Bram R. Kaufman

Molecular inflammation and adipose tissue matrix remodeling precede physiological adaptations to pregnancy

Changes in adipose tissue metabolism are central to adaptation of whole body energy homeostasis to pregnancy. To gain insight into the molecular mechanisms supporting tissue remodeling, we have characterized the longitudinal changes of the adipose transcriptome in human pregnancy. Healthy nonobese women recruited pregravid were followed in early (8-12 wk) and in late (36-38 wk) pregnancy. Adipose tissue biopsies were obtained in the fasting state from the gluteal depot. The adipose transcriptome was examined via whole genome DNA microarray. Expression of immune-related genes and extracellular matrix components was measured using real-time RT-PCR. Adipose mass, adipocyte size, and cell number increased in late pregnancy compared with pregravid measurements (P < 0.001) but remained unchanged in early pregnancy. The adipose transcriptome evolved during pregnancy with 10-15% of genes being differently expressed compared with pregravid. Functional gene cluster analysis revealed that the early molecular changes affected immune responses, angiogenesis, matrix remodeling, and lipid biosynthesis. Increased expression of macrophage markers (CD68, CD14, and the mannose-6 phosphate receptor) emphasized the recruitment of the immune network in both early and late pregnancy. The TLR4/NF-κB signaling pathway was enhanced specifically in relation to inflammatory adipokines and chemokines genes. We conclude that early recruitment of metabolic and immune molecular networks precedes the appearance of pregnancy-related physiological changes in adipose tissue. This biphasic pattern suggests that physiological inflammation is an early step preceding the development of insulin resistance, which peaks in late pregnancy.

Increased platelet-derived growth factor production and intimal thickening during healing of Dacron grafts in a canine model*

PURPOSE Growth factor production by endothelial cells on grafts may play a role in the development of intimal hyperplasia and subsequent graft failure. METHODS To study the relationship between platelet-derived growth factor production and graft healing, 26 beagles underwent placement of 20 cm long, 6 mm internal diameter, knitted Dacron thoracoabdominal grafts, either seeded with autologous endothelial cells (n = 14) or unseeded controls (n = 12). The grafts and adjacent arteries were removed 4 or 20 weeks after implantation for measurement of platelet-derived growth factor production in organ culture, endothelial cell coverage, and intimal thickness. RESULTS Midgraft platelet-derived growth factor production by seeded graft segments increased from 41 +/- 6 to 148 +/- 27 pg/cm2/72 hr (p < 0.002) between 4 and 20 weeks. This was accompanied by a significant increase in inner-capsule thickness. Platelet-derived growth factor production by control graft segments also increased from 58 +/- 21 to 163 +/- 42 pg (p < 0.05) and was similar to that of seeded grafts despite more rapid endothelialization of seeded grafts. The increase in growth factor production by Dacron grafts was greater than that of the expanded polytetrafluoroethylene grafts studied previously despite similar endothelial cell coverage. CONCLUSION This increase corresponded with the rapid appearance of smooth muscle cells in the pseudointima of Dacron grafts, suggesting that these cells may be responsible for the observed increase in platelet-derived growth factor production.

Platelet-derived growth factor production by canine aortic grafts seeded with endothelial cells

The advantages of an endothelial cell surface on a prosthetic graft may be compromised by endothelial cell production of mitogens for smooth muscle cells. To study platelet-derived growth factor (PDGF) production by cells lining prosthetic grafts, 15 beagles underwent placement of 20 to 22 cm long, 8 mm inner diameter, expanded polytetrafluoroethylene thoracoabdominal aortic grafts, of which seven were seeded with autologous jugular vein endothelial cells, and eight were unseeded control grafts. Grafts and adjacent arteries were explanted after 4 weeks, divided into segments, and studied in organ culture. Platelet-derived growth factor production during a 72-hour incubation period was measured by radioreceptor assay. Midgraft segments of seeded grafts produced significantly more PDGF than control grafts, 43 +/- 8 pg/cm2 and 22 +/- 5 pg/cm2, respectively (mean +/- SEM), p less than 0.05. Platelet-derived growth factor production correlated directly with endothelial cell coverage on graft segments as measured by scanning electron microscopy (r = 0.63, p = 0.01), and inversely with platelet deposition (r = -0.48, p = 0.07). For all dogs, PDGF production by the distal aorta was significantly greater than that by the proximal aorta, 89 +/- 6 and 17 +/- 4 pg/cm2, respectively (p less than 0.0001). These results suggest that endothelial cells on prosthetic vascular grafts are a significant source of PDGF. Furthermore, the higher PDGF production by the distal arteries may offer an explanation for the clinical finding of more severe intimal hyperplasia adjacent to the distal anastomosis.

Elevated platelet-derived growth factor production by aortic grafts implanted on a long-term basis in a canine model

An endothelial cell lining in a prosthetic vascular graft has been shown to decrease graft thrombogenicity. However, previous studies in our laboratory demonstrated that grafts seeded with endothelial cells produced platelet-derived growth factor, a potent smooth muscle cell mitogen that may promote intimal hyperplasia. This study was undertaken to assess temporal changes in platelet-derived growth factor production by grafts seeded with endothelial cells and unseeded grafts and adjacent arteries. Adult beagles underwent placement of 20 to 22 cm long, 8 mm inner diameter, expanded polytetrafluoroethylene thoracoabdominal aortic grafts that were either seeded with autologous jugular vein endothelial cells or were unseeded controls. Grafts and adjacent arteries were removed at times up to 2 years after implantation. The tissue was studied in organ culture and platelet-derived growth factor production was measured after 72 hours with use of a radioreceptor assay. Platelet-derived growth factor production by endothelialized grafts increased significantly over the period studied, especially at the anastomoses, whereas that by arterial segments did not change significantly. The increase in platelet-derived growth factor production was greater in the distal than the proximal anastomotic segment suggesting a possible explanation for the clinical finding of more severe intimal hyperplasia at the distal anastomosis.

