Biodegradable poly(caprolactone fumarate) 3D printed scaffolds for segmental bone defects within the Masquelet technique

Segmental bone defects, often clinically treated with nondegradable poly(methylmethacrylate) (PMMA) in multistage surgeries, present a significant clinical challenge. Our study investigated the efficacy of 3D printed biodegradable polycaprolactone fumarate (PCLF)/PCL spacers in a one-stage surgical intervention for these defects, focusing on early bone regeneration influenced by spacer porosities. We compared nonporous PCLF/PCL and PMMA spacers, conventionally molded into cylinders, with porous PCLF/PCL spacers, 3D printed to structurally mimic segmental defects in rat femurs for a 4-week implantation study. Histological analysis, including tissue staining and immunohistochemistry with bone-specific antibodies, was conducted for histomorphometry evaluation. The PCLF/PCL spacers demonstrated compressive properties within 6 ± 0.5 MPa (strength) and 140 ± 15 MPa (modulus). Both porous PCLF/PCL and Nonporous PMMA formed collagen-rich membranes (PCLF/PCL: 92% ± 1.3%, PMMA: 86% ± 1.5%) similar to those induced in the Masquelet technique, indicating PCLF/PCL's potential for one-stage healing. Immunohistochemistry confirmed biomarkers for tissue regeneration, underscoring PCLF/PCL's regenerative capabilities. This research highlights PCLF/PCL scaffolds' ability to induce membrane formation in critical-sized segmental bone defects, supporting their use in one-stage surgery. Both solid and porous PCLF/PCL spacers showed adequate compressive properties, with the porous variants exhibiting BMP-2 expression and woven bone formation, akin to clinical standard PMMA. Notably, the early ossification of the membrane into the pores of porous scaffolds suggests potential for bone interlocking and regeneration, potentially eliminating the need for a second surgery required for PMMA spacers. The biocompatibility and biodegradability of PCLF/PCL make them promising alternatives for treating critical bone defects, especially in vulnerable patient groups.

Visible light-induced 3D bioprinted injectable scaffold for minimally invasive tissue regeneration

Pre-formed hydrogel scaffolds have emerged as favorable vehicles for tissue regeneration, promoting minimally invasive treatment of native tissue. However, due to the high degree of swelling and inherently poor mechanical properties, development of complex structural hydrogel scaffolds at different dimensional scales has been a continuous challenge. Herein, we take a novel approach at the intersections of engineering design and bio-ink chemistry to develop injectable pre-formed structural hydrogel scaffolds fabricated via visible light (VL) induced digital light processing (DLP). In this study, we first determined the minimum concentration of poly(ethylene glycol) diacrylate (PEGDA) to be added to the gelatin methacrylate (GelMA) bio-ink in order to achieve scalable and high printing-fidelity with desired cell adhesion, viability, spreading, and osteogenic differentiation characteristics. Despite the advantages of hybrid GelMA-PEGDA bio-ink in improving scalability and printing-fidelity, compressibility, shape-recovery, and injectability of the 3D bioprinted scaffolds were compromised. To restore these needed characteristics for minimally invasive tissue regeneration applications, we performed topological optimization to design highly compressible and injectable pre-formed (i.e., 3D bioprinted) microarchitectural scaffolds. The designed injectable pre-formed microarchitectural scaffolds showed a great capacity to retain the viability of the encapsulated cells (>72 % after 10 cycles of injection). Lastly, ex ovo chicken chorioallantoic membrane (CAM) studies revealed that the optimized injectable pre-formed hybrid hydrogel scaffold is biocompatible and supports angiogenic growth.

MicroRNA-101a enhances trabecular bone accrual in male mice

High-throughput microRNA sequencing was performed during differentiation of MC3T3-E1 osteoblasts to develop working hypotheses for specific microRNAs that control osteogenesis. The expression data show that miR-101a, which targets the mRNAs for the epigenetic enzyme Ezh2 and many other proteins, is highly upregulated during osteoblast differentiation and robustly expressed in mouse calvaria. Transient elevation of miR-101a suppresses Ezh2 levels, reduces tri-methylation of lysine 27 in histone 3 (H3K27me3; a heterochromatic mark catalyzed by Ezh2), and accelerates mineralization of MC3T3-E1 osteoblasts. We also examined skeletal phenotypes of an inducible miR-101a transgene under direct control of doxycycline administration. Experimental controls and mir-101a over-expressing mice were exposed to doxycycline in utero and postnatally (up to 8 weeks of age) to maximize penetrance of skeletal phenotypes. Male mice that over-express miR-101a have increased total body weight and longer femora. MicroCT analysis indicate that these mice have increased trabecular bone volume fraction, trabecular number and trabecular thickness with reduced trabecular spacing as compared to controls. Histomorphometric analysis demonstrates a significant reduction in osteoid volume to bone volume and osteoid surface to bone surface. Remarkably, while female mice also exhibit a significant increase in bone length, no significant changes were noted by microCT (trabecular bone parameters) and histomorphometry (osteoid parameters). Hence, miR-101a upregulation during osteoblast maturation and the concomitant reduction in Ezh2 mediated H3K27me3 levels may contribute to the enhanced trabecular bone parameters in male mice. However, the sex-specific effect of miR-101a indicates that more intricate epigenetic mechanisms mediate physiological control of bone formation and homeostasis.

