Jochen Ringe

Porcine mesenchymal stem cells

Abstract. The potential of mesenchymal stem and progenitor cells (MSC) to replicate undifferentiated and to mature into distinct mesenchymal tissues suggests these cells as an attractive source for tissue engineering. The objective was to establish a protocol for the isolation of porcine MSC from bone marrow and to demonstrate their ex vivo differentiation into various mesenchymal tissue cells. MSC from passage 2 were selected for differentiation analysis. Differentiation along the osteogenic lineage was documented by deposition of calcium, visualization of alkaline phosphatase activity, and by analysis of osteogenic marker genes. Adipocytes were identified morphologically and by gene-expression analysis. Deposition of type II collagen and histological staining of proteoglycan indicated chondrogenic differentiation. Therefore, porcine MSC may be introduced as a valuable model system with which to study the mesenchymal lineages for basic research and tissue engineering.

Stem cells for regenerative medicine: advances in the engineering of tissues and organs

Abstract. The adult bone marrow stroma contains a subset of nonhematopoietic cells referred to as mesenchymal stem or mesenchymal progenitor cells (MSC). These cells have the capacity to undergo extensive replication in an undifferentiated state ex vivo. In addition, MSC have the potential to develop either in vitro or in vivo into distinct mesenchymal tissues, including bone, cartilage, fat, tendon, muscle, and marrow stroma, which suggest these cells as an attractive cell source for tissue engineering approaches. The interest in modern biological technologies such as tissue engineering has dramatically increased since it is feasible to isolate living, healthy cells from the body, expand them under cell culture conditions, combine them with biocompatible carrier materials and retransplant them into patients. Therefore, tissue engineering gives the opportunity to generate living substitutes for tissues and organs, which may overcome the drawbacks of classical tissue reconstruction: lacking quality and quantity of autologous grafts, immunogenicity of allogenic grafts and loosening of alloplastic implants. Due to the prerequisite for tissue engineering to ensure a sufficient number of tissue specific cells without donor site morbidity, much attention has been drawn to multipotential progenitor cells such as embryonic stem cells, periosteal cells and mesenchymal stem cells. In this report we review the state of the art in tissue engineering with mesenchymal stem and mesenchymal progenitor cells with emphasis on bone and cartilage reconstruction. Furthermore, several issues of importance, especially with regard to the clinical application of mesenchymal stem cells, are discussed.

In vitro expression of cartilage-specific markers by chondrocytes on a biocompatible hydrogel: implications for engineering cartilage tissue.

Natural cartilage tissue has a limited self-regenerative capacity; thus, strategies to replenish the lost cartilage are desired in reconstructive and plastic surgery. Tissue-engineered cartilage using biodegradable polymeric scaffolds is one such approach gaining wide attention. We have earlier demonstrated the biocompatible nature and ability of chitosan-gelatin hydrogel to maintain differentiated populations of respiratory epithelial cells. The aim of the present study was to evaluate its suitability as a substratum for inducing chondrocyte growth and differentiation. Electron microscopic (SEM) analysis of freeze-dried hydrogels showed a highly porous morphology with interconnections as seen in cross section. Chondrocytes were observed to attach and exhibited a differentiated phenotype with proper cell-cell contact on three-dimensional freeze-dried hydrogels. When cultured on two-dimensional hydrogel films they showed higher growth rates (4–6%) compared with a polystyrene (TCPS) control until 6 days (p > 0.05), which slowed down after 10 days. Immunofluorescent microscopic studies revealed that chondrocytes on hydrogel films exhibited comparable expression of β1 integrin (CD29) to TCPS controls, indicating the ability of the hydrogel substrate to maintain normal expression of β1 integrin. RT-PCR analysis of chondrocytes grown on hydrogel films showed that chondrocytes express the mRNA for extracellular matrix proteins such as collagen type IIα1 (COL IIα1), COL III, COL IXα3. Expression of COL I was less prominent than COL II as indication of differentiation. Expression of COL X could not be detected, suggesting an absence of chondrocyte hypertrophy. Chondrocytes also showed weak mRNA expression of aggrecan, a cartilage-specific proteoglycan. All of these results point out the ability of the chitosan-gelatin hydrogel to induce the expression of mRNAs for cartilage-specific extracellular matrix proteins by nasal septal chondrocytes. This hydrogel needs to be further evaluated for its ability to support chondrocyte-specific marker expression to explore the possibility of forming a tissue resembling natural cartilage in vitro.

