Pretreatment of rat bone marrow mesenchymal stem cells with a combination of hypergravity and 5-azacytidine enhances therapeutic efficacy for myocardial infarction.

Background And Purpose: The in vivo cardiac differentiation and functional effects of unmodified adult bone marrow mesenchymal stem cells (BMSCs) after myocardial infarction (MI) is controversial. Our previous results suggested that hypergravity promoted the cardiomyogenic differentiation of BMSCs, and thus we postulated that ex vivo pretreatment of BMSCs using hypergravity and 5-azacytidine (5-Aza) would lead to cardiomyogenic differentiation and result in superior biological and functional effects on cardiac regeneration of infarcted myocardium.

Methods: We used a rat MI model generated by ligation of the coronary artery.

The effects of low frequency electrical stimulation on satellite cell activity in rat skeletal muscle during hindlimb suspension.

Background: The ability of skeletal muscle to grow and regenerate is dependent on resident stem cells called satellite cells. It has been shown that chronic hindlimb unloading downregulates the satellite cell activity. This study investigated the role of low-frequency electrical stimulation on satellite cell activity during a 28 d hindlimb suspension in rats.

Gravity, a regulation factor in the differentiation of rat bone marrow mesenchymal stem cells.

Background: Stem cell therapy has emerged as a potential therapeutic option for tissue engineering and regenerative medicine, but many issues remain to be resolved, such as the amount of seed cells, committed differentiation and the efficiency. Several previous studies have focused on the study of chemical inducement microenvironments. In the present study, we investigated the effects of gravity on the differentiation of bone marrow mesenchymal stem cells (BMSCs) into force-sensitive or force-insensitive cells.

[Effects of rotation on osteonectin and osteopontin mRNA level of cultured osteoblasts in rats].

Conditions of disuse such as bed rest, space flight, and immobilization result in decreased mechanical loading of bone, which is associated with reduced bone mineral density and increased fracture risk. Mechanisms involved in this process are not well understood except the suppression of osteoblast function. To investigate the effect of simulated weightlessness on mRNA level of extracellular matrix proteins, osteoblasts were rotated in horizontal plane as a model of simulated microgravity.

[Effects of Naoyaojia on structural mechanical properties of femur in rats].

Objective: To study the effect of long term Naoyaojia administration on the structural mechanical properties of rat femurs.

Method: Young wistar rats were treated orally with Naoyaojia at doses of 3, 6, and 12 mg/kg body weight every 2 weeks for 1 year. Beary's bending test was used for determining physical properties of the femur.

[Simulation of the rat tibial bone density changes with the finite element method].

Objective: To calculate changes of rat tibial density induced by mechanical load with the finite element method.

Method: A three-dimensional computer model was formed by processing the industrial CT image of rat tibia; bone remodeling results were predicted by using the internal bone remodeling theory presented by Beaupre in conjunction with the finite element method.

Result: The increments of the elements density and its distribution plot were obtained.

[Effects of hindlimb unloading on bone histomorphometry and bone mass in rats].

Objective: To study the effects of hindlimb unloading on bone histomorphometry, bone local growth factor, bone biomechanical properties and bone contents in rats.

Method: Male SD rats were arranged into free active control group (CON) and tail-suspended group (TS) with 9 rats in each group. The experiment lasted for 3 weeks.

[Effects of simulated weightlessness on reproduction in male rats].

Objective: To study the effects of tail-suspension on gonad and spermatic hormone in male rats.

Method: After tail-suspension and reambulation some times in male rats, weight of testis was measured, sperm of epididymis was inspected, morphology of testicular cell was compared, and antent of testosterone assay by radioimmunoassay ratio of LH-beta positive cell in pituitary was measured by immunohistochemic.

Result: After tail-suspension, weight of testis in male rats decreased significantly.

[Changes of endocrine hormones during -6 degrees head down bed rest in human].

Objective: To investigate changes of endocrine hormones during 7 d head down bed rest (HDBR).

Method: Six healthy male volunteers served as the subjects and experienced 7 d -6 degrees HDBR. Urine was collected from 6:00-22:00 and from 22:00-6:00.

[Effects of simulated weightlessness and mechanical loading on bone interstitial fluid flow in rats].

Objective: To investigate the effects of simulated weightlessness and mechanical loading on bone interstitial fluid flow.

Method: Thirty-six male Sprague-Dawley [correction of Spargue-Danley] rats were divided into 3 groups: the control group, the tail-suspension group, and the tail-suspension plus mechanical loading group, with four rats in each group. All the rats were injected via a lateral tail vein with horseradish peroxidase on the 21st day of the experiment.