Comparison of fetal cartilage-derived progenitor cells isolated at different developmental stages in a rat model

An Injectable Engineered Cartilage Gel Improves Intervertebral Disc Repair in a Rat Nucleotomy Model

Lower back pain is a major problem caused by intervertebral disc degeneration. A common surgical procedure is lumbar partial discectomy (excision of the herniated disc causing nerve root compression), which results in further disc degeneration, severe lower back pain, and disability after discectomy. Thus, the development of disc regenerative therapies for patients who require lumbar partial discectomy is crucial. Here, we investigated the effectiveness of an engineered cartilage gel utilizing human fetal cartilage-derived progenitor cells (hFCPCs) on intervertebral disc repair in a rat tail nucleotomy model. Eight-week-old female Sprague-Dawley rats were randomized into three groups to undergo intradiscal injection of (1) cartilage gel, (2) hFCPCs, or (3) decellularized extracellular matrix (ECM) (n = 10/each group). The treatment materials were injected immediately after nucleotomy of the coccygeal discs. The coccygeal discs were removed six weeks after implantation for radiologic and histological analysis. Implantation of the cartilage gel promoted degenerative disc repair compared to hFCPCs or hFCPC-derived ECM by increasing the cellularity and matrix integrity, promoting reconstruction of nucleus pulposus, restoring disc hydration, and downregulating inflammatory cytokines and pain. Our results demonstrate that cartilage gel has higher therapeutic potential than its cellular or ECM component alone, and support further translation to large animal models and human subjects.

Motorized Shaver Harvest Results in Similar Cell Yield and Characteristics Compared With Rongeur Biopsy During Arthroscopic Synovium-Derived Mesenchymal Stem Cell Harvest

PURPOSE

To compare cell yield and character of synovium-derived mesenchymal stem cell (SDMSC) harvested by 2 different techniques using rongeur and motorized shaver during knee arthroscopy.

METHODS

This study was performed in 15 patients undergoing partial meniscectomy. Two different techniques were used to harvest SDMSCs in each patient from the synovial membrane at 2 different locations overlying the anterior fat pad, each within 1 minute of harvest time. Cell yield and proliferation rates were evaluated. Cell surface marker analysis was done after passage 2 (P2). Trilineage differentiation potential was evaluated by real-time quantitative polymerase chain reaction and histology. Statistical analysis between the 2 methods was done using the Mann-Whitney U test.

RESULTS

Wet weight of total harvested tissue was 69.93 (± 20.02) mg versus 378.91 (± 168.87) mg for the rongeur and shaver group, respectively (P < .0001). Mononucleated cell yield was 3.32 (± 0.89) versus 3.18 (± 0.97) × 10³ cells/mg, respectively (P = .67). Fluorescence-activated cell sorting analysis revealed similar SDMSC-related cell surface marker expression levels in both groups, with positive expression for CD44, CD73, CD90, and CD105 and decreased expression for CD34 and CD45. Both groups showed similar trilineage differentiation potential in histology. Chondrogenic (SOX9, ACAN, COL2), adipogenic (LPL, PLIN1, PPAR-γ), and osteogenic (OCN, OSX, RUNX2) gene marker expression levels also were similar between both groups.

CONCLUSIONS

No difference was observed between rongeur biopsy and motorized shaver harvest methods regarding SDMSC yield and cell characteristics.

CLINICAL RELEVANCE

The current study shows that both rongeur and motorized shaver harvest are safe and effective methods for obtaining SDMSCs. Motorized shaver harvest results in higher volume of tissue acquisition per time, thereby leading to higher number of SDMSCs which may be useful during clinical application.

Exosomes from IL-1β-Primed Mesenchymal Stem Cells Inhibited IL-1β- and TNF-α-Mediated Inflammatory Responses in Osteoarthritic SW982 Cells

BACKGROUND

Exosomes from mesenchymal stem cells (MSCs) show anti-inflammatory effect on osteoarthritis (OA); however, their biological effect and mechanism are not yet clearly understood. This study investigated the anti-inflammatory effect and mechanism of MSC-derived exosomes (MSC-Exo) primed with IL-1β in osteoarthritic SW982 cells.

METHODS

SW982 cells were treated with interleukin (IL)-1β and tumor necrosis factor (TNF)-α to induce the OA phenotype. The effect of exosomes without priming (MSC-Exo) or with IL-1β priming (MSC-IL-Exo) was examined on the expression of pro- or anti-inflammatory factors, and the amount of IκBα was examined in SW982 cells. Exosomes were treated with RNase to remove RNA. The role of miR-147b was examined using a mimic and an inhibitor.

