Ultrastructural aspects of preeclampsia. II. Mitochondrial changes.

Biopsy specimens were obtained under direct vision at the time of cesarean section from 47 patients (35 with preeclampsia and 12 normotensive patients) and from four women with cesarean section hysterectomies (all normotensive) as an extension of previous work. Tissues were obtained from the myometrium near the placental bed and from the opposite side of the uterus. Skin biopsies were also obtained from eight women with preeclampsia and liver biopsies were obtained from two patients with acute microvesicular fatty change of pregnancy (one with and one without concomitant preeclampsia). Specimens were examined histologically and by electron microscopy. Mitochondrial changes in small vessels, principally venules, in myometrial smooth muscle, myometrial interstitial cells, circulating leukocytes, epidermal and dermal cells, and hepatocytes were examined and compared between women with preeclamptic and normotensive pregnancies. These findings were then compared with mitochondria from 500 biopsies over the same 3-year interval to assess the possible role of delay in tissue fixation. There were 12 other biopsies from nonpregnant women of childbearing age. As further control on artifact, other specimens were initially sampled immediately in the operating room and then serially for up to 2 hours later. Artifact as a basis for the mitochondrial changes was ruled out by these procedures. Normal mitochondria undergo a morphologic conformational sequence with physiologic changes in substrate, oxygen consumption, adenosine diphosphate, and respiratory rate. The mitochondria of preeclamptic tissues show a central disruption that is outside this normal sequence or cycle. This disruption occurs more often and is more severe in preeclampsia than in normotensive pregnancies. In addition, the hypertrophic smooth muscle of the pregnant uterus has a complex of cytoplasmic organelles in a paranuclear location, usually apical, that contains a variable mixture of glycogen, the Golgi apparatus, endoplasmic reticulum, mitochondria, and small unidentified microvesicles. This complex has the location and appearance suggestive of a myometrial "power pack" of significance in metabolism and contraction. The presence of similar mitochondrial changes in a limited sample of nonuterine tissues is suggestive of a systemic metabolic disorder as an important feature of preeclampsia.