Biomedical subjects

Gary S Beaupre

Publications and source records attributed to Gary S Beaupre.

4 recordsLinked to original sources

PubMed2006

Gene regulation ex vivo within a wrap-around tendon.

This study tested the hypothesis that physiologic tendon loading modulates the fibrous connective tissue phenotype in undifferentiated skeletal cells. Type I collagen sponges containing human bone marrow stromal cells (MSCs) were implanted into the midsubstance of excised sheep patellar tendons. An ex vivo loading system was designed to cyclically stretch each tendon from 0 to 5% at 1.0 Hz. The MSC-sponge constructs were implanted into 2 tendon sites: the first site subjected to tension only and a second site located at an artificially created wrap-around region in which an additional compressive stress was generated transverse to the longitudinal axis of the tendon. The induced contact pressure at the wraparound site was 0.55 +/- 0.12 MPa, as quantified by pressure-sensitive film. An MSC-sponge construct was maintained free swelling in the same bath as an unloaded control. After 2 h of tendon stretching, the MSC-sponge constructs were harvested and real-time PCR was used to quantify Fos, Sox9, Cbfa1 (Runx2), and scleraxis mRNA expression as markers of skeletal differentiation. Two hours of mechanical loading distinctly altered MSC differentiation in the wrap-around region and the tensile-only region, as evidenced by differences in Fos and Sox9 mRNA expression. Expression of Fos mRNA was 13 and 52 times higher in the tensile-only and wrap-around regions, respectively, compared to the free-swelling controls. Expression of Sox9 mRNA was significantly higher (2.5-3 times) in MSCs from the wraparound region compared to those from the tensile-only region or in free-swelling controls. In contrast, expression levels for Cbfa1 did not differ among constructs. Scleraxis mRNA was not detected in any construct. This study demonstrates that the physiologic mechanical environment in the wrap-around regions of tendons provides stimuli for upregulating early response genes and transcription factors associated with chondrogenic differentiation. These differentiation responses begin within as little as 2 h after the onset of mechanical stimulation and may be the basis for the formation of fibrocartilage that is typically found in the wrap-around region of mature tendons in vivo.

Animals↗

PubMed2006

Bone-density changes after stroke.

It has been many years since bone loss and fracture risk were first recognized as serious complications of stroke. Hip fracture is associated with a substantial increase in morbidity and mortality for stroke survivors, and therefore, assessing and maintaining skeletal health after stroke should be an important clinical goal. Recent long-term, prospective studies have illustrated a highly nonuniform pattern of bone changes after stroke. In general, there is significant bone loss on the paretic side, which is greatest in those patients with the most severe functional deficits. In some patients, bone loss in the paretic arm during the first year after stroke is the equivalent of >20 yrs of bone loss in healthy individuals of comparable age. Bone density in the nonparetic upper limb can actually increase after stroke, consistent with an increase in habitual use of the nonparetic hand. Bone density in the paretic lower limb can decrease by >10% in <1 yr, with smaller decreases being typical for the nonparetic lower limb. Despite the recent increase in the number of prospective, longitudinal studies, important questions about bone changes after stroke remain unanswered. Longer-term studies quantifying bone loss for periods of >12 mos poststroke are needed to determine how long excess bone loss continues after stroke. Studies with more subjects and with more varied disability levels are needed to better understand the relationships between functional deficits and bone loss. New metrics are needed to quantify the intensity and duration of physical activity in the upper and lower limbs that are consistent with previous research on the role of mechanical stimuli in bone adaptation. Finally, an assessment of skeletal health and the factors that affect bone quantity and quality should be a standard component in the clinical management of all survivors of stroke.

Absorptiometry, Photon↗

PubMed2004

Weight-bearing MRI of patellofemoral joint cartilage contact area.

PURPOSE: To measure contact area of cartilage in the patellofemoral joint during weight bearing using an open MRI scanner. MATERIALS AND METHODS: We developed an MR-compatible back support that allows three-dimensional imaging of the patellofemoral cartilage under physiologic weight-bearing conditions with negligible motion artifact in an open MRI scanner. To measure contact areas, we trained observers using a phantom of known area and tested intra- and interobserver variability. We measured in vivo contact areas between the patella and femoral cartilage with the knee in 30 degrees of flexion, loaded and unloaded, in six volunteers. RESULTS: We were able to measure the contact area of the patellofemoral cartilage with small interobserver (CV 7.0%) and intraobserver (CV 3.0%) variation. At 30 degrees of knee flexion, mean contact area increased from 400 mm2 (unloaded) to 522 mm2(loaded to 0.45 times body weight per leg). CONCLUSION: Using an open magnet and specially designed apparatus, it is possible to image the patellar cartilage during physiologic loading. Knowledge of patellar cartilage contact area is needed to assess patellofemoral stress, which may be increased in patients with patellofemoral pain syndrome.

Cartilage, Articular↗

PubMedDate not supplied

Key characteristics of walking correlate with bone density in individuals with chronic stroke.

Several recent studies of ambulatory stroke survivors have shown decreased bone mineral density (BMD) in the lower limbs and an elevated risk of hip fracture. Because bone mass is linked to skeletal loading, weight-bearing activities of daily living such as walking are considered critically important for maintenance of femoral BMD in ambulatory individuals. Little is known about the relationships between walking characteristics, skeletal loading, and bone maintenance in individuals who have experienced a stroke. This study determined whether certain gait-related parameters correlate with proximal femoral BMD in ambulatory individuals with poststroke walking deficits. We analyzed data from 33 individuals with chronic stroke and found that a recently introduced metric, the Bone Density Index, which incorporates body weight, number of steps per day, and ground reaction force magnitude, predicted proximal femoral BMD better than other commonly measured demographic and gait-related parameters that we examined.

Age Factors↗