RESULTS

MSC-IL-Exo showed stronger inhibitory effects on the expression of pro-inflammatory cytokines (IL-1β, IL-6, and monocyte chemoattractant protein-1) than MSC-Exo. The expression of anti-inflammatory factors (SOCS3 and SOCS6) was enhanced by MSCs-IL-Exo. Priming with IL-1β increased RNA content in MSC-IL-Exo, and pretreatment with RNase abolished anti-inflammatory effect in SW982 cells. miR-147b was found in much larger amounts in MSC-IL-Exo than in MSC-Exo. The miR-147b mimic significantly inhibited the expression of inflammatory cytokines, while the miR-147b inhibitor only partially blocked the anti-inflammatory effect of MSC-IL-Exo. MSC-IL-Exo and miR-147b mimic inhibited the reduction of IκBα, an nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) inhibitor, by IL-1β and TNF-α.

CONCLUSION

This study showed that MSC exosomes with IL-1β priming exhibit significantly enhanced anti-inflammatory activity in osteoarthritic SW982 cells. The effect of IL-1β-primed MSC exosomes is mediated by miRNAs such as miR-147b and involves inhibition of the NF-κB pathway.

Exosomes Derived From M2 Macrophages Facilitate Osteogenesis and Reduce Adipogenesis of BMSCs

Bone regeneration is a complex process that requires the coordination of osteogenesis and osteoclastogenesis. The balance between osteogenesis and adipogenesis of bone marrow mesenchymal stem cells (BMSCs) plays a major role in the process of bone formation. Recently, intercellular communication between bone cells and surrounding cells has been gradually recognized, and macrophages on the surface of bone have been proven to regulate bone metabolism. However, the underlying mechanisms have not been fully elucidated. Recent studies have indicated that exosomes are vital messengers for cell-cell communication in various biological processes. In this experiment, we found that exosomes derived from M2 macrophages (M2D-Exos) could inhibit adipogenesis and promote osteogenesis of BMSCs. M2D-Exo intervention increased the expression of miR-690, IRS-1, and TAZ in BMSCs. Additionally, miR-690 knockdown in M2 macrophages with a miR-690 inhibitor partially counteracted the effect of M2D-Exos on BMSC differentiation and the upregulation of IRS-1 and TAZ expression. Taken together, the results of our study indicate that exosomes isolated from M2 macrophages could facilitate osteogenesis and reduce adipogenesis through the miR-690/IRS-1/TAZ axis and might be a therapeutic tool for bone loss diseases.

Engineered cartilage utilizing fetal cartilage-derived progenitor cells for cartilage repair

The aim of this study was to develop a fetal cartilage-derived progenitor cell (FCPC) based cartilage gel through self-assembly for cartilage repair surgery, with clinically useful properties including adhesiveness, plasticity, and continued chondrogenic remodeling after transplantation. Characterization of the gels according to in vitro self-assembly period resulted in increased chondrogenic features over time. Adhesion strength of the cartilage gels were significantly higher compared to alginate gel, with the 2-wk group showing a near 20-fold higher strength (1.8 ± 0.15 kPa vs. 0.09 ± 0.01 kPa, p < 0.001). The in vivo remodeling process analysis of the 2 wk cultured gels showed increased cartilage repair characteristics and stiffness over time, with higher integration-failure stress compared to osteochondral autograft controls at 4 weeks (p < 0.01). In the nonhuman primate investigation, cartilage repair scores were significantly better in the gel group compared to defects alone after 24 weeks (p < 0.001). Cell distribution analysis at 24 weeks showed that human cells remained within the transplanted defects only. A self-assembled, FCPC-based cartilage gel showed chondrogenic repair potential as well as adhesive properties, beneficial for cartilage repair.

