investigated in two types of calcium phosphate scaffolds in a goat model of ectopic bone formation. Culture-expanded bone-marrow stromal cells from eight goats were seeded onto two types of hydroxyapatite granules: HA60/400 (60% porosity, 400-microm average pore size) and HA70/800. Scaffolds seeded with cells and control scaffolds were cultured for 6 days in medium containing autologous or semisynthetic serum, in the presence or absence of dexamethasone. Other scaffolds were seeded with cells just before implantation in medium with or without serum. All conditions were implanted autologously in the paraspinal muscles. After 12 weeks, bone had formed in 87% of all TE constructs, as demonstrated by histology. Histomorphometry indicated significantly more bone in the HA70/800 scaffolds. Furthermore, a significant advantage in bone formation was found when the constructs had been cultured for 6 days. In conclusion, both scaffold characteristics (porosity) and TE strategy (culturing of the constructs) were demonstrated to be important for bone TE.

Viable osteogenic cells are obligatory for tissue-engineered ectopic bone formation in goats

In this study we investigated the bone-forming capacity of tissue-engineered (TE) constructs implanted ectopically in goats. As cell survival is questionable in large animal models, we investigated the significance of vitality, and thus whether living cells instead of only the potentially osteoinductive extracellular matrix are required to achieve bone formation. Vital TE constructs of porous hydroxyapatite (HA) covered with differentiated bone marrow stromal cells (BMSCs) within an extracellular matrix (ECM) were compared with identical constructs that were devitalized before implantation. The devitalized implants did contain the potentially osteoinductive ECM. Furthermore, we evaluated HA impregnated with fresh bone marrow and HA only. Two different types of HA granules with a volume of approximately 40 microm were investigated: HA70/800, a microporous HA with 70% interconnected macroporosity and an average pore size of 800 microm, and HA60/400, a smooth HA with 60% interconnected macropores and an average size of 400 microm. Two granules of each type were combined and then treated as a single unit for cell seeding, implantation, and histology. The tissue-engineered samples were obtained by seeding culture-expanded goat BMSCs on the HA and subsequently culturing these constructs for 6 days to allow cell differentiation and ECM formation. To devitalize, TE constructs were frozen in liquid nitrogen according to a validated protocol. Fresh bone marrow impregnation was performed perioperatively (4 mL per implant unit). All study groups were implanted in bilateral paraspinal muscles. Fluorochromes were administered at three time points to monitor bone mineralization. After 12 weeks the units were explanted and analyzed by histology of nondecalcified sections. Bone formation was present in all vital tissue-engineered implants. None of the other groups showed any bone formation. Histomorphometry indicated that microporous HA70/800 yielded more bone than did HA60/400. Within the newly formed bone, the fluorescent labels showed that mineralization had occurred before 5 weeks of implantation and was directed from the HA surface toward the center of the pores. In conclusion, tissue-engineered bone formation in goats can be achieved only with viable constructs of an appropriate scaffold and sufficient BMSCs.