Serum adipocytokines and adipose weight gain: a pilot study in adolescent females initiating depot medroxyprogesterone acetate.

OBJECTIVE To evaluate whether serum adipocytokine concentrations, controlling for baseline adiposity, are predictive of adipose weight gain in adolescents initiating depot medroxyprogesterone acetate (DMPA). METHODS Percent body fat was measured at baseline and 6 months. Baseline serum adipocytokine concentrations were quantified. RESULTS Mean percent body fat was 31.6% (±7.6) at baseline and 33.5% (±7.6) at 6 months. In multivariable linear regression modeling (adjusted for baseline percent body fat), Hispanic ethnicity and baseline serum adiponectin concentration were inversely associated (p≤.05) with absolute change in percent body fat at 6 months. CONCLUSIONS Serum adiponectin concentration may be useful for assessing risk of DMPA-associated adipose gains.

Regional differences in platelet-derived growth factor production by the canine aorta

Platelet-derived growth factor (PDGF) is a potent mitogen and chemotactic agent which may be involved in the formation of proliferative lesions of the arterial system, such as intimal hyperplasia and atherosclerosis. To examine the regional variation in vessel wall production of this mitogen, PDGF production and PDGF A chain mRNA expression by normal arterial wall was studied as a function of vessel location. PDGF production by canine aortic segments was measured after 72 h in organ culture, revealing significantly more PDGF produced by the distal compared to proximal aorta at 77 +/- 10 versus 14 +/- 6 pg/cm2/72 h (p<0.05). Endothelial cells (EC) and smooth muscle cells (SMC), isolated from analogous aortic sites, were grown in tissue culture and the conditioned medium was assayed for PDGF. EC in vitro demonstrated a similar geographic trend in PDGF production (distal=1,501 +/- 389 pg/microgram DNA/72 h, proximal=759 +/- 230 pg/microgram DNA/72 h; p=0.17). PDGF production by SMC in cell culture had a similar pattern with cells from the distal aorta producing 58 +/- 28 pg PDGF/microgram DNA/72 h, compared to cells from the proximal aorta producing 37 +/- 15 pg PDGF/microgram DNA/72 h (p=0.13). Freshly harvested EC and SMC, isolated from the same aortic sites, were subjected to quantitation of PDGF mRNA levels using a coupled reverse transcriptase and polymerase chain reaction amplification method, with glyceraldehyde-phosphate dehydrogenase (GAPDH) as a control. The ratio of PDGF A chain:GAPDH mRNA was significantly greater in distal aortic SMC, 2.30 +/- 0.99, compared to proximal aortic SMC, 1.27 +/- 0.46 (p=0.05), but was not significantly different between proximal and distal aortic EC (p=0.86). These findings demonstrate significant regional differences in PDGF production in the normal canine aorta. Additionally, SMC are implicated as a significant contributor to the regional variation in PDGF production.

The Effect of a Liner on the Dispersion of Sacral Interface Pressures During Spinal Immobilization

Sacral pressure ulcers are a significant problem following spinal cord injury and are felt to be in part due to the high interface-pressures generated while strapped to the spine board. The objective of this study was to determine sacral interface-pressure and sensing area in healthy volunteers on a spine board and the effects of a gel pressure dispersion liner. Thirty-seven volunteers were placed on a pressure-sensing mat between the subject and the spine board. Measurements were carried out with and without a gel liner. Pressures and sensing area were recorded every minute for 40 minutes. The highest pressure was generated at the sacral prominence of each subject. Mean interface-pressures were higher on the spine board alone than with the gel liner (p < .0001). Overall, mean sensing area was lower on the spine board than with the gel liner (p < .0001). Standard spinal immobilization causes high sacral interface-pressures. The addition of a gel liner on the spine board decreased overall mean sacral pressures and increased mean sensing area. Generation of sacral pressure ulcers may be related to the initial interface-pressures generated while the patient is strapped to the spine board. The addition of a gel liner may reduce the incidence of sacral pressure ulcers.

Limited incision harvest of the rectus abdominis muscle flap

BackgroundRectus abdominis muscle harvest typically uses a long and continuous paramedian approach. To limit donor site morbidity, the senior author performs a limited incision approach particularly useful in medically vulnerable patients, including patients with sternal wound infections.MethodsAll patients of a single surgeon from 2000 to 2014 who underwent rectus harvest by one or two transverse incisions and use of lighted retractor were identified. Patients were categorized by indication, for “sternal wound coverage” or “non-sternal wound coverage.” Co-morbidities, operative notes, and post-operative courses were evaluated. Comparisons were made to patients undergoing harvest by paramedian approach.ResultsSeventeen patients with a mean age of 61 underwent limited-incision rectus harvest. Nine patients had indication for “sternal wound coverage.” Three patients had single transverse incision and six patients had double transverse incisions. One patient expired post-reconstruction day 3. One patient had complete abdominal and partial sternal wound dehiscence. No other donor site complications were observed. Eight patients had indication for “non-sternal wound coverage,” including seven patients requiring free rectus for lower extremity defects and one a pedicled rectus abominis for pelvic osteomyelitis. No post-operative complications were observed in these non-sternal wound coverage patients. There was a trend toward improved wound healing and hospitalization time using the transverse compared to paramedian technique, although this was not significant.ConclusionsThe morbidity of the traditional paramedian incision for rectus harvest may be avoided using a limited skin incision approach. This is useful in patients with attenuated healing capacity and offers a lower risk approach to a traditionally risky donor site.Level of Evidence: Level IV, therapeutic study.