Biocompatible hydrogel supports the growth of respiratory epithelial cells: possibilities in tracheal tissue engineering.

Extensive tracheal defect reconstruction is a major challenge in plastic and reconstructive surgery. The lack of an epithelial lining on the luminal surfaces of tracheal prostheses is among the major causes of their failure. Chitosan-gelatin hydrogels were synthesized for the development of biocompatible, growth-supportive substrata for respiratory epithelial cells. We employed J774 macrophages to test the immunocompatibility of this gel. The hydrogel did not exert a cytotoxic effect on macrophages, as confirmed by tetrazolium reduction and neutral red uptake assay. Flow cytometric analysis of macrophages cultured on the hydrogel showed a comparable expression of activation markers CD11b/CD18, CD45, and CD14 to the control. Semiquantitative RT-PCR results showed an absence of upregulation of interleukin-6 (IL-6) and TNF-alpha in these macrophages with respect to the controls. Primary human respiratory epithelial cells cultured on the hydrogel showed proper attachment, normal morphology, and growth. A small proportion of cells on the hydrogel showed synchronously beating cilia. RT-PCR analysis showed that cells on the hydrogel expressed mucins 2 and 5 and cytokeratin 13, which are markers for secretory goblet and squamous cells, respectively. All these results demonstrate that the hydrogel supports the growth of a mixed population of differentiated epithelial cells. This hydrogel is suitable as a culture substratum for respiratory epithelial cells and could be used as a potential candidate for coating tracheal prostheses.

Biomimetic sulfated polyethylene glycol hydrogel inhibits proteoglycan loss and tumor necrosis factor-α-induced expression pattern in an osteoarthritis in vitro model: dPGS HYDROGEL INHIBITS PROTEOGLYCAN LOSS

This study aimed to evaluate the potential of an anti-inflammatory polyethylene glycol (PEG) hydrogel for osteoarthritis (OA) management in an OA in vitro model. Freshly isolated porcine chondrocytes were maintained in high-density cultures to form cartilage-like three-dimensional micromasses. Recombinant porcine tumor necrosis factor-alpha (TNF-α) was used to induce OA-like changes. Normal and OA-like micromasses were treated with dendritic polyglycerol sulfate-based PEG hydrogel. Live/dead staining showed that all micromasses remained vital and presented similar morphological characteristics. Safranin-O staining demonstrated a typical depletion of glycosaminoglycans in TNF-α-treated micromasses but not in the presence of the hydrogel. There was no distinct difference in immunohistochemical detection of type II collagen. Microarray data showed that rheumatoid arthritis and TNF signaling pathways were down regulated in hydrogel-treated OA-like micromasses compared to nontreated OA-like micromasses. The hydrogel alone did not affect genes related to OA such as ANPEP, COMP, CXCL12, PTGS2, and TNFSF10, but it prevented their regulation caused by TNF-α. This study provides valuable insights toward a fully synthetic hydrogel for the intra-articular treatment of OA. The findings proved the potential of this hydrogel to prevent the development of TNF-α-induced OA with regard to proteoglycan loss and TNF-α-induced expression pattern without additional signs of differentiation and inflammation.

Delayed release of chemokine CCL25 with bioresorbable microparticles for mobilization of human mesenchymal stem cells

Chemokines are guiding cues for directional trafficking of mesenchymal stem cells (MSC) upon injury and local chemokine delivery at injury sites is an up-to-date strategy to potentiate and prolong recruitment of MSC. In this study we present the chemokine CCL25, also referred to as thymus-expressed chemokine, to mobilize human MSC along positive but not along negative gradients. We hence proceeded to design a biodegradable and injectable release device for CCL25 on the basis of poly(lactic-co-glycolic acid) (PLGA). The conducted studies had the objective to optimize PLGA microparticle fabrication by varying selected formulation parameters, such as polymer type, microparticle size and interior phase composition. We found that microparticles of DV,50∼75u202fµm and fabricated using end-capped polymers, BSA as carrier protein and vortex mixing to produce the primary emulsion yielded high chemokine loading and delayed CCL25 release. To determine bioactivity, we investigated CCL25 released during the microparticle erosion phase and showed that deacidification of the release medium was required to induce significant MSC mobilization. The designed PLGA microparticles represent an effective and convenient off-the-shelf delivery tool for the delayed release of CCL25. However, continuative in vivo proof-of-concept studies are required to demonstrate enhanced recruitment of MSC and/or therapeutical effects in response to CCL25 release microparticles.nnnSTATEMENT OF SIGNIFICANCEnWith the discovery of chemokines, particularly CXCL12, as stimulators of stem cell migration, the development of devices that release CXCL12 has proceeded quickly in the last few years. In this manuscript we introduce CCL25 as chemokine to induce mobilization of human MSC. This study proceeds to demonstrate how selection of key formulation parameters of CCL25 loading into PLGA microparticles exerts considerable influence on CCL25 release. This is important for a broad range of efforts in in situ tissue engineering where the candidate chemokine and the delivery device need to be selected carefully. The use of such a cell-free CCL25 release device may provide a new therapeutic option in regenerative medicine.

