Healing of iatrogenic skeletal muscle wounds is affected by incision device.

Orthopedic joint procedures frequently require extensive dissection of skeletal muscles resulting in tissue injury, formation of scar tissue, pain, and potentially, functional impairment. The authors hypothesized that using a low-temperature ultrasonic cutting and coagulating device (Harmonic Blade, Ethicon Endo-Surgery, Cincinnati, OH) would result in reduction in tissue trauma in terms of reducing acute and chronic inflammation during healing. Bilateral longitudinal incisions were made into the tibialis cranialis muscles of rabbits with either a Harmonic Blade or a standard monopolar electrosurgical scalpel. At 3, 7, and 21 days postoperatively, necropsy and histological evaluations indicated a significant attenuation of acute inflammation (P = .011) for the Harmonic incisions compared with electrosurgery. No significant differences were observed for chronic inflammation, necrosis, or fibrosis. Use of a Harmonic scalpel during dissection of skeletal muscle in orthopedic surgery may result in reduced influx of neutrophils, reducing acute inflammation, and potentially aid in reducing postoperative pain and functional impairment.

Fatty infiltration of the gastrocsoleus after tendo-achilles lengthening and gastrocnemius recession in a rabbit model.

BACKGROUND: Tendo-Achilles lengthening (TAL) and gastrocnemius recession (GR) are components of the operative treatment for certain foot conditions. We investigated changes in rabbit gastrocsoleus weight, volume, and percent fat resulting from TAL, GR, and immobilization. MATERIALS AND METHODS: Eighteen rabbits were randomized into three groups. Group I = gastrocnemius recession; Group II = (TAL) Z-plasty lengthening; Group III = immobilization only. Treatment limbs were randomized. Six randomly selected contralateral limbs were used for controls. At 12 weeks the gastrocnemius and soleus were weighed (g) and measured (ml) separately. Values were combined and analyzed as a gastrocsoleus complex. The weight, volume, and percentage of fatty infiltration were analyzed using one-way analysis of variance (ANOVA). RESULTS: The following differences were statistically significant. GR volume was less than control (p < 0.01); TAL weight and volume was less than control (p < 0.01); GR percent fat was greater than control (p < 0.05) and TAL percent fat was greater than control (p < 0.05). GR weight and volume was less than cast only (p < 0.01); TAL weight and volume was less than cast only (p < 0.01); TAL percent fat was greater than cast only (p < 0.01); GR percent fat was greater than cast only (p < 0.05); GR weight was greater than TAL (p < 0.05). CONCLUSION: In a rabbit model, the findings suggest the gastrocsoleus undergoes atrophy and fatty infiltration after TAL or GR. Immobilization does not contribute to either process. CLINICAL RELEVANCE: These findings correlate with human functional studies documenting the relationship between TAL or GR and decrease in plantarflexion strength. Further studies are needed to determine if significant variation in functional differences due to TAL versus GR exists.

Inflammatory cytokines and cell adhesion molecules in a rat model of decompression sickness.

To characterize early blood and tissue markers predictive of decompression sickness (DCS), this study focused on identifying changes in inflammatory mediators during the 24-h period immediately following compression-decompression of female Sprague-Dawley rats. Early blood and tissue markers predictive of DCS include inflammatory cytokines and cell adhesion molecules (CAMs). Increased levels of inflammatory cytokines, especially tumor necrosis factor-alpha (TNF-alpha), interleukin-6 (IL-6), and interferon-gamma (IFN-gamma), were detected in the circulation 6 h after decompression. Increased levels of only IL-6 were observed at 24 h. Compared with control animals maintained at 1 atmospheres absolute pressure ATA (101 kPascal), significant increases in expression of E-selectin, and L-selectin, as well as intercellular adhesion molecule-1 (ICAM-1), were observed immunohistochemically in the lungs and brains of the rats 6 h after exposure to 2 (203 kPascal), 3 (303 kPascal), or 4 (404 kPascal) ATA, followed by rapid decompression. These levels drop by 24 h. In contrast to the observations in brain, greater increases in expression of E-selectin and L-selectin around vessels and connective tissue were seen at 24 h after decompression in the quadriceps of rats exposed to either 3 or 4 ATA. Significant increases in expression of the A(2A) receptor, which modulates inflammation by downregulating production of these cytokines, were detected only in the quadriceps removed at 24 h after decompression from 4 ATA. This study demonstrated that rapid decompression induces the release of mediators of inflammation and resulting tissue inflammation cascades, as well as a protective anti-inflammatory response.