Injectable catalyst-free "click" organic-inorganic nanohybrid (click-ON) cement for minimally invasive in vivo bone repair

Injectable polymers have attracted intensive attention in tissue engineering and drug delivery applications. Current injectable polymer systems often require free-radical or heavy-metal initiators and catalysts for the crosslinking process, which may be extremely toxic to the human body. Here, we report a novel polyhedral oligomeric silsesquioxane (POSS) based strain-promoted alkyne-azide cycloaddition (SPAAC) "click" organic-inorganic nanohybrids (click-ON) system that can be click-crosslinked without any toxic initiators or catalysts. The click-ON scaffolds supported excellent adhesion, proliferation, and osteogenesis of stem cells. In vivo evaluation using a rat cranial defect model showed outstanding bone formation with minimum cytotoxicity. Essential osteogenic alkaline phosphatase (ALP) and vascular CD31 marker expression were detected on the defect site, indicating excellent support of in vivo osteogenesis and vascularization. Using salt leaching techniques, an injectable porous click-ON cement was developed to create porous structures and support better in vivo bone regeneration. Beyond defect filling, the click-ON cement also showed promising application for spinal fusion using rabbits as a model. Compared to the current clinically used poly (methyl methacrylate) (PMMA) cement, this click-ON cement showed great advantages of low heat generation, better biocompatibility and biodegradability, and thus has great potential for bone and related tissue engineering applications.

Mechanical strain-mediated reduction in RANKL expression is associated with RUNX2 and BRD2

Mechanical loading-related strains trigger bone formation by osteoblasts while suppressing resorption by osteoclasts, uncoupling the processes of formation and resorption. Osteocytes may orchestrate this process in part by secreting sclerostin (SOST), which inhibits osteoblasts, and expressing receptor activator of nuclear factor-κB ligand (RANKL/TNFSF11) which recruits osteoclasts. Both SOST and RANKL are targets of the master osteoblastic transcription factor RUNX2. Subjecting human osteoblastic Saos-2 cells to strain by four point bending down-regulates their expression of SOST and RANKL without altering RUNX2 expression. RUNX2 knockdown increases basal SOST expression, but does not alter SOST down-regulation following strain. Conversely, RUNX2 knockdown does not alter basal RANKL expression, but prevents its down-regulation by strain. Chromatin immunoprecipitation revealed RUNX2 occupies a region of the RANKL promoter containing a consensus RUNX2 binding site and its occupancy of this site decreases following strain. The expression of epigenetic acetyl and methyl writers and readers was quantified by RT-qPCR to investigate potential epigenetic bases for this change. Strain and RUNX2 knockdown both down-regulate expression of the bromodomain acetyl reader BRD2. BRD2 and RUNX2 co-immunoprecipitate, suggesting interaction within regulatory complexes, and BRD2 was confirmed to interact with the RUNX2 promoter. BRD2 also occupies the RANKL promoter and its occupancy was reduced following exposure to strain. Thus, RUNX2 may contribute to bone remodeling by suppressing basal SOST expression, while facilitating the acute strain-induced down-regulation of RANKL through a mechanosensitive epigenetic loop involving BRD2.

Loss of histone methyltransferase Ezh2 stimulates an osteogenic transcriptional program in chondrocytes but does not affect cartilage development

Ezh2 is a histone methyltransferase that suppresses osteoblast maturation and skeletal development. We evaluated the role of Ezh2 in chondrocyte lineage differentiation and endochondral ossification. Ezh2 was genetically inactivated in the mesenchymal, osteoblastic, and chondrocytic lineages in mice using the Prrx1-Cre, Osx1-Cre, and Col2a1-Cre drivers, respectively. WT and conditional knockout mice were phenotypically assessed by gross morphology, histology, and micro-CT imaging. Ezh2-deficient chondrocytes in micromass culture models were evaluated using RNA-Seq, histologic evaluation, and Western blotting. Aged mice with Ezh2 deficiency were also evaluated for premature development of osteoarthritis using radiographic analysis. Ezh2 deficiency in murine chondrocytes reduced bone density at 4 weeks of age but caused no other gross developmental effects. Knockdown of Ezh2 in chondrocyte micromass cultures resulted in a global reduction in trimethylation of histone 3 lysine 27 (H3K27me3) and altered differentiation in vitro RNA-Seq analysis revealed enrichment of an osteogenic gene expression profile in Ezh2-deficient chondrocytes. Joint development proceeded normally in the absence of Ezh2 in chondrocytes without inducing excessive hypertrophy or premature osteoarthritis in vivo In summary, loss of Ezh2 reduced H3K27me3 levels, increased the expression of osteogenic genes in chondrocytes, and resulted in a transient post-natal bone phenotype. Remarkably, Ezh2 activity is dispensable for normal chondrocyte maturation and endochondral ossification in vivo, even though it appears to have a critical role during early stages of mesenchymal lineage commitment.

