Canine tissue-specific expression of multiple small leucine rich proteoglycans

Immunostaining for VEGF and Decorin Predicts Poor Survival and Recurrence in Canine Soft Tissue Sarcoma

The aim of this study was to investigate whether using immunohistochemistry to detect the angiogenic proteins vascular endothelial growth factor (VEGF) and decorin can help predict the risk of local recurrence of, or death from, canine soft tissue sarcoma (STS). VEGF and decorin were detected using validated immunohistochemical methods on 100 formalin-fixed paraffin-embedded samples of canine STS. The tumours had been resected previously, with clinical outcome determined by questionnaire. Each slide was assessed by light microscopy and the pattern of immunostaining with VEGF and decorin determined. Patterns of immunostaining were then analysed to detect associations with outcome measures of local recurrence and tumour-related death. High VEGF immunostaining was significantly (p < 0.001) associated with both increased local recurrence and reduced survival time. The distribution of decorin immunostaining within the tumour was significantly associated with survival time (p = 0.04) and local tumour recurrence (p = 0.02). When VEGF and decorin scores were combined, STS with both high VEGF and low decorin immunostaining were more likely to recur or cause patient death (p < 0.001). The results of this study suggest that immunostaining of VEGF and decorin may help predict the risk of local recurrence of canine STS.

Effective protein extraction combined with data independent acquisition analysis reveals a comprehensive and quantifiable insight into the proteomes of articular cartilage and subchondral bone

OBJECTIVE

The objectives of this study was to establish a sensitive and reproducible method to map the cartilage and subchondral bone proteomes in quantitative terms, and mine the proteomes for proteins of particular interest in the pathogenesis of osteoarthritis (OA). The horse was used as a model animal.

DESIGN

Protein was extracted from articular cartilage and subchondral bone samples from three horses in triplicate by pressure cycling technology or ultrasonication. Digested proteins were analysed by data independent acquisition based mass spectrometry. Data was processed using a pre-established spectral library as reference database (FDR 1%).

RESULTS

We identified to our knowledge the hitherto most comprehensive quantitative cartilage (1758 proteins) and subchondral bone (1482 proteins) proteomes in all species presented to date. Both extraction methods were sensitive and reproducible and the high consistency of the identified proteomes (>97% overlap) indicated that both methods preserved the diversity among the extracted proteins. Proteome mining revealed a substantial number of quantifiable cartilage and bone matrix proteins and proteins involved in osteogenesis and bone remodeling, including ACAN, BGN, PRELP, FMOD, COMP, ACP5, BMP3, BMP6, BGLAP, TGFB1, IGF1, ALP, MMP3, and collagens. A number of proteins, including COMP and TNN, were identified in different protein isoforms with potential unique biological roles.

CONCLUSION

We have successfully developed two sensitive and reproducible non-species specific workflows enabling a comprehensive quantitative insight into the proteomes of cartilage and subchondral bone. This facilitates the prospect of investigating the molecular events at the osteochondral unit in the pathogenesis of OA in future projects.

Characterisation of key proteoglycans in the cranial cruciate ligaments (CCLs) from two dog breeds with different predispositions to CCL disease and rupture

Cranial cruciate ligament disease and rupture (CCLD/R) is one of the most common orthopaedic conditions in dogs, eventually leading to osteoarthritis of the stifle joint. Certain dog breeds such as the Staffordshire bull terrier have an increased risk of developing CCLD/R. Previous studies into CCLD/R have found that glycosaminoglycan levels were elevated in cranial cruciate ligament (CCL) tissue from high-risk breeds when compared to the CCL from a low-risk breed to CCLD/R. Our objective was to determine specific proteoglycans/glycosaminoglycans in the CCL and to see whether their content was altered in dog breeds with differing predispositions to CCLD/R. Disease-free CCLs from Staffordshire bull terriers (moderate/high-risk to CCLD/R) and Greyhounds (low-risk to CCLD/R) were collected and key proteoglycan/glycosaminoglycans were determined by semi-quantitative Western blotting, quantitative biochemistry, quantitative reverse transcription polymerase chain reaction, and immunohistochemistry. Gene expression of fibromodulin (P = 0.03), aggrecan (P = 0.0003), and chondroitin-6-sulphate stubs (P = 0.01) were significantly increased, and for fibromodulin this correlated with an increase in protein content in Staffordshire bull terriers compared to Greyhound CCLs (P = 0.02). Decorin (P = 0.03) and ADAMTS-4 (P = 0.04) gene expression were significantly increased in Greyhounds compared to Staffordshire bull terrier CCLs. The increase of specific proteoglycans and glycosaminoglycans within the Staffordshire bull terrier CCLs may indicate a response to higher compressive loads, potentially altering their risk to traumatic injury. The higher decorin content in the Greyhound CCLs is essential for maintaining collagen fibril strength, while the increase of ADAMTS-4 indicates a higher rate of turnover helping to regulate normal CCL homeostasis in Greyhounds.

