Nell-1 Is a Key Functional Modulator in Osteochondrogenesis and Beyond

Neural EGFL-like 1 (Nell-1) is a well-studied osteogenic factor that has comparable osteogenic potency with the Food and Drug Administration-approved bone morphogenic protein 2 (BMP-2). In this review, which aims to summarize the advanced Nell-1 research in the past 10 y, we start with the correlation of structural and functional relevance of the Nell-1 protein with the identification of a specific receptor of Nell-1, contactin-associated protein-like 4 (Cntnap4), for osteogenesis. The indispensable role of Nell-1 in normal craniofacial and appendicular skeletal development and growth was also defined by using the newly developed tissue-specific Nell-1 knockout mouse lines in addition to the existing transgenic mouse models. With the achievements on Nell-1's osteogenic therapeutic evaluations from multiple preclinical animal models for local and systemic bone regeneration, the synergistic effect of Nell-1 with BMP-2 on osteogenesis, as well as the advantages of Nell-1 as an osteogenic protein with antiadipogenic, anti-inflammatory, and provascularized characteristics over BMP-2 in bone tissue engineering, is highlighted, which lays the groundwork for the clinical trial approval of Nell-1. At the molecular level, besides the mitogen-activated protein kinase (MAPK) signaling pathway, we emphasize the significant involvement of the Wnt/β-catenin pathway as well as the key regulatory molecules Runt-related transcription factor 2 (Runx2) in Nell-1-induced osteogenesis. In addition, the involvement of Nell-1 in chondrogenesis and its relevant pathologies have been revealed with the participation of the nuclear factor of activated T cells 1 (Nfatc1), Runx3, and Indian hedgehog (Ihh) signaling pathways, although the mechanistic insights of Nell-1's osteochondrogenic property will be continuously evolving. With this perspective, we elucidate some emerging and novel functional properties of Nell-1 in oral-dental and neural tissues that will be the frontiers of future Nell-1 studies beyond the context of bone and cartilage. As such, the therapeutic potential of Nell-1 continues to evolve and grow with continuous pursuit.

Prospective purification of perivascular presumptive mesenchymal stem cells from human adipose tissue: process optimization and cell population metrics across a large cohort of diverse demographics

BACKGROUND

Adipose tissue is an attractive source of mesenchymal stem cells (MSC) as it is largely dispensable and readily accessible through minimally invasive procedures such as liposuction. Until recently MSC could only be isolated in a process involving ex-vivo culture and their in-vivo identity, location and frequency remained elusive. We have documented that pericytes (CD45-, CD146+, and CD34-) and adventitial cells (CD45-, CD146-, CD34+) (collectively termed perivascular stem cells or PSC) represent native ancestors of the MSC, and can be prospectively purified using fluorescence activated cell sorting (FACS). In this study we describe an optimized protocol that aims to deliver pure, viable and consistent yields of PSC from adipose tissue. We analysed the frequency of PSC within adipose tissue, and the effect of patient and procedure based variables on this yield.

METHODS

Within this twin centre study we analysed the adipose tissue of n = 131 donors using flow cytometry to determine the frequency of PSC and correlate this with demographic and processing data such as age, sex, BMI and cold storage time of the tissue.

RESULTS

The mean number of stromal vascular fraction (SVF) cells from 100 ml of lipoaspirate was 34.4 million. Within the SVF, mean cell viability was 83 %, with 31.6 % of cells being haematopoietic (CD45+). Adventitial cells and pericytes represented 33.0 % and 8 % of SVF cells respectively. Therefore, a 200 ml lipoaspirate would theoretically yield 23.2 million viable prospectively purified PSC - sufficient for many reconstructive and regenerative applications. Minimal changes were observed in respect to age, sex and BMI suggesting universal potential application.