The Atrial Appendage as a Suitable Source to Generate Cardiac-derived Adherent Proliferating Cells for Regenerative Cell-based Therapies

Cardiac‐derived adherent proliferating (CardAP) cells obtained from endomyocardial biopsies (EMBs) with known anti‐fibrotic and pro‐angiogenic properties are good candidates for the autologous therapy of end‐stage cardiac diseases such as dilated cardiomyopathy. However, due to the limited number of CardAP cells that can be obtained from EMBs, our aim is to isolate cells with similar properties from other regions of the heart with comparable tissue architecture. Here, we introduce the atrial appendage as a candidate region. Atrial appendage‐derived cells were sorted with CD90 microbeads to obtain a CD90low cell population, which were subsequently analysed for their surface marker and gene expression profiles via flow cytometry and micro array analysis. Enzyme‐linked immunosorbent assays for vascular endothelial growth factor and interleukin‐8 as well as tube formation assays were performed to investigate pro‐angiogenic properties. Furthermore, growth kinetic assays were performed to estimate the cell numbers needed for cell‐based products. Microarray analysis revealed the expression of numerous pro‐angiogenic genes and strong similarities to CardAP cells with which they also share expression levels of defined surface antigens, that is, CD29+, CD44+, CD45−, CD73+, CD90low, CD105+, and CD166+. High secretion levels of vascular endothelial growth factor and interleukin‐8 as well as improved properties of vascular structures in vitro could be detected. Based on growth parameters, cell dosages for the treatment of more than 250 patients are possible using one appendage. These results lead to the conclusion that isolating cells with regenerative characteristics from atrial appendages is feasible and permits further investigations towards allogenic cell‐based therapies.

Standardisation of basal medium for reproducible culture of human annulus fibrosus and nucleus pulposus cells

BackgroundThe lifetime prevalence of degenerative disc disease is dramatically high. Numerous investigations on disc degeneration have been performed on cells from annulus fibrosus (AF) and nucleus pulposus (NP) of the intervertebral disc (IVD) in cell culture experiments utilising a broad variety of basal culture media. Although the basal media differ in nutrient formulation, it is not known whether the choice of the basal media itself has an impact on the cell’s behaviour in vitro. In this study, we evaluated the most common media used for monolayer expansion of AF and NP cells to set standards for disc cell culture.MethodsHuman AF and NP cells were isolated from cervical discs. Cells were expanded in monolayer until passage P2 using six different common culture media containing alpha-Minimal Essential Medium (alpha-MEM), Dulbecco’s Modified Eagle’s Medium (DMEM) or Ham’s F-12 medium (Ham’s F-12) as single medium or in a mixture of two media (alpha/F-12,xa0DMEM/alpha, DMEM/F-12). Cell morphology, cell growth, glycosaminoglycan production and quantitative gene expression of cartilage- and IVD-related markers aggrecan, collagen type II, forkhead box F1 and keratin 18 were analysed. Statistical analysis was performed with two-way ANOVA testing and Bonferroni compensation.ResultsAF and NP cells were expandable in all tested media. Both cell types showed similar cell morphology and characteristics of dedifferentiation known for cultured disc cells independently from the media. However, proceeding culture in Ham’s F-12 impeded cell growth of both AF and NP cells. Furthermore, the keratin 18 gene expression profile of NP cells was changed in alpha-MEM and Ham’s F-12.ConclusionThe impact of the different media itself on disc cell’s behaviour in vitro was low. However, AF and NP cells were only robust, when DMEM was used as single medium or in a mixture (DMEM/alpha, DMEM/F-12). Therefore, we recommend using these media as standard medium for disc cell culture. Our findings are valuable for the harmonisation of preclinical study results and thereby push the development of cell therapies for clinical treatment of disc degeneration.