Fatty infiltration does not progress after rotator cuff repair in a rabbit model.

PURPOSE: The purpose of this study is to evaluate the changes in fatty infiltration of the rotator cuff after it is repaired. METHODS: The supraspinatus muscle was unilaterally detached from the greater tuberosity in 15 New Zealand white rabbits. Six weeks after muscle detachment, 5 rabbits were killed to halt the process of fatty infiltration and 10 rabbits underwent primary repair of the rotator cuff. Six months after repair, the remaining 10 rabbits were killed, and the muscle specimens were examined microscopically to evaluate the muscle with respect to fatty infiltration. RESULTS: Fatty infiltration was evident 6 weeks after detachment of the supraspinatus tendon (P = .0012, analysis of variance). This infiltration was greatest at the musculotendinous junction (P = .0005) and decreased toward the muscle origin (P = .29). Six months after repair of the supraspinatus, there was no progression of fatty infiltration in the repaired muscle as compared with the controls (P = .3). CONCLUSIONS: Fatty infiltration of the rotator cuff in this animal model occurs as early as 6 weeks after a rotator cuff tear. After repair of the rotator cuff, the process of fatty infiltration does not progress any further. The changes that take place in this rabbit model in the first 6 weeks after a rotator cuff tear appear to be irreversible even with successful rotator cuff repair. CLINICAL RELEVANCE: The presence of fatty infiltration of a torn rotator cuff does not preclude a successful repair. The repair can prevent further progression and atrophy of the rotator cuff, but the changes that appear in the muscle as early as 6 weeks after a rotator cuff tear appear to be irreversible.

Effects of peritoneal closure and suture material on adhesion formation in a rabbit model.

OBJECTIVE: This study was designed to determine whether postoperative adhesions to the peritoneum beneath the anterior abdominal wall incision could be decreased by peritoneal closure using less reactive suture material. STUDY DESIGN: Six longitudinal abdominal incisions were made in each of 16 New Zealand white female rabbits. The peritoneum was randomly assigned to nonclosure or closure with chromic gut, braided nylon, braided coated polyglactin 910, polydioxanone monofilament, or poliglecaprone 25 suture. On postoperative day 14, adhesion formation was scored and evaluated microscopically. RESULTS: Peritoneal closure decreased adhesion scores, compared with nonclosure, regardless of type of suture, and no particular suture was superior. Braided coated polyglactin 910 resulted in the least chronic inflammation and fibrosis. CONCLUSION: Peritoneal closure of peritoneum immediately below laparotomy incisions results in decreased adhesion scores, compared with nonclosure in our rabbit model. Adhesion formation could not be decreased further using less reactive suture.

Fatty infiltration of the torn rotator cuff worsens over time in a rabbit model.

PURPOSE: The purpose of this investigation is to document quantitatively and qualitatively the changes that occur over time in the rotator cuff muscle after surgical detachment, simulating a chronic, unrepaired rotator cuff tear. METHODS: The supraspinatus muscle was unilaterally detached from the greater tuberosity in 20 New Zealand white rabbits. All tendons were tagged and retracted from the insertion on the greater tuberosity. Five rabbits were killed at each designated time interval of 6 weeks, 3 months, 6 months, or 1 year after surgery. All animals underwent whole-body perfusion at the time of death for tissue preservation. Gross and histologic evaluations were performed to quantify the progression of fatty infiltration over time. RESULTS: Loss of muscle and fatty infiltration were evident 6 weeks after detachment of the supraspinatus tendon. The fatty infiltration increased over time from 6 weeks to 1 year (P = .002, analysis of variance). The fatty infiltration was most pronounced near the supraspinatus insertion, and it progressed from the musculotendinous junction toward the muscle origin (Pearson correlation, r = -0.51; P < .0001). CONCLUSIONS: In this rabbit model of a surgically created rotator cuff tear, fatty infiltration is a progressive, infiltrative process that increases over time in the unrepaired rotator cuff. In addition, the muscle atrophy and fatty infiltration seen in rotator cuff tears progress from the musculotendinous junction toward the muscle origin. CLINICAL RELEVANCE: This animal model of a chronic rotator cuff tear shows that fatty infiltration of the supraspinatus muscle appears as early as 6 weeks and worsens over time in the unrepaired rotator cuff. This may have implications on both the timing and management of rotator cuff tears.