Abstract 2264: RNA sequencing based analysis of transposon-induced tumors reveals novel insights into cancer pathogenesis and progression

Current challenges in oncology include the discovery of drivers suitable for targeting using small molecules or antibodies and predictive animal models. We're addressing these challenges in several ways. We have developed mouse models using the Sleeping Beauty (SB) transposon system to perform unbiased, forward genetic screens to define strong candidate cancer genes. Further, our studies and others have utilized transposon mutagenesis to derive cancers from all three germ layers including carcinomas, sarcomas, neuroectodermal tumors, and hematopoietic malignancies. We hypothesize that data from these screens will help to identify genetic drivers of human cancer that are altered at the gene copy number or epigenetic levels. Our T2/Onc SB transposons create fusions with endogenous gene transcripts and RNA sequencing (RNA-seq) reveals the genes targeted in the tumor. From these results, correlations can be drawn between the alteration of specific genes and changes in tumor gene expression patterns. Thus, the goals of our recent research have been to discover novel associations between SB-induced tumor phenotypes and specific driver gene alterations (i.e. the tumor genotype). Moreover, RNA-seq has also revealed tumor molecular subtypes, in many cases with correlating transposon insertion mutations. Several examples will be described: mammary tumors, osteosarcoma (OS), medulloblastoma and central nervous system primitive neuro-ectodermal tumors. In each case, RNA-seq has revealed novel genotype-phenotype correlations including drivers of high cell cycle activity, metastasis, white blood cell exclusion from the tumor, SHH pathway activation, and hormone receptor signaling. These models provide a source of genetically heterogenous tumors with the same initiating mutation useful for identifying cooperating pathways and drivers of specific tumor phenotypes. Secondly, we are using SB transposon mutagenesis to understand the genetic basis of chemotherapy resistance in cancer including OS. In our OS model, SB mutagenesis is an ongoing process due to the constitutive expression of SB transposase, which permits the continued mobilization of transposons. We hypothesize that in vivo treatment with chemotherapy agents will allow tumor cells that contain transposon mutations in chemoresistance genes to persist. Preliminary studies with primary tumor cells derived from SB-enhanced OS tumors demonstrate resistance to combination chemotherapy treatment in vivo. Further analysis to identify candidate chemotherapy resistance genes are currently underway.

Citation Format: Emily T. Camilleri, Pauli J. Beckmann, Jon D. Larson, Morito Kurata, Jingmin Shu, Emily Pope, Wendy A. Hudson, Nuri A. Temiz, Susan K. Rathe, Rebecca S. LaRue, Anne E. Sarver, Milcah C. Scott, Jyotika Varshney, Jaime F. Modiano, Branden S. Moriarity, Aaron L. Sarver, Somasekar Seshagiri, David A. Largaespada. RNA sequencing based analysis of transposon-induced tumors reveals novel insights into cancer pathogenesis and progression [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 2264.

Enhancer of zeste homolog 2 (Ezh2) controls bone formation and cell cycle progression during osteogenesis in mice

Epigenetic mechanisms control skeletal development and osteoblast differentiation. Pharmacological inhibition of the histone 3 Lys-27 (H3K27) methyltransferase enhancer of zeste homolog 2 (EZH2) in WT mice enhances osteogenesis and stimulates bone formation. However, conditional genetic loss of Ezh2 early in the mesenchymal lineage (i.e. through excision via Prrx1 promoter-driven Cre) causes skeletal abnormalities due to patterning defects. Here, we addressed the key question of whether Ezh2 controls osteoblastogenesis at later developmental stages beyond patterning. We show that Ezh2 loss in committed pre-osteoblasts by Cre expression via the osterix/Sp7 promoter yields phenotypically normal mice. These Ezh2 conditional knock-out mice (Ezh2 cKO) have normal skull bones, clavicles, and long bones but exhibit increased bone marrow adiposity and reduced male body weight. Remarkably, in vivo Ezh2 loss results in a low trabecular bone phenotype in young mice as measured by micro-computed tomography and histomorphometry. Thus, Ezh2 affects bone formation stage-dependently. We further show that Ezh2 loss in bone marrow-derived mesenchymal cells suppresses osteogenic differentiation and impedes cell cycle progression as reflected by decreased metabolic activity, reduced cell numbers, and changes in cell cycle distribution and in expression of cell cycle markers. RNA-Seq analysis of Ezh2 cKO calvaria revealed that the cyclin-dependent kinase inhibitor Cdkn2a is the most prominent cell cycle target of Ezh2 Hence, genetic loss of Ezh2 in mouse pre-osteoblasts inhibits osteogenesis in part by inducing cell cycle changes. Our results suggest that Ezh2 serves a bifunctional role during bone formation by suppressing osteogenic lineage commitment while simultaneously facilitating proliferative expansion of osteoprogenitor cells.

Extracellular matrix protein production in human adipose-derived mesenchymal stem cells on three-dimensional polycaprolactone (PCL) scaffolds responds to GDF5 or FGF2

Purpose

The poor healing potential of intra-articular ligament injuries drives a need for the development of novel, viable 'neo-ligament' alternatives. Ex vivo approaches combining stem cell engineering, 3-dimensional biocompatible scaffold design and enhancement of biological and biomechanical functionality via the introduction of key growth factors and morphogens, represent a promising solution to ligament regeneration.

Methods

We investigated growth, differentiation and extracellular matrix (ECM) protein production of human adipose-derived mesenchymal stem/stromal cells (MSCs), cultured in 5% human platelet lysate (PL) and seeded on three-dimensional polycaprolactone (PCL) scaffolds, in response to the connective-tissue related ligands fibroblast growth factor 2 (basic) (FGF2) and growth and differentiation factor-5 (GDF5). Phenotypic alterations of MSCs under different biological conditions were examined using cell viability assays, real time qPCR analysis of total RNA, as well as immunofluorescence microscopy.

