The critical role of the TB5 domain of Fibrillin-1 in endochondral ossification

Immunomodulation Effects of Porcine Cartilage Acellularized Matrix (pCAM) for Osteoarthritis Treatment

BACKGROUND

Pain reduction, immunomodulation, and cartilage repair are key therapeutic goals in osteoarthritis (OA) treatment. In this study, we evaluated the therapeutic effects of porcine cartilage acellularized matrix (pCAM) derived from naive tissue and compared it with the synthetic material polynucleotides (PN) for OA treatment.

METHODS

pCAM was produced from porcine cartilage through physicochemical processing. LC-MS protein profiling identified the key proteins. In vitro experiments involved treating human synovial cell with pCAM and PN to assess cell viability and reductions in pro-inflammatory cytokines (IL-1β and IL-6). In vivo studies utilized a rat DMM-induced OA model. Pain was evaluated in weight-bearing tests, and inflammation reduction was confirmed using specific macrophage markers of CD68, CD86, and CD163 in immunohistochemical staining of synovial tissue. Cartilage regeneration was evaluated by histopathological analyses.

RESULTS

The major protein components of pCAM include factors integral to cartilage and ECM integrity. They also contain proteins that help reduce inflammation. In vitro studies revealed a decrease in pro-inflammatory cytokines and survival of synovial cells were observed. In vivo treatment with pCAM resulted in a reduction of pain and inflammation, while promoting cartilage regeneration, thereby accelerating the healing process in OA.

CONCLUSION

Our findings suggest that pCAM may contribute to the treatment of OA by alleviating synovial inflammation and supporting cartilage regeneration, thereby addressing both the inflammatory and degenerative aspects of the disease.

Geleophysic dysplasia and Weill-Marchesani syndrome: ADAMTSL2 a possible common gene

BACKGROUND

Geleophysic dysplasia (GD) and Weill-Marchesani syndrome (WMS) are two rare genetic disorders that are classified as acromelic dysplasias and have many common features that overlap clinically and genetically in some patients. Both diseases are characterized by acromelic features, including short stature, brachydactyly, joint limitations, and cardiac involvement. WMS is distinguished from GD mainly by ocular abnormalities, including high myopia, microspherophakia, ectopia lentis, and glaucoma and the absence of the life-threatening airway stenosis and early lethality. These two syndromes are allelic diseases of the FBN1 gene, with the gene families including A Disintegrin and Metalloproteinase with Thrombospondin motifs (ADAMTS) and latent transforming growth factor-beta-binding protein (LTBP). Although the ADAMTSL2 gene has been associated only with GD within the acromelic dysplasias, there have been reports of patients with ADAMTSL2-related GD exhibiting ocular abnormalities that resemble WMS.

METHODS AND RESULTS

We present a 24-year-old female patient with microspherophakia, ectopia lentis, myopia, short stature, joint stiffness, thick skin, short hands and feet, and cardiac valve disease consistent with WMS. The virtual panel analysis, including WMS and GD-related genes, revealed a homozygous c.493 G>A (p.Ala165Thr) variant in the ADAMTSL2 gene (NM_014694.4), which has been previously reported in a geleophysic dysplasia patient.

CONCLUSIONS

Mounting evidence suggests that GD and WMS may be allelic diseases of the ADAMTSL2 gene.

Pathogenic variants affecting the TB5 domain of the fibrillin-1 protein: not only in geleophysic/acromicric dysplasias but also in Marfan syndrome

BACKGROUND

Marfan syndrome (MFS) is a multisystem disease with a unique combination of skeletal, cardiovascular and ocular features. Geleophysic/acromicric dysplasias (GPHYSD/ACMICD), characterised by short stature and extremities, are described as 'the mirror image' of MFS. The numerous FBN1 pathogenic variants identified in MFS are located all along the gene and lead to the same final pathogenic sequence. Conversely, in GPHYSD/ACMICD, the 28 known heterozygous FBN1 pathogenic variants all affect exons 41-42 encoding TGFβ-binding protein-like domain 5 (TB5).

METHODS

Since 1996, more than 5000 consecutive probands have been referred nationwide to our laboratory for molecular diagnosis of suspected MFS.

RESULTS

We identified five MFS probands carrying distinct heterozygous pathogenic in-frame variants affecting the TB5 domain of FBN1. The clinical data showed that the probands displayed a classical form of MFS. Strikingly, one missense variant affects an amino acid that was previously involved in GPHYSD.

CONCLUSION

Surprisingly, pathogenic variants in the TB5 domain of FBN1 can lead to two opposite phenotypes: GPHYSD/ACMICD and MFS, suggesting the existence of different pathogenic sequences with the involvement of tissue specificity. Further functional studies are ongoing to determine the precise role of this domain in the physiopathology of each disease.

The extracellular matrix glycoprotein fibrillin-1 in health and disease

Fibrillin-1 (FBN1) is a large, cysteine-rich, calcium binding extracellular matrix glycoprotein encoded by FBN1 gene. It serves as a structural component of microfibrils and provides force-bearing mechanical support in elastic and nonelastic connective tissue. As such, mutations in the FBN1 gene can cause a wide variety of genetic diseases such as Marfan syndrome, an autosomal dominant disorder characterized by ocular, skeletal and cardiovascular abnormalities. FBN1 also interacts with numerous microfibril-associated proteins, growth factors and cell membrane receptors, thereby mediating a wide range of biological processes such as cell survival, proliferation, migration and differentiation. Dysregulation of FBN1 is involved in the pathogenesis of many human diseases, such as cancers, cardiovascular disorders and kidney diseases. Paradoxically, both depletion and overexpression of FBN1 upregulate the bioavailability and signal transduction of TGF-β via distinct mechanisms in different settings. In this review, we summarize the structure and expression of FBN1 and present our current understanding of the functional role of FBN1 in various human diseases. This knowledge will allow to develop better strategies for therapeutic intervention of FBN1 related diseases.

TGF-β and BMP Signaling Pathways in Skeletal Dysplasia with Short and Tall Stature

The transforming growth factor β (TGF-β) and bone morphogenetic protein (BMP) signaling pathways play a pivotal role in bone development and skeletal health. More than 30 different types of skeletal dysplasia are now known to be caused by pathogenic variants in genes that belong to the TGF-β superfamily and/or regulate TGF-β/BMP bioavailability. This review describes the latest advances in skeletal dysplasia that is due to impaired TGF-β/BMP signaling and results in short stature (acromelic dysplasia and cardiospondylocarpofacial syndrome) or tall stature (Marfan syndrome). We thoroughly describe the clinical features of the patients, the underlying genetic findings, and the pathomolecular mechanisms leading to disease, which have been investigated mainly using patient-derived skin fibroblasts and mouse models. Although no pharmacological treatment is yet available for skeletal dysplasia due to impaired TGF-β/BMP signaling, in recent years advances in the use of drugs targeting TGF-β have been made, and we also discuss these advances.