Resilience of the human fetal lung following stillbirth: potential relevance for pulmonary regenerative medicine

Plumping up a Cushion of Human Biowaste in Regenerative Medicine: Novel Insights into a State-of-the-Art Reserve Arsenal

Major breakthroughs and disruptive methods in disease treatment today owe their thanks to our inch by inch developing conception of the infinitive aspects of medicine since the very beginning, among which, the role of the regenerative medicine can on no account be denied, a branch of medicine dedicated to either repairing or replacing the injured or diseased cells, organs, and tissues. A novel means to accomplish such a quest is what is being called “medical biowaste”, a large assortment of biological samples produced during a surgery session or as a result of physiological conditions and biological activities. The current paper accentuating several of a number of promising sources of biowaste together with their plausible applications in routine clinical practices and the confronting challenges aims at inspiring research on the existing gap between clinical and basic science to further extend our knowledge and understanding concerning the potential applications of medical biowaste.

Intussusceptive-like angiogenesis in human fetal lung xenografts: Link with bronchopulmonary dysplasia-associated microvascular dysangiogenesis?

BACKGROUND

Human fetal lung xenografts display an unusual pattern of non-sprouting, plexus-forming angiogenesis that is reminiscent of the dysmorphic angioarchitecture described in bronchopulmonary dysplasia (BPD). The aim of this study was to determine the clinicopathological correlates, growth characteristics and molecular regulation of this aberrant form of graft angiogenesis.

METHODS

Fetal lung xenografts, derived from 12 previable fetuses (15 to 22 weeks' gestation) and engrafted in the renal subcapsular space of SCID-beige mice, were analyzed 4 weeks posttransplantation for morphology, vascularization, proliferative activity and gene expression.

RESULTS

Focal plexus-forming angiogenesis (PFA) was observed in 60/230 (26%) of xenografts. PFA was characterized by a complex network of tortuous nonsprouting vascular structures with low endothelial proliferative activity, suggestive of intussusceptive-type angiogenesis. There was no correlation between the occurrence of PFA and gestational age or time interval between delivery and engraftment. PFA was preferentially localized in the relatively hypoxic central subcapsular area. Microarray analysis suggested altered expression of 15 genes in graft regions with PFA, of which 7 are known angiogenic/lymphangiogenic regulators and 5 are known hypoxia-inducible genes. qRT-PCR analysis confirmed significant upregulation of SULF2, IGF2, and HMOX1 in graft regions with PFA.

CONCLUSION

These observations in human fetal lungs ex vivo suggest that postcanalicular lungs can switch from sprouting angiogenesis to an aberrant intussusceptive-type of angiogenesis that is highly reminiscent of BPD-associated dysangiogenesis. While circumstantial evidence suggests hypoxia may be implicated, the exact triggering mechanisms, molecular regulation and clinical implications of this angiogenic switch in preterm lungs in vivo remain to be determined.

Developmental exposure to estrogen alters differentiation and epigenetic programming in a human fetal prostate xenograft model

Prostate cancer is the most frequent non-cutaneous malignancy in men. There is strong evidence in rodents that neonatal estrogen exposure plays a role in the development of this disease. However, there is little information regarding the effects of estrogen in human fetal prostate tissue. This study explored early life estrogen exposure, with and without a secondary estrogen and testosterone treatment in a human fetal prostate xenograft model. Histopathological lesions, proliferation, and serum hormone levels were evaluated at 7, 30, 90, and 200-day time-points after xenografting. The expression of 40 key genes involved in prostatic glandular and stromal growth, cell-cycle progression, apoptosis, hormone receptors and tumor suppressors was evaluated using a custom PCR array. Epigenome-wide analysis of DNA methylation was performed on whole tissue, and laser capture-microdissection (LCM) isolated epithelial and stromal compartments of 200-day prostate xenografts. Combined initial plus secondary estrogenic exposures had the most severe tissue changes as revealed by the presence of hyperplastic glands at day 200. Gene expression changes corresponded with the cellular events in the KEGG prostate cancer pathway, indicating that initial plus secondary exposure to estrogen altered the PI3K-Akt signaling pathway, ultimately resulting in apoptosis inhibition and an increase in cell cycle progression. DNA methylation revealed that differentially methylated CpG sites significantly predominate in the stromal compartment as a result of estrogen-treatment, thereby providing new targets for future investigation. By using human fetal prostate tissue and eliminating the need for species extrapolation, this study provides novel insights into the gene expression and epigenetic effects related to prostate carcinogenesis following early life estrogen exposure.

