Auricular surface morphology and surface area does not influence subchondral bone density distribution in the dysfunctional sacroiliac joint.

The subchondral lamella of the sacroiliac auricular surface is morphologically inconsistent. Its morpho-mechanical relationship with dysfunction (SIJD) remains unstudied. Here, the iliac and sacral subchondral bone mineralization is compared between morphological subtypes and in large and small surfaces, in SIJD joints and controls. CT datasets from 29 patients with bilateral or unilateral SIJD were subjected to CT-osteoabsorptiometry. Surface areas and posterior angles were calculated and surfaces were classified by size: small (<15 cm3 ) and large (≥15 cm3 ), and morphological types: 1 (>160°), 2 (130°-160°), and 3 (<130°). Mineralization patterns were identified: two marginal (M1 and M2) and two non-marginal (N1 and N2). Each sacral and iliac surface was subsequently classified. Dysfunctional cohort area averaged 15.0 ± 2.4 cm2 (males 16.2 ± 2.5 cm2 , females 13.7 ± 1.6 cm2 ). No age correlations with surface area were found nor mean Hounsfield Unit differences when comparing sizes, sexes or morphology-type. Controls and dysfunctional cohort comparison revealed differences in female sacra (p = 0.02) and small sacra (p = 0.03). There was low-conformity in marginal and non-marginal patterns, 26% for contralateral non-dysfunctional joints, and 46% for dysfunctional joints. The majority of painful joints was of type 2 morphology (59%), equally distributed between small (49%) and large joints (51%). Larger joints had the highest frequency of dysfunctional joints (72%). Auricular surface morphology seems to have little impact on pain-related subchondral lamella adaptation in SIJD. Larger joints may be predisposed to the onset of pain due to the weakening of the extracapsular structures. Dysfunctional joints reflect common conformity patterns of sacral-apex mineralization with corresponding superior corner iliac mineralization.

Computed tomography osteoabsorptiometry for imaging of degenerative disc disease.

BACKGROUND: Lower back pain is a common condition with significant morbidity and economic impact. The pathophysiology is poorly understood but is in part attributable to degenerative disc disease (DDD). The healthy intervertebral disc ensures spine functionality by transferring the perceived load to the caudally adjacent vertebrae. The exposure to recurring mechanical load is mirrored in the mineralization pattern of the subchondral bone plate (SBP), where increased bone density is a sign of repetitive localized high stress. Computed tomography -osteoabsorptiometry (CT-OAM) is a technique based on conventional CT scans that displays the mineral density distribution in the SBP as a surface-color map. The objective of this study was to measure and analyze the SBP mineral density patterns of healthy lumbar intervertebral disc (IVDs) and those suffering DDD using CT-OAM densitograms. These findings should provide in vitro insight into the long-term morphological properties of the IVD and how these differ in the state of disc degeneration. METHODS: The CT-data sets of spines from 17 healthy individuals and 18 patients displaying DDD in the lumbar spine were acquired. Individual vertebrae of both cohorts were 3D reconstructed, processed using image analysis software, and compared to one another. Maximum intensity projection of the subchondral mineralization provided surface densitograms of the SBP. The relative calcium concentration, the local maxima of mineralization, and a mean surface projection of level-defined SBPs were calculated from the densitogram and statistically compared. RESULTS: The inferior SBP, adjacent to degenerating disc, display an 18-41 % higher relative calcium concentration than their healthy counterparts. In the opposing superior SBPs the relative calcium content is significantly increased. Whereas it is reasonably consistent for L1-L3 (L1: 132 %, L2: 127 %, L3: 120 %), the increase grows in caudal direction (L4: 131 %, L5: 148 %, S1: 152 %). Furthermore, a change in the areal distribution of excessive mineralization can be differentiated between healthy and diseased motion segments. CONCLUSIONS: The acquired data provide in vitro proof of the mechanical and anatomical properties of the SBP in relation to the state of disc degeneration. In conjunction with the diagnostic use of CT-osteoabsorptiometry, our data provide a basis for a non-invasive and sensitive technique that correlates with disc functionality. This could be promising in various cases, from early identification of early stages of DDD, tracking disease progression, and assessing the repercussions of surgical procedures or experimental therapies.

Nose to Spine: spheroids generated by human nasal chondrocytes for scaffold-free nucleus pulposus augmentation.

