Interaction between oocytes, cortical germ cells and granulosa cells of the mouse and bat, following the dissociation-re-aggregation of adult ovaries

It is widely accepted that the oocyte plays a very active role in promoting the growth of the follicle by directing the differentiation of granulosa cells and secreting paracrine growth factors. In turn, granulosa cells regulate the development of the oocytes, establishing close bidirectional communication between germ and somatic cells. The presence of cortical cells with morphological characteristics, similar to primordial germ cells that express specific germline markers, stem cells and cell proliferation, known as adult cortical germ cells (ACGC) have been reported in phyllostomid bats. Using magnetic cell separation techniques, dissociation-cellular re-aggregation and organ culture, the behaviour of oocytes and ACGC was analyzed by interacting in vitro with mouse ovarian cells. Bat ACGC was mixed with disaggregated ovaries from a transgenic mouse that expressed green fluorescent protein. The in vitro reconstruction of the re-aggregates was evaluated. We examined the viability, integration, cellular interaction and ovarian morphogenesis by detecting the expression of Vasa, pH3, Cx43 and Laminin. Our results showed that the interaction between ovarian cells is carried out in the adult ovary of two species, without them losing their capacity to form follicular structures, even after having been enzymatically dissociated.

Quantification of viable granulosa cells in murine ovarian follicles

Ovarian follicle growth and oocyte maturation depend on the viability of granulosa cells (GC). We quantified GC in whole mouse follicles. Single follicles were isolated from adult mouse ovaries and stained with DAPI or Live-Dead stain before fixation. An objective image analysis protocol for counting fluorescent labeled GC was developed that used Image J software to measure GC cytoplasmic and nuclear areas. These data were compared to the number of GC obtained by disaggregating 96 follicles with enzymes to produce a suspension of GC, which then was stained with trypan blue and assessed using a hemocytometer. We found a linear relation between GC/follicle and follicle diameter. Viability of GC/follicle ranged from 40 ± 11 to 72 ± 7%. The coefficient of variation for image analysis of DAPI stained GC by different assessors was 4%, but the number of GC obtained from image analysis was approximately 50% less than from disaggregated follicles. The number of GC in intact mouse follicles was greater than the number reported earlier for fixed ovarian sections. We found that the number of GC was less in fluorescence labeled follicles; it is possible that the three-dimensional structure of the intact follicles obscured the fluorescent signal. Direct quantification of viable GC isolated from follicles appears to be the most accurate method.

Establishment of a protocol for the isolation of ovarian preantral follicles derived from collared peccaries (Pecari tajacu)

We compare the efficiency of mechanical or enzymatic methods, and their combination, for the isolation of ovarian preantral follicles (PFs) from collared peccaries. The ovaries from six females were subjected to the different methods investigated here. For the enzymatic method, ovary fragments were exposed to collagenase type IV in TCM-HEPES medium; the mechanical procedure was based on ovarian cortex dissociation by using a scalpel blade. The residual solution obtained after the mechanical isolation was subjected to the enzymatic procedure. The number of isolated PFs was quantified and classified as primordial, primary, or secondary; their viability was assessed using trypan blue dye assay. To confirm the results, PFs derived from the most efficient method were evaluated for integrity using scanning electron microscopy (SEM) and subjected to a 24 h in vitro culture for subsequent evaluation of viability by using fluorescent probes. A higher number of PFs (P < 0.05) was obtained from the enzymatic method (961.7 ± 132.9) in comparison with the mechanical method (434.3 ± 88.9), but no difference was observed between the two methods and their combination (743.2 ± 92.8). The trypan blue assay showed that the enzymatic method (98.7 ± 0.6%) provided the highest percentage of viable follicles (P < 0.05). Furthermore, SEM confirmed the ultrastructural integrity of the surface architecture of peccary PFs isolated by the enzymatic procedure; epifluorescence microscopy was used to confirm their viability (86.0%). In conclusion, we suggest that the enzymatic method investigated here is useful for the isolation of viable ovarian PFs from collared peccaries.