Perturbations in Lineage Specification of Granulosa and Theca Cells May Alter Corpus Luteum Formation and Function

Anovulation is a major cause of infertility, and it is the major leading reproductive disorder in mammalian females. Without ovulation, an oocyte is not released from the ovarian follicle to be fertilized and a corpus luteum is not formed. The corpus luteum formed from the luteinized somatic follicular cells following ovulation, vasculature cells, and immune cells is critical for progesterone production and maintenance of pregnancy. Follicular theca cells differentiate into small luteal cells (SLCs) that produce progesterone in response to luteinizing hormone (LH), and granulosa cells luteinize to become large luteal cells (LLCs) that have a high rate of basal production of progesterone. The formation and function of the corpus luteum rely on the appropriate proliferation and differentiation of both granulosa and theca cells. If any aspect of granulosa or theca cell luteinization is perturbed, then the resulting luteal cell populations (SLC, LLC, vascular, and immune cells) may be reduced and compromise progesterone production. Thus, many factors that affect the differentiation/lineage of the somatic cells and their gene expression profiles can alter the ability of a corpus luteum to produce the progesterone critical for pregnancy. Our laboratory has identified genes that are enriched in somatic follicular cells and luteal cells through gene expression microarray. This work was the first to compare the gene expression profiles of the four somatic cell types involved in the follicle-to-luteal transition and to support previous immunofluorescence data indicating theca cells differentiate into SLCs while granulosa cells become LLCs. Using these data and incorporating knowledge about the ways in which luteinization can go awry, we can extrapolate the impact that alterations in the theca and granulosa cell gene expression profiles and lineages could have on the formation and function of the corpus luteum. While interactions with other cell types such as vascular and immune cells are critical for appropriate corpus luteum function, we are restricting this review to focus on granulosa, theca, and luteal cells and how perturbations such as androgen excess and inflammation may affect their function and fertility

Quantification of Phenotypic Change Resulting in Sensitization of Primary Sensory Neurons due to Oxidative Stress

84% of the population will suffer from low back pain at some point in their lives, and 39% of the cases may be related to pain originating from the intervertebral disc (IVD) also known as discogenic pain. Age or injury can cause progressive degeneration of the IVD, and this can allow innervation by nociceptive (pain-sensing) neurons from the dorsal root ganglion (DRG) into the inner IVD.6 Long-term exposure to pain-inducing stimuli can cause nociceptor sensitization, manifested as increased pain sensation in response to non-painful or painful stimuli.7 Sensitization results in the nociceptors responding more strongly to a stimulus, and the activation energy required for response is reduced.8 During IVD degeneration, inflammation and oxidative stress create excess reactive oxygen species (ROS) .9 ROS such as superoxide may play a role in nociceptive signaling and lead to nociceptor sensitization.8 ROS are involved in the chronic pain that results from nerve injury or inflammation in many contexts and may be involved in discogenic pain as well.10 The focus of this study is to determine if long-term oxidative stress causes a change in the DRG nociceptive neuron phenotype related to sensitization. This would increase the expression of pain-related ion channels and lower the neuronal activation threshold. 1. DePalma et al. (2011) 2. Balague et al. (2012) 3. Zhang et al. (2010) 4. Humzah et al. (1988) 5. Ohtori et al. (2015) 6. Yang et al. (2018) 7. Woolf et al. (2010) 8. Chung et al. (2004) 9. Nasto et al. (2013) 10. Yowtak et al. (2011

A Tunable, Three-Dimensional \u3ci\u3eIn Vitro\u3c/i\u3e Culture Model of Growth Plate Cartilage Using Alginate Hydrogel Scaffolds

Defining the final size and geometry of engineered tissues through precise control of the scalar and vector components of tissue growth is a necessary benchmark for regenerative medicine, but it has proved to be a significant challenge for tissue engineers. The growth plate cartilage that promotes elongation of the long bones is a good model system for studying morphogenetic mechanisms because cartilage is composed of a single cell type, the chondrocyte; chondrocytes are readily maintained in culture; and growth trajectory is predominately in a single vector. In this cartilage, growth is generated via a differentiation program that is spatially and temporally regulated by an interconnected network composed of long- and short-range signaling mechanisms that together result in the formation of functionally distinct cellular zones. To facilitate investigation of the mechanisms underlying anisotropic growth, we developed an in vitro model of the growth plate cartilage by using neonatal mouse growth plate chondrocytes encapsulated in alginate hydrogel beads. In bead cultures, encapsulated chondrocytes showed high viability, cartilage matrix deposition, low levels of chondrocyte hypertrophy, and a progressive increase in cell proliferation over 7 days in culture. Exogenous factors were used to test functionality of the parathyroid-related protein–Indian hedgehog (PTHrP-IHH) signaling interaction, which is a crucial feedback loop for regulation of growth. Consistent with in vivo observations, exogenous PTHrP stimulated cell proliferation and inhibited hypertrophy, whereas IHH signaling stimulated chondrocyte hypertrophy. Importantly, the treatment of alginate bead cultures with IHH or thyroxine resulted in formation of a discrete domain of hypertrophic cells that mimics tissue architecture of native growth plate cartilage. Together, these studies are the first demonstration of a tunable in vitro system to model the signaling network interactions that are required to induce zonal architecture in growth plate chondrocytes, which could also potentially be used to grow cartilage cultures of specific geometries to meet personalized patient needs