Cell-based strategies for nucleus pulposus (NP) regeneration that adequately support the engraftment and functionality of therapeutic cells are still lacking. This study explores a scaffold-free approach for NP repair, which is based on spheroids derived from human nasal chondrocytes (NC), a resilient cell type with robust cartilage-regenerative capacity. We generated NC spheroids (NCS) in two types of medium (growth or chondrogenic) and analyzed their applicability for NP repair with regard to injectability, biomechanical and biochemical attributes, and integration potential in conditions simulating degenerative disc disease (DDD). NCS engineered in both media were compatible with a typical spinal needle in terms of size (lower than 600µm), shape (roundness greater than 0.8), and injectability (no changes in morphology and catabolic gene expression after passing through the needle). While growth medium ensured stable elastic modulus (E) at 5 kPa, chondrogenic medium time-dependently increased E of NCS, in correlation with gene/protein expression of collagen. Notably, DDD-mimicking conditions did not impair NCS viability nor NCS fusion with NP spheroids simulating degenerated NP in vitro. To assess the feasibility of this approach, NCS were injected into an ex vivo-cultured bovine intervertebral disc (IVD) without damage using a spinal needle. In conclusion, our data indicated that NC cultured as spheroids can be compatible with strategies for minimally invasive NP repair in terms of injectability, tuneability, biomechanical features, and resilience. Future studies will address the capacity of NCS to integrate within degenerated NP under long-term loading conditions. STATEMENT OF SIGNIFICANCE: Current regenerative strategies still do not sufficiently support the engraftment of therapeutic cells in the nucleus pulposus (NP). We present an injectable approach based on spheroids derived from nasal chondrocytes (NC), a resilient cell type with robust cartilage-regenerative capacity. NC spheroids (NCS) generated with their own matrix and demonstrated injectability, tuneability of biomechanical/biochemical attributes, and integration potential in conditions simulating degenerative disc disease. To our knowledge, this is the first study that explored an injectable spheroid-based scaffold-free approach, which showed potential to support the adhesion and viability of therapeutic cells in degenerated NP. The provided information can be of substantial interest to a wide audience, including biomaterial scientists, biomedical engineers, biologists and medical researchers.

The Survey on Cellular and Tissue-Engineered Therapies in Europe in 2016 and 2017.

This report describes activity in Europe for the years 2016 and 2017 in the area of cellular and tissue-engineered therapies, excluding hematopoietic stem cell treatments for the reconstitution of hematopoiesis. It is the eighth of its kind and is supported by five established scientific organizations. In 2016 and 2017, a combined 234 teams from 29 countries responded to the cellular and engineered tissue therapy survey; 227 teams reported treating 8236 patients in these 2 years. Indications were categorized in hematology/oncology (40%; predominantly prevention or treatment of graft vs. host disease and hematopoietic graft enhancement), musculoskeletal/rheumatological disorders (29%), cardiovascular disorders (6%), neurological disorders (4%), gastrointestinal disorders (<1%), as well as miscellaneous disorders (20%), which were not assigned to the previous indications. The predominantly used cells were autologous (61%). The majority of autologous cells were used to treat musculoskeletal/rheumatological (44%) disorders, whereas allogeneic cells were mainly used for hematology/oncology (78%). The reported cell types were mesenchymal stem/stromal cells (MSCs) (56%), hematopoietic cells (21%), keratinocytes (7%), chondrocytes (6%) dermal fibroblasts (4%), dendritic cells (2%), and other cell types (4%). Cells were expanded in vitro in 62% of the treatments, sorted in 11% of the cases, and rarely transduced (2%). The processing of cells was outsourced to external facilities in 30% of the cases. Cells were delivered predominantly intravenously or intra-arterially [47%], as suspension [36%], or using a membrane/scaffold (16%). The data are compared with those from previous years to identify trends in a rapidly evolving field. In this edition, the report includes a critical discussion of data collected in the space of orthopedics and the use of MSCs.

The survey on cellular and tissue-engineered therapies in Europe and neighboring Eurasian countries in 2014 and 2015.

BACKGROUND AIMS: With the support of five established scientific organizations, this report, the seventh of its kind, describes activity in Europe for the years 2014 and 2015 in the area of cellular and tissue-engineered therapies, excluding hematopoietic stem cell (HSC) treatments for the reconstitution of hematopoiesis. METHODS: In 2015 [respectively 2014], 205 [276] teams from 32 countries responded to the cellular and tissue-engineered therapy survey; 178 [126] teams reported treating 3686 [2665] patients. RESULTS: Indications were musculoskeletal/rheumatological disorders (32% [33%]), cardiovascular disorders (12% [21%]), hematology/oncology (predominantly prevention or treatment of graft versus host disease and HSC graft enhancement; 20% [20%]), neurological disorders (4% [6%]), gastrointestinal disorders (<1% [1%]) and other indications (31% [20%]). The majority of autologous cells (60% [73%]) were used to treat musculoskeletal/rheumatological (44% [36%]) disorders, whereas allogeneic cells were used mainly for hematology/oncology (61% [68%]). The reported cell types were mesenchymal stromal cells (40% [49%]), chondrocytes (13% [6%]), hematopoietic stem cells (12% [23%]), dermal fibroblasts (8% [3%]), dendritic cells (2% [2%]), keratinocytes (1% [2%]) and others (24% [15%]). Cells were expanded in vitro in 63% [40%] of the treatments, sorted in 16% [6%] of the cases and rarely transduced (<1%). Cells were delivered predominantly as suspension 43% [51%], intravenously or intra-arterially (30% [30%]), or using a membrane/scaffold (25% [19%]). DISCUSSION: The data are compared with those from previous years to identify trends in a still unpredictably evolving field. Perspectives of representatives from plastic surgery practitioners, Iran and ISCT are presented (contributing authors D.A. Barbara, B. Hossein and W.L. Mark, respectively).