Results

Phenotypic conversion of MSCs into ECM producing fibroblastic cells proceeds spontaneously in the presence of human platelet lysate. Administration of FGF2 and/or GDF5 enhances production of mRNAs for several ECM proteins including Collagen types I and III, as well as Tenomodulin (e.g., COL1A1, TNMD), but not Tenascin-C (TNC). Differences in the in situ deposition of ECM proteins Collagen type III and Tenascin-C were validated by immunofluorescence microscopy.

Summary

Treatment of MSCs with FGF2 and GDF5 was not synergistic and occasionally antagonistic for ECM production. Our results suggest that GDF5 alone enhances the conversion of MSCs to fibroblastic cells possessing a phenotype consistent with that of connective-tissue fibroblasts.

Histone Deacetylase 3 Deletion in Mesenchymal Progenitor Cells Hinders Long Bone Development

Long bone formation is a complex process that requires precise transcriptional control of gene expression programs in mesenchymal progenitor cells. Histone deacetylases (Hdacs) coordinate chromatin structure and gene expression by enzymatically removing acetyl groups from histones and other proteins. Hdac inhibitors are used clinically to manage mood disorders, cancers, and other conditions but are teratogenic to the developing skeleton and increase fracture risk in adults. In this study, the functions of Hdac3, one of the enzymes blocked by current Hdac inhibitor therapies, in skeletal mesenchymal progenitor cells were determined. Homozygous deletion of Hdac3 in Prrx1-expressing cells prevented limb lengthening, altered pathways associated with endochondral and intramembranous bone development, caused perinatal lethality, and slowed chondrocyte and osteoblast differentiation in vitro. Transcriptomic analysis revealed that Hdac3 regulates vastly different pathways in mesenchymal cells expressing the Prxx1-Cre driver than those expressing the Col2-CreERT driver. Notably, Fgf21 was elevated in Hdac3-CKO_Prrx1 limbs as well as in chondrogenic cells exposed to Hdac3 inhibitors. Elevated expression of Mmp3 and Mmp10 transcripts was also observed. In conclusion, Hdac3 regulates distinct pathways in mesenchymal cell populations and is required for mesenchymal progenitor cell differentiation and long bone development. © 2017 American Society for Bone and Mineral Research.

Molecular Validation of Chondrogenic Differentiation and Hypoxia Responsiveness of Platelet-Lysate Expanded Adipose Tissue-Derived Human Mesenchymal Stromal Cells

OBJECTIVE

To determine the optimal environmental conditions for chondrogenic differentiation of human adipose tissue-derived mesenchymal stromal/stem cells (AMSCs). In this investigation we specifically investigate the role of oxygen tension and 3-dimensional (3D) culture systems.

DESIGN

Both AMSCs and primary human chondrocytes were cultured for 21 days in chondrogenic media under normoxic (21% oxygen) or hypoxic (2% oxygen) conditions using 2 distinct 3D culture methods (high-density pellets and poly-ε-caprolactone [PCL] scaffolds). Histologic analysis of chondro-pellets and the expression of chondrocyte-related genes as measured by reverse transcriptase quantitative polymerase chain reaction were used to evaluate the efficiency of differentiation.

RESULTS

AMSCs are capable of expressing established cartilage markers including COL2A1, ACAN, and DCN when grown in chondrogenic differentiation media as determined by gene expression and histologic analysis of cartilage markers. Expression of several cartilage-related genes was enhanced by low oxygen tension, including ACAN and HAPLN1. The pellet culture environment also promoted the expression of hypoxia-inducible cartilage markers compared with cells grown on 3D scaffolds.

CONCLUSIONS

Cell type-specific effects of low oxygen and 3D environments indicate that mesenchymal cell fate and differentiation potential is remarkably sensitive to oxygen. Genetic programming of AMSCs to a chondrocytic phenotype is effective under hypoxic conditions as evidenced by increased expression of cartilage-related biomarkers and biosynthesis of a glycosaminoglycan-positive matrix. Lower local oxygen levels within cartilage pellets may be a significant driver of chondrogenic differentiation.

Autologous Mesenchymal Stem Cells, Applied in a Bioabsorbable Matrix, for Treatment of Perianal Fistulas in Patients With Crohn's Disease

In patients with Crohn's disease, perianal fistulas recur frequently, causing substantial morbidity. We performed a 12-patient, 6-month, phase 1 trial to determine whether autologous mesenchymal stem cells, applied in a bioabsorbable matrix, can heal the fistula. Fistula repair was not associated with any serious adverse events related to mesenchymal stem cells or plug placement. At 6 months, 10 of 12 patients (83%) had complete clinical healing and radiographic markers of response. We found placement of mesenchymal stem cell-coated matrix fistula plugs in 12 patients with chronic perianal fistulas to be safe and lead to clinical healing and radiographic response in 10 patients. ClinicalTrials.gov Identifier: NCT01915927.

