Energy economy of human uterine muscle strips under different in vitro conditions and its dependence on tissue redox potential

Experimental uterus transplantation

BACKGROUND

Uterus transplantation (UTx) is developed in animal models as a future method to treat uterine factor infertility.

METHODS

All published studies in the area of UTx research were identified. Aspects relating to surgery, cold-ischemia/reperfusion, rejection, immunosuppression, pregnancy, ethics and institutional requirements were examined.

RESULTS

Uterus retrieval surgery has been solved in animals, including primates. Studies on cold-ischemia/reperfusion indicate an ischemic tolerance of >24 h. The transplantation procedure, with vascular anastomosis, has not been fully developed in animal models, indicated by frequent thrombosis formation. Pregnancies have only been reported in syngenic/auto-UTx animal models. Several ethical issues in relation to UTx, and requirements for a team that would be suitable to undertake human UTx, exist.

CONCLUSION

Much research on UTx has been performed in appropriate animal models. Several aspects of the procedure have been optimized but some remain to be solved. It is predicted that the research will soon reach a stage that could merit introduction of human UTx as an experimental procedure.

Short-term ischaemic storage of human uterine myometrium--basic studies towards uterine transplantation

BACKGROUND

Transplantation of the uterus has been suggested as a possible future treatment of absolute uterine infertility. The tolerability of human uterine tissue to cold ischaemic storage was tested in the present study.

METHODS

Small tissue samples of human uteri were subjected to cold (4 degrees C) ischaemia (6 and 24 h) in Ringer acetate (RIN), the intracellular-like University of Wisconsin solution (UW) or the extracellular-like Perfadex solution (PER). The ability of myometrial strips to contract, histology by light and electron microscopy as well as tissue concentrations of glutathione, ATP and protein were used as parameters to detect cold ischaemic injuries.

RESULTS

Contractile ability and response to prostaglandin F(2alpha) (PGF(2alpha)) was better preserved after 6 h cold ischaemia in UW and PER in comparison with the other groups. Histological examination did not reveal any major changes after 6 and 24 h cold ischaemic storage in UW and PER solutions, while specimens stored in RIN for 24 h displayed degenerative changes on the electron microscopy level. UW and PER preserved ATP concentrations significantly better than RIN. Myometrium stored in UW contained more total glutathione but also a larger proportion of oxidized glutathione than specimens stored in RIN and PER. Protein concentrations did not change with storage time in any of the solutions.

CONCLUSIONS

The results show that human uterine myometrial tissue is resistant towards cold ischaemia for at least 6 h if stored in UW and PER solutions.

Human epidermal energy metabolism is functionally anaerobic

We have reported that epidermal Langerhans cells possess an H(+)-extruding mechanism signalling their existence in an anaerobic environment. This study highlights the energy metabolism of human epidermis. In their habitual state the keratinocytes contain more lactate than do most other cell types. Their lactate production in vitro is vigorous and independent of oxygen and most of it is released to the medium. Autoincubation of the epidermis under starved conditions resulted in a 30% increase of lactate, indicating ongoing glycogenolysis. Iodoacetate inhibited lactate production by > 90%. Energy charge values were low, approximately 0.82, and comparable with those previously reported for smooth muscle. Moreover, the overwhelming majority of the keratinocytic mitochondria had an appearance markedly deviating from those in the Langerhans cells, melanocytes and fibroblasts, and, above all, were characterized by an enormous reduction of the inner membrane. This structure is in all probability incompatible with an effective oxidative metabolism of glucose. We conclude that epidermal energy metabolism is predominantly anaerobic in spite of the formal presence of mitochondria. The high production of lactate obviously demands extracellular transport pathways for rapid elimination of this organic acid. An extracellular space complying with such a demand emerges on electron microscopy when an isotonic glutaraldehyde-based fixative is used. The prevailing view regarding the size of the extracellular space is based on the common use of hypotonic fixatives, such as Karnovski's fixative, which causes gross cellular swelling and concomitant near total elimination of the extracellular space, leaving interstices with a diameter significantly smaller than that allowing fluid flow.

The importance of the measurement of ATP depletion and subsequent cell damage with an estimate of size and nature of the market for a practicable method: a review designed for technology transfer

ATP is the energy currency of cells. ATP depletion is a central process in pathogenesis, in particular ischaemia, hypoxia and hypoglycaemia. ATP depletion in cells can be indirectly measured from the increased concentrations of extracellular hypoxanthine, a central intermediate in the metabolism of ATP. Cell damage secondary to ATP depletion can also be measured from extracellular hypoxanthine. The relevant biochemistry and physiology is briefly reviewed. Since market size is needed for investment decisions that would allow technology transfer, the numbers of hypoxanthine analyses that are clinically justified from the extensive published evidence are calculated per million population from UK, Norwegian and other evidence. The concentration of oxygen in blood is measured to estimate whether mitochondrial oxidative phosphorylation is adequate. Measurements of bicarbonate are used to estimate anaerobic glycolysis. Since the indirect estimation of ATP depletion is a major objective of blood gas and acid-base analyses, the number of such analyses per million population provides a good estimate of potential market size for a more direct method of estimating ATP depletion. A method is required for the rapid, dispersed emergency analyses needed clinically. Routes for method development are indicated. Competition, risks, acceptability, consumer motivation and timetables are indicated for the development phase. There are medicolegal pressures, especially in the USA, for the proposed advances to be widely used.

Is post-hypoxic-ischemic cell damage associated with excessive ATP consumption rather than a failure of ATP production?

Secondary cell damage after ATP depletion due to hypoxia or ischemia is clinically important because it correlates with residual effects; post-hypoxic-ischemic fits can be associated with later cerebral palsy. The mechanisms involved in delayed secondary cell damage are not clear, possibly because extensive relevant evidence is often fragmented. However, a sequence of changes can be suggested; this cross-linked sequence is tentatively outlined in this review. The outline suggests explanations for otherwise ill-understood clinical disturbances such as the loss of inhibitory control in damaged cells and the well documented reduction of cellular ATP. Loss of control may be due to reduced synthesis of control proteins and the reduced ATP concentration may be due to increased energy consumption.