Absence Of Systemic Factors Research Articles

Changes in extracellular matrix in failing human non-ischemic and ischemic hearts with mechanical unloading

Ischemic and non-ischemic cardiomyopathies have distinct etiologies and underlying disease mechanisms, which require in-depth investigation for improved therapeutic interventions. The goal of this study was to use clinically obtained myocardium from healthy and heart failure patients, and characterize the changes in extracellular matrix (ECM) in ischemic and non-ischemic failing hearts, with and without mechanical unloading. Using tissue engineering methodologies, we also investigated how diseased human ECM, in the absence of systemic factors, can influence cardiomyocyte function. Heart tissues from heart failure patients with ischemic and non-ischemic cardiomyopathy were compared to explore differential disease phenotypes and reverse remodeling potential of left ventricular assisted device (LVAD) support at transcriptomic, proteomic and structural levels. The collected data demonstrated that the differential ECM compositions recapitulated the disease microenvironment and induced cardiomyocytes to undergo disease-like functional alterations. In addition, our study also revealed molecular profiles of non-ischemic and ischemic heart failure patients and explored the underlying mechanisms of etiology-specific impact on clinical outcome of LVAD support and tendency towards reverse remodeling.

Induction of hypertrophy in vitro by mechanical loading in adult rabbit myocardium

To study myocardial hypertrophy under in vitro conditions, we developed an experimental system and protocol in which mechanical conditions of isolated multicellular myocardium can be controlled while function can be continuously assessed. This in vitro culture system now allows us to investigate how mechanical overload impacts on cardiac hypertrophy in the absence of systemic factors. In this system, small right ventricular rabbit trabeculae were subjected to different modes of mechanical load, while being electrically stimulated to contract at 1 Hz at 37 degrees C. Muscles subjected to prolonged isometric contractions at high, but physiological, pre- and afterload showed a rapid induction of cardiac hypertrophy; overall muscle diameter increased by 4.3 +/- 1.4 and 17.9 +/- 4.0% after 24 and 48 h, respectively. This finding was confirmed at the cellular level; individual myocyte width significantly increased after 24 and 48 h. In muscles subjected to a low preload, or in the absence of afterload, this hypertrophic response was absent. Functionally, after 24 h of isometric contractions at high load, active developed tension had gradually increased to 168 +/- 22% of starting values. Proteomic analysis of this cultured myocardium demonstrated reproducible changes in the protein expression pattern and included an upregulation of myofilament proteins, myosin light chain isoforms, alpha-b crystalline, and breast cancer 1 protein, and a downregulation of myoglobin. We conclude that multicellular myocardium can be stressed to undergo rapid hypertrophy in vitro, and changes in function and protein expression can be investigated during the transition from healthy myocardium to early hypertrophy.

In vivo and in vitro evidence that the high osteoblastic activity in C3H/HeJ mice compared to C57BL/6J mice is intrinsic to bone cells

Two inbred mouse strains, C3H/HeJ (C3H) and C57BL/6J (B6), displayed a profound difference in femoral peak bone density. We have previously shown that the difference could be attributed to a greater bone formation rate (BFR) that was due to a higher osteoblastic activity [measured by a mineral apposition rate (MAR)] in the C3H (high density) than B6 (low density) mice. The present study sought to determine (1) whether the BFR/MAR differences between the two mouse strains present in weight-loaded endochondral bones are also seen in less weight-loaded membranous bones and (2) whether the difference in osteoblastic activity was seen in vitro in the absence of systemic factors. To address the first objective, we performed histomorphometric measurements on the weakly loaded membranous bones (i.e., parietal bones of the calvaria) to determine if there were similar differences in MAR and BFR of membranous bones as those of highly loaded, endochondral bones. The parietal bones of adult C3H mice showed similar increases in MAR and BFR as the endochondral bones, compared to B6 mice of same age, suggesting that the differences in the MAR and BFR in the two mouse strains are probably not related to differences in mechanical strain. These findings also suggest that the gene(s) responsible for the difference in MAR between strains may not be a mechanical response gene. With respect to the second objective, we isolated osteoblasts from the parietal bones and determined their differentiation status (i.e., ALP-specific activity) and bone-forming ability (i.e., mineralized nodule formation) in vitro. Consistent with the premise that C3H osteoblasts have an intrinsic, higher differentiation status and bone-forming ability than B6 osteoblasts, osteoblasts isolated from C3H mice as compared with those from B6 mice had a significantly greater ALP-specific activity and a greater ability to form mineralized nodules in vitro in the absence of systemic factors. Because differences in ALP activity, bone-forming ability, cortical bone width, and osteoblastic activity were detected at birth, the different MAR/BFR phenotypes develop at very early life and even perhaps during embryogenesis. In conclusion, we have for the first time provided evidence that the genetic differences responsible for the observed MAR/BFR phenotype in the C3H-B6 strains are intrinsic to osteoblasts and might not depend on responses to mechanical loading and/or alterations in systemic factors.