Hypoxia-related microRNA-210 is a diagnostic marker for discriminating osteoblastoma and osteosarcoma

Osteoblastoma is a benign bone tumor that can often be difficult to distinguish from malignant osteosarcoma. Because misdiagnosis can result in unfavorable clinical outcomes, we have investigated microRNAs as potential diagnostic biomarkers for distinguishing between these two tumor types. Next generation RNA sequencing was used as an expression screen to evaluate >2,000 microRNAs present in tissue derived from rare formalin fixed paraffin embedded (FFPE) archival tumor specimens. MicroRNAs displaying the greatest ability to discriminate between these two tumors were validated on an independent tumor set, using qPCR assays. Initial screening by RNA-seq identified four microRNA biomarker candidates. Expression of three miRNAs (miR-451a, miR-144-3p, miR-486-5p) was higher in osteoblastoma, while the miR-210 was elevated in osteosarcoma. Validation of these microRNAs on an independent data set of 22 tumor specimens by qPCR revealed that miR-210 is the most discriminating marker. This microRNA displays low levels of expression across all of the osteoblastoma specimens and robust expression in the majority of the osteosarcoma specimens. Application of these biomarkers to a clinical test case showed that these microRNA biomarkers permit re-classification of a misdiagnosed FFPE tumor sample from osteoblastoma to osteosarcoma. Our findings establish that the hypoxia-related miR-210 is a discriminatory marker that distinguishes between osteoblastoma and osteosarcoma. This discovery provides a complementary molecular approach to support pathological classification of two diagnostically challenging musculoskeletal tumors. Because miR-210 is linked to the cellular hypoxia response, its detection may be linked to well-established pro-angiogenic and metastatic roles of hypoxia in osteosarcomas and other tumor cell types. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:1137-1146, 2017.

RNA-seq analysis of clinical-grade osteochondral allografts reveals activation of early response genes

Preservation of osteochondral allografts used for transplantation is critical to ensure favorable outcomes for patients after surgical treatment of cartilage defects. To study the biological effects of protocols currently used for cartilage storage, we investigated differences in gene expression between stored allograft cartilage and fresh cartilage from living donors using high throughput molecular screening strategies. We applied next generation RNA sequencing (RNA-seq) and real-time reverse transcription quantitative polymerase chain reaction (RT-qPCR) to assess genome-wide differences in mRNA expression between stored allograft cartilage and fresh cartilage tissue from living donors. Gene ontology analysis was used to characterize biological pathways associated with differentially expressed genes. Our studies establish reduced levels of mRNAs encoding cartilage related extracellular matrix (ECM) proteins (i.e., COL1A1, COL2A1, COL10A1, ACAN, DCN, HAPLN1, TNC, and COMP) in stored cartilage. These changes occur concomitantly with increased expression of "early response genes" that encode transcription factors mediating stress/cytoprotective responses (i.e., EGR1, EGR2, EGR3, MYC, FOS, FOSB, FOSL1, FOSL2, JUN, JUNB, and JUND). The elevated expression of "early response genes" and reduced levels of ECM-related mRNAs in stored cartilage allografts suggests that tissue viability may be maintained by a cytoprotective program that reduces cell metabolic activity. These findings have potential implications for future studies focused on quality assessment and clinical optimization of osteochondral allografts used for cartilage transplantation. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:1950-1959, 2016.

Safety Studies for Use of Adipose Tissue-Derived Mesenchymal Stromal/Stem Cells in a Rabbit Model for Osteoarthritis to Support a Phase I Clinical Trial

Adipose‐derived mesenchymal stem cells (AMSCs) offer potential as a therapeutic option for clinical applications in musculoskeletal regenerative medicine because of their immunomodulatory functions and capacity for trilineage differentiation. In preparation for a phase I clinical trial using AMSCs to treat patients with osteoarthritis, we carried out preclinical studies to assess the safety of human AMSCs within the intra‐articular joint space. Culture‐expanded human AMSCs grown in human platelet‐lysate were delivered via intra‐articular injections into normal healthy rabbit knees and knees at risk for the development of osteoarthritis after bilateral medial anterior hemimeniscectomy. Treatment outcomes and safety were evaluated by assessing the general health, function, and behavior of the animals. Joint tissues were analyzed by x‐ray, magnetic resonance imaging, and histopathology. Intra‐articular AMSC therapy was well tolerated in this study. We did not observe adverse systemic reactions, nor did we find evidence of damage to intra‐articular joint tissues. Thus, the data generated in this study show a favorable safety profile for AMSCs within the joint space in support of a phase I clinical trial evaluating the clinical utility of AMSCs to treat osteoarthritis. Stem Cells Translational Medicine2017;6:910–922

Enhancer of Zeste Homolog 2 Inhibition Stimulates Bone Formation and Mitigates Bone Loss Caused by Ovariectomy in Skeletally Mature Mice

Perturbations in skeletal development and bone degeneration may result in reduced bone mass and quality, leading to greater fracture risk. Bone loss is mitigated by bone protective therapies, but there is a clinical need for new bone-anabolic agents. Previous work has demonstrated that Ezh2 (enhancer of zeste homolog 2), a histone 3 lysine 27 (H3K27) methyltransferase, suppressed differentiation of osteogenic progenitors. Here, we investigated whether inhibition of Ezh2 can be leveraged for bone stimulatory applications. Pharmacologic inhibition and siRNA knockdown of Ezh2 enhanced osteogenic commitment of MC3T3 preosteoblasts. Next generation RNA sequencing of mRNAs and real time quantitative PCR profiling established that Ezh2 inactivation promotes expression of bone-related gene regulators and extracellular matrix proteins. Mechanistically, enhanced gene expression was linked to decreased H3K27 trimethylation (H3K27me3) near transcriptional start sites in genome-wide sequencing of chromatin immunoprecipitations assays. Administration of an Ezh2 inhibitor modestly increases bone density parameters of adult mice. Furthermore, Ezh2 inhibition also alleviated bone loss in an estrogen-deficient mammalian model for osteoporosis. Ezh2 inhibition enhanced expression of Wnt10b and Pth1r and increased the BMP-dependent phosphorylation of Smad1/5. Thus, these data suggest that inhibition of Ezh2 promotes paracrine signaling in osteoblasts and has bone-anabolic and osteoprotective potential in adults.