A human fetal prostate xenograft model of developmental estrogenization

Prostate cancer is a common disease in older men. Rodent models have demonstrated that an early and later-life exposure to estrogen can lead to cancerous lesions and implicated hormonal dysregulation as an avenue for developing future prostate neoplasia. This study utilizes a human fetal prostate xenograft model to study the role of estrogen in the progression of human disease. Histopathological lesions were assessed in 7-, 30-, 90-, 200-, and 400-day human prostate xenografts. Gene expression for cell cycle, tumor suppressors, and apoptosis-related genes (ie, CDKN1A, CASP9, ESR2, PTEN, and TP53) was performed for 200-day estrogen-treated xenografts. Glandular hyperplasia was observed in xenografts given both an initial and secondary exposure to estradiol in both 200- and 400-day xenografts. Persistent estrogenic effects were verified using immunohistochemical markers for cytokeratin 10, p63, and estrogen receptor α. This model provides data on the histopathological state of the human prostate following estrogenic treatment, which can be utilized in understanding the complicated pathology associated with prostatic disease and early and later-life estrogenic exposures.

Xenotransplantation models to study the effects of toxicants on human fetal tissues

Many diseases that manifest throughout the lifetime are influenced by factors affecting fetal development. Fetal exposure to xenobiotics, in particular, may influence the development of adult diseases. Established animal models provide systems for characterizing both developmental biology and developmental toxicology. However, animal model systems do not allow researchers to assess the mechanistic effects of toxicants on developing human tissue. Human fetal tissue xenotransplantation models have recently been implemented to provide human-relevant mechanistic data on the many tissue-level functions that may be affected by fetal exposure to toxicants. This review describes the development of human fetal tissue xenotransplant models for testis, prostate, lung, liver, and adipose tissue, aimed at studying the effects of xenobiotics on tissue development, including implications for testicular dysgenesis, prostate disease, lung disease, and metabolic syndrome. The mechanistic data obtained from these models can complement data from epidemiology, traditional animal models, and in vitro studies to quantify the risks of toxicant exposures during human development.

Maturation of the developing human fetal prostate in a rodent xenograft model

BACKGROUND

Prostate cancer is the most commonly diagnosed nonskin cancer in men. The etiology of prostate cancer is unknown, although both animal and epidemiologic data suggest that early life exposures to various toxicants, may impact DNA methylation status during development, playing an important role.

METHODS

We have developed a xenograft model to characterize the growth and differentiation of human fetal prostate implants (gestational age 12-24 weeks) that can provide new data on the potential role of early life stressors on prostate cancer. The expression of key immunohistochemical markers responsible for prostate maturation was evaluated, including p63, cytokeratin 18, α-smooth muscle actin, vimentin, caldesmon, Ki-67, prostate-specific antigen, estrogen receptor-α, and androgen receptor. Xenografts were separated into epithelial and stromal compartments using laser capture microdissection (LCM), and the DNA methylation status was assessed in >480,000 CpG sites throughout the genome.

RESULTS

Xenografts demonstrated growth and maturation throughout the 200 days of post-implantation evaluation. DNA methylation profiles of laser capture microdissected tissue demonstrated tissue-specific markers clustered by their location in either the epithelium or stroma of human prostate tissue. Differential methylated promoter region CpG-associated gene analysis revealed significantly more stromal than epithelial DNA methylation in the 30- and 90-day xenografts. Functional classification analysis identified CpG-related gene clusters in methylated epithelial and stromal human xenografts.

CONCLUSION

This study of human fetal prostate tissue establishes a xenograft model that demonstrates dynamic growth and maturation, allowing for future mechanistic studies of the developmental origins of later life proliferative prostate disease.

Differential response to abiraterone acetate and di-n-butyl phthalate in an androgen-sensitive human fetal testis xenograft bioassay

In utero exposure to antiandrogenic xenobiotics such as di-n-butyl phthalate (DBP) has been linked to congenital defects of the male reproductive tract, including cryptorchidism and hypospadias, as well as later life effects such as testicular cancer and decreased sperm counts. Experimental evidence indicates that DBP has in utero antiandrogenic effects in the rat. However, it is unclear whether DBP has similar effects on androgen biosynthesis in human fetal testis. To address this issue, we developed a xenograft bioassay with multiple androgen-sensitive physiological endpoints, similar to the rodent Hershberger assay. Adult male athymic nude mice were castrated, and human fetal testis was xenografted into the renal subcapsular space. Hosts were treated with human chorionic gonadotropin for 4 weeks to stimulate testosterone production. During weeks 3 and 4, hosts were exposed to DBP or abiraterone acetate, a CYP17A1 inhibitor. Although abiraterone acetate (14 d, 75 mg/kg/d po) dramatically reduced testosterone and the weights of androgen-sensitive host organs, DBP (14 d, 500 mg/kg/d po) had no effect on androgenic endpoints. DBP did produce a near-significant trend toward increased multinucleated germ cells in the xenografts. Gene expression analysis showed that abiraterone decreased expression of genes related to transcription and cell differentiation while increasing expression of genes involved in epigenetic control of gene expression. DBP induced expression of oxidative stress response genes and altered expression of actin cytoskeleton genes.