Regionally distinct progenitor cells in the lower airway give rise to neuroendocrine and multiciliated cells in the developing human lung

Using scRNA-seq and microscopy, we describe a cell that is enriched in the lower airways of the developing human lung and identified by the unique coexpression of SCGB3A2/SFTPB/CFTR. To functionally interrogate these cells, we apply a single-cell barcode-based lineage tracing method, called CellTagging, to track the fate of SCGB3A2/SFTPB/CFTR cells during airway organoid differentiation in vitro. Lineage tracing reveals that these cells have a distinct differentiation potential from basal cells, giving rise predominantly to pulmonary neuroendocrine cells and a subset of multiciliated cells distinguished by high C6 and low MUC16 expression. Lineage tracing results are supported by studies using organoids and isolated cells from the lower noncartilaginous airway. We conclude that SCGB3A2/SFTPB/CFTR cells are enriched in the lower airways of the developing human lung and contribute to the epithelial diversity and heterogeneity in this region.

IRE1α drives lung epithelial progenitor dysfunction to establish a niche for pulmonary fibrosis

After lung injury, damage-associated transient progenitors (DATPs) emerge, representing a transitional state between injured epithelial cells and newly regenerated alveoli. DATPs express profibrotic genes, suggesting that they might promote idiopathic pulmonary fibrosis (IPF). However, the molecular pathways that induce and/or maintain DATPs are incompletely understood. Here we show that the bifunctional kinase/RNase-IRE1α-a central mediator of the unfolded protein response (UPR) to endoplasmic reticulum (ER) stress is a critical promoter of DATP abundance and function. Administration of a nanomolar-potent, monoselective kinase inhibitor of IRE1α (KIRA8)-or conditional epithelial IRE1α gene knockout-both reduce DATP cell number and fibrosis in the bleomycin model, indicating that IRE1α cell-autonomously promotes transition into the DATP state. IRE1α enhances the profibrotic phenotype of DATPs since KIRA8 decreases expression of integrin αvβ6, a key activator of transforming growth factor β (TGF-β) in pulmonary fibrosis, corresponding to decreased TGF-β-induced gene expression in the epithelium and decreased collagen accumulation around DATPs. Furthermore, IRE1α regulates DNA damage response (DDR) signaling, previously shown to promote the DATP phenotype, as IRE1α loss-of-function decreases H2AX phosphorylation, Cdkn1a (p21) expression, and DDR-associated secretory gene expression. Finally, KIRA8 treatment increases the differentiation of Krt19CreERT2-lineage-traced DATPs into type 1 alveolar epithelial cells after bleomycin injury, indicating that relief from IRE1α signaling enables DATPs to exit the transitional state. Thus, IRE1α coordinates a network of stress pathways that conspire to entrap injured cells in the DATP state. Pharmacological blockade of IRE1α signaling helps resolve the DATP state, thereby ameliorating fibrosis and promoting salutary lung regeneration.

Multiple 9-1-1 complexes promote homolog synapsis, DSB repair, and ATR signaling during mammalian meiosis

DNA damage response mechanisms have meiotic roles that ensure successful gamete formation. While completion of meiotic double-strand break (DSB) repair requires the canonical RAD9A-RAD1-HUS1 (9A-1-1) complex, mammalian meiocytes also express RAD9A and HUS1 paralogs, RAD9B and HUS1B, predicted to form alternative 9-1-1 complexes. The RAD1 subunit is shared by all predicted 9-1-1 complexes and localizes to meiotic chromosomes even in the absence of HUS1 and RAD9A. Here, we report that testis-specific disruption of RAD1 in mice resulted in impaired DSB repair, germ cell depletion, and infertility. Unlike Hus1 or Rad9a disruption, Rad1 loss in meiocytes also caused severe defects in homolog synapsis, impaired phosphorylation of ATR targets such as H2AX, CHK1, and HORMAD2, and compromised meiotic sex chromosome inactivation. Together, these results establish critical roles for both canonical and alternative 9-1-1 complexes in meiotic ATR activation and successful prophase I completion.

Efficacy of debridement alone versus debridement combined with topical antifungal nail lacquer for the treatment of pedal onychomycosis: a randomized, controlled trial

Pedal onychomycosis is a common malady caused by dermatophytes, saprophytes, and yeasts. Traditional treatment options for this condition include toenail debridement, and pharmacological therapies that range from the application of topical agents to the oral administration of antifungal medications. In this study, 55 patients (289 toenails) were randomly allocated to either nail debridement (27 [49.09%] patients) or debridement plus application of topical antifungal nail lacquer (28 [50.91%] patients). The primary outcome was mycological cure, and secondary outcomes included foot-related quality of life, and a number of clinically important toenail characteristics. After a median follow-up of 10.5 months (range, 3.25-14.25) months), patients in the antifungal nail lacquer group improved statistically significantly more than did those in the debridement alone group, and displayed a 76.74% rate of mycological cure. None of the patients in the debridement-only group experienced mycological cure. Variables that statistically significantly decreased the likelihood of cure included yeast on culture, pedal hyperhidrosis, cigarette smoking, involvement of the lunula, and involvement of >50% of the transverse width of the nail. Variables statistically significantly associated with an increased likelihood of cure included intervention before 6 months' duration, treatment at a large, urban practice, black race, and loss of protective sensation.

LEVEL OF CLINICAL EVIDENCE

1.