Identification and validation of multiple cell surface markers of clinical-grade adipose-derived mesenchymal stromal cells as novel release criteria for good manufacturing practice-compliant production

Background

Clinical translation of mesenchymal stromal cells (MSCs) necessitates basic characterization of the cell product since variability in biological source and processing of MSCs may impact therapeutic outcomes. Although expression of classical cell surface markers (e.g., CD90, CD73, CD105, and CD44) is used to define MSCs, identification of functionally relevant cell surface markers would provide more robust release criteria and options for quality control. In addition, cell surface expression may distinguish between MSCs from different sources, including bone marrow-derived MSCs and clinical-grade adipose-derived MSCs (AMSCs) grown in human platelet lysate (hPL).

Methods

In this work we utilized quantitative PCR, flow cytometry, and RNA-sequencing to characterize AMSCs grown in hPL and validated non-classical markers in 15 clinical-grade donors.

Results

We characterized the surface marker transcriptome of AMSCs, validated the expression of classical markers, and identified nine non-classical markers (i.e., CD36, CD163, CD271, CD200, CD273, CD274, CD146, CD248, and CD140B) that may potentially discriminate AMSCs from other cell types. More importantly, these markers exhibit variability in cell surface expression among different cell isolates from a diverse cohort of donors, including freshly prepared, previously frozen, or proliferative state AMSCs and may be informative when manufacturing cells.

Conclusions

Our study establishes that clinical-grade AMSCs expanded in hPL represent a homogeneous cell culture population according to classical markers,. Additionally, we validated new biomarkers for further AMSC characterization that may provide novel information guiding the development of new release criteria.

Clinical trials

Use of Autologous Bone Marrow Aspirate Concentrate in Painful Knee Osteoarthritis (BMAC): Clinicaltrials.gov NCT01931007. Registered August 26, 2013.

MSC for Occlusive Disease of the Kidney: Clinicaltrials.gov NCT01840540. Registered April 23, 2013.

Mesenchymal Stem Cell Therapy in Multiple System Atrophy: Clinicaltrials.gov NCT02315027. Registered October 31, 2014.

Efficacy and Safety of Adult Human Mesenchymal Stem Cells to Treat Steroid Refractory Acute Graft Versus Host Disease. Clinicaltrials.gov NCT00366145. Registered August 17, 2006.

A Dose-escalation Safety Trial for Intrathecal Autologous Mesenchymal Stem Cell Therapy in Amyotrophic Lateral Sclerosis. Clinicaltrials.gov NCT01609283. Registered May 18, 2012.

Electronic supplementary material

The online version of this article (doi:10.1186/s13287-016-0370-8) contains supplementary material, which is available to authorized users.

Genetic and epigenetic variants in the MTHFR gene are not associated with non-Hodgkin lymphoma

The methylenetetrahydrofolate reductase (MTHFR) gene codes for the MTHFR enzyme which plays a key role in the pathway of folate and methionine metabolism. Polymorphisms of genes in this pathway affect its regulation and have been linked to lymphoma. In this study we examined whether we could detect an association between two common non-synonymous MTHFR polymorphisms, 677C > T (rs1801133) and 1298A > C (rs1801131), and susceptibility to non-Hodgkin lymphoma (NHL) in an Australian case-control cohort. We found no significant differences between genotype or allele frequencies for either polymorphisms between lymphoma cases and controls. We also explored whether epigenetic modification of MTHFR, specifically DNA methylation of a CpG island in the MTHFR promoter region, is associated with NHL using blood samples from patients. No difference in methylation levels was detected between the case and control samples suggesting that although hypermethylation of MTHFR has been reported in tumour tissues, particularly in the diffuse large B-cell lymphoma subtype of NHL, methylation of this MTHFR promoter CpG island is not a suitable epigenetic biomarker for NHL diagnosis or prognosis in peripheral blood samples. Further studies into epigenetic variants could focus on genes that are robustly associated with NHL susceptibility.

Effect of heparin on the biological properties and molecular signature of human mesenchymal stem cells

Chronic use of heparin as an anti-coagulant for the treatment of thrombosis or embolism invokes many adverse systemic events including thrombocytopenia, vascular reactions and osteoporosis. Here, we addressed whether adverse effects might also be directed to mesenchymal stem cells that reside in the bone marrow compartment. Harvested human bone marrow-derived mesenchymal stem cells (hMSCs) were exposed to varying doses of heparin and their responses profiled. At low doses (<200 ng/ml), serial passaging with heparin exerted a variable effect on hMSC proliferation and multipotentiality across multiple donors, while at higher doses (≥ 100 μg/ml), heparin supplementation inhibited cell growth and increased both senescence and cell size. Gene expression profiling using cDNA arrays and RNA-seq analysis revealed pleiotropic effects of low-dose heparin on signaling pathways essential to hMSC growth and differentiation (including the TGFβ/BMP superfamily, FGFs, and Wnts). Cells serially passaged in low-dose heparin possess a donor-dependent gene signature that reflects their altered phenotype. Our data indicate that heparin supplementation during the culturing of hMSCs can alter their biological properties, even at low doses. This warrants caution in the application of heparin as a culture supplement for the ex vivo expansion of hMSCs. It also highlights the need for careful evaluation of the bone marrow compartment in patients receiving chronic heparin treatment.