Loss of Ezh2 promotes a midbrain-to-forebrain identity switch by direct gene derepression and Wnt-dependent regulation.

BACKGROUND: Precise spatiotemporal control of gene expression is essential for the establishment of correct cell numbers and identities during brain development. This process involves epigenetic control mechanisms, such as those mediated by the polycomb group protein Ezh2, which catalyzes trimethylation of histone H3K27 (H3K27me3) and thereby represses gene expression. RESULTS: Herein, we show that Ezh2 plays a crucial role in the development and maintenance of the midbrain. Conditional deletion of Ezh2 in the developing midbrain resulted in decreased neural progenitor proliferation, which is associated with derepression of cell cycle inhibitors and negative regulation of Wnt/ß-catenin signaling. Of note, Ezh2 ablation also promoted ectopic expression of a forebrain transcriptional program involving derepression of the forebrain determinants Foxg1 and Pax6. This was accompanied by reduced expression of midbrain markers, including Pax3 and Pax7, as a consequence of decreased Wnt/ß-catenin signaling. CONCLUSION: Ezh2 is required for appropriate brain growth and maintenance of regional identity by H3K27me3-mediated gene repression and control of canonical Wnt signaling.

Distinct adhesion-independent functions of ß-catenin control stage-specific sensory neurogenesis and proliferation.

BACKGROUND: ß-catenin plays a central role in multiple developmental processes. However, it has been difficult to study its pleiotropic effects, because of the dual capacity of ß-catenin to coordinate cadherin-dependent cell adhesion and to act as a component of Wnt signal transduction. To distinguish between the divergent functions of ß-catenin during peripheral nervous system development, we made use of a mutant allele of ß-catenin that can mediate adhesion but not Wnt-induced TCF transcriptional activation. This allele was combined with various conditional inactivation approaches. RESULTS: We show that of all peripheral nervous system structures, only sensory dorsal root ganglia require ß-catenin for proper formation and growth. Surprisingly, however, dorsal root ganglia development is independent of cadherin-mediated cell adhesion. Rather, both progenitor cell proliferation and fate specification are controlled by ß-catenin signaling. These can be divided into temporally sequential processes, each of which depends on a different function of ß-catenin. CONCLUSIONS: While early stage proliferation and specific Neurog2- and Krox20-dependent waves of neuronal subtype specification involve activation of TCF transcription, late stage progenitor proliferation and Neurog1-marked sensory neurogenesis are regulated by a function of ß-catenin independent of TCF activation and adhesion. Thus, switching modes of ß-catenin function are associated with consecutive cell fate specification and stage-specific progenitor proliferation.

Probing transcription-specific outputs of ß-catenin in vivo.

ß-Catenin, apart from playing a cell-adhesive role, is a key nuclear effector of Wnt signaling. Based on activity assays in Drosophila, we generated mouse strains where the endogenous ß-catenin protein is replaced by mutant forms, which retain the cell adhesion function but lack either or both of the N- and the C-terminal transcriptional outputs. The C-terminal activity is essential for mesoderm formation and proper gastrulation, whereas N-terminal outputs are required later during embryonic development. By combining the double-mutant ß-catenin with a conditional null allele and a Wnt1-Cre driver, we probed the role of Wnt/ß-catenin signaling in dorsal neural tube development. While loss of ß-catenin protein in the neural tube results in severe cell adhesion defects, the morphology of cells and tissues expressing the double-mutant form is normal. Surprisingly, Wnt/ß-catenin signaling activity only moderately regulates cell proliferation, but is crucial for maintaining neural progenitor identity and for neuronal differentiation in the dorsal spinal cord. Our model animals thus allow dissecting signaling and structural functions of ß-catenin in vivo and provide the first genetic tool to generate cells and tissues that entirely and exclusively lack canonical Wnt pathway activity.