Faculty Bibliography

Aging is associated with impaired tissue regeneration. Stem cell number and function have been identified as potential culprits. We first demonstrate a direct correlation between stem cell number and time to bone fracture union in a human patient cohort. We then devised an animal model recapitulating this age-associated decline in bone healing and identified increased cellular senescence caused by a systemic and local proinflammatory environment as the major contributor to the decline in skeletal stem/progenitor cell (SSPC) number and function. Decoupling age-associated systemic inflammation from chronological aging by using transgenic Nfkb1KO mice, we determined that the elevated inflammatory environment, and not chronological age, was responsible for the decrease in SSPC number and function. By using a pharmacological approach inhibiting NF-κB activation, we demonstrate a functional rejuvenation of aged SSPCs with decreased senescence, increased SSPC number, and increased osteogenic function. Unbiased, whole-genome RNA sequencing confirmed the reversal of the aging phenotype. Finally, in an ectopic model of bone healing, we demonstrate a functional restoration of regenerative potential in aged SSPCs. These data identify aging-associated inflammation as the cause of SSPC dysfunction and provide mechanistic insights into its reversal.

The next frontier of orthopedic implants are resorbable devices. Tissue engineering advances have created a demand for scaffolds that can facilitate biologic regeneration. Scaffolds that will degrade over time with the infiltration of host cells are of particular interest. Several principles have been identified as desirable design features for such scaffolds. Furthermore, the era of 3D printing has ushered new possibilities for scaffold production that brings this technology closer to market use. This article explores the future of the design and manufacture of resorbable scaffolds.

Niche cell enwrapment of stem cells and their differentiating progeny is common and provides a specialized signaling and protective environment. Elucidating the mechanisms underlying enwrapment behavior has important basic and clinical significance in not only understanding how niches are formed and maintained but also how they can be engineered and how they are misregulated in human pathologies, such as cancer. Previous work in C. elegans found that, when germ cells, which are enwrapped by somatic gonadal niche cells, are freed into the body cavity, they embed into other tissues. We investigated this phenomenon using live-cell imaging and discovered that ectopic germ cells preferentially induce body-wall muscle to extend cellular processes that enwrap the germ cells, the extent of which was strikingly similar to the distal tip cell (DTC)-germ stem cell niche. Enwrapment was specific for escaped germ cells, and genetic analysis revealed it did not depend on pathways that control cell death and engulfment or muscle arm extension. Instead, using a large-scale RNAi screen and GFP knockin strains, we discovered that the enwrapping behavior of muscle relied upon the same suite of cell-cell adhesion molecules that functioned in the endogenous niche: the C. elegans E-cadherin HMR-1, its intracellular associates α-catenin (HMP-1) and β-catenin (HMP-2), and the L1CAM protein SAX-7. This ectopic niche-like behavior resembles the seed-and-soil model of cancer metastasis and offers a new model to understand factors regulating ectopic niche formation.

PTSD is heterogeneous disorder that can be long lasting and often has delayed onset following exposure to a traumatic event. Therefore, it is important to take a staging approach to evaluate progression of biological mechanisms of the disease. Here, we begin to evaluate the temporal trajectory of changes following exposure to traumatic stressors in the SPS rat PTSD model. The percent of animals displaying severe anxiety on EPM increased from 17.5% at one week to 57.1% two weeks after SPS stressors, indicating delayed onset or progressive worsening of the symptoms. The LC displayed prolonged activation, and dysbalance of the CRH/NPY systems, with enhanced CRHR1 gene expression, coupled with reduced mRNAs for NPY and Y2R. In the mediobasal hypothalamus, increased CRH mRNA levels were sustained, but there was a flip in alterations of HPA regulatory molecules, GR and FKBP5 and Y5 receptor at two weeks compared to one week. Two weeks after SPS, intranasal NPY at 300 µg/rat, but not 150 µg which was effective after one week, reversed SPS triggered elevated anxiety. It also reversed SPS elicited depressive/despair symptoms and hyperarousal. Overall, the results reveal time-dependent progression in development of anxiety symptoms and molecular impairments in gene expression for CRH and NPY systems in LC and mediobasal hypothalamus by SPS. With longer time afterwards only a higher dose of NPY was effective in reversing behavioral impairments triggered by SPS, indicating that therapeutic approaches should be adjusted according to the degree of biological progression of the disorder.