RNA sequencing reveals a depletion of collagen targeting microRNAs in Dupuytren's disease

Background

Dupuytren’s disease is an inherited disorder in which patients develop fibrotic contractures of the hand. Current treatment strategies include surgical excision or enzymatic digestion of fibrotic tissue. MicroRNAs, which are key posttranscriptional regulators of genes expression, have been shown to play an important regulatory role in disorders of fibrosis. Therefore in this investigation, we apply high throughput next generation RNA sequencing strategies to characterize microRNA expression in diseased and healthy palmar fascia to elucidate molecular mechanisms responsible for pathogenic fibrosis.

Methods

We applied high throughput RNA sequencing techniques to quantify the expression of all known human microRNAs in Dupuytren’s and control palmar fascia. MicroRNAs that were differentially expressed between diseased and healthy tissue samples were used for computational target prediction using the bioinformatics tool ComiR. Molecular pathways that were predicted to be differentially expressed based on computational analysis were validated by performing RT-qPCR on RNA extracted from diseased and non-diseased palmar fascia biopsies.

Results

A comparison of microRNAs expressed in Dupuytren’s fascia and control fascia identified 74 microRNAs with a 2-fold enrichment in Dupuytren’s tissue, and 32 microRNAs with enrichment in control fascia. Computational target prediction for differentially expressed microRNAs indicated preferential targeting of collagens and extracellular matrix related proteins in control palmar fascia. RT-qPCR confirmed the decreased expression of microRNA targeted collagens in control palmar fascia tissues.

Discussion

Control palmar fascia show decreased expression of mRNAs encoding collagens that are preferentially targeted by microRNAs enriched in non-diseased fascia. Thus alterations in microRNA regulatory networks may play an important role in driving the pathogenic fibrosis seen in Dupuytren’s disease via direct regulatory effects on extracellular matrix protein synthesis.

Conclusion

Dupuytren’s fascia and healthy palmar fascia can be distinguished by unique microRNA profiles, which are predicted to preferentially target collagens and other extracellular matrix proteins.

Electronic supplementary material

The online version of this article (doi:10.1186/s12920-015-0135-8) contains supplementary material, which is available to authorized users.

Epigenetic Control of Skeletal Development by the Histone Methyltransferase Ezh2

Epigenetic control of gene expression is critical for normal fetal development. However, chromatin-related mechanisms that activate bone-specific programs during osteogenesis have remained underexplored. Therefore, we investigated the expression profiles of a large cohort of epigenetic regulators (>300) during osteogenic differentiation of human mesenchymal cells derived from the stromal vascular fraction of adipose tissue (AMSCs). Molecular analyses establish that the polycomb group protein EZH2 (enhancer of zeste homolog 2) is down-regulated during osteoblastic differentiation of AMSCs. Chemical inhibitor and siRNA knockdown studies show that EZH2, a histone methyltransferase that catalyzes trimethylation of histone 3 lysine 27 (H3K27me3), suppresses osteogenic differentiation. Blocking EZH2 activity promotes osteoblast differentiation and suppresses adipogenic differentiation of AMSCs. High throughput RNA sequence (mRNASeq) analysis reveals that EZH2 inhibition stimulates cell cycle inhibitory proteins and enhances the production of extracellular matrix proteins. Conditional genetic loss of Ezh2 in uncommitted mesenchymal cells (Prrx1-Cre) results in multiple defects in skeletal patterning and bone formation, including shortened forelimbs, craniosynostosis, and clinodactyly. Histological analysis and mRNASeq profiling suggest that these effects are attributable to growth plate abnormalities and premature cranial suture closure because of precocious maturation of osteoblasts. We conclude that the epigenetic activity of EZH2 is required for skeletal patterning and development, but EZH2 expression declines during terminal osteoblast differentiation and matrix production.

Human Mesenchymal Stem Cells Retain Multilineage Differentiation Capacity Including Neural Marker Expression after Extended In Vitro Expansion

The suitability of human mesenchymal stem cells (hMSCs) in regenerative medicine relies on retention of their proliferative expansion potential in conjunction with the ability to differentiate toward multiple lineages. Successful utilisation of these cells in clinical applications linked to tissue regeneration requires consideration of biomarker expression, time in culture and donor age, as well as their ability to differentiate towards mesenchymal (bone, cartilage, fat) or non-mesenchymal (e.g., neural) lineages. To identify potential therapeutic suitability we examined hMSCs after extended expansion including morphological changes, potency (stemness) and multilineage potential. Commercially available hMSC populations were expanded in vitro for > 20 passages, equating to > 60 days and > 50 population doublings. Distinct growth phases (A-C) were observed during serial passaging and cells were characterised for stemness and lineage markers at representative stages (Phase A: P+5, approximately 13 days in culture; Phase B: P+7, approximately 20 days in culture; and Phase C: P+13, approximately 43 days in culture). Cell surface markers, stem cell markers and lineage-specific markers were characterised by FACS, ICC and Q-PCR revealing MSCs maintained their multilineage potential, including neural lineages throughout expansion. Co-expression of multiple lineage markers along with continued CD45 expression in MSCs did not affect completion of osteogenic and adipogenic specification or the formation of neurospheres. Improved standardised isolation and characterisation of MSCs may facilitate the identification of biomarkers to improve therapeutic efficacy to ensure increased reproducibility and routine production of MSCs for therapeutic applications including neural repair.