Oxidative stress-induced JNK/AP-1 signaling is a major pathway involved in selective apoptosis of myelodysplastic syndrome cells by Withaferin-A.

Myelodysplastic syndromes (MDS) are a diverse group of malignant clonal hematopoietic stem cell disorders characterized by ineffective hematopoiesis, dysplastic cell morphology in one or more hematopoietic lineages, and a risk of progression to acute myeloid leukemia (AML). Approximately 50% of MDS patients respond to current FDA-approved drug therapies but a majority of responders relapse within 2-3 years. There is therefore a compelling need to identify potential new therapies for MDS treatment. We utilized the MDS-L cell line to investigate the anticancer potential and mechanisms of action of a plant-derived compound, Withaferin A (WFA), in MDS. WFA was potently cytotoxic to MDS-L cells but had no significant effect on the viability of normal human primary bone marrow cells. WFA also significantly reduced engraftment of MDS-L cells in a xenotransplantation model. Through transcriptome analysis, we identified reactive oxygen species (ROS)-activated JNK/AP-1 signaling as a major pathway mediating apoptosis of MDS-L cells by WFA. We conclude that the molecular mechanism mediating selective cytotoxicity of WFA on MDS-L cells is strongly associated with induction of ROS. Therefore, pharmacologic manipulation of redox biology could be exploited as a selective therapeutic target in MDS.

Adjuvants and antibody production: dispelling the myths associated with Freund's complete and other adjuvants.

Adjuvants have been used for more than 70 yr to enhance the immune response of the host animal to an antigen. Among the mechanisms that adjuvants use to enhance the immune response are the "depot" effect, antigen presentation, antigen targeting, immune activation/modulation, and cytotoxic lymphocyte induction. The immunostimulatory properties of adjuvants result in inflammation, tissue destruction, and the potential for resulting pain and distress in the host animal. The inflammatory lesions produced by adjuvants such as Freund's complete adjuvant (FCA) have led some to conclude that pain and distress are present, even in cases where the scientific evidence fails to support this conclusion. Recommendations and regulations in the literature, based on available scientific evidence, provide guidance on total adjuvant volumes, volumes per site, routes of injection, booster injections, and adjuvants used for antibody production. Among the numerous adjuvants that are used for experimental antibody production reviewed in this article, many claim to be less inflammatory, tissue destructive, and painful than FCA while producing equal or superior antibody responses. Although no adjuvant surpasses FCA for experimental antibody production against a wide range of antigenic molecules, many produce excellent antibody responses with less inflammation and tissue destruction. Balancing the requisite degree of immuno-stimulation and the extent of inflammation, necrosis, and potential pain and distress requires consideration of the nature of the antigen, the host immune responsiveness, the adjuvant's mechanisms of action, and the desired end-product. In cases where the antigen is a weak immunogen or has a very limited availability, the type and role of adjuvant becomes a critical component in producing an acceptable immune response and humoral antibody response.

Sub-isotypic differences in the immunoglobulin G response to Lawsonia intracellularis in vaccinated, seropositive, and equine proliferative enteropathy-affected horses.

