Three-dimensional (3D) in vitro modeling is increasingly relevant as two-dimensional (2D) cultures have been recognized with limits to recapitulate the complex endogenous conditions in the body. Additionally, fabrication technology is more accessible than ever. Bioprinting, in particular, is an additive manufacturing technique that expands the capabilities of in vitro studies by precisely depositing cells embedded within a 3D biomaterial scaffold that acts as temporary extracellular matrix (ECM). More importantly, bioprinting has vast potential for customization. This allows users to manipulate parameters such as scaffold design, biomaterial selection, and cell types, to create specialized biomimetic 3D systems.The development of a 3D system is important to recapitulate the bone marrow (BM) microenvironment since this particular organ cannot be mimicked with other methods such as organoids. The 3D system can be used to study the interactions between native BM cells and metastatic breast cancer cells (BCCs). Although not perfect, such a system can recapitulate the BM microenvironment. Mesenchymal stem cells (MSCs), a key population within the BM, are known to communicate with BCCs invading the BM and to aid in their transition into dormancy. Dormant BCCs are cycling quiescent and resistant to chemotherapy, which allows them to survive in the BM to resurge even after decades. These persisting BCCs have been identified as the stem cell subset. These BCCs exhibit self-renewal and can be induced to differentiate. More importantly, this BCC subset can initiate tumor formation, exert chemoresistance, and form gap junction with endogenous BM stroma, including MSCs. The bioprinted model detailed in this chapter creates a MSC-BC stem cell coculture system to study intercellular interactions in a model that is more representative of the endogenous 3D microenvironment than conventional 2D cultures. The method can reliably seed primary BM MSCs and BC stem cells within a bioprinted scaffold fabricated from CELLINK Bioink. Since bioprinting is a highly customizable technique, parameters described in this method (i.e., cell-cell ratio, scaffold dimensions) can easily be altered to serve other applications, including studies on hematopoietic regulation.

SUMMARYAngioleiomyomas are a benign group of tumours rarely documented in the head and neck region. We present a case of a 47-year-old man attending the ear, nose and throat outpatient clinic, with a history of hoarseness over many years. Investigation revealed a left-sided subglottic lesion. He underwent microlaryngoscopy and biopsy, and the lesion was sent for histological analysis. Postoperatively, the patient began to expectorate fresh red blood that continued for several hours, requiring surgical intervention. Haemostatic control was achieved and a tracheostomy was sited for airway protection. Histopathology identified angioleiomyoma as the cause of his symptoms. Following multidisciplinary team discussion, this was managed with injection of bleomycin and subsequent surgical excision. This case is a reminder that subglottic lesions are often vascular in nature, and should be investigated with imaging and angiography prior to surgery, to avoid complications. BACKGROUND

IntroductionUp to 5% of all children have prominent ears. Psychological distress and bullying adversely affect these children and can cause significant social exclusion. In times of austerity, cosmetic procedures such as surgical correction of prominent ears are felt to be an unnecessary cost to the health service.Materials and methodsA retrospective case note review of all patients undergoing pinnaplasty was undertaken. Postoperative outcomes were compared against the Royal College of Surgeons of England standards. The Glasgow Benefit Inventory, a validated post-intervention questionnaire, was then posted out to all patients.ResultsA total of 72 patients were identified. Average age at procedure was 13 years. Eleven patients were above the age of 19 years. Twenty-eight patients were male and forty-four female. Sixty-two cases underwent bilateral pinnaplasty. No patients developed hematoma, and there were no readmissions within 30 days of surgery. Twenty-nine patients responded to the questionnaire (40%), of whom 27 reported a positive impact on their psychosocial well-being with a mean score of 36.ConclusionPinnaplasty offers patients an opportunity to alleviate the psychological distress of bullying and harassment secondary to the appearance of prominent ears.

Mastoiditis can result from untreated otitis media. If unrecognised, it can result in life-threatening complications. We present a 69-year-old woman with a history of left-sided otitis media admitted to intensive care unit following collapse with a decreasing Glasgow Coma Scale. Myringotomy and ventilator insertion revealed pus in the middle ear, which grew Group A Streptococcus. Her fever persisted and blood samples cultured Group A Streptococcus. Echocardiogram confirmed subacute bacterial endocarditis. Subacute bacterial endocarditis is a rare complication of mastoiditis. A literature review detected no previous case reports. A high suspicion of potential complications can prevent morbidity and mortality.

The seeming setbacks noted for stem cells underscore the need for experimental studies for safe and efficacious application to patients. Both clinical and experimental researchers have gained valuable knowledge on the characteristics of stem cells, and their behavior in different microenvironment. This introductory chapter focuses on adult mesenchymal stem cells (MSCs) based on the predominance in the clinic. MSCs can be influenced by inflammatory mediators to exert immune suppressive properties, commonly referred to as "licensing." Interestingly, while there are questions if other stem cells can be delivered across allogeneic barrier, there is no question on the ability of MSCs to provide this benefit. This property has been a great advantage since MSCs could be available for immediate application as "off-the-shelf" stem cells for several disorders, tissue repair and gene/drug delivery. Despite the benefit of MSCs, it is imperative that research continues with the various types of stem cells. The method needed to isolate these cells is outlined in this book. In parallel, safety studies are needed; particularly links to oncogenic event. In summary, this introductory chapter discusses several potential areas that need to be addressed for safe and efficient delivery of stem cells, and argue for the incorporation of microenvironmental factors in the studies. The method described in this chapter could be extrapolated to the field of chimeric antigen receptor T-cells (CAR-T). This will require application to stem cell hierarchy of memory T-cells.