Associations of Circulating Osteoglycin With Bone Parameters and Metabolic Markers in Patients With Diabetes

Objective

Circulating osteoglycin may facilitate the crosstalk between bone and pancreas to empower adaptation of bone mass to whole body energy balance. We aimed to examine whether osteoglycin is associated with bone and metabolic parameters and if osteoglycin levels differ between patients with type 1 and 2 diabetes (T1D and T2D).

Design and methods

A cross-sectional study of 190 patients with diabetes mellitus and stable hemoglobin A1c (HbA1c) (97 T1D and 93 T2D) was conducted. S-osteoglycin was analyzed by ELISA. Unpaired t-tests were performed to test differences between patients with T1D and T2D and linear regression analyses were performed to investigate associations between osteoglycin, glycemic markers, bone turnover markers and characteristics.

Results

S-osteoglycin did not differ between patients with T1D and T2D (p=0.10). No associations were present between osteoglycin and age, gender, microvascular complications, HbA1c, or plasma glucose in T1D or T2D patients (p>0.05 for all). S-osteoglycin was not associated with levels of bone turnover markers (C-terminal cross-linked telopeptide of type-I collagen (CTX), P-procollagen type 1 amino terminal propeptide (P1NP), P-osteocalcin (OC), P-sclerostin, S-osteoprotegerin (OPG) or S-Receptor Activator of Nuclear factor Kappa beta Ligand (RANKL)) in neither T1D or T2D patients (p>0.05 for all).

Conclusion

Osteoglycin levels were similar in T1D and T2D patients. Osteoglycin did not correlate with glucose, HbA1c or any other biochemical marker of bone turnover. Thus, we did not find evidence supporting the existence of an osteoglycin-bone-pancreas axis.

Clinical Trial Registration

ClinicalTrials.gov, identifier NCT01870557.

Osteoglycin and Bone-a Systematic Review

PURPOSE OF REVIEW

Bone turnover is a regulated process. Osteoglycin is suggested to have an important impact on bone function but may also affect cardiovascular and metabolic functions. This review investigates the action of osteoglycin in bone as well as its potential endocrine effects.

RECENT FINDINGS

Osteoglycin is expressed by several tissues including bone and muscle. Some studies suggest that osteoglycin increases osteoblast differentiation whereas others suggest that osteoglycin decreases osteoblast differentiation. Thus, findings on the influence of osteoglycin in bone are conflicting. A recent study found increased bone mass in osteoglycin deficient mice. Another study reported that osteoglycin is a marker of low bone mineral density and vertebral fractures in women with type 2 diabetes. Furthermore, clinical studies link osteoglycin to insulin resistance and cardiovascular disease. Osteoglycin may be a novel marker of a muscle, pancreatic, and bone axis. However, current evidence is limited and further research investigating osteoglycin in both a pre-clinical and a clinical setting is needed.

Variations in internal structure, composition and protein distribution between intra- and extra-articular knee ligaments and tendons