A Free Radical Scavenger Ameliorates Teratogenic Activity of a DNA Hypomethylating Hematological Therapeutic

The spin-trap free radical scavenger N-tert-butyl-α-phenylnitron (PBN) ameliorated effects of several teratogens involving reactive oxygen species (ROS). We investigated for the first time whether PBN could ameliorate teratogenesis induced by a DNA hypomethylating hematological therapeutic 5-azacytidine (5azaC). At days 12 and 13 of gestation, Fisher rat dams were pretreated by an i.v. injection of PBN (40 mg/kg) and 1 h later by an i.p. injection of 5azaC (5mg/kg). Development was analyzed at gestation day 15 in embryos and day 20 in fetuses. PBN alone did not significantly affect development. PBN pretreatment restored survival of 5azaC-treated dams' embryos to the control level, restored weight of embryos and partially of fetuses, and partially restored crown-rump lengths. PBN pretreatment converted limb adactyly to less severe oligodactyly. PBN pretreatment restored global DNA methylation level in the limb buds to the control level. Cell proliferation in limb buds of all 5azaC-treated dams remained significantly lower than in controls. In the embryonic liver, PBN pretreatment normalized proliferation diminished significantly by 5azaC; whereas in embryonic vertebral cartilage, proliferation of all 5azaC-treated dams was significantly higher than in PBN-treated dams or controls. Apoptotic indices significantly enhanced by 5azaC in liver and cartilage were not influenced by PBN pretreatment. However, PBN significantly diminished ROS or reactive nitrogen species markers nitrotyrosine and 8-hydroxy-2'deoxyguanosine elevated by 5azaC in embryonic tissues, and, therefore, activity of this DNA hypomethylating agent was associated to the activation of free radicals. That pretreatment with PBN enhanced proliferation in the liver and not in immature tissue is interesting for the treatment of 5azaC-induced hepatotoxicity and liver regeneration.

IRS-1 targets TAZ to inhibit adipogenesis of rat bone marrow mesenchymal stem cells through PI3K-Akt and MEK-ERK pathways

Gene modification of mesenchymal stem cells (MSCs) offers a promising approach for clinical stem cell therapy. Transcriptional co-activator with PDZ-binding motif (TAZ) plays a vital role in MSCs' differentiation. We aim to explore the interaction of insulin receptor substrate-1 (IRS-1) with TAZ to regulate MSCs' adipogenesis in this study. Initially, IRS-1 and TAZ followed similar decreasing expression pattern at the early stage of adipogenesis. And, overexpression of IRS-1 decreased the CCAAT/enhancer binding protein β (C/EBPβ) and peroxi-some proliferator-activated receptor gamma (PPARγ) expression with TAZ upregulation. Accordingly, knockdown of IRS-1 induced the upexpression of C/EBPβ and PPARγ with TAZ downregulation. Indeed, IRS-1 targeted TAZ to downregulate the C/EBPβ and PPARγ expression, while knockdown of TAZ attenuated the IRS-1 inhibited adipogenesis. Furthermore, both LY294002 (the PI3K-Akt inhibitor) and U0126 (the MEK-ERK inhibitor) blocked the regulation of IRS-1 on TAZ during adipogenesis. Additionally, IRS-1 and TAZ influenced the cell proliferation in the above process. Taken together, this study suggests for the first time that IRS-1 is a key regulator of the MSCs' adipogenesis and may serve as a potential therapeutic target for differential alterations in bone marrow.

IRS-1 increases TAZ expression and promotes osteogenic differentiation in rat bone marrow mesenchymal stem cells

Whether insulin receptor substrate 1 (IRS-1) inhibits or promotes the osteogenic proliferation and differentiation in vitro remains controversial. Transcriptional co-activator with PDZ-binding motif (TAZ) plays a vital role in the osteogenesis of bone marrow mesenchymal stem cells (BMSCs), and strongly activates the expression of the osteogenic differentiation markers. In this study, we found that IRS-1 and TAZ followed similar increasing expression patterns at the early stage of osteogenic differentiation. Knocking down IRS-1 decreased the TAZ, RUNX2 and OCN expression, and overexpressing IRS induced the upregulation of the TAZ, RUNX2 and OCN expression. Furthermore, our results showed that it was LY294002 (the PI3K-Akt inhibitor), other than UO126 (the MEK-ERK inhibitor), that inhibited the IRS-1 induced upregulation of TAZ expression. Additionally, SiTAZ blocked the cell proliferation in G1 during the osteogenic differentiation of BMSCs. Taken together, we provided evidence to demonstrate that IRS-1 gene modification facilitates the osteogenic differentiation of rat BMSCs by increasing TAZ expression through the PI3K-Akt signaling pathway.This article has an associated First Person interview with the first author of the paper.

Three-Dimensional Spheroid Culture Increases Exosome Secretion from Mesenchymal Stem Cells

BACKGROUND

Mass production of exosomes is a prerequisite for their commercial utilization. This study investigated whether three-dimensional (3D) spheroid culture of mesenchymal stem cells (MSCs) could improve the production efficiency of exosomes and if so, what was the mechanism involved.