CONCLUSIONS

Adipose tissue contains two anatomically and phenotypically discreet populations of MSC precursors - adventitial cells and pericytes - together referred to as perivascular stem cells (PSC). More than 9 million PSC per 100 ml of lipoaspirate can be rapidly purified to homogeneity using flow cytometry in clinically relevant numbers potentially circumventing the need for purification and expansion by culture prior to clinical use. The number and viability of PSC are minimally affected by patient age, sex, BMI or the storage time of the tissue, but the quality and consistency of yield can be significantly influenced by procedure based variables.

Recent insights into the identity of mesenchymal stem cells

The ability of mesenchymal stem cells (MSCs) to differentiate in vitro into chondrocytes, osteocytes and myocytes holds great promise for tissue engineering. Skeletal defects are emerging as key targets for treatment using MSCs due to the high responsiveness of bone to interventions in animal models. Interest in MSCs has further expanded in recognition of their ability to release growth factors and to adjust immune responses.

Despite their increasing application in clinical trials, the origin and role of MSCs in the development, repair and regeneration of organs have remained unclear. Until recently, MSCs could only be isolated in a process that requires culture in a laboratory; these cells were being used for tissue engineering without understanding their native location and function. MSCs isolated in this indirect way have been used in clinical trials and remain the reference standard cellular substrate for musculoskeletal engineering. The therapeutic use of autologous MSCs is currently limited by the need for ex vivo expansion and by heterogeneity within MSC preparations. The recent discovery that the walls of blood vessels harbour native precursors of MSCs has led to their prospective identification and isolation. MSCs may therefore now be purified from dispensable tissues such as lipo-aspirate and returned for clinical use in sufficient quantity, negating the requirement for ex vivo expansion and a second surgical procedure.

In this annotation we provide an update on the recent developments in the understanding of the identity of MSCs within tissues and outline how this may affect their use in orthopaedic surgery in the future.

Cite this article: Bone Joint J 2014;96-B:291–8.

A preliminary investigation into psychosocial outcome and quality-of-life in adolescents following childhood traumatic brain injury

OBJECTIVE

This study investigated the long-term psychosocial outcome and quality-of-life (QoL) of 15-18 year olds, sustaining childhood traumatic brain injury (TBI) between birth and 5 years.

METHOD

Thirty-three participants (17 TBI parent-proxies, 16 control parent-proxies) were involved in the present study which compared parent-ratings for the TBI group and healthy controls on the Sydney Psychosocial Reintegration Scale-Child form (SPRS-C) and the Paediatric Quality of Life Inventory (PedsQL).

RESULTS

Despite comparable overall psychosocial reintegration scores, parents reported that their teens with TBI were more likely to experience poor QoL compared to controls. On further analysis, some aspects of psychosocial outcome appear to be compromised following childhood TBI.

CONCLUSIONS

Interventions targeting childhood TBI must consider QoL in addition to symptom reduction and be extended throughout adolescence. The limitations of the sample size are cause for concern; however, preliminary results do validate the need for future research efforts.

The role of NELL-1, a growth factor associated with craniosynostosis, in promoting bone regeneration

Efforts to enhance bone regeneration in orthopedic and dental cases have grown steadily for the past decade, in line with increasingly sophisticated regenerative medicine. To meet the unprecedented demand for novel osteospecific growth factors with fewer adverse effects compared with those of existing adjuncts such as BMPs, our group has identified a craniosynostosis-associated secreted molecule, NELL-1, which is a potent growth factor that is highly specific to the osteochondral lineage, and has demonstrated robust induction of bone in multiple in vivo models from rodents to pre-clinical large animals. NELL-1 is preferentially expressed in osteoblasts under direct transcriptional control of Runx2, and is well-regulated during skeletal development. NELL-1/Nell-1 can promote orthotopic bone regeneration via either intramembranous or endochondral ossification, both within and outside of the craniofacial complex. Unlike BMP-2, Nell-1 cannot initiate ectopic bone formation in muscle, but can induce bone marrow stromal cells (BMSCs) to form bone in a mouse muscle pouch model, exhibiting specificity that BMPs lack. In addition, synergistic osteogenic effects of Nell-1 and BMP combotherapy have been observed, and are likely due to distinct differences in their signaling pathways. NELL-1's unique role as a novel osteoinductive growth factor makes it an attractive alternative with promise for future clinical applications. [Note: NELL-1 and NELL-1 indicate the human gene and protein, respectively; Nell-1 and Nell-1 indicate the mouse gene and protein, respectively.]