Tendons and ligaments play key roles in the musculoskeletal system in both man and animals. Both tissues can undergo traumatic injury, age‐related degeneration and chronic disease, causing discomfort, pain and increased susceptibility to wider degenerative joint disease. To date, tendon and ligament ultrastructural biology is relatively under‐studied in healthy, non‐diseased tissues. This information is essential to understand the pathology of these tissues with regard to function‐related injury and to assist with the future development of tissue‐engineered tendon and ligament structures. This study investigated the morphological, compositional and extracellular matrix protein distribution differences between tendons and ligaments around the non‐diseased canine stifle joint. The morphological, structural characteristics of different regions of the periarticular tendons and ligaments (the intra‐articular anterior cruciate ligament, the extra‐articular medial collateral ligament, the positional long digital extensor tendon and energy‐storing superficial digital flexor tendons) were identified using a novel semi‐objective histological scoring analysis and by determining their biochemical composition. Protein distribution of extracellular matrix collagens, proteoglycans and elastic fibre proteins in anterior cruciate ligament and long digital extensor tendon were also determined using immunostaining techniques. The anterior cruciate ligament was found to have significant morphological differences in comparison with the other three tissues, including less compact collagen architecture, differences in cell nuclei phenotype and increased glycosaminoglycan and elastin content. Intra‐ and interobserver differences of histology scoring resulted in an average score 0.7, indicative of good agreement between observers. Statistically significant differences were also found in the extracellular matrix composition in terms of glycosaminoglycan and elastin content, being more prominent in the anterior cruciate ligament than in the other three tissues. A different distribution of several extracellular matrix proteins was also found between long digital extensor tendon and anterior cruciate ligament, with a significantly increased immunostaining of aggrecan and versican in the anterior cruciate ligament. These findings directly relate to the different functions of tendon and ligament and indicate that the intra‐articular anterior cruciate ligament is subjected to more compressive forces, reflecting an adaptive response to normal or increased loads and resulting in different extracellular matrix composition and arrangement to protect the tissue from damage.

The diverse functions of osteoglycin: a deceitful dwarf, or a master regulator of disease?

Small leucine-rich proteoglycans are emerging as important regulatory proteins within the extracellular matrix, where they exert both structural and nonstructural functions and hence are modulators of numerous biological processes, such as inflammation, fibrosis, and cell proliferation. One proteoglycan in particular, osteoglycin (OGN), also known as mimecan, shows great structural and functional diversity in normal physiology and in disease states, therefore making it a very interesting candidate for the development of novel therapeutic strategies. Unfortunately, the literature on OGN is confusing, as it has different names, and different transcript and protein variants have been identified. This review will give a clear overview of the different structures and functions of OGN that have been identified to date, portray its central role in pathophysiology, and highlight the importance of posttranslational processing, such as glycosylation, for the diversity of its functions.-Deckx, S., Heymans, S., Papageorgiou, A.-P. The diverse functions of osteoglycin: a deceitful dwarf, or a master regulator of disease?

Developmental pathways and endothelial to mesenchymal transition in canine myxomatous mitral valve disease

Epithelial to mesenchymal transition (EMT) and the cardiovascular equivalent, endothelial to mesenchymal transition (EndoMT), contribute to a range of chronic degenerative diseases and cancer metastasis. Chronic valvulopathies exhibit some features of EndoMT and activation of developmental signalling pathways, such as osteogenesis and chondrogenesis, expression of cell differentiation markers, basement membrane damage and endothelial transformation. The aim of the present study was to investigate the potential role of developmental mechanisms in canine myxomatous mitral valve disease (MMVD) using a combination of transcriptomic array technology, RT-PCR and immunohistochemistry. There was significant differential expression for genes typically associated with valvulogenesis and EndoMT, including markers of inflammation (IL6, IL18 and TLR4), basement membrane disarray (NID1, LAMA2 and CTSS), mesenchymal and endothelial cell differentiation (MYH11 and TAGLN) and EndoMT (ACTA2, SNAI1, CTNNB1, HAS2, CDH5, and NOTCH1), with fold changes from +15.35 (ACTA2) to -5.52 (LAMA2). These changes in gene expression were confirmed using RT-PCR, except for HAS2. In silico analysis identified important gene networks and canonical pathways in MMVD that have associations with development and organogenesis, including inflammation, valve morphogenesis and EMT, as well as components of the basement membrane and extra-cellular matrix. Immunohistochemistry identified changes in the expression of hyaluronic acid synthase (Has2), Snai1, α-smooth muscle actin (α-SMA) and VE-cadherin (CDH5), and co-expression of Has2 with α-SMA. These research findings strongly suggest involvement of developmental signalling pathways and mechanisms, including EndoMT, in the pathogenesis of canine MMVD.

