Hemoglobin: a gas transport molecule that is hormonally regulated in the ovarian follicle in mice and humans.
An increasing number of nonerythroid tissues are found to express hemoglobin mRNA and protein. Hemoglobin is a well-described gas transport molecule, especially for O2, but also for NO, CO2, and CO, and also acts as a reactive oxygen species scavenger. We previously found Hba-a1 and Hbb mRNA and protein at high levels within mouse periovulatory cumulus cells, but not in cumulus following in vitro maturation. This led us to investigate the temporal and spatial regulation in follicular cells during the periovulatory period. Cumulus-oocyte complexes were collected from equine chorionic gonadotropin/human chorionic gonadotropin-treated peripubertal SV129 female mice and collected and analyzed for gene expression and protein localization at a variety of time points over the periovulatory period. A further cohort matured in vitro with different forms of hemoglobin (ferro- and ferrihemoglobin) under different O2 atmospheric conditions (2%, 5%, and 20% O2) were subsequently fertilized in vitro and cultured to the blastocyst stage. Murine mRNA transcripts for hemoglobin were regulated by stimulation of the ovulatory cascade, in both granulosa and cumulus cells, and expression of HBA1 and HBB was highly significant in human granulosa and cumulus, but erythrocyte cell marker genes were not. Several other genes involved in hemoglobin function were similarly luteinizing hormone-regulated, including genes for heme biosynthesis. Immunohistochemistry revealed a changing localization pattern of HBA-A1 protein in murine cumulus cells and oocytes following the ovulatory signal. Significantly, no positive staining for HBA-A1 protein was observed within in vitro-matured oocytes, but, if coincubated with ferro- or ferrihemoglobin, cytoplasmic HBA-A1 was observed, similar to in vivo-derived oocytes. Addition of ferro-, but not ferrihemoglobin, had a small, positive effect on blastocyst yield, but only under either 2% or 20% O2 gas atmosphere. The identification of hemoglobin within granulosa and cumulus cells poses many questions as to its function in these cells. There are several possible roles, the most likely of which is either an O2 or NO sequestering molecule; perhaps both roles are engaged. The strong endocrine regulation during the periovulatory period suggests to us that one potential function of hemoglobin is to provide a short-lived hypoxic environment by binding very tightly any available O2. This, in turn, facilitates the differentiation of the follicle towards corpus luteum formation by enabling the stabilization of a key transcription factor known to initiate such differentiation: hypoxia inducible factor.
School of Pediatrics and Reproductive Health, School of Animal and Veterinary Sciences, Robinson Research Institute, University of Adelaide, Adelaide, South Australia, Australia.
Hannah M
HM
Brown
School of Pediatrics and Reproductive Health, School of Animal and Veterinary Sciences, Robinson Research Institute, University of Adelaide, Adelaide, South Australia, Australia.
Marie R
MR
Anastasi
School of Pediatrics and Reproductive Health, School of Animal and Veterinary Sciences, Robinson Research Institute, University of Adelaide, Adelaide, South Australia, Australia.
Laura A
LA
Frank
School of Pediatrics and Reproductive Health, School of Animal and Veterinary Sciences, Robinson Research Institute, University of Adelaide, Adelaide, South Australia, Australia.
Karen L
KL
Kind
School of Pediatrics and Reproductive Health, School of Animal and Veterinary Sciences, Robinson Research Institute, University of Adelaide, Adelaide, South Australia, Australia.
Dulama
D
Richani
School of Pediatrics and Reproductive Health, School of Animal and Veterinary Sciences, Robinson Research Institute, University of Adelaide, Adelaide, South Australia, Australia.
Rebecca L
RL
Robker
School of Pediatrics and Reproductive Health, School of Animal and Veterinary Sciences, Robinson Research Institute, University of Adelaide, Adelaide, South Australia, Australia.
Darryl L
DL
Russell
School of Pediatrics and Reproductive Health, School of Animal and Veterinary Sciences, Robinson Research Institute, University of Adelaide, Adelaide, South Australia, Australia.
Robert B
RB
Gilchrist
School of Pediatrics and Reproductive Health, School of Animal and Veterinary Sciences, Robinson Research Institute, University of Adelaide, Adelaide, South Australia, Australia Centre of Excellence for Nanoscale BioPhotonics, University of Adelaide, Adelaide, South Australia, Australia jeremy.thompson@adelaide.edu.au.
Jeremy G
JG
Thompson
D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D002478:Cells, Cultured; D054885:Cumulus Cells / Q000187:drug effects / Q000502:physiology; D004622:Embryo, Mammalian; D005260:Female; D005740:Gases / Q000378:metabolism*; D012739:Gonadal Steroid Hormones / Q000494:pharmacology*; D006107:Granulosa Cells / Q000187:drug effects / Q000502:physiology; D006441:Hemoglobin A / Q000235:genetics / Q000378:metabolism; D006454:Hemoglobins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D006801:Humans; D051379:Mice; D009569:Nitric Oxide / Q000378:metabolism; D006080:Ovarian Follicle / Q000187:drug effects* / Q000378:metabolism*; D010100:Oxygen / Q000378:metabolism
D005740:Gases; D012739:Gonadal Steroid Hormones; D006454:Hemoglobins; D009569:Nitric Oxide; C028672:hemoglobin AA; D006441:Hemoglobin A; C020622:hemoglobin B; D010100:Oxygen
IVM; embryo; hemoglobin; hypoxia; maturation; oocyte; oxygen