Characterization of distinct mesenchymal-like cell populations from human skeletal muscle in situ and in vitro.

Human skeletal muscle is an essential source of various cellular progenitors with potential therapeutic perspectives. We first used extracellular markers to identify in situ the main cell types located in a satellite position or in the endomysium of the skeletal muscle. Immunohistology revealed labeling of cells by markers of mesenchymal (CD13, CD29, CD44, CD47, CD49, CD62, CD73, CD90, CD105, CD146, and CD15 in this study), myogenic (CD56), angiogenic (CD31, CD34, CD106, CD146), hematopoietic (CD10, CD15, CD34) lineages. We then analysed cell phenotypes and fates in short- and long-term cultures of dissociated muscle biopsies in a proliferation medium favouring the expansion of myogenic cells. While CD56(+) cells grew rapidly, a population of CD15(+) cells emerged, partly from CD56(+) cells, and became individualized. Both populations expressed mesenchymal markers similar to that harboured by human bone marrow-derived mesenchymal stem cells. In differentiation media, both CD56(+) and CD15(+) cells shared osteogenic and chondrogenic abilities, while CD56(+) cells presented a myogenic capacity and CD15(+) cells presented an adipogenic capacity. An important proportion of cells expressed the CD34 antigen in situ and immediately after muscle dissociation. However, CD34 antigen did not persist in culture and this initial population gave rise to adipogenic cells. These results underline the diversity of human muscle cells, and the shared or restricted commitment abilities of the main lineages under defined conditions.

Interleukin-1 and transforming growth factor-beta 1 as crucial factors in osteoarthritic cartilage metabolism.

In osteoarthritis (OA), interleukin-1 (IL-1) stimulates the expression of metalloproteinases and aggrecanases, which induce cartilage degradation. IL-1 is also capable of reducing the production of cartilage-specific macromolecules, including type II collagen, through modulation of the transcription factors Sp1 and Sp3. Conversely, Transforming growth factor-beta (TGF-beta) counteracts with most of the IL-1 deleterious effects and contributes to cartilage homeostasis. However, OA chondrocytes progressively loose the expression of TGF-beta type II receptor and become insensitive to the factor. This downregulation is also driven by IL-1. This review provides insights into the molecular mechanisms that underly the interplay between IL-1 and TGF-beta in OA cartilage metabolism and enlightens the central role of Sp1 and Sp3 transcription factors in the matrix pathological alterations.

Hypoxia affects mesenchymal stromal cell osteogenic differentiation and angiogenic factor expression.

Mesenchymal stromal cells (MSCs) seeded onto biocompatible scaffolds have been proposed for repairing bone defects. When transplanted in vivo, MSCs (expanded in vitro in 21% O(2)) undergo temporary oxygen deprivation due to the lack of pre-existing blood vessels within these scaffolds. In the present study, the effects of temporary (48 h) exposure to hypoxia (

Molecular mechanism of hypoxia-induced chondrogenesis and its application in in vivo cartilage tissue engineering.

Cartilage engineering is one of the most challenging issue in regenerative medicine, due to its limited self-ability to repair. Here, we assessed engineering of cartilage tissue starting from human bone marrow (hBM) stem cells under hypoxic environment and delineated the mechanism whereby chondrogenesis could be conducted without addition of exogenous growth factors. hBM stem cells were cultured in alginate beads and chondrogenesis was monitored by chondrocyte phenotypic markers. Activities and roles of Sox and HIF-1α transcription factors were investigated with complementary approaches of gain and loss of function and provided evidences that HIF-1α is essential for hypoxic induction of chondrogenesis. Thereafter, hBM cells and human articular chondrocytes (HAC) underwent chondrogenesis by 3D and hypoxic culture for 7 days or by ectopic expression of HIF-1α. After subcutaneous implantation of 3 weeks into athymic mice, tissue analysis showed that hypoxia or HIF-1α overexpression is effective and sufficient to induce chondrocyte phenotype in hBM cells, without use of exogenous growth factors. Therefore, this study brings interesting data for a simple and affordable system in biotechnology of cartilage engineering.

Comparative effects of 2 antioxidants, selenomethionine and epigallocatechin-gallate, on catabolic and anabolic gene expression of articular chondrocytes.

OBJECTIVE: . To determine the effects of selenomethionine (Se-met) and epigallocatechin-gallate (EGCg) on gene expression, activation of mitogen-activating kinases, and DNA binding of nuclear factor-kappaB (NF-kappaB) and apolipoprotein-1 (AP-1) in articular chondrocytes. METHODS: Chondrocytes, cultured in low-oxygen tension, were pretreated with L-selenomethionine or EGCg for 24 h, followed by interleukin 1 (IL-1beta) for 1 h (nuclear and cytoplasmic extracts) or 24 h (RNA extraction). Reverse transcription-polymerase chain reaction was performed to determine mRNA levels of matrix metalloproteinases (MMP-1, -3, -13), aggrecanases (-1, -2), IL-1beta, inducible nitric oxide synthase, cyclooxygenases (-1, -2), type II collagen and aggrecan, and transforming growth factor-beta (TGF-beta1, -2, -3) and their receptors I and II. Activity of mitogen-activating protein kinases (MAPK) was assayed by Western blot and AP-1/NF-kB DNA binding by electrophoretic mobility shift assay. RESULTS: Pretreatment with 0.5 microM Se-met prevented IL-1beta-induced MMP-1 and aggrecanase-1 expression, and reduced the cytokine inhibitory effect on type II collagen, aggrecan core protein, and TGF-beta receptor II (TGF-betaRII) mRNA levels. EGCg was more efficient in modulating the effects of IL-1beta on the genes studied. Whereas EGCg inhibited the IL-1beta-activated MAPK, NF-kappaB, and AP-1, Se-met stimulated that signaling pathway. This could account for the differential effects exerted by these antioxidants on chondrocytes. CONCLUSION: Our data provide insights into the mechanisms whereby ECGg and selenium modulate chondrocyte metabolism. Despite their differential mechanisms of action, the 2 compounds may exert global beneficial effects on articular cartilage.