METHODS

We adopted two models of 3D spheroid culture using the hanging-drop (3D-HD) and poly(2-hydroxyethyl methacrylate) (poly-HEMA) coating methods (3D-PH). The efficiency of exosome production from MSCs in the 3D spheroids was compared with that of monolayer culture in various conditions. We then investigated the mechanism of the 3D spheroid culture-induced increase in exosome production.

RESULTS

The 3D-HD formed a single larger spheroid, while the 3D-PH formed multiple smaller ones. However, MSCs cultured on both types of spheroids produced significantly more exosomes than those cultured in conventional monolayer culture (2D). We then investigated the cause of the increased exosome production in terms of hypoxia within the 3D spheroids, high cell density, and non-adherent cell morphology. With increasing spheroid size, the efficiency of exosome production was the largest with the least amount of cells in both 3D-HD and 3D-PH. An increase in cell density in 2D culture (2D-H) was less efficient in exosome production than the conventional, lower cell density, 2D culture. Finally, when cells were plated at normal density on the poly-HEMA coated spheroids (3D-N-PH); they formed small aggregates of less than 10 cells and still produced more exosomes than those in the 2D culture when plated at the same density. We also found that the expression of F-actin was markedly reduced in the 3D-N-PH culture.

CONCLUSION

These results suggested that 3D spheroid culture produces more exosomes than 2D culture and the non-adherent round cell morphology itself might be a causative factor. The result of the present study could provide useful information to develop an optimal process for the mass production of exosomes.

Link Protein N-Terminal Peptide as a Potential Stimulating Factor for Stem Cell-Based Cartilage Regeneration

Background

Link protein N-terminal peptide (LPP) in extracellular matrix (ECM) of cartilage could induce synthesis of proteoglycans and collagen type II in cartilaginous cells. Cartilage stem/progenitor cells (CSPCs), the endogenous stem cells in cartilage, are important in cartilage degeneration and regeneration. We hypothesized that LPP could be a stimulator for stem cell-based cartilage regeneration by affecting biological behaviors of CSPC.

Methods

CSPCs were isolated from rat knee cartilage. We evaluated the promoting effect of LPP on proliferation, migration, and chondrogenic differentiation of CSPCs. The chondrogenic differentiation-related genes and proteins were quantitated. Three-dimensional culture of CSPC was conducted in the presence of TGF-β3 or LPP, and the harvested pellets were analyzed to assess the function of LPP on cartilage regeneration.

Results

LPP stimulated the proliferation of CSPC and accelerated the site-directional migration. Higher expression of SOX9, collagen II, and aggrecan were demonstrated in CSPCs treated with LPP. The pellets treated with LPP showed more distinct characteristics of chondroid differentiation than those with TGF-β3.

Conclusion

LPP showed application prospect in cartilage regeneration medicine by stimulating proliferation, migration, and chondrogenic differentiation of cartilage stem/progenitor cells.

Characteristics and Cardiomyogenic Potential of Rat Fetal Cardiac Progenitor Cells at Different Developmental Stage

In recent years, several kinds of cardiac progenitor cells have been identified and isolated from heart tissue. These cells showed differentiation potential into cardiomyocytes, smooth muscle cells, and endothelial cells in vitro and in vivo. Morphogenetic events are tightly regulated during development to determine cell destiny and reshape the embryonic lineage. In this study, we directly compared the characteristics of rat fetal cardiac progenitor cells (rFCPCs) isolated from the chamber formation stage at embryonic day 12 (E12) and at the septation stage of E15. Both kinds of rFCPCs expressed mesenchymal stem cell markers (CD105, CD73, and CD29) but not CD34 and CD45. The E12 rFCPCs expressed a high level of Oct4 compared to E15 until passage 5 and showed a steep decline of Nkx2.5 expression at passage 5. However, Nkx2.5 expression at E15 was maintained until passage 5 and Oct4 expression slightly increased at passage 5. We also detected an intense staining for Oct4 antibody in E12 heart tissue sections. The average doubling time of the E12 rFCPCs from passage 3 to passage 15 was about 5 hours longer than E15. These cells could also be induced into cardiomyocytes expressing α-MHC, cTnT, cTnC, and Cx43 under cardiomyogenic culture conditions and rFCPCs at E15 showed more intense staining of α-MHC than cells at E12 by immunocytochemistry. Taken together, our results show that developmental differences between E12 and E15 may influence their properties and differentiation. Furthermore those differences should be considered when deciding on the optimal cell source for cell replacement therapy in cardiovascular regeneration.