Management of postburn recalcitrant knee ulcers in pediatric patients.

The sequelae of severe lower-extremity burn injuries in children include ulcerations and unstable scars of the anterior knee. Although the weight-bearing and ambulatory demands on this joint predispose the ulcers to chronicity, recalcitrance to treatment in the absence of systemic factors may be indicative of the presence of less-than-optimal local factors mitigating against healing. In our experience, excessive skin tightness around the knee joint has played a key role in this respect. This retrospective study on 10 patients with 16 recalcitrant knee ulcers demonstrated the inadequacy of the traditional treatment approach of ulcer excision and grafting. However, incisional release of tight skin above the knee joint and resurfacing the defect with split-thickness skin graft (mean size, 118.26 +/- 35.32 cm2) eliminated excessive tension and allowed the ulcers to heal spontaneously and permanently. We found this approach useful in select patients, and we are favorably disposed to additional releasing incision and grafting if the need arises in the growing child.

Contraction Regulation of Akt in Rat Skeletal Muscle

The protein serine/threonine kinase Akt/protein kinase B has been recognized as a critical signaling mediator for multiple cell systems. The function of Akt in skeletal muscle is not well understood, and whether contractile activity stimulates Akt activity has been controversial. In the current study, contraction in situ, induced via sciatic nerve stimulation, significantly increased Akt Ser(473) phosphorylation in multiple muscle types including the extensor digitorum longus (13-fold over basal), plantaris (5.8-fold), red gastrocnemius (4.7-fold), white gastrocnemius (3.3-fold), and soleus (1.6-fold). In addition to increasing phosphorylation, contraction in situ significantly increased the activity of all three Akt isoforms (Akt1 > Akt2 > Akt3) with maximal activation occurring at 2.5 min and returning to base line with 15 min of contraction. Akt phosphorylation and activity were also increased when isolated muscles were contracted in vitro in the absence of systemic factors, although to a much lesser extent. The phosphatidylinositol 3-kinase inhibitors wortmannin and LY294002 fully inhibited contraction-stimulated Akt phosphorylation and activity but did not diminish contraction-stimulated glycogen synthase kinase-3 phosphorylation and glycogen synthase activity. These results demonstrate that contraction increases Akt phosphorylation and activity in skeletal muscle and that this stimulation is rapid, transient, muscle fiber type-specific, and wortmannin- and LY294002-inhibitable. Akt signaling is not necessary for the regulation of glycogen synthase activity in contracting skeletal muscle.

Root resorption of upper permanent incisor caused by impacted canine: An analysis of 23 cases

Unusual root resorption of 12 central and 11 lateral upper permanent incisors in 11 patients is described. The degree of resorption ranged from loss of the apical 1/4 to almost complete loss of root structure. Excepting 1 case, permanent canines were partially or completely impacted and their crowns were in close apposition to the resorbed surfaces of the incisors. The roots of the canines were either in the process of formation or completely formed. The findings suggest that the pressure from the canine which persists in moving downward despite the lack of space to permit normal eruption could cause root resorption of adjacent incisors even in the absence of systemic factors. Of 14 extracted incisors, 10 were replaced orthodontically by the impacted canines, whereas the spaces of the extracted incisors were restored by prosthetic means in the 4 other cases. 6 incisors were preserved without any treatment and 2 with the aid of a sapphire dento-osseous anchor pin. Since the resorbed incisors were mostly free of pain, early detection by radiographic examination is essential to establish a proper diagnosis.