Transcription restores DNA repair to heterochromatin, determining regional mutation rates in cancer genomes

Somatic mutations in cancer are more frequent in heterochromatic and late-replicating regions of the genome. We report that regional disparities in mutation density are virtually abolished within transcriptionally silent genomic regions of cutaneous squamous cell carcinomas (cSCCs) arising in an XPC(-/-) background. XPC(-/-) cells lack global genome nucleotide excision repair (GG-NER), thus establishing differential access of DNA repair machinery within chromatin-rich regions of the genome as the primary cause for the regional disparity. Strikingly, we find that increasing levels of transcription reduce mutation prevalence on both strands of gene bodies embedded within H3K9me3-dense regions, and only to those levels observed in H3K9me3-sparse regions, also in an XPC-dependent manner. Therefore, transcription appears to reduce mutation prevalence specifically by relieving the constraints imposed by chromatin structure on DNA repair. We model this relationship among transcription, chromatin state, and DNA repair, revealing a new, personalized determinant of cancer risk.

Latissimus dorsi free flap for sacral wound closure: the world's longest vein grafts for free tissue transfer

In 1983, Salibian et al. reported the use of a two-stage latissimus dorsi free tissue transfer to cover a sacral radiation ulcer using 28-centimeter thoracodorsal interposition vein grafts. In 1985, Nahai and Hagerty reported a similar case in which the procedure was performed in one stage with 25-centimeter vein grafts. We present a case in which a large sacral osteoradionecrosis ulcer is closed using this one-stage technique with 46-centimeter vein grafts, the longest ever reported for free tissue transfer.

Brachioradialis musculocutaneous flap closure of the elbow utilizing a distal skin island: a case report

A brachioradialis musculocutaneous flap with a distal skin island is described to close a chronic elbow wound. This newly described distal skin island directly over the brachioradialis tendon provides viable and durable coverage for the olecranon/posterior elbow region. The advantages and disadvantages of this treatment as compared with other historical reconstructive options for this region are analyzed. The patient has a stable healed wound at 2 years of follow-up.

The microvenous valvular anatomy of the human dorsal thoracic fascia

The use of free scapular fasciocutaneous flaps for reconstruction of recalcitrant grade 6 venous stasis ulcers has shown excellent early success rates. Venous refilling times measured postoperatively over the flaps by photoplethysmography have noted improvements to normal levels. Preliminary anatomic studies have demonstrated valves in the circumflex scapular veins of flaps used in reconstruction. The purpose of this study was to investigate and document the number, morphology, size, and location of valves in the human dorsal thoracic fascia. Ten scapular flaps were obtained from unembalmed cadavers and injected with methyl methacrylate. Each flap cast was divided into four parts: proximal, right and left, and distal, right and left. We reduced the size of specimens (the largest being 24 x 11 mm) and studied them in a scanning electron microscope. We identified all valves, estimated the diameter of the corresponding vein, calculated the depth of the valvular sinus, and related it to the corresponding venous size. Light microscopy and transmission electron microscopy were used as assisting tools applied to glutaraldehyde-fixed specimens. Analysis of injected specimens showed that valves were most abundant in veins with a luminal diameter of 30 to 120 microns (59.3 percent of 905 valves). The depth of valves became larger with increasing venous diameter. The sizes of valve sinuses were not different for individual valves. Except for veins larger than 1000 microns in diameter, there was no significant difference between the number of valves in different parts of an individual flap, nor were there significant differences between the valve numbers in different flaps. Most valves were bicuspid; only in the vein category of 30 to 120 microns were unicuspid valves encountered. Valves sometimes were located in series in a short segment of a vein; occasionally, they were found at the merging site of two veins. Transmission electron microscopy showed that valve leaflets had collagen fibers that ascended toward the tip of the leaflet and occasionally were accompanied by elastic fibers. Myofibroblasts were regularly present in the valve leaflets. These data show that fasciocutaneous flaps from the scapular region have numerous valves (90 valves on average in each flap) in the venous microcirculation. The microvenous valves in the dorsal thoracic fascia appear to be structurally similar to valves in larger veins. These valves may play a role in the improved hemodynamics and promising clinical outcome of patients with chronic venous insufficiency who have undergone free scapular flap reconstruction.

Continued tumor necrosis factor receptor expression by trauma patients' monocytes (Mphi) despite TNF alpha secretion

In investigating various mechanisms for continued elevated tumor necrosis factor alpha (TNF alpha) production in trauma patients' monocytes (Mphi), we examined TNF receptor (TNFR) levels on the patients' Mphi as a possible altered pathway leading to continued autocrine TNF alpha stimulation. Mphi TNFR synthesis and shedding are both increased as TNF alpha protein production increases. In fatal meningococcal infections, TNFR shedding fails to pace TNF alpha production. Here, isolated normal and trauma patients' Mphi (injury severity score greater than 30), were examined by flow cytometry using phycoerythrin-labeled TNF alpha to detect increased or decreased TNFR expression concomitant to Mphi production of secreted TNF alpha (as measured in the LM bioassay). Immunoaberrant patients (mitogen proliferation depressed) had reduction in detectable TNF alpha binding by their TNFR, while Mphi from immunocompetent (normal mitogen response) trauma patients' Mphi had a TNFR expression intensity comparable to normals' Mphi. Upon in vitro stimulation of TNF alpha (IFN gamma + muramyl dipeptide) normals' and immunocompetent patients' MO TNFR expression is decreased for the entire 18 h period during which secreted TNF alpha is produced, but immunoaberrant trauma patients' Mphi increased their TNFR expression, while concomitantly producing both secreted and cell-associated TNF alpha protein. Patients' Mphi with highly elevated TNF alpha levels are still expressing high levels of TNFR and capable of auto-stimulating TNF alpha production. This elevated TNFR expression could be due to reduced shedding, overproduction of TNFR, or both.

