Inhibition of myoblast differentiation by Sfrp1 and Sfrp2.

Secreted Frizzled-related proteins (Sfrps) are extracellular regulators of Wnt signalling and play important roles in developmental and oncogenic processes. They are known to be upregulated in regenerating muscle and in myoblast cultures but their function is unknown. Here, we show that the addition of recombinant Sfrp1 or Sfrp2 to C2C12 cell line cultures or to primary cultures of satellite cells results in the inhibition of myotube formation with no significant effect on the cell cycle or apoptosis.

Transplantation of adult myoblasts or adipose tissue precursor cells by high-density injection failed to improve reinnervated skeletal muscles.

We previously showed that transfer of adult myoblasts (MB) into cardiotoxin-damaged muscle improved the properties of reinnervated tibialis anterior muscle of rabbits. However, this cell therapy protocol cannot be applied to humans because of the hazardous effects of the myotoxin. To circumvent this approach, we used the recently developed high-density injection technique to autotransplant cultured cells 1 mm from each other into the tibialis anterior muscle without previous cardiotoxin-induced damage.

Short- or long-term effects of adult myoblast transfer on properties of reinnervated skeletal muscles.

Skeletal muscle demonstrates a force deficit after repair of injured peripheral nerves. Data from the literature indicate that myoblast transfer enhances recovery of muscle function. Thus, we tested the hypothesis that transfer of adult myoblasts improves the properties of reinnervated rabbit tibialis anterior (TA) muscles in both the short term (4 months) and long term (14 months).

Transplantation of adipose tissue-derived stromal cells increases mass and functional capacity of damaged skeletal muscle.

The regenerating skeletal muscle environment is capable of inducing uncommitted progenitors to terminally differentiate. The aim of this work was to determine whether adipose tissue-derived stromal cells were able to participate in muscle regeneration and to characterize the effect on muscle mass and functional capacities after transplantation of these cells. Adipose tissue stromal cells labeled with Adv cyto LacZ from 3-day-old primary cultures (SVF1) were autotransplanted into damaged tibialis anterior muscles.

Transplantation of Adipose Tissue-Derived Stromal Cells Increases Mass and Functional Capacity of Damaged Skeletal Muscle.

The regenerating skeletal muscle environment is capable of inducing uncommitted progenitors to terminally differentiate. The aim of this work was to determine whether adipose tissue-derived stromal cells were able to participate in muscle regeneration and to characterize the effect on muscle mass and functional capacities after transplantation of these cells. Adipose tissue stromal cells labeled with Adv cyto LacZ from 3-day-old primary cultures (SVF1) were autotransplanted into damaged tibialis anterior muscles.

Transplantation of primary satellite cells improves properties of reinnervated skeletal muscles.

Skeletal muscle demonstrates a force deficit after repair of injured peripheral nerves. We tested the hypothesis that transplantation of satellite cells into reinnervated rabbit tibialis anterior (TA) muscles improves their properties. Adult rabbits underwent transection and immediate suture of the common peroneal nerve.

Changes in mass and performance in rabbit muscles after muscle damage with or without transplantation of primary satellite cells.

Changes in morphology, metabolism, myosin heavy chain gene expression, and functional performances in damaged rabbit muscles with or without transplantation of primary satellite cells were investigated. For this purpose, we damaged bilaterally the fast muscle tibialis anterior (TA) with either 1.5 or 2.

Changes in Mass and Performance in Rabbit Muscles after Muscle Damage with or without Transplantation of Primary Satellite Cells.

Changes in morphology, metabolism, myosin heavy chain gene expression, and functional performances in damaged rabbit muscles with or without transplantation of primary satellite cells were investigated. For this purpose, we damaged bilaterally the fast muscle tibialis anterior (TA) with either 1.5 or 2.

SFRP2 expression in rabbit myogenic progenitor cells and in adult skeletal muscles.

Satellite cells derived from fast- and slow-twitch muscles have different properties in culture. We have used the differential display technique to retrieve genes differentially expressed in fast- and slow-twitch muscle satellite cell cultures. Amongst these genes we have identified, cloned, sequenced and studied the expression in muscle of rabbit secreted frizzled related protein 2 (SFRP2) mRNA, whose importance in cell fate determination has been well documented.

In vitro induction of UCP1 mRNA in preadipocytes from rabbit considered as a model of large mammals brown adipose tissue development: importance of PPARgamma agonists for cells isolated in the postnatal period.

Unlabelled: In mammals with a lower mass-specific metabolic rate than small laboratory rodents, the brown adipose tissue (BAT) loses its thermogenic activity after birth and undergoes a transformation into white adipose tissue (WAT). Rabbit is a model of these mammals of larger body mass. Preadipocytes from cervical BAT of foetal or newborn rabbits differentiated in a chemically-defined medium and expressed low levels of uncoupled protein-1 (UCP1) mRNA, greatly increased by beta3-adrenergic or retinoic acid stimulations.

Expression of specific white adipose tissue genes in denervation-induced skeletal muscle fatty degeneration.