Psychological treatment for anxiety in people with traumatic brain injury

BACKGROUND

Psychological treatments are commonly used in the management of anxiety. Certain types of psychological treatments are well suited to needs of people with traumatic brain injury (TBI). We have systematically reviewed studies examining the effectiveness of these approaches for TBI.

OBJECTIVES

To assess the effects of psychological treatments for anxiety in people with TBI.

SEARCH STRATEGY

We searched the following databases up until March 2006: Cochrane Injuries Group's specialised register, Cochrane Depression, Anxiety and Neurosis Group's specialised register, Cochrane Central Register of Controlled Trials, MEDLINE, PsycINFO, EMBASE, CINAHL, AMED, ERIC, and PsycBITE. Additionally, key journals were handsearched and reference lists of included trials were examined to identify further studies meeting inclusion criteria.

SELECTION CRITERIA

Randomised controlled trials of psychological treatments for anxiety, with or without pharmacological treatment, for people with TBI were included in the review. Pharmacological treatments for anxiety in isolation (without psychological intervention) were excluded.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed methodological quality and extracted data from the included trials.

MAIN RESULTS

Three trials were identified in this review as satisfying inclusion criteria. Results of all three trials were evaluated, however, one of these trials had compromised methodological quality and, therefore the focus was placed on the other two trials. Data were not pooled due to the heterogeneity between trials. The first trial (n = 24) showed a benefit of cognitive behavioural therapy (CBT) in people with mild TBI and acute stress disorder. Fewer people receiving CBT had diagnosis of post-traumatic stress disorder (PTSD) at post-treatment compared to the control supportive counselling group, with maintenance of treatment gains found at six-month follow up. The second trial (n = 20) showed that post-treatment anxiety symptomatology of people with mild to moderate TBI was lower in the combined CBT and neurorehabilitation group compared to the no intervention control group.

AUTHORS' CONCLUSIONS

This review provides some evidence for the effectiveness of CBT for treatment of acute stress disorder following mild TBI and CBT combined with neurorehabilitation for targeting general anxiety symptomatology in people with mild to moderate TBI. These findings need to be viewed in light of the small number, small sample size and heterogeneous characteristics of current trials published in this area. More trials focusing on comparable psychological interventions, severity of injury of participants and diagnosis of anxiety disorder(s) are needed.

Down-regulation of decorin, a transforming growth factor-beta modulator, is associated with scarless fetal wound healing

PURPOSE

Transforming growth factor beta (TGF-beta) bioactivity has been implicated as a potential regulator of the transition from scarless healing to scar formation in fetal wounds. Decorin is an extracellular matrix proteoglycan that regulates TGF-beta bioactivity and assists in collagen fibrillogenesis. To determine its role in scarless repair, the authors examined decorin expression in fetal fibroblasts, skin, and wounds.

METHODS

A single, full-thickness, 2-mm open wound was created on the dorsal surface of fetal rats at 16.5 days (E16) and 18.5 days (E18) gestational age (term, 21.5 days [E21]). Wounds were harvested at 24 and 72 hours (n = 12 wounds per time-point). Nonwounded fetal skin at E17, E19, and E21 was harvested for analysis of decorin expression during skin development and as controls for wounds. In addition, fetal (E14, E18) and adult dermal fibroblasts were cultured for in vitro analysis. Reduced-cycle, specific primer, reverse transcriptase polymerase chain reaction was performed to quantitate decorin expression.

RESULTS

Decorin expression increased rapidly with increasing gestational age in both fetal fibroblasts and skin. Expression was increased 22-fold in E18 fibroblasts (P <.002) and 300-fold in adult fibroblasts (P <.001) compared with E14 fibroblasts. In skin, expression increased 74% (P <.01) during the fetal wound healing transition period between E17 and E19. However, in E16 wounds (scarless), decorin expression decreased 59% (P <.006) at 24 hours and 45% (P <.02) at 72 hours. Decorin expression did not change in E18 (scar) wounds at 24 and 72 hours (P >.05).