Characterization of Skin Aging-Associated Secreted Proteins (SAASP) Produced by Dermal Fibroblasts Isolated from Intrinsically Aged Human Skin

Most molecular hallmarks of cellular senescence have been identified in studies of cells aged in vitro by driving them into replicative or stress-induced senescence. Comparatively, less is known about the characteristic features of cells that have aged in vivo. Here we provide a systematic molecular analysis of normal human dermal fibroblasts (NHDFs) that were isolated from intrinsically aged human skin of young versus middle aged versus old donors. Intrinsically aged NHDFs in culture exhibited more frequently nuclear foci positive for p53 binding protein 1 and promyelocytic leukemia protein reminiscent of 'DNA segments with chromatin alterations reinforcing senescence (DNA-SCARS)'. Formation of such foci was neither accompanied by increased DNA double strand breaks, nor decreased cell viability, nor telomere shortening. However, it was associated with the development of a secretory phenotype, indicating incipient cell senescence. By quantitative analysis of the entire secretome present in conditioned cell culture supernatant, combined with a multiplex cytokine determination, we identified 998 proteins secreted by intrinsically aged NHDFs in culture. Seventy of these proteins exhibited an age-dependent secretion pattern and were accordingly denoted 'skin aging-associated secreted proteins (SAASP)'. Systematic comparison of SAASP with the classical senescence-associated secretory phenotype (SASP) revealed that matrix degradation as well as proinflammatory processes are common aspects of both conditions. However, secretion of 27 proteins involved in the biological processes of 'metabolism' and 'adherens junction interactions' was unique for NHDFs isolated from intrinsically aged skin. In conclusion, fibroblasts isolated from intrinsically aged skin exhibit some, but not all, molecular hallmarks of cellular senescence. Most importantly, they secrete a unique pattern of proteins that is distinct from the canonical SASP and might reflect specific processes of skin aging.

Proteoglycans in Normal and Healing Skin

Significance: Proteoglycans have a distinct spatial localization in normal skin and are essential for the correct structural development, organization, hydration, and functional properties of this tissue. The extracellular matrix (ECM) is no longer considered to be just an inert supportive material but is a source of directive, spatial and temporal, contextual information to the cells via components such as the proteoglycans. There is a pressing need to improve our understanding of how these important molecules functionally interact with other matrix structures, cells and cellular mediators in normal skin and during wound healing. Recent Advances: New antibodies to glycosaminoglycan side chain components of skin proteoglycans have facilitated the elucidation of detailed localization patterns within skin. Other studies have revealed important proliferative activities of proteinase-generated fragments of proteoglycans and other ECM components (matricryptins). Knockout mice have further established the functional importance of skin proteoglycans in the assembly and homeostasis of the normal skin ECM. Critical Issues: Our comprehension of the molecular and structural complexity of skin as a complex, dynamic, constantly renewing, layered connective tissue is incomplete. The impact of changes in proteoglycans on skin pathology and the wound healing process is recognized as an important area of pathobiology and is an area of intense investigation. Future Directions: Advanced technology is allowing the development of new artificial skins. Recent knowledge on skin proteoglycans can be used to incorporate these molecules into useful adjunct therapies for wound healing and for maintenance of optimal tissue homeostasis in aging skin.

Small leucine-rich proteoglycans in the vertebrae of Atlantic salmon Salmo salar

We analysed the distribution and expression of the small leucine-rich proteoglycans (SLRPs) decorin, biglycan and lumican in vertebral columns of Atlantic salmon Salmo salar L. with and without radiographically detectable deformities. Vertebral deformities are a reoccurring problem in salmon and other intensively farmed species, and an understanding of the components involved in the pathologic development of the vertebrae is important in order to find adequate solutions to this problem. Using immunohistology and light microscopy, we found that in non-deformed vertebrae biglycan, lumican and decorin were all expressed in osteoblasts at the vertebral growth zones and at the ossification front of the chondrocytic arches. Hence, the SLRPs are expressed in regions where intramembranous and endochondral ossification take place. In addition, mRNA expression of biglycan, decorin and lumican was demonstrated in a primary osteoblast culture established from Atlantic salmon, supporting the in vivo findings. Transcription of the SLRPs increased during differentiation of the osteoblasts in vitro and where lumican mRNA expression increased later in the differentiation compared with decorin and biglycan. Intriguingly, in vertebral fusions, biglycan, decorin and lumican protein expression was extended to trans-differentiating cells at the border between arch centra and osteoblast growth zones. In addition, mRNA expression of biglycan, decorin and lumican differed between non-deformed and fused vertebrae, as shown by quantitative PCR (qPCR). Western blotting revealed an additional band of biglycan in fused vertebrae which had a higher molecular weight than in non-deformed vertebrae. Fourier-transform infrared (FTIR) spectroscopy revealed more spectral focality in the endplates of vertebral fusions and significantly more non-reducible collagen crosslinks compared with non-deformed vertebrae, thus identifying differences in bone structure.