Tissue chondrification and ossification in keloids with primary report of five cases

Keloid is commonly regarded as a benign skin tumour. Some keloids clinically exhibit hard tissue texture similar to that of cartilage or bone. We hypothesized that the keloid pathological niche environment is likely to induce keloid MSCs towards chondrogenic or osteogenic differentiation and leads to cartilage or bone‐like tissue formation. The differences in tissue ossification, histology, mechanical properties, abnormal extracellular matrices and chondrogenic/osteogenic gene expression among sclerous keloids (SKs), regular keloids (RKs) and normal skins (NKs) were carefully examined. The sporadic ossified islets existed in SK group whereas no ossified/chondrified islet was found in other groups by micro‐CT reconstruction. H&E, Masson trichrome and safranin O staining revealed lacuna‐like structures in SKs, which were featured as bone/cartilage histology. Immunohistochemical staining showed overproduction of osteoprotegerin, type I and III collagen in SK group but similar production level of aggrecan among three groups. The biomechanical analysis demonstrated the weakest compliance of SK tissues. In addition, SK fibroblasts exhibited a relatively slower proliferation rate but higher expression levels of osteogenic and chondrogenic genes among all three groups. These cell populations also showed the strongest potential for lineage transformation. In conclusion, we first reported the presence of ossified and chondrified matrices in some extremely hard keloids in the present study.

Heterotopic ossification: Mechanistic insights and clinical challenges

Bone formation is exquisitely controlled both spatially and temporally. Heterotopic ossification (HO) is pathological bone formation in soft tissues that often leads to deleterious outcomes. Inherited genetic forms of HO can be life-threatening and can happen as early as in infancy. However, there is currently no effective treatment for HO as the underlying cellular and molecular mechanisms have not been completely elucidated. Trauma-induced non-genetic forms of HO often occur as a common complication after surgeries or accidents, and the location of HO occurrence largely determines the symptom and outcome. While it has been difficult to determine the complicated factors causing HO, recent advancement in identifying cellular and molecular mechanism causing the genetic forms of HO may provide important insights in all HO. Here in this review, we summarize recent studies on HO to provide a current status of both clinical options of HO treatments and mechanical understanding of HO.

A case report of mesenteric heterotopic ossification: Histopathologic and genetic findings

Mesenteric heterotopic ossification (MHO) is very rare and occurs in mid- to late-adulthood, usually in the context of prior abdominal surgery. The mechanisms of MHO are unknown. Here we describe the case of a 72-year-old man with MHO. Standard histological staining revealed that MHO occurred through an endochondral process. By comparison to known mutations in genetic conditions of HO such as fibrodysplasia ossificans progressiva (FOP) and progressive osseous heteroplasia (POH), DNA sequencing analysis demonstrated the presence of a commonly occurring heterozygous synonymous polymorphism (c.690G>A; E230E) in the causative gene for FOP (ACVR1/ALK2). However, no frameshift, missense, or nonsense mutations in ACVR1, or in the causative gene for POH (GNAS), were found. Although genetic predisposition may play a role in MHO, our data suggest that mutations which occur in known hereditary conditions of HO are not the primary cause.