Histone deacetylase inhibition destabilizes the multi-potent state of uncommitted adipose-derived mesenchymal stromal cells

Human adipose-derived mesenchymal stromal cells (AMSCs) grown in platelet lysate are promising agents for therapeutic tissue regeneration. Here, we investigated whether manipulation of epigenetic events by the clinically relevant histone deacetylase inhibitor suberoylanilide hydroxamic acid (SAHA) alters differentiation of AMSCs. The multipotency of AMSCs was validated by their ability to differentiate into osteogenic, chondrogenic, and adipogenic lineages. High-throughput RNA sequencing and RT-qPCR established that human histone deacetylases (HDAC1 to HDAC11, and SIRT1 to SIRT7) are differentially expressed in AMSCs. SAHA induces hyper-acetylation of histone H3 and H4, stimulates protein expression of the HDAC-responsive gene SLC9A3R1/NHERF1 and modulates the AKT/FOXO1 pathway. Biologically, SAHA interferes with osteogenic, chondrogenic and adipogenic lineage commitment of multipotent AMSCs. Mechanistically, SAHA-induced loss of differentiation potential of uncommitted AMSCs correlates with multiple changes in the expression of principal transcription factors that control mesenchymal or pluripotent states. We propose that SAHA destabilizes the multi-potent epigenetic state of uncommitted human AMSCs by hyper-acetylation and perturbation of key transcription factor pathways. Furthermore, AMSCs grown in platelet lysate may provide a useful biological model for screening of new HDAC inhibitors that control the biological fate of human mesenchymal stromal cells.

RUNX3 facilitates growth of Ewing sarcoma cells

Ewing sarcoma is an aggressive pediatric small round cell tumor that predominantly occurs in bone. Approximately 85% of Ewing sarcomas harbor the EWS/FLI fusion protein, which arises from a chromosomal translocation, t(11:22)(q24:q12). EWS/FLI interacts with numerous lineage-essential transcription factors to maintain mesenchymal progenitors in an undifferentiated state. We previously showed that EWS/FLI binds the osteogenic transcription factor RUNX2 and prevents osteoblast differentiation. In this study, we investigated the role of another Runt-domain protein, RUNX3, in Ewing sarcoma. RUNX3 participates in mesenchymal-derived bone formation and is a context dependent tumor suppressor and oncogene. RUNX3 was detected in all Ewing sarcoma cells examined, whereas RUNX2 was detected in only 73% of specimens. Like RUNX2, RUNX3 binds to EWS/FLI via its Runt domain. EWS/FLI prevented RUNX3 from activating the transcription of a RUNX-responsive reporter, p6OSE2. Stable suppression of RUNX3 expression in the Ewing sarcoma cell line A673 delayed colony growth in anchorage independent soft agar assays and reversed expression of EWS/FLI-responsive genes. These results demonstrate an important role for RUNX3 in Ewing sarcoma.

Abstract 1413: RUNX3 plays an oncogenic role in Ewing sarcoma cells

Ewing sarcomas are aggressive, poorly differentiated pediatric tumors of bone and soft tissue. Ewing sarcoma affects one to three people per million every year and is the second most common pediatric bone malignancy after osteosarcoma. Approximately 85% of Ewing sarcomas harbor the EWS-FLI fusion protein, which arises from a chromosomal translocation, t(11:22)(q24:q12). EWS-FLI interacts with numerous lineage-essential transcription factors to maintain mesenchymal progenitors in an undifferentiated state. We previously showed that EWS-FLI binds the osteogenic transcription factor RUNX2, and prevents osteoblast differentiation. RUNX3 is highly homologous to RUNX2 and participates in the mesenchymal-derived bone formation. RUNX3 has been described as both a tumor suppressor and an oncogene in different tumor types.

In this study, we investigated the role of RUNX3 in Ewing Sarcoma. RUNX3 was detected in all Ewing sarcoma cells examined (7/7 cell lines, and 4/4 primary tumors), whereas RUNX2 was detected in only 73% of these specimens. Immunoprecipitation experiments revealed that RUNX3 binds to EWS-FLI via its Runt domain, which is &gt;91% identical to the Runt domain in RUNX2. The interaction between RUNX3 and EWS-FLI in cell nuclei was confirmed by immunofluorescence. Moreover, EWS-FLI interactions prevented RUNX3 from activating the transcription of a RUNX-responsive reporter, p6OSE2.

To determine the role of RUNX3 in Ewing sarcoma cell growth, we stably suppressed RUNX3 expression in the Ewing sarcoma cell line A673 with shRNAs. In anchorage independent growth assays in soft agar, RUNX3-deficient A673 cells formed smaller colonies than cells expressing scrambled shRNAs. Consistent with the smaller colonies, RUNX3 suppressed cells had increased expression of the cyclin dependent kinase inhibitor p21. Taken together, these results suggest and oncogenic role for RUNX3 in Ewing sarcoma.

Citation Format: Krista L. Bledsoe, Meghan E. McGee-Lawrence, Emily T. Camilleri, Andre M. Oliveira, Andre J. van Wijnen, Jennifer J. Westendorf. RUNX3 plays an oncogenic role in Ewing sarcoma cells. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1413. doi:10.1158/1538-7445.AM2014-1413