Denervation of skeletal muscle results in rapid atrophy with loss of contractile mass and/or progressive degeneration of muscle fibers which are replaced to a greater or lesser degree by connective and fatty tissues. In this study, we show that denervated rabbit muscles are transformed into a white adipose tissue, depending on their fiber types. This tissue does express LPL, G3PDH and particularly the ob gene, a white adipose tissue-specific marker, and does not express the brown adipose tissue molecular marker UCP1 mRNA.

Expression of c-erbA alpha, c-erbA beta and Rev-erbA alpha mRNA during the conversion of brown adipose tissue into white adipose tissue.

The levels of mRNA encoding uncoupling protein (UCP), thyroid hormone receptors (c-erbA alpha, c-erbA beta) and a related protein Rev-erbA alpha have been studied in brown (pericervical) and white (perirenal) rabbit adipose tissues from birth to 180 days. The c-erbA alpha and c-erbA beta genes are expressed at similar levels in the two tissues. The alpha 1, alpha 2 and beta 1 transcripts do not change notably during development or during the conversion from brown to white phenotype which occurs in pericervical during postnatal life.

The beta 3-adrenoceptor agonist ICI-D7114 is not as efficient on reinduction of uncoupling protein mRNA in sheep as it is in dogs and smaller species.

Adipose tissue in newborn lambs is brown, but within a few days it is transformed into white adipose tissue. In the same way, preadipocytes cultured in serum-free chemically defined medium achieve full differentiation and express uncoupling protein (UCP), a marker of brown adipose tissue, when isolated from perirenal adipose tissue of the newborn, whereas they no longer express UCP when isolated from older lambs. The effects of a chronic stimulation of adipose tissue by novel beta 3-adrenoceptor agonist (ICI D7114) on the maintenance after birth and on the reinduction in older lambs of UCP mRNA in adipose tissue were studied.

Differentiation of adipocyte precursors in a serum-free medium is influenced by glucocorticoids and endogenously produced insulin-like growth factor-I.

Stromal vascular cells from rabbit perirenal adipose tissue differentiated at a high frequency in a chemically-defined serum-free medium containing insulin, transferrin, tri-iodothyronine and dexamethasone. The omission from the culture medium of dexamethasone resulted in a lack of adipose conversion. Addition of IGF-I increased glycerol-3-phosphate dehydrogenase (GPDH) activity.

Differentiation of ovine brown adipocyte precursor cells in a chemically defined serum-free medium. Importance of glucocorticoids and age of animals.

The rapid apparent conversion of brown adipose tissue into white adipose tissue in newborn offspring of large mammals, such as sheep and cattle is not explained at the cellular level. To study the differentiation of lamb brown adipocyte, a genomic fragment corresponding to the uncoupling protein was cloned from an ovine DNA library. Stromal vascular fibroblasts isolated from the perirenal adipose tissue of newborn lambs completely differentiated into brown adipocytes expressing the uncoupling protein gene, in a chemically defined serum-free medium.

In vivo effects of a treatment with antibodies to adipocyte plasma membranes in the rabbit.

Antibodies against rabbit adipocyte plasma membranes were injected in 6-week-old rabbits. Controls received normal IgG. Animals were killed 1, 2, 5 or 9 weeks after treatment.

Differentiation of rabbit adipocyte precursor cells in a serum-free medium.

A serum-free, hormone-supplemented medium containing insulin, transferrin, and triiodothyronine (ITT medium), able to support differentiation of rat adipose precursor cells, has been used to study the regulation of the development of adipocytes in the rabbit. Adipose conversion was assessed by the appearance of glycerol-3-phosphate dehydrogenase activity. Stromal-vascular cells from rabbit perirenal adipose tissue differentiated to a very low extent or not at all in ITT medium.

Differentiation of rabbit adipocyte precursors in primary culture.

A primary culture system was used to study the adipose conversion of adipocyte precursors derived from the stromal-vascular fraction of perirenal adipose tissue of rabbit fetuses Differentiation was assessed by the development of glycerol-3-phosphate dehydrogenase, Acid:CoA ligase and lipoprotein lipase activities. Stromal-vascular cells were not able to differentiate when maintained in a medium supplemented with fetal calf serum or with rabbit serum. In contrast, differentiation was induced when the medium was supplemented with rabbit plasma.

Longitudinal study of adipose cell size in the dorsoscapular and perirenal depots of the growing rabbit.

The changes in fat cell size during normal growth of New Zealand rabbits were investigated longitudinally with serial dorsoscapular and perirenal fat biopsies. A remarkably complex pattern of changes appeared when individual evolutions were considered. About 50% of the rabbits were characterized by "significant drops" of mean diameter during fat tissue growth with shifting of distributions toward the smaller cells.

Adipose tissue regeneration in 6-month-old and adult rabbits following lipectomy.

The effects of surgical ablation of adipose tissue were studied in male New Zealand rabbits. They were lipectomized or sham-operated either at 6 or 12 months, ages at which size and number of adipocytes are, respectively, stabilized in this species. The lipectomized animals were subjected to removal of about 80% of the perirenal and omental and to the totality of the dorsoscapular and inguinal fat tissues.

[Methodological approach to the circadian pattern of food intake in the growing domestic rabbit].

We graphically recorded the feeding pattern of 9 New Zealand male rabbits during weeks 6, 9, 12, 15 and 18 of age. Feeding was considered as a periodic series of discrete events. We fitted a periodic Poisson process to each particular series.