The sensory nervous system of C. elegans comprises cells with varied molecular and functional characteristics and is, therefore, a powerful model for understanding mechanisms that generate neuronal diversity. We report here that VAB-3, a C. elegans homolog of the homeodomain-containing protein Pax6, has opposing functions in regulating expression of a specific chemosensory fate. A homeodomain-only short isoform of VAB-3 is expressed in BAG chemosensory neurons, where it promotes gene expression and cell function. In other cells, a long isoform of VAB-3 comprised of a Paired homology domain and a homeodomain represses expression of ETS-5, a transcription factor required for expression of BAG fate. Repression of ets-5 requires the Eyes Absent homolog EYA-1 and the Six-class homeodomain protein CEH-32. We determined sequences that mediate high-affinity binding of ETS-5, VAB-3, and CEH-32. The ets-5 locus is enriched for ETS-5-binding sites but lacks sequences that bind VAB-3 and CEH-32, suggesting that these factors do not directly repress ets-5 expression. We propose that a promoter-selection system together with lineage-specific expression of accessory factors allows VAB-3/Pax6 to either promote or repress expression of specific cell fates in a context-dependent manner.

The use of depot medroxyprogesterone acetate (DMPA), a 3-monthly injectable hormonal contraceptive, is associated with an increased risk of HIV acquisition possibly through alteration of the vaginal microbiome. In this longitudinal interventional study, we investigated the impact of DMPA administration on the vaginal microbiome in Hispanic White and Black women at the baseline (visit 1), 1 month (visit 2), and 3 months (visit 3) following DMPA treatment by using 16S rRNA gene sequencing. No significant changes in the vaginal microbiome were observed after DMPA treatment when Hispanic White and Black women were analysed as a combined group. However, DMPA treatment enriched total vaginosis-associated bacteria (VNAB) and Prevotella at visit 2, and simplified the correlational network in the vaginal microbiome in Black women, while increasing the network size in Hispanic White women. The microbiome in Black women became more diversified and contained more VNAB than Hispanic White women after DMPA treatment. While the Firmicutes to Bacteroidetes (F/B) ratio and Lactobacillus to Prevotella (L/P) ratio were comparable between Black and Hispanic White women at visit 1, both ratios were lower in Black women than in Hispanic White women at visit 2. In conclusion, DMPA treatment altered the community network and enriched VNAB in Black women but not in Hispanic White women. The Lactobacillus deficiency and enrichment of VNAB may contribute to the increased risk of HIV acquisition in Black women. Future studies on the impact of racial differences on the risk of HIV acquisition will offer insights into developing effective strategies for HIV prevention. Abbreviations: DMPA: depot medroxyprogesterone acetate; PCR: polymerase chain reaction; OTU: operational taxonomic unit; STI: sexually transmitted infections; VNAB: vaginosis-associated bacteria.

Genomic instability is widespread during early embryo development. Aneuploidy, mosaicism, and copy number variants (CNVs) commonly appear in human preimplantation embryos. Both age-dependent meiotic aneuploidy and age-independent mitotic aneuploidy and CNVs occur In human embryos. Telomere attrition, which contributes to genomic instability in somatic cells, also may promote genomic instability in preimplantation embryos. Telomere dynamics during gametogenesis are strikingly dimorphic between females and males. Sperm telomeres lengthen with advancing paternal age, while oocyte telomeres are among the shortest in the body. Spermatogonia express telomerase activity throughout the life of the male, while oocytes and cleavage stage embryos express low or un-measureable levels of telomerase activity. Telomere attrition in oocytes contributes to meiotic dysfunction, including spindle dysmorphologies, reduced synapsis and chiasmata, as well as delayed, arrested and fragmented embryos. Cleavage stage embryos, with such inefficient telomere reconstitution, likely undergo NHEJ, which produces anaphase lag, chromosome bridges, micronuclei, and genomic instability, including mosaicism and CNVs. Cleavage stage embryos reconstitute the short telomeres inherited from their mothers by Alternative Lengthening of Telomeres (ALT), a DNA recombination based method involving RAD 50, MRE 11, Werner and Bloom proteins, as well as telomere sister chromatid exchange. ALT robustly reconstitutes telomeres, but also predisposes to genomic instability.