Autogenous bone graft interpositional arthrodesis for the correction of flail toe. A retrospective analysis of 22 procedures

Digital surgery is one of the most common types of surgery performed by foot and ankle surgeons. Flail toe is a complication that may occur after overaggressive resection arthroplasty of the proximal interphalangeal joint of the lesser toes. Correction of flail toe deformity has received little attention and has predominantly involved soft-tissue procedures. The authors' preferred technique for the surgical correction of flail toe is to place a unicortical autogenous bone graft (harvested from the ipsilateral calcaneus) within the revised proximal interphalangeal joint of the lesser toes to create a distraction arthrodesis. This technique allows restoration of digital length, stability, and purchase. A retrospective review of 22 such procedures in 13 patients is presented, along with a literature review of other procedures and a description of the authors' current surgical technique and postoperative management protocol. Overall success using the authors' procedure was 82%. Complications occurred in three patients, with one of the grafts showing complete resorption and two requiring additional surgical intervention owing to nonunion and malunion of toes.

Metastatic malignant melanoma to the foot and ankle: a review of the literature and case report

The lower extremity is a frequent site for malignant melanomas. However, skeletal metastases involving the foot and ankle are a rarity. Nearly all documented cases of secondary pedal bone metastasis have originated from a primary subungual melanoma. The following case study illustrates an unusual skeletal metastasis to the foot and ankle arising from a primary malignant melanoma of the torso.

Polymicrobial septic arthritis due to Clostridium species: case report and review

Clostridium species are capable of producing several types of infectious processes, many of which have proven to be life-threatening. Septic arthritis caused by Clostridium, however, is not a very frequent finding. Currently, only 37 cases of infectious arthritis due to Clostridium species have been reported. We report a case of septic arthritis in which Clostridium perfringens, Clostridium sordellii, and Clostridium tertium were each isolated from the synovial aspirate. In addition, the 37 previously reported cases are summarized to compare the similarities and differences of the clinical course, treatment, and outcome, in order to help establish guidelines for the proper management of this infectious process.

Retrospective analysis of neurapraxia and axonotmesis injuries of select peripheral nerves of the foot and ankle and their conservative and surgical treatment (external neurolysis and neurectomy)

There is a paucity of scientific literature that has reviewed the conservative and surgical treatment efficacy for the management of injuries causing neurapraxia and axonotmesis. This retrospective study evaluates the clinical outcomes of certain treatments for these injuries. Twenty-seven patients fulfilled the inclusion/exclusion criteria for the study, and represented both genders and a wide variety of ages, weights, levels of education, and backgrounds. Surgical intervention resulted in a slightly better clinical outcome when compared to conservative therapies. Patients undergoing surgery for a single nerve problem improved more than those who underwent surgery when three or more nerves were involved. Failure was most often associated with: 1) multiple nerve injuries, 2) a previous history of psychopathology, and 3) application of conservative therapy without surgical intervention for single nerve injury.

Peripheral nerve surgery of the foot and ankle. A review of current principles

Planning for peripheral nerve surgery requires consideration of a multitude of factors, as well as a surgeon's meticulous skill and experience. With so little room for error, every advantage must be taken to optimize repair. Peripheral nerve surgery of the foot and ankle is an underappreciated area of neurosurgery with comparatively limited published reports and data. The authors reviewed the current trends in the surgical management of peripheral nerve injuries of the foot and ankle in the hope that an understanding of the basic principles involved will allow for future study of the results of such surgery by more surgeons who deal with these problems.

Accessory soleus muscle: a review of the literature and case report

The accessory soleus is a rare anatomic variant that must be considered in the differential diagnosis of all posteromedial soft tissue masses of the ankle. The authors review and discuss the pertinent findings of the previously reported 70 cases of accessory soleus muscles cited in English literature. A case report is presented that highlights the diagnosis of the accessory soleus muscle with magnetic resonance imaging studies and surgical excision of the mass in a symptomatic patient.

Complications of the Kalish bunionectomy

The Kalish osteotomy has become a popular method for the correction of mild-to-moderate hallux abducto valgus deformities associated with metatarsus primus adductus. This paper reviews the common pitfalls associated with this procedure, including failure to observe the indications for the procedure, technical failures when performing the procedure, and the most frequent postoperative complications.

Tarsal coalitions. A surgical classification

The surgical alternatives for the treatment of tarsal coalitions include procedures as diverse as arthroplasty and arthrodesis. Traditional classifications of tarsal coalitions are primarily descriptive and afford little information regarding preferred treatment. For this reason, the author introduces the Articular Classification System, which is based on the patient's osseous age, the articular involvement of the coalition, and the associated secondary arthritic changes. This classification system can be used as a framework to discuss recommended surgical procedures and their long-term results.

Postoperative infections: general principles and considerations

Every surgeon should have a thorough knowledge and awareness of the general principles of postoperative infections. The key to postoperative infections is in their prevention. Even with the most prudent and ardent regimens, however, postoperative wound infections will occasionally occur. Thus, the aforementioned knowledge will allow an improved clinical acumen and permit the early diagnosis of postoperative infection. Early and vigorous local wound care combined with systemic antibiotics are necessary to minimize the potentially debilitating sequelae of the postoperative wound infection.

Gastrocnemius recession in the treatment of nonspastic ankle equinus. A retrospective study

An updated and thorough review of the gastrocnemius equinus deformity and its surgical correction is presented. For the first time, a long-term retrospective study documents the overall improvement in the symptoms and architecture of the lower extremity and foot following gastrocnemius recession. Additionally, numerous associated concerns and the surgical procedure are examined retrospectively.