In the horse, Lawsonia intracellularis infection results in equine proliferative enteropathy (EPE). While upwards of 100% of weanlings on an endemic farm may seroconvert, only a small percentage (approximately 5%) will develop clinical disease. Cell-mediated immune mechanisms likely play a role in resistance to L. intracellularis and the absence of a L. intracellularis-specific IFN-γ response has been associated with the development of EPE. The goal of this study was to determine whether protection from clinical EPE is associated with the induction of a systemic IgG sub-isotypic response consistent with a Th1-type cytokine response. To describe their L. intracellularis/EPE status, horses enrolled in this study were placed into one of three categories: seropositive-only, vaccinated, and presumptive clinical EPE. An existing ELISA method was modified to detect L. intracellularis-specific IgG(a), IgG(b), and IgG(t) antibodies using the mouse anti-equine hybridomas CVS-48, CVS-39, and CVS-40, respectively. Additionally, the existing ELISA method was used to quantify total IgG antibodies specific for L. intracellularis for comparison between the groups. Total L. intracellularis-specific IgG was found to be significantly higher (p<0.05) in presumptive clinical EPE cases (n=21) when compared with seropositive (exposed but unaffected) (n=36) and vaccinated horses (n=27). Further, a similar pattern for IgG(a) was seen in that the presumptive clinical EPE horses had significantly more L. intracellularis-specific IgG(a) (p<0.05) than the seropositive or vaccinated horses. With IgG(b), however, the vaccinated horses had significantly more IgG(b) (p<0.05) than the presumptive clinical or seropositive horses. No L. intracellularis-specific IgG(t) was detected in samples from any of the groups. While the results presented here with respect to IgG(a) response in the presumptive clinical EPE group were expected, a higher concentration of IgG(a) was anticipated in the seropositive horses that failed to develop clinical disease as well as in the vaccinated horses. Future work utilizing newer reagents against a broader range of equine IgG sub-isotypes may provide additional information once these become commercially available.

Semitendinosus muscle fatty infiltration following tendon harvest in rabbits.

The hamstring tendon autograft is one of the most commonly used graft choices in Anterior cruciate ligament (ACL) reconstruction. There are conflicting results regarding postoperative hamstring strength deficits in patients who have had a hamstring graft. The semitendinosus tendon has been shown to regenerate after harvesting for ACL autograft, suggesting that the muscle has the potential to regain normal function. However, no studies have been performed to define the microstructural changes that occur in the semitendinosus muscle after tendon resection. In this study, we hypothesized that fatty infiltration of the semitendinosus muscle after tendon harvest in New Zealand White rabbits increases postoperatively and remains constant or increases during the first year of repair. The semitendinosus tendon was unilaterally detached and harvested from 15 rabbits. Five rabbits were sacrificed at 3-, 6-, and 12-month intervals, and the semitendinosus muscle-tendon units were analyzed. The contralateral unoperated limb served as the control. The gross tendon and muscle dimensions and histologic percentage of fatty infiltration were measured. We found no significant difference in fatty infiltration at any time point between the control muscle and test specimens and that there was no progression of fatty infiltration over time. If these results hold true in humans, natural repair of the hamstring muscle following tendon harvest during ACL autograft reconstruction is not inhibited by fatty infiltration.

Innate immune response to encephalomyocarditis virus infection mediated by CD1d.

CD1d-reactive natural killer T (NKT) cells can rapidly produce T helper type 1 (Th1) and/or Th2 cytokines, can activate antigen-presenting cell (APC) interleukin-12 (IL-12) production, and are implicated in the regulation of adaptive immune responses. The role of the CD1d system was assessed during infection with encephalomyocarditis virus (EMCV-D), a picornavirus that causes acute diabetes, paralysis and myocarditis. EMCV-D resistance depends on IL-12-mediated interferon-gamma (IFN-gamma) production. CD1d-deficient mice, which also lack CD1d-reactive NKT cells, were substantially more sensitive to infection with EMCV-D. Infected CD1d knockout mice had decreased IL-12 levels in vitro and in vivo, and indeed were protected by treatment with exogenous IL-12. IFN-gamma production in CD1d knockout mice was decreased compared with that in wild-type (WT) mice in response to EMCV-D in vitro, although differences were not detected in vivo. Treatment with anti-asialo-GM1 antibody, to deplete NK cells, caused a marked increase in susceptibility of WT mice to EMCV-D infection, whereas CD1d knockout mice were little affected, suggesting that NK-cell-mediated protection is CD1d-dependent. Therefore, these data indicate that CD1d is essential for optimal responses to acute picornaviral infection. We propose that CD1d-reactive T cells respond to early immune signals and function in the innate immune response to a physiological viral infection by rapidly augmenting APC IL-12 production and activating NK cells.