PG-EASIA Kit

The hallmark of endochondral bone development is the presence of cartilaginous templates, in which osteoblasts and stromal cells are generated to form mineralized matrix and support bone marrow haematopoiesis. However, the ultimate source of these mesenchymal cells and the relationship between bone progenitors in fetal life and those in later life are unknown. Fate-mapping studies revealed that cells expressing cre-recombinases driven by the collagen II (Col2) promoter/enhancer and their descendants contributed to, in addition to chondrocytes, early perichondrial precursors before Runx2 expression and, subsequently, to a majority of osteoblasts, Cxcl12 (chemokine (C-X-C motif) ligand 12)-abundant stromal cells and bone marrow stromal/mesenchymal progenitor cells in postnatal life. Lineage-tracing experiments using a tamoxifen-inducible creER system further revealed that early postnatal cells marked by Col2-creER, as well as Sox9-creER and aggrecan (Acan)-creER, progressively contributed to multiple mesenchymal lineages and continued to provide descendants for over a year. These cells are distinct from adult mesenchymal progenitors and thus provide opportunities for regulating the explosive growth that occurs uniquely in growing mammals.

Bone marrow-derived mesenchymal stem cells (BMSCs) have the potential to form the mechanically responsive matrices of joint tissues, including the menisci of the knee joint. The purpose of this study is to assess BMSC's potential to engineer meniscus-like tissue relative to meniscus fibrochondrocytes (MFCs). MFCs were isolated from castoffs of partial meniscectomy from nonosteoarthritic knees. BMSCs were developed from bone marrow aspirates of the iliac crest. All cells were of human origin. Cells were cultured in type I collagen scaffolds under normoxia (21% O-2) for 2 weeks followed by hypoxia (3% O-2) for 3 weeks. The structural and functional assessment of the generated meniscus constructs were based on glycosaminoglycan (GAG) content, histological appearance, gene expression, and mechanical properties. The tissues formed by both cell types were histologically positive for Safranin O stain and appeared more intense in the BMSC constructs. This observation was confirmed by a 2.7-fold higher GAG content. However, there was no significant difference in collagen I (COL1A2) expression in BMSC- and MFC-based constructs (p = 0.17). The expression of collagen II (COL2A1) and aggrecan (ACAN) were significantly higher in BMSCs than MFC (p <= 0.05). Also, the gene expression of the hypertrophic marker collagen X (COL10A1) was 199-fold higher in BMSCs than MFC (p < 0.001). Moreover, relaxation moduli were significantly higher in BMSC-based constructs at 10-20% strain step than MFC-based constructs. BMSC-based constructs expressed higher COL2A1, ACAN, COL10A1, contained higher GAG content, and exhibited higher relaxation moduli at 10-20% strain than MFC-based construct. Impact statement Cell-based tissue engineering (TE) has the potential to produce functional tissue replacements for irreparably damaged knee meniscus. But the source of cells for the fabrication of the tissue replacements is currently unknown and of research interest in orthopedic TE. In this study, we fabricated tissue-engineered constructs using type I collagen scaffolds and two candidate cell sources in meniscus TE. We compared the mechanical properties of the tissues formed from human meniscus fibrochondrocytes and bone marrow-derived mesenchymal stem cells (BMSCs). Our data show that the tissues engineered from the BMSC are mechanically superior in relaxation modulus.