CONCLUSIONS

Early gestation fetal fibroblasts and fetal skin express decorin at lower levels than late gestation fetal and adult fibroblasts and skin. Decorin expression is down-regulated in scarless (E16) compared with scar (E18) wounds. Thus, increased decorin expression is associated with both skin development and scar formation. Conversely, decreased decorin expression is associated with scarless repair.

Differential expression of matrix metalloproteinases and their tissue-derived inhibitors in cutaneous wound repair

Wound extracellular matrix is a key regulator of cell adhesion, migration, proliferation, and differentiation during cutaneous repair. The amount and organization of normal wound extracellular matrix are determined by a dynamic balance among overall matrix synthesis, deposition, and degradation. Matrix metalloproteinases (MMPs) are one family of structurally related enzymes that have the collective ability to degrade nearly all extracellular matrix components. The MMPs are broadly categorized into collagenases, gelatinases, stromelysins, and membrane-type MMPs by their substrate specificity. The aim of this study was to characterize the temporal changes in mRNA profiles for rat collagenase [matrix metalloproteinase-1 (MMP-1)], gelatinase A (MMP-2), matrilysin (MMP-7), gelatinase B (MMP-9), and membrane type 1-MMP (MT1-MMP), as well as tissue inhibitor of metalloproteinases-1 (TIMP-1), TIMP-2, and TIMP-3 during the inflammatory, granulation, and early remodeling phases of excisional skin repair. Eight full-thickness skin wounds were made on the backs of each rat (7-mm2 wounds; 16 rats; n = 128 wounds). Two animals at a time were reanesthetized, and all eight wounds on each animal were excised at 12 and 24 hours and at 2, 3, 5, 7, 10, and 14 days after injury. Six wounds from each animal were excised for RNA isolation, whereas two wounds were excised for histology. Controls consisted of nonwounded skin from identical locations in four animals. Total RNA from each time point was isolated and relative mRNA quantitation performed by using reduced-cycle reverse transcription-polymerase chain reaction. Correct polymerase chain reaction product amplification was confirmed by probing the blotted polymerase chain reaction product with a 32P-labeled oligonucleotide specific for a given MMP or TIMP. We demonstrated that the majority of MMP and TIMP mRNA induction and peak expression coincided temporally with the well-characterized inflammatory and granulation stages of repair. In conclusion, there is a distinct pattern of MMP and TIMP expression during normal excisional wound repair.

Downregulation of apoptosis-related genes in keloid tissues

BACKGROUND

Physiologically programmed cell death or apoptosis occurs during the natural balance between cellular proliferation and demise.

MATERIALS AND METHODS

We compared the expression of 64 apoptosis-related genes in keloids and normal scars to investigate the potential role of apoptosis in keloid formation. Two sets of mRNA were isolated from keloids excised from four previously untreated patients and four normal scar patients separately. Human cDNA arrayed hybridization was performed to compare the apoptosis-related gene expression between these two groups. In addition, TUNEL assays were performed to evaluate the percentage of apoptotic cells in keloids (center and periphery) versus normal scars.

RESULTS

Eight of the sixty-four apoptosis-related genes studied were significantly underexpressed in keloid tissue. The underexpressed genes and their relative expression compared with normal scar were defender against cell death 1 (DAD-1) (34.1% of normal scar); nucleoside diphosphate kinase B (c-myc transcription factor) (24.7%); glutathione S-transferase (17.9%); glutathione S-transferase microsomal (28.1%); glutathione peroxidase (47.2%); tumor necrosis factor receptor 1-associated protein (TRADD) (51.0%); 19-kDa interacting protein 3 (NIP3) (36.0%); and cytoplasmic dynein light chain 1 (HDLC1) (47.7%). Spatial analysis of apoptosis using TUNEL assays revealed apoptosis indices of 0.83 for keloid periphery and 0.63 for keloid center.