Free flap valvular transplantation for refractory venous ulceration

PURPOSE

Nonoperative therapeutic approaches to chronic venous ulceration, although effective, often require prolonged dressing care and immobilization with leg elevation. Results of skin grafting, perforator ligation, and valve interpositions and reconstructions improve results of ulcer healing but have not uniformly prevented ulcer recurrence. Our hypothesis is that reconstruction of chronic venous ulcers by excision of the diseased tissue bed and replacement with a free flap containing multiple competent microvenous valves and a normal tissue microcirculation will result in long-term cure of these debilitated patients.

METHODS

Six patients with chronic venous insufficiency and recurrent ulceration (class 3) underwent excision of ulcers and surrounding liposclerotic tissue beds and reconstruction with fasciocutaneous free flaps (two bilateral). Preoperative and postoperative photoplethysmography was used to assess venous refilling times. Duplex scanning was performed to assess deep venous reflux.

RESULTS

There were no flap failures. Photoplethysmographic venous refilling times measured on flaps demonstrated significant immediate and long-term increases from preoperative values (all results +3 by Society of Vascular Surgery outcome grading). Long-term maintenance of tissue integrity is shown by absence of recurrent ulceration and no evidence of recurrent tissue lipodermatosclerosis in all flaps at follow-up (8 months to 7.5 years; mean 24 months). No recurrent lipodermatosclerosis was seen on flap biopsy at 2 and 7 years. Separate cadaveric injection studies, including scanning electron microscopy, revealed numerous microvenous valves directed toward the draining pedicle in the flaps used for reconstruction.

CONCLUSIONS

This is the first comprehensive report providing combined laboratory and clinical evaluation, anatomic rationale, and long-term outcome of surgical rehabilitation of patients with chronic venous ulceration who have undergone microsurgical flap reconstruction.

Thumb replantation after cardiac transplantation

Generally, severe medical illnesses, including chronic immunosuppression and heavy steroid use, have been deemed relative contraindications for replantation surgery. We report the successful replantation of an amputated thumb in a patient who had previously undergone heart transplantation and was on therapeutic immunosuppression. Despite extensive soft-tissue damage and joint involvement, thumb function and sensibility returned to acceptable levels. This case demonstrates that digital bony union, tendon repair healing, and nerve regeneration are not significantly altered by the standard immunosuppressive regimen following major organ transplant. The implications raised by this case for possible transplantation of allograft digits or limbs are discussed in detail.

Rectus abdominis flap closure of ischiosacral pressure sore

An inferiorly based rectus abdominis musculocutaneous flap was used to close a large ischiosacral pressure sore refractory to the usual methods of closure in a paraplegic patient. The functions of the rectus abdominis muscle to initiate vertebral flexion from a supine position and aid in respiration, urination, defecation, and vomiting may play a proportionately greater role in the paraplegic patient. Although our patient did not experience any noticeable clinical deficits, this donor site is theoretically less functionally expendable in the paraplegic patient.

Microvascular thrombolysis to salvage a free flap using human recombinant tissue plasminogen activator

Nonsurgical thrombolysis using tissue plasminogen activator (t-PA) in conjunction with intravenous heparin infusion was successfully used to salvage a free flap with acutely decreased arterial inflow thought to be due to anastomotic thrombosis. Intravenous infusion (12 mg/hr) of t-PA was stopped after 15 min of therapy when spontaneous bleeding was noted at the groin flap donor site. Concomitant treatment with intravenous heparin resulted in rapid improvement of flap perfusion and ultimately complete survival without surgical intervention. This report suggests that in selected cases, target-specific anticoagulant therapy may be beneficial in salvaging microvascular reconstructions complicated by thrombosis. Further experience is warranted to define more clearly the role, the risks, and the extended benefits of this new mode of nonsurgical therapy.

Growth of forelimb allografts in young rabbits immunosuppressed with cyclosporine

Seventeen forelimbs were transplanted orthotopically from young Dutch rabbits to young New Zealand rabbits treated with cyclosporine. The transplanted limbs demonstrated significant bone growth. The growth in the transplanted limbs was about 75 to 80% of that observed in the unoperated limb. The long bones of the 3 longest surviving rabbits (133 days, 150 days, 150 days) studied radiographically demonstrated increases in length over their original lengths (humerus 22%, ulna 26%, and radius 31%). Hair and nail growth were noted at about day 10. Response to pain stimuli (withdrawal of forelimb) and functional use (ambulation with 50% weight bearing) was seen at two to three months. Permanent survival was not achieved because of a species-specific toxic wasting syndrome from cyclosporine.