Letrozole: A Steroid-Free Estrous Synchronization Method

Most bovine estrous synchronization protocols utilize progesterone plus estrogen to control ovulation timing. A drug that inhibits estrogen production (Letrozole) may be an alternative, steroid-free synchronization method (not yet commercially available). However, low estrogen can negatively affect the health of follicles/oocytes and impact fertility. To determine its effects, Letrozole was administered intramuscularly while tracking follicle growth and circulating hormones. Letrozole response was variable. Two of three cows experienced delayed luteolysis/ovulation and extended progesterone production. This preliminary data indicates that Letrozole treatment allows normal follicle progression but drug response may vary and little is known about effects on oocyte quality

Harmonization and standardization of nucleus pulposus cell extraction and culture methods

Background: In vitro studies using nucleus pulposus (NP) cells are commonly used to investigate disc cell biology and pathogenesis, or to aid in the development of new therapies. However, lab‐to‐lab variability jeopardizes the much‐needed progress in the field. Here, an international group of spine scientists collaborated to standardize extraction and expansion techniques for NP cells to reduce variability, improve comparability between labs and improve utilization of funding and resources. Methods: The most commonly applied methods for NP cell extraction, expansion, and re‐differentiation were identified using a questionnaire to research groups worldwide. NP cell extraction methods from rat, rabbit, pig, dog, cow, and human NP tissue were experimentally assessed. Expansion and re‐differentiation media and techniques were also investigated. Results: Recommended protocols are provided for extraction, expansion, and re‐differentiation of NP cells from common species utilized for NP cell culture. Conclusions: This international, multilab and multispecies study identified cell extraction methods for greater cell yield and fewer gene expression changes by applying species‐specific pronase usage, 60–100 U/ml collagenase for shorter durations. Recommendations for NP cell expansion, passage number, and many factors driving successful cell culture in different species are also addressed to support harmonization, rigor, and cross‐lab comparisons on NP cells worldwide

Quantification of Phenotypic Change Resulting in Sensitization of Primary Sensory Neurons due to Oxidative Stress

84% of the population will suffer from low back pain at some point in their lives, and 39% of the cases may be related to pain originating from the intervertebral disc (IVD) also known as discogenic pain. Age or injury can cause progressive degeneration of the IVD, and this can allow innervation by nociceptive (pain-sensing) neurons from the dorsal root ganglion (DRG) into the inner IVD.6 Long-term exposure to pain-inducing stimuli can cause nociceptor sensitization, manifested as increased pain sensation in response to non-painful or painful stimuli.7 Sensitization results in the nociceptors responding more strongly to a stimulus, and the activation energy required for response is reduced.8 During IVD degeneration, inflammation and oxidative stress create excess reactive oxygen species (ROS) .9 ROS such as superoxide may play a role in nociceptive signaling and lead to nociceptor sensitization.8 ROS are involved in the chronic pain that results from nerve injury or inflammation in many contexts and may be involved in discogenic pain as well.10 The focus of this study is to determine if long-term oxidative stress causes a change in the DRG nociceptive neuron phenotype related to sensitization. This would increase the expression of pain-related ion channels and lower the neuronal activation threshold. 1. DePalma et al. (2011) 2. Balague et al. (2012) 3. Zhang et al. (2010) 4. Humzah et al. (1988) 5. Ohtori et al. (2015) 6. Yang et al. (2018) 7. Woolf et al. (2010) 8. Chung et al. (2004) 9. Nasto et al. (2013) 10. Yowtak et al. (2011

Development of an In Vitro Intervertebral Disc Innervation Model to Screen Neuroinhibitory Biomaterials

Pain originating from an intervertebral disc (discogenic pain) is a major source of chronic low back pain. Pathological innervation of the disc by pain‐sensing nerve fibers is thought to be a key component of discogenic pain, so treatment with biomaterials that have the ability to inhibit neurite growth will greatly benefit novel disc therapeutics. Currently, disc therapeutic biomaterials are rarely screened for their ability to modulate nerve growth, mainly due to a lack of models to screen neuromodulation. To address this deficit, our lab has engineered a three dimensional in vitro disc innervation model that mimics the interface between primary sensory nerves and the intervertebral disc. Further, herein we have demonstrated the utility of this model to screen the efficacy of chondroitin sulfate biomaterials to inhibit nerve fiber invasion into the model disc. Biomaterials containing chondroitin‐4‐sulfate (CS‐A) decrease neurite growth in a uniform gel and at an interface between a growth‐permissive and a growth‐inhibitory gel, while chondroitin‐6‐sulfate (CS‐C) is less neuroinhibitory. This in vitro model holds great potential for screening inhibitors of nerve fiber growth to further improve intervertebral disc replacements and therapeutics