Touch sensation is initiated by mechanosensory neurons that innervate distinct skin structures; however, little is known about how these neurons are patterned during mammalian skin development. We explored the cellular basis of touch-receptor patterning in mouse touch domes, which contain mechanosensory Merkel cell-neurite complexes and abut primary hair follicles. At embryonic stage 16.5 (E16.5), touch domes emerge as patches of Merkel cells and keratinocytes clustered with a previously unsuspected population of Bmp4-expressing dermal cells. Epidermal Noggin overexpression at E14.5 disrupted touch-dome formation but not hair-follicle specification, demonstrating a temporally distinct requirement for BMP signaling in placode-derived structures. Surprisingly, two neuronal populations preferentially targeted touch domes during development but only one persisted in mature touch domes. Finally, Keratin-17-expressing keratinocytes but not Merkel cells were necessary to establish innervation patterns during development. These findings identify key cell types and signaling pathways required for targeting Merkel-cell afferents to discrete mechanosensory compartments.

STUDY OBJECTIVE/OBJECTIVE:To clarify the relationship of hypogastric nerves (HNs) with several pelvic anatomic landmarks and to assess any anatomic differences between the 2 sides of the pelvis, both in cadaveric and in vivo dissections. DESIGN/METHODS:Prospective observational study. SETTING/METHODS:An anatomic theater for cadaveric dissections and a university hospital for in vivo laparoscopy. PATIENTS/METHODS:Five nulliparous female cadavers underwent laparotomic dissection; 10 nulliparous patients underwent laparoscopic surgery for rectosigmoid endometriosis without posterolateral parametrial infiltration. INTERVENTIONS/METHODS:Measurements of the closest distance between HNs and ureters, the midsagittal plane, the midcervical plane, and uterosacral ligaments on both hemipelvises. A comparison of anatomic data of the 2 hemipelvises was conducted. MEASUREMENTS AND MAIN RESULTS/RESULTS:The right and left HNs were identified in all specimens, both on cadavers and in vivo dissections. A wide anatomic variability was reported. Regarding the differences between the 2 hemipelvises, we found that the right HN was significantly (p <.001) farther to the ureter (mean = 14.5 mm; range, 10-25 mm) than the left one (mean = 8.6 mm; range, 7-12 mm). The HN was closer to the midsagittal plane on the right side (mean = 14.6 mm; range, 12-17 mm) than on the left side (mean = 21.6 mm; range, 19-25 mm). The midcervical plane was found 2.7 mm (range, 2-4 mm) to the left of the midsagittal one. The right HN was found to be nonsignificantly closer to the midcervical plane and the uterosacral ligament on the right side than on the left side (p >.05). CONCLUSIONS:Despite a wide anatomic variability of position and appearance, the HNs are reproducibly identifiable using an "interfascial" technique and considering the ureters and uterosacral ligaments as anatomic landmarks.

Background: The occurrence of bifid mandibular canals is unusual but not rare. Previous reviews and case studies have described numerous types of bifid canals based on location, anatomy, and contents. Developmentally, ossification of the mandible begins at the region of the mental foramen and continues posteriorly, forming the mandibular canal around the neurovascular bundle within. This process explains the creation of multiple mandibular canals and the diversity of canal types previously recorded in the literature. However, the presence of two distinct mandibular canals, each originating from its own mandibular foramen, is even more unusual. Material(s) and Method(s): This case report describes a unilateral variant discovered during the dissection of a 92-year-old African American female. Result(s): On the left side, the cadaver presents two distinct mandibular canals, each containing a branch of the inferior alveolar artery and mandibular nerve, the third division of the trigeminal. The nerves within the two canals were distinct from each other at the level of the posterior division of the mandibular nerve, within 1 cm of foramen ovale. Conclusion(s): This is the first description of such an occurrence and emphasizes the need for identification of the contents of a bifid or accessory mandibular canal prior to invasive procedures.