Liver mesenchymal stem cells are superior inhibitors of NK cell functions through differences in their secretome compared to other mesenchymal stem cells.

Liver-resident mesenchymal stem cells (L-MSCs) are superior inhibitors of alloreactive T cell responses compared to their counterparts from bone marrow (BM-MSCs) or adipose tissue (A-MSCs), suggesting a role in liver's overall tolerogenic microenvironment. Whether L-MSCs also impact NK cell functions differently than other MSCs is not known. We generated and characterized L-MSCs, A-MSCs and BM-MSCs from human tissues. The mass spectrometry analysis demonstrated that L-MSC secretome is uniquely different than that of A-MSC/BM-MSC, with enriched protein sets involved in IFNγ responses and signaling. When co-cultured with primary human NK cells, L-MSCs but not other MSCs, decreased surface expression of activating receptors NKp44 and NKG2D. L-MSCs also decreased IFNγ secretion by IL-2-stimulated NK cells more effectively than other MSCs. Cytolytic function of NK cells were reduced significantly when co-cultured with L-MSCs, whereas A-MSCs or BM-MSCs did not have a major impact. Mechanistic studies showed that the L-MSC-mediated reduction in NK cell cytotoxicity is not through changes in secretion of the cytotoxic proteins Perforin, Granzyme A or B, but through increased production of HLA-C1 found in L-MSC secretome that inhibits NK cells by stimulating their inhibitory receptor KIRDL2/3. L-MSCs are more potent inhibitors of NK cell functions than A-MSC or BM-MSC. Combined with their T cell inhibitory features, these results suggest L-MSCs contribute to the tolerogenic liver microenvironment and liver-induced systemic tolerance often observed after liver transplantation.

Bone marrow derived long-lived plasma cell phenotypes are heterogeneous and can change in culture.

Bone marrow-derived long-lived plasma cells (LLPCs) are thought to be a major source of alloantibody in sensitized transplant patients. However, studies of LLPCs have been hampered not only by the fact that they are rare and difficult to isolate and culture but also due to the lack of consensus regarding a definitive cell-surface phenotype. The goal of the current study was to determine if LLPCs have a specific, stable cell-surface phenotype. PCs were isolated from high-volume (120cc) bone marrow aspirates that were enriched first by negative selection then positive selection using anti-CD38 antibody-coated beads and purified by cell sorting. A typical isolation resulted in >100,000 PCs that were sorted into 4 populations with variable numbers of PCs: CD19+/CD138+/CD38Hi (64.1% of the PCs), CD19-/CD138+/CD38Hi (20.9%), CD19+/CD138-/CD38Hi (10.7%), and CD19-/CD138-/CD38Hi (4.3%). The purity of each subset was 96-99%. Each subset contained PCs secreting IgG and IgA. Measles- and tetanus-specific PCs (i.e. putative IgG secreting, antigen-specific LLPCs). LLPCs were identified in both the CD19+/CD138+/CD38Hi and CD19-/CD138+/CD38Hi subsets and in the smaller CD138- subsets (when pooled). Thus, all CD38Hi subsets contained LLPCs. Cultured PCs maintained viability (>50%) and function and could be retrieved for analyses. During 7 days of culture, cell surface expression changed from baseline in many PCs. For example, approximately 20% of CD19 + CD138+/CD38Hi cells (the largest PC subset) became CD19-. CFSE assays showed no division and only a small percentage of LLPCs were Ki-67 positive suggesting that the cells did not divide in culture and that the antibody detected was not from plasmablasts. We conclude that human bone marrow LLPCs have a heterogeneous expression of CD19 and CD138, which can change during cell culture. The fact that LLPCs were found in all four subsets raises the possibility that a large percentage of PCs in the bone marrow may be LLPCs.

Complications After Hand-Assisted Laparoscopic Living Donor Nephrectomy.

OBJECTIVE: To study the complications of hand-assisted laparoscopic living donor nephrectomy (HALLDN) with an emphasis on complications occurring early after hospital discharge up to 120 days after surgery. PATIENTS AND METHODS: We retrospectively categorized complications using the Clavien-Dindo classification in 3002 HALLDNs performed at 1 center from January 1, 2000, through December 31, 2019. In addition to overall summaries, modeling was used to identify correlates of complications before and after living donation. RESULTS: Of these donors, 87% were White, 59% were female, the mean age was 45 years (range, 18-77 years), 30.3% had a body mass index of at least 30, and 36.3% had previous abdominopelvic surgery. There were no deaths related to the surgery. The incidence of major complications (intraoperative complications plus Clavien-Dindo grade ≥III postoperatively) was 2.5% (n=74). The overall complication rate was 12.4% (n=371), including 15 intraoperative, 76 postoperative before discharge, and 280 after discharge to 120 days. Reoperation was required in 1.8% of patients (n=54), and all but 1 of these were incision-related problems. Seventy-six percent of all complications occurred after discharge, including 85% of the reoperations. For major complications, no risk factor was found. Risk factors for any complication included paramedian incision (hazard ratio [HR], 2.54; 95% CI, 1.49 to 4.34; P<.001); a history of abdominopelvic surgery (HR, 1.37; 95% CI, 1.07 to 1.76; P=.01), male sex (HR, 1.37; 95% CI, 1.07 to 1.76; P=.01), non-White race (HR, 1.40; 95% CI, 1.05 to 1.88; P=.02), and early era of the experience. CONCLUSION: Most major complications of HALLDN occur after discharge, suggesting that close follow-up is warranted and that the current literature may underestimate the true incidence.

Comparable in vitro Function of Human Liver-Derived and Adipose Tissue-Derived Mesenchymal Stromal Cells: Implications for Cell-Based Therapy.

Mesenchymal stem/stromal cells (MSCs) have been investigated extensively for their immunotherapeutic and regenerative properties, which may differ by cell source. In MSCs harvested from donors matched for sex, age, and body mass index, we compared the proliferative and migration functions of liver-derived MSCs (L-MSCs) and adipose tissue-derived MSCs (A-MSCs) (n = 6 donors each). Cellular senescence was evaluated by senescence-associated beta-galactosidase enzyme activity and expression of senescence-associated secretory phenotype (SASP) factors using real-time quantitative polymerase chain and by western blot assay. The pro-angiogenic and reparative potency of MSCs was compared by co-culturing MSCs with injured human umbilical vein endothelial cells (HUVEC). The proliferation and migration properties were similar in L-MSCs and A-MSCs. Although cell cycle arrest and SASP genes were similarly expressed in both MSCs, tumor necrosis factor alpha gene and protein expression were significantly downregulated in L-MSCs. In co-cultured injured HUVEC, A-MSCs restored significantly more tubes and tube connections than L-MSCs. Therefore, despite many functional similarities between L-MSCs and A-MSCs, L-MSCs have enhanced immunomodulatory properties, while A-MSCs appear to have better pro-angiogenic and vascular reparative potency. Availability of a broad range of cellular options might enable selecting cell-based therapy appropriate for the specific underlying disease.

Metal allergy hypersensitivity after posterior thoracic spinal fusion: A case report and review of the literature.

Background: Spine surgeons rarely consider metal allergies when placing hardware, as implants are thought to be inert. Case Description: A 32-year-old male presented with a skin rash attributed to the trace metal in his spinal fusion instrumentation. Patch testing revealed sensitivities to cobalt, manganese, and chromium. He underwent hardware removal and replacement with constructs of commercially pure titanium. His skin findings resolved at 2 weeks after surgery and were stable at 6 weeks. Conclusion: Hypersensitivity to metal (i.e., metal allergy) should be considered before performing instrumented spinal fusions.