Development of an In Vitro Intervertebral Disc Innervation Model to Screen Neuroinhibitory Biomaterials

Pain originating from an intervertebral disc (discogenic pain) is a major source of chronic low back pain. Pathological innervation of the disc by pain‐sensing nerve fibers is thought to be a key component of discogenic pain, so treatment with biomaterials that have the ability to inhibit neurite growth will greatly benefit novel disc therapeutics. Currently, disc therapeutic biomaterials are rarely screened for their ability to modulate nerve growth, mainly due to a lack of models to screen neuromodulation. To address this deficit, our lab has engineered a three dimensional in vitro disc innervation model that mimics the interface between primary sensory nerves and the intervertebral disc. Further, herein we have demonstrated the utility of this model to screen the efficacy of chondroitin sulfate biomaterials to inhibit nerve fiber invasion into the model disc. Biomaterials containing chondroitin‐4‐sulfate (CS‐A) decrease neurite growth in a uniform gel and at an interface between a growth‐permissive and a growth‐inhibitory gel, while chondroitin‐6‐sulfate (CS‐C) is less neuroinhibitory. This in vitro model holds great potential for screening inhibitors of nerve fiber growth to further improve intervertebral disc replacements and therapeutics

Perturbations in Lineage Specification of Granulosa and Theca Cells May Alter Corpus Luteum Formation and Function

Anovulation is a major cause of infertility, and it is the major leading reproductive disorder in mammalian females. Without ovulation, an oocyte is not released from the ovarian follicle to be fertilized and a corpus luteum is not formed. The corpus luteum formed from the luteinized somatic follicular cells following ovulation, vasculature cells, and immune cells is critical for progesterone production and maintenance of pregnancy. Follicular theca cells differentiate into small luteal cells (SLCs) that produce progesterone in response to luteinizing hormone (LH), and granulosa cells luteinize to become large luteal cells (LLCs) that have a high rate of basal production of progesterone. The formation and function of the corpus luteum rely on the appropriate proliferation and differentiation of both granulosa and theca cells. If any aspect of granulosa or theca cell luteinization is perturbed, then the resulting luteal cell populations (SLC, LLC, vascular, and immune cells) may be reduced and compromise progesterone production. Thus, many factors that affect the differentiation/lineage of the somatic cells and their gene expression profiles can alter the ability of a corpus luteum to produce the progesterone critical for pregnancy. Our laboratory has identified genes that are enriched in somatic follicular cells and luteal cells through gene expression microarray. This work was the first to compare the gene expression profiles of the four somatic cell types involved in the follicle-to-luteal transition and to support previous immunofluorescence data indicating theca cells differentiate into SLCs while granulosa cells become LLCs. Using these data and incorporating knowledge about the ways in which luteinization can go awry, we can extrapolate the impact that alterations in the theca and granulosa cell gene expression profiles and lineages could have on the formation and function of the corpus luteum. While interactions with other cell types such as vascular and immune cells are critical for appropriate corpus luteum function, we are restricting this review to focus on granulosa, theca, and luteal cells and how perturbations such as androgen excess and inflammation may affect their function and fertility

A Tunable, Three-Dimensional \u3ci\u3eIn Vitro\u3c/i\u3e Culture Model of Growth Plate Cartilage Using Alginate Hydrogel Scaffolds

Defining the final size and geometry of engineered tissues through precise control of the scalar and vector components of tissue growth is a necessary benchmark for regenerative medicine, but it has proved to be a significant challenge for tissue engineers. The growth plate cartilage that promotes elongation of the long bones is a good model system for studying morphogenetic mechanisms because cartilage is composed of a single cell type, the chondrocyte; chondrocytes are readily maintained in culture; and growth trajectory is predominately in a single vector. In this cartilage, growth is generated via a differentiation program that is spatially and temporally regulated by an interconnected network composed of long- and short-range signaling mechanisms that together result in the formation of functionally distinct cellular zones. To facilitate investigation of the mechanisms underlying anisotropic growth, we developed an in vitro model of the growth plate cartilage by using neonatal mouse growth plate chondrocytes encapsulated in alginate hydrogel beads. In bead cultures, encapsulated chondrocytes showed high viability, cartilage matrix deposition, low levels of chondrocyte hypertrophy, and a progressive increase in cell proliferation over 7 days in culture. Exogenous factors were used to test functionality of the parathyroid-related protein–Indian hedgehog (PTHrP-IHH) signaling interaction, which is a crucial feedback loop for regulation of growth. Consistent with in vivo observations, exogenous PTHrP stimulated cell proliferation and inhibited hypertrophy, whereas IHH signaling stimulated chondrocyte hypertrophy. Importantly, the treatment of alginate bead cultures with IHH or thyroxine resulted in formation of a discrete domain of hypertrophic cells that mimics tissue architecture of native growth plate cartilage. Together, these studies are the first demonstration of a tunable in vitro system to model the signaling network interactions that are required to induce zonal architecture in growth plate chondrocytes, which could also potentially be used to grow cartilage cultures of specific geometries to meet personalized patient needs