Biomedical subjects

Marc T Galloway

Publications and source records attributed to Marc T Galloway.

9 recordsLinked to original sources

PubMed2006

Effects of mechanical stimulation on the biomechanics and histology of stem cell-collagen sponge constructs for rabbit patellar tendon repair.

The objective of this study was to determine how mechanical stimulation affects the biomechanics and histology of stem cell-collagen sponge constructs used to repair central rabbit patellar tendon defects. Autogenous tissue-engineered constructs were created for both in vitro and in vivo analyses by seeding mesenchymal stem cells from 10 adult rabbits at 0.14x10(6) cells/construct in type I collagen sponges. Half of these constructs were mechanically stimulated once every 5 min for 8 h/day to a peak strain of 4% for 2 weeks. The other half remained in an incubator without mechanical stimulation for 2 weeks. Samples allocated for in vitro testing revealed that mechanically stimulated constructs had 2.5 times the linear stiffness of nonstimulated constructs. The remaining paired constructs for in vivo studies were implanted in bilateral full-thickness, full-length defects in the central third of rabbit patellar tendons. Twelve weeks after surgery, repair tissues were assigned for biomechanical (7 pairs) and histologic (3 pairs) analyses. Maximum force, linear stiffness, maximum stress, and linear modulus for the stimulated (vs. nonstimulated) repairs averaged 70% (vs. 55%), 85% (vs. 55%), 70% (vs. 50%), and 50% (vs. 40%) of corresponding values for the normal central third of the patellar tendons. The average force-elongation curve for the mechanically stimulated repairs also matched the corresponding curve for the normal patellar tendons, up to 150% of the peak in vivo force values recorded in a previous study. Construct and repair linear stiffness and linear modulus were also positively correlated (r = 0.6 and 0.7, respectively). Histologically both repairs showed excellent cellular alignment and mild staining for decorin and collagen type V, and moderate staining for fibronectin and collagen type III. This study shows that mechanical stimulation of stem cell-collagen sponge constructs can significantly improve tendon repair biomechanics up to and well beyond the functional limits of in vivo loading.

Animals↗

PubMed2006

The effect of autologous mesenchymal stem cells on the biomechanics and histology of gel-collagen sponge constructs used for rabbit patellar tendon repair.

The objective of this study was to introduce mesenchymal stem cells (MSCs) into a gel-sponge composite and examine the effect the cells have on repair biomechanics and histology 12 weeks postsurgery. We tested two related hypotheses-adding MSCs would significantly improve repair biomechanics and cellular organization, and would result in higher failure forces than peak in vivo patellar tendon (PT) forces recorded for an inclined hopping activity. Autogenous tissue-engineered constructs were created by seeding MSCs from 15 adult rabbits at 0.1 x 10(6) cells/mL in 2.6 mg/mL of collagen gel in collagen sponges. Acellular constructs were created using the same concentration of collagen gel in matching collagen sponges. These cellular and acellular constructs were implanted in bilateral full-thickness, full-length defects in the central third of patellar tendons. At 12 weeks after surgery, repair tissues were assigned for biomechanical (n = 12 pairs) and histological (n = 3 pairs) analyses. Maximum force and maximum stress for the cellular repairs were about 60 and 50% of corresponding values for the normal central third of the PT, respectively. Likewise, linear stiffness and linear modulus for these cellular repairs averaged 75 and 30% of normal PT values, respectively. By contrast, the acellular repairs exhibited lower percentages of normal PT values for maximum force (40%), maximum stress (25%), linear stiffness (30%), and linear modulus (20%). Histologically, both repairs showed strong staining for collagen types III and V, fibronectin, and decorin. The cellular repairs also showed cellular alignment comparable to that of normal tendon. This study shows that introducing autogenous mesenchymal stem cells into a gel-collagen sponge composite significantly improves tendon repair compared to the use of a gel-sponge composite alone in the range of in vivo loading.

Animals↗

PubMed2006

Effects of cell-to-collagen ratio in stem cell-seeded constructs for Achilles tendon repair.

The objective of the present study was to test the hypotheses that implantation of cell-seeded constructs in a rabbit Achilles tendon defect model would 1) improve repair biomechanics and matrix organization and 2) result in higher failure forces than measured in vivo forces in normal rabbit Achilles tendon (AT) during an inclined hopping activity. Autogenous tissue-engineered constructs were fabricated in culture between posts in the wells of silicone dishes at four cell-to-collagen ratios by seeding mesenchymal stem cells (MSC) from 18 adult rabbits at each of two seeding densities (0.1 x 10(6) and 1 x 10(6) cell/mL) in each of two collagen concentrations (1.3 and 2.6 mg/mL). After 5 days of contraction, constructs having the two highest ratios (0.4 and 0.8 M/mg) were damaged by excessive cell traction forces and could not be used in subsequent in vivo studies. Constructs at the lower ratios (0.04 and 0.08 M/mg) were implanted in bilateral, 2 cm long gap defects in the rabbit's lateral Achilles tendon. At 12 weeks after surgery, both repair tissues were isolated and either failed in tension (n = 13) to determine their biomechanical properties or submitted for histological analysis (n = 5). No significant differences were observed in any structural or mechanical properties or in histological appearance between the two repair conditions. However, the average maximum force and maximum stress of these repairs achieved 50 and 85% of corresponding values for the normal AT and exceeded the largest peak in vivo forces (19% of failure) previously recorded in the rabbit AT. Average stiffness and modulus were 60 and 85% of normal values, respectively. New constructs with lower cell densities and higher scaffold stiffness that do not excessively contract and tear in culture and that further improve the repair stiffness needed to withstand various levels of expected in vivo loading are currently being investigated.