CONCLUSIONS

In this study we demonstrated underexpression of apoptosis-related genes in human keloid tissue and decreased apoptotic activity in fibroblasts derived from keloids versus normal scars. We hypothesized that keloid fibroblasts fail to undergo physiologically programmed cell death and, thus, continue to produce and secrete connective tissue beyond the period expected in normal scar formation, accounting for the progressive and hypertrophic nature of keloids. This mechanism leads to new possibilities for treatment of keloids through induction of apoptosis.

Cutaneous rat wounds express c49a, a novel gene with homology to the human melanoma differentiation associated gene, mda-7

We have used DD-PCR (differential display-polymerase chain reaction) to identify new genes that are over- or underexpressed during wound repair. DD-PCR performed on excisional wounds identified the expression of rat c49a. Cloning and sequence analysis of the rat c49a gene revealed high homology to a novel human melanoma differentiation associated gene, mda-7. The human mda-7gene isolated from melanoma cell lines, has been linked with human melanoma differentiation, and growth suppression. Moreover, transfection of human mda-7 constructs into human tumor cells suppresses the growth and colony formation of tumor cells from diverse origins. To confirm and relatively quantitate expression of rat c49a gene during repair, specific primer, reduced cycle RT-PCR (reverse transcription-PCR) was performed. RT-PCR showed an approximately 9 to 12-fold elevation of rat c49a mRNA at 12 h to 5 days above nonwounded controls that gradually decreased to approximately 1.5 to 3-fold by day 14. Cloning and sequence analysis of the entire 1200 base pair c49a gene product showed 78% nucleotide homology to human mda-7. Immunohistochemistry studies localized rat C49A expression primarily to fibroblast-like cells at the wound edge and base. The marked up-regulation of rat c49a transcripts during the inflammatory and early granulation tissue phases of wound repair where cellular processes such as re-epithelialization, angiogenesis, and fibroplasia predominate--suggest that c49a is associated with proliferation of fibroblasts in wound healing.

Human NELL-1 expressed in unilateral coronal synostosis

Surgical correction of unilateral coronal synostosis offers a unique opportunity to examine the molecular differences between an abnormal and a normal cranial suture. We isolated and identified a cDNA fragment whose expression was up-regulated in the premature fusing and fused coronal sutures, as compared with normal coronal sutures. The nucleotide sequence of the full-length cDNA of this gene, human NELL-1, has approximately 61% homology with the chicken Nel gene. Both chicken Nel and human NELL-1 are comprised of six epidermal growth factor-like repeats. The human NELL-1 messages were localized primarily in the mesenchymal cells and osteoblasts at the osteogenic front, along the parasutural bone margins, and within the condensing mesenchymal cells of newly formed bone in sites of premature sutural fusion. Human multiorgan tissue mRNA blot showed that NELL-1 was specifically expressed in fetal brain but not in fetal kidney, liver, or lung. We also showed that Nell-1 was expressed in rat calvarial osteoprogenitor cells and was largely absent in rat tibiae and fibroblast cell cultures. In conclusion, our data suggest that the NELL-1 gene is preferentially expressed in cranial intramembranous bone and neural tissue (both of neural crest cell origin) and is up-regulated during unilateral premature closure of the coronal suture. The precise role of this gene is unknown.

Influence of severe protein malnutrition on rat lacrimal, salivary and gastrointestinal immune expression during development, adulthood and ageing

The objective of the present study was to examine and to compare the impact of severe protein malnutrition during development, adulthood and ageing on secretory immune expression in the eye, mouth and small intestine. In addition, we sought to determine whether potential abrogation of mucosal immunity by protein deprivation might be reversed by the administration of a balanced diet. Weanling, adult and aged rats were provided isocaloric diets containing 24% (control), 19%, 14%, 10%, 6% and/or 3.2% protein levels for defined periods and various immunological parameters were evaluated before, during and after the dietary regimen. Our results demonstrated the following. (1) Severe protein malnutrition (3.2%) dramatically suppressed the secretory immune system in eyes of weanling rats. After 8 weeks of protein insufficiency, tear IgA concentrations in young rats had undergone a precipitous decrease, such that IgA could not be detected in tears. This response was paralleled by a significant decline in the tear volume, tear secretory component (SC), IgG and total protein content, number of IgA-containing cells in lacrimal tissue, as well as the amounts of SC and/or IgA in saliva, intestinal secretions and serum. In contrast, the immunological effects of protein malnutrition in adult or aged animals varied considerably depending upon the specific mucosal site. (2) The influence of protein deprivation was dose dependent and reversible: maintenance of weanling rats on 10%, 6% or 3.2% protein diets interfered with the establishment of ocular and intestinal mucosal immunity, but later administration of optimal diets to these malnourished animals permitted a rapid immune recovery. (3) The impact of protein malnutrition on tear IgA levels in weanling animals, as shown by pair-feeding experiments, appeared to reflect primarily protein deficiency and not caloric restriction. Overall, these findings show that dietary protein plays a significant, site-specific role in the developmental expression of the secretory immune system.

Testosterone-induced suppression of autoimmune disease in lacrimal tissue of a mouse model (NZB/NZW F1) of Sjögren's syndrome

The current investigation was designed to examine whether androgen administration might suppress autoimmune disease in lacrimal glands of a mouse model (NZB/NZW F1) of Sjögren's syndrome. Autoimmune, female mice were treated with vehicle or varying concentrations of testosterone for 0, 17, 34, or 51 days, and tears, lacrimal glands, as well as submandibular tissue, were collected from killed mice after androgen exposure. Glands were histologically processed and evaluated with a computer-assisted image analysis system. Results showed that testosterone administration induced a significant, time-dependent decrease in the extent of lymphocytic accumulation in the lacrimal gland. After 34-51 days of androgen therapy, the magnitude of lymphocyte infiltration had been suppressed 22- to 46-fold, compared with that in placebo-treated tissue. This hormone effect was associated with significant reductions in the number of focal infiltrates, the area of individual foci, and the total quantity of lymphocyte infiltration per lacrimal section. Testosterone exposure also stimulated an increase in lacrimal gland weight and a rise in tear volumes, relative to those measured in the same mice before treatment. In addition, androgens significantly diminished the extent of lymphocyte accumulation in submandibular tissue. In summary, our results demonstrate that androgen administration may inhibit the progression of autoimmune disease in lacrimal and submandibular glands of NZB/NZW F1 mice.

Oral (n-3) fatty acid supplementation suppresses cytokine production and lymphocyte proliferation: comparison between young and older women

The effect of (n-3) fatty acid supplementation on cytokine production and lymphocyte proliferation was investigated in young (23-33 y) and older (51-68 y) women. Subjects supplemented their diets with 2.4 g of (n-3) fatty acid/d for 3 mo. Blood was collected before and after 1, 2 and 3 mo of supplementation. The (n-3) fatty acid supplementation reduced total interleukin (IL)-1 beta synthesis by 48% in young women but by 90% in older women; tumor necrosis factor was reduced by 58% in young and 70% in older women. Interleukin-6 was reduced in young women by 30% but by 60% in older women. Older women produced less IL-2 and had lower mitogenic responses to phytohemagglutinin (PHA) than young women prior to (n-3) fatty acid supplementation. The (n-3) fatty acid supplementation reduced IL-2 production in both groups; however, this reduction was significant only in older women. The PHA-stimulated mitogenic response was significantly reduced by (n-3) fatty acid in older women (36%). Thus, long-term (n-3) fatty acid supplementation reduced cytokine production in young women and cytokine production and T cell mitogenesis in older women. The reduction was more dramatic in older women than in young women. Although (n-3) fatty acid-induced reduction in cytokine production may have beneficial anti-inflammatory effects, its suppression of IL-2 production and lymphocyte proliferation in older women may not be desirable.