Achilles Tendon↗

PubMed2004

Characterization of in vivo Achilles tendon forces in rabbits during treadmill locomotion at varying speeds and inclinations.

The objective of this study was to test the hypothesis that increasing the speed and inclination of the treadmill increases the peak Achilles tendon forces and their rates of rise and fall in force. Implantable force transducers (IFT) were inserted in the confluence of the medial and lateral heads of the left gastrocnemius tendon in 11 rabbits. IFT voltages were successfully recorded in 8 animals as the animals hopped on a treadmill at each of two speeds (0.1 and 0.3 mph) and inclinations (0 degrees and 12 degrees). Instrumented tendons were isolated shortly after sacrifice and calibrated. Contralateral unoperated tendons were failed in uniaxial tension to determine maximum or failure force, from which safety factor (ratio of maximum force to peak in vivo force) was calculated for each activity. Peak force and the rates of rise and fall in force significantly increased with increasing treadmill inclination (p<0.001). Safety factors averaged 30.8+/-7.5 for quiet standing, 7.0+/-2.9 for level hopping, and 5.2+/-0.7 for inclined hopping (mean+/-SEM). These in vivo force parameters will help tissue engineers better design functional tissue engineered constructs for rabbit Achilles tendon and other tendon repairs. Force patterns can also serve as input data for mechanical stimulation of tissue-engineered constructs in culture. Such approaches are expected to help accelerate tendon repair after injury.

Achilles Tendon↗

PubMed2003

In vivo forces used to develop design parameters for tissue engineered implants for rabbit patellar tendon repair.

Previous studies in tissue engineering have shown that suspending undifferentiated mesenchymal stem cells in collagen gels and wrapping them about a suture causes alignment of cells and contraction of constructs in culture in a form that is suitable for implantation for tendon repair. Little is known about the patterns of these in vivo signals that might improve tendon repair biomechanics. Three hypotheses were tested in this study using the rabbit patellar tendon (PT) model: (1) peak in vivo forces and the rates of rise and fall in these forces will increase significantly with increasing levels of activity; (2) the PTs safety factor for all activities will be in the range of values found for tendons (2.5-3); (3) rabbits will not "favor" the operated limb at the time of evaluation but maintain similar vertical ground reaction forces in both limbs during quiet standing (QS). In vivo rabbit PT forces were measured during QS and while the animal hopped on a treadmill whose speed (0.04 and 0.13 m/s) and inclination (0 degrees and 12 degrees) were controlled. Implantable force transducers were surgically placed in one PT and data collected three days post surgery in each of eight New Zealand White rabbits. Peak tensile forces increased significantly with inclination of the treadmill and the rates of rise and fall in tendon force increased significantly with both speed and inclination (p<0.001). Such design criteria should be useful in mechanically stimulating cell-gel constructs for tendon repair.

Animals↗

PubMed2002

Grade 2C signal in the meniscus [correction of mensicus] on MR imaging of the knee.

OBJECTIVE: The objective of our study was to evaluate the clinical significance of grade 2C meniscal [corrected] signal (an extensive triangular or wedge-shaped signal that does not reach the surface on more than one image) on MR imaging of the knee. MATERIALS AND METHODS: Review of 1106 MR imaging reports over 2 years revealed 88 patients with menisci described as containing triangular, wedge-shaped, extensive, or grade 2C signal. Image review by consensus of two radiologists found 34 menisci in 29 patients that fit criteria for grade 2C signal. Seven menisci containing grade 2C signal were evaluated with arthroscopy. An additional three patients with grade 2C meniscal signal with arthroscopic correlation were identified from 4 previous years. RESULTS: Prevalence of grade 2C signal was 1.5% (34/2212 menisci). Seven (21%) of these 34 menisci had subsequent arthroscopy and three of these had meniscal tears. Including the three additional menisci with grade 2C signal from 4 previous years, five (50%) of 10 menisci with grade 2C signal were torn at arthroscopy. No difference was noted between torn and intact menisci in the number of images with grade 2C signal. In patients with tears, the range was three to 10 images (mean, 6.6 images) compared with a range of two to 10 images (mean, 6.6 images) in patients without tears. The maximal percentage of area of abnormal signal in patients with tears ranged from 70% to 90% (mean, 80%) compared with a range of 60-90% (mean, 82%) in patients without tears. The patient age range was 23-64 years (mean, 47 years) in patients with tears and 16-67 years (mean, 47 years) in patients without tears. CONCLUSION: Grade 2C meniscal signal has a low incidence. Although half of patients with symptoms meriting arthroscopy have tears, most patients with grade 2C signal are not treated with arthroscopy.

Adolescent↗

PubMed2002

Neuromuscular function in athletes following recovery from a recent acute low back injury.

STUDY DESIGN: Observational case control design. OBJECTIVES: To examine muscle response to sudden trunk loading in athletes with and without a recent history of acute low back injury (LBI). BACKGROUND: Impaired neuromuscular function is associated with chronic low back pain. This study examined whether such impairment persists after recovery from an acute LBI. METHODS AND MEASURES: Seventeen athletes who had a recent history of acute LBI and 17 matched healthy controls were tested. At the time of testing (mean = 56 days postinjury, range = 7-120 days postinjury), all athletes were symptom free and had returned to regular competition. Subjects performed isometric exertions in trunk flexion, extension, and left and right lateral bending against a trunk restraining cable. Upon reaching the target isometric force, the cable was released to impose sudden loading on the lumbar spine. Surface EMG signals from 12 major trunk muscles were recorded. The shut-off and switch-on latencies and number of muscles responding to sudden loading were compared between the 2 groups. RESULTS: In all 4 testing directions, the athletes with a recent history of acute LBI shut off significantly fewer muscles and did so with delayed latency. On average, the injured subjects shut off 4.0 out of 6.0 (SD = 1.3) muscles compared to 4.6 out of 6.0 (SD = 1.3) muscles in the control group. The average muscle shut-off latency was 71 (SD = 31) milliseconds for the injured and 50 (SD = 21) milliseconds for the control subjects. No differences were found in number or latency of muscles switching on. CONCLUSIONS: These objective measures of neuromuscular function indicated an altered muscle response pattern to sudden trunk loading in athletes following their clinical recovery from a recent acute LBI.

Acute Disease↗

PubMed2002

Effect of aging on male and female master athletes' performance in strength versus endurance activities.

Aging has traditionally been associated with several functional declines within the musculoskeletal system. In this study, we characterized and compared age-related changes in performance in power and endurance activities (ie, power-lifting, stationary rowing). From age 25 to age 85, men's and women's rowing performance decreases 29%; from age 25 to age 55, men's rowing performance decreases 0.12% per year, and women's performance decreases 0.23% per year. The pattern of decline in power-lifting performance is characterized by earlier onset and more rapid progression. During the fourth decade, men's and women's power-lifting performance decreases 3% per year; thereafter, their performance decreases 1% per year. The difference between the age-related change rates for rowing and power-lifting is statistically significant (P = .05). The older athletes' performance in both activities suggests that the capacity for significant function in activities requiring power and endurance persists throughout life in individuals who train and who remain in good health. That strength decreases more rapidly than endurance capacity points to the importance of resistance exercises for minimizing muscle weakness in an aging population.

Adult↗

PubMedDate not supplied

Effects of cell-to-collagen ratio in mesenchymal stem cell-seeded implants on tendon repair biomechanics and histology.

Autogenous tissue-engineered constructs were fabricated at four cell-to-collagen ratios (0.08, 0.04, 0.8, and 0.4 M/mg) by seeding mesenchymal stem cells (MSCs) from 16 adult rabbits at one of two seeding densities (0.1 x 10(6) and 1 x 10(6) cells/mL) in one of two collagen concentrations (1.3 and 2.6 mg/mL). The highest two ratios (0.4 and 0.8 M/mg) were damaged by excessive cell contraction and could not be used in subsequent in vivo studies. The remaining two sets of constructs were implanted into bilateral full-thickness, full-length defects created in the central third of the patellar tendon (PT). At 12 weeks after surgery, repair tissues were assigned for biomechanical (n = 13) and histological (n = 3) analyses. A second group of rabbits (n = 6) received bilateral acellular implants with the same two collagen concentrations. At 12 weeks, repair tissues were also assigned for biomechanical (n = 4) and histological (n = 2) analyses. No significant differences were observed in any structural or material properties or in histological appearance among the two cell-seeded and two acellular repair groups. Average maximum force and maximum stress of the repairs were approximately 30% of corresponding values for the central one-third of normal PT and higher than peak in vivo forces measured in rabbit PT from one of our previous publications. However, average repair stiffness and modulus were only 30 and 20% of normal PT values, respectively. Current repairs achieved higher maximum forces than in previous studies and without ectopic bone, but will need to achieve sufficient stiffness as well to be effective in the